Enhanced nonlinear optical properties of octa-substituted lead and cadmium phthalocyanines when embedded in poly (bisphenol A carbonate) as thin films
- Mkhize, Colin, Britton, Jonathan, Nyokong, Tebello
- Authors: Mkhize, Colin , Britton, Jonathan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241459 , vital:50941 , xlink:href="https://doi.org/10.1016/j.poly.2014.07.025"
- Description: This work presents photophysical and nonlinear optical properties of a novel Cd 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (CdOtBPPc) and compare them with those of Pb 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (PbOtBPPc). For both the CdOtBPPc and PbOtBPPc, third order imaginary susceptibility and second order hyperpolarizability values were found to be within the limit set for good optical limiters. The Pcs were embedded in poly (methyl methacrylate) (PMMA) and poly(bisphenol A carbonate) (PBC) as thin films. The optical limiting values of the Pcs once embedded in film were found to be greatly improved and the limiting fluence of each film was well below the maximum threshold. Both PbOtBPPc and CdOtBPPc showed better optical limiting when embedded in PBC compared to PMMA. CdOtBPPc shows better nonlinear optical behavior than PbOtBPPc in solution and as thin films, even though the former is aggregated in solution.
- Full Text:
- Date Issued: 2014
- Authors: Mkhize, Colin , Britton, Jonathan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241459 , vital:50941 , xlink:href="https://doi.org/10.1016/j.poly.2014.07.025"
- Description: This work presents photophysical and nonlinear optical properties of a novel Cd 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (CdOtBPPc) and compare them with those of Pb 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (PbOtBPPc). For both the CdOtBPPc and PbOtBPPc, third order imaginary susceptibility and second order hyperpolarizability values were found to be within the limit set for good optical limiters. The Pcs were embedded in poly (methyl methacrylate) (PMMA) and poly(bisphenol A carbonate) (PBC) as thin films. The optical limiting values of the Pcs once embedded in film were found to be greatly improved and the limiting fluence of each film was well below the maximum threshold. Both PbOtBPPc and CdOtBPPc showed better optical limiting when embedded in PBC compared to PMMA. CdOtBPPc shows better nonlinear optical behavior than PbOtBPPc in solution and as thin films, even though the former is aggregated in solution.
- Full Text:
- Date Issued: 2014
Enhanced Optical Limiting Behavior of an Indium Phthalocyanine–Single-Walled Carbon Nanotube Composite
- Sanusi, Kayode, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Sanusi, Kayode , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193871 , vital:45401 , xlink:href="https://doi.org/10.1021/jp501469e "
- Description: The nonlinear optical behavior of 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy) phthalocyaninato indium (III) chloride (2) and its carbon nanotube composite in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solutions is described. The nonlinear third-order susceptibility and second-order hyperpolarizability values are also reported. A large nonlinear absorption that increased on covalent linking with single-walled carbon nanotubes (SWCNTs) was observed for the compound in DMSO. The nanosecond nonlinear absorption and the optical limiting behavior of this complex are shown to be dominated by a strong excited state absorption from a two-photon pumped state. The optical limiter using the new nanocomposite material (SWCNT-2) in the appropriate solvent showed a much lower threshold for optical limiting together with a much lower transmission at high fluences than previously reported nanocomposite limiters. The optical properties of the phthalocyanine and its conjugate were found to show high sensitivity toward the change of solvent matrix.
- Full Text:
- Date Issued: 2014
- Authors: Sanusi, Kayode , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193871 , vital:45401 , xlink:href="https://doi.org/10.1021/jp501469e "
- Description: The nonlinear optical behavior of 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy) phthalocyaninato indium (III) chloride (2) and its carbon nanotube composite in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solutions is described. The nonlinear third-order susceptibility and second-order hyperpolarizability values are also reported. A large nonlinear absorption that increased on covalent linking with single-walled carbon nanotubes (SWCNTs) was observed for the compound in DMSO. The nanosecond nonlinear absorption and the optical limiting behavior of this complex are shown to be dominated by a strong excited state absorption from a two-photon pumped state. The optical limiter using the new nanocomposite material (SWCNT-2) in the appropriate solvent showed a much lower threshold for optical limiting together with a much lower transmission at high fluences than previously reported nanocomposite limiters. The optical properties of the phthalocyanine and its conjugate were found to show high sensitivity toward the change of solvent matrix.
- Full Text:
- Date Issued: 2014
Enhanced optical limiting performance in phthalocyanine-quantum dot nanocomposites by free-carrier absorption mechanism
- Sanusi, Kayode, Khene, Samson M, Nyokong, Tebello
- Authors: Sanusi, Kayode , Khene, Samson M , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193904 , vital:45404 , xlink:href="https://doi.org/10.1016/j.optmat.2014.07.024"
- Description: Enhanced nonlinear optical properties (in dimethyl sulphoxide) is observed for 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy)phthalocyaninato indium(III) chloride (InPc) when covalently linked to CdSe/ZnS or CdSe quantum dots (QDs). The experimental nonlinear optical parameters were obtained from Z-Scan measurements. Contributions from two-photon absorption (2PA) due to the InPc, and free-carrier absorption (FCA) by QDS have been identified as the main factors responsible for the enhanced optical limiting. The effective nonlinear absorption coefficient for InPc-CdSe/ZnS was found to be 700.0 cm/GW. The FCA cross-sections for InPc-CdSe/ZnS and InPc-CdSe composites were found to be 1.52 × 10−19 and 6.00 × 10−20 cm2 respectively. A much lower limiting threshold of 92 mJ cm−2 was observed for InPc-CdSe/ZnS nanocomposite, hence, making it suitable for use as optical limiting material. Density Functional Theory (DFT) calculations on similar phthalocyanine-quantum dots system was modeled in order to explain the enhancement in the observed nonlinear optical properties of the Pc in the presence of the QDs. The experimentally determined nonlinear optical properties are well within the range of the DFT calculated properties.
- Full Text:
- Date Issued: 2014
- Authors: Sanusi, Kayode , Khene, Samson M , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193904 , vital:45404 , xlink:href="https://doi.org/10.1016/j.optmat.2014.07.024"
- Description: Enhanced nonlinear optical properties (in dimethyl sulphoxide) is observed for 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy)phthalocyaninato indium(III) chloride (InPc) when covalently linked to CdSe/ZnS or CdSe quantum dots (QDs). The experimental nonlinear optical parameters were obtained from Z-Scan measurements. Contributions from two-photon absorption (2PA) due to the InPc, and free-carrier absorption (FCA) by QDS have been identified as the main factors responsible for the enhanced optical limiting. The effective nonlinear absorption coefficient for InPc-CdSe/ZnS was found to be 700.0 cm/GW. The FCA cross-sections for InPc-CdSe/ZnS and InPc-CdSe composites were found to be 1.52 × 10−19 and 6.00 × 10−20 cm2 respectively. A much lower limiting threshold of 92 mJ cm−2 was observed for InPc-CdSe/ZnS nanocomposite, hence, making it suitable for use as optical limiting material. Density Functional Theory (DFT) calculations on similar phthalocyanine-quantum dots system was modeled in order to explain the enhancement in the observed nonlinear optical properties of the Pc in the presence of the QDs. The experimentally determined nonlinear optical properties are well within the range of the DFT calculated properties.
- Full Text:
- Date Issued: 2014
Exploring a knowledge-focused trajectory for researching environmental learning in the South African curriculum
- Authors: Schudel, Ingrid J
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/294375 , vital:57216 , xlink:href="https://www.researchgate.net/publication/305730521"
- Description: This paper explores the past twenty years of environmental learning in the South African curriculum in order to consider how one might best research a knowledge focus within the Fundisa for Change national teacher education programme. In exploring this knowledge focus, the paper draws on international literature. It also extensively, but not exclusively, draws on two key publications which informed the 2002 and the 2011 curriculum changes in South Africa. The paper draws on social realist curriculum theory, underpinned by critical realism. This theoretical perspective, which includes Bernstein’s pedagogic device and particularly recontextualisation of knowledge across the pedagogical landscape, provides a language of description for critically reviewing knowledge and environmental learning. In particular, the review develops five perspectives on environmental knowledge as it pertains to curriculum which include: Perspective #1) new environmental knowledge in the curriculum; Perspective #2) environmental knowledge in local and global contexts; Perspective # 3) dynamic knowledge for open-ended and futuristic thinking; Perspective #4) depth and complexity of environmental knowledge; and Perspective #5) combining discipline-specific core knowledge and skills with a systems perspective. The paper argues for a re-emphasis and review of new environmental knowledge and learning support materials. It suggests a consideration of context-rich but not context-bound explorations of local and global environmental issues and the need for adopting open-ended and futuristic thinking in the context of the dynamism of environmental knowledge. This involves exploring systems of meaning and structures of knowledge in dealing with the complexity of environmental knowledge and acknowledging the challenges of a transformative ideology within such a complex knowledge system. Additionally, the paper argues for creative ways of working across disciplines to develop better understanding of discipline-specific concepts and their potential to contribute to meaningful learning. The paper concludes by suggesting a research trajectory for future environmental education research in the context of the new South African Curriculum and Assessment Policy Statement (CAPS) extending the emphasis in this paper on the official recontextualising field, to fields across the entire pedagogic device.
- Full Text:
- Date Issued: 2014
- Authors: Schudel, Ingrid J
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/294375 , vital:57216 , xlink:href="https://www.researchgate.net/publication/305730521"
- Description: This paper explores the past twenty years of environmental learning in the South African curriculum in order to consider how one might best research a knowledge focus within the Fundisa for Change national teacher education programme. In exploring this knowledge focus, the paper draws on international literature. It also extensively, but not exclusively, draws on two key publications which informed the 2002 and the 2011 curriculum changes in South Africa. The paper draws on social realist curriculum theory, underpinned by critical realism. This theoretical perspective, which includes Bernstein’s pedagogic device and particularly recontextualisation of knowledge across the pedagogical landscape, provides a language of description for critically reviewing knowledge and environmental learning. In particular, the review develops five perspectives on environmental knowledge as it pertains to curriculum which include: Perspective #1) new environmental knowledge in the curriculum; Perspective #2) environmental knowledge in local and global contexts; Perspective # 3) dynamic knowledge for open-ended and futuristic thinking; Perspective #4) depth and complexity of environmental knowledge; and Perspective #5) combining discipline-specific core knowledge and skills with a systems perspective. The paper argues for a re-emphasis and review of new environmental knowledge and learning support materials. It suggests a consideration of context-rich but not context-bound explorations of local and global environmental issues and the need for adopting open-ended and futuristic thinking in the context of the dynamism of environmental knowledge. This involves exploring systems of meaning and structures of knowledge in dealing with the complexity of environmental knowledge and acknowledging the challenges of a transformative ideology within such a complex knowledge system. Additionally, the paper argues for creative ways of working across disciplines to develop better understanding of discipline-specific concepts and their potential to contribute to meaningful learning. The paper concludes by suggesting a research trajectory for future environmental education research in the context of the new South African Curriculum and Assessment Policy Statement (CAPS) extending the emphasis in this paper on the official recontextualising field, to fields across the entire pedagogic device.
- Full Text:
- Date Issued: 2014
Fabrication of phthalocyanine-magnetic nanoparticles hybrid nanofibers for degradation of Orange-G
- Modisha, Phillimon, Nyokong, Tebello
- Authors: Modisha, Phillimon , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190394 , vital:44990 , xlink:href="https://doi.org/10.1016/j.molcata.2013.10.012"
- Description: Conjugates of zinc octacarboxy phthalocyanine (ZnOCPc) with magnetic nanoparticles (MNPs) were electrospun into fibers using polyamide-6 (PA-6) polymer. The ZnOCPc or ZnOCPc-MNPs conjugates on the fiber were employed for the photodegradation of an azo dye (Orange-G). The functionality of the ZnOCPc and ZnOCPc-MNPs was maintained within a solid fiber core. The singlet oxygen generation increases as we increase the fiber diameter by increasing the ZnOCPc concentration. The singlet oxygen quantum yield was higher for PA-6/ZnOCPc-MNPs nanofibers compared to PA-6/ZnOCPc. The rate of degradation of Orange-G increased with an increase in singlet oxygen quantum yield. Moreover, the kinetic analysis of the photodecomposition of Orange-G showed that its disappearance followed the Langmuir–Hinshelwood model.
- Full Text:
- Date Issued: 2014
- Authors: Modisha, Phillimon , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190394 , vital:44990 , xlink:href="https://doi.org/10.1016/j.molcata.2013.10.012"
- Description: Conjugates of zinc octacarboxy phthalocyanine (ZnOCPc) with magnetic nanoparticles (MNPs) were electrospun into fibers using polyamide-6 (PA-6) polymer. The ZnOCPc or ZnOCPc-MNPs conjugates on the fiber were employed for the photodegradation of an azo dye (Orange-G). The functionality of the ZnOCPc and ZnOCPc-MNPs was maintained within a solid fiber core. The singlet oxygen generation increases as we increase the fiber diameter by increasing the ZnOCPc concentration. The singlet oxygen quantum yield was higher for PA-6/ZnOCPc-MNPs nanofibers compared to PA-6/ZnOCPc. The rate of degradation of Orange-G increased with an increase in singlet oxygen quantum yield. Moreover, the kinetic analysis of the photodecomposition of Orange-G showed that its disappearance followed the Langmuir–Hinshelwood model.
- Full Text:
- Date Issued: 2014
Family functioning and life satisfaction and happiness in South African households
- Botha, Ferdi, Booysen, Frikkie
- Authors: Botha, Ferdi , Booysen, Frikkie
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396048 , vital:69146 , xlink:href="https://doi.org/10.1007/s11205-013-0485-6"
- Description: Families form an integral part of society and in fostering individual well-being. Despite the acknowledged importance of family, the association between family functioning and individual well-being outcomes have remained unexplored in the current body of knowledge. This paper explores the association between family functioning and reported levels of life satisfaction and happiness in South Africa. The paper employs the Family Attachment and Changeability Index (FACI8) to measure family functioning, using data from the 2011 South African Social Attitudes Survey. Four measures of family functioning are utilised, namely the aggregate FACI8 scale, the attachment and changeability sub-scales, and family functioning type. Improvements in the level of family functioning as well as in the levels of attachment and changeability are positively associated with life satisfaction and happiness. In addition, individuals living in midrange or balanced family functioning types are more satisfied with life and happier compared to persons living in extremely or moderately dysfunctional families. The findings highlight the importance of supportive intra-family dynamics in fostering greater individual well-being. This in turn places emphasis on the investigation of likely correlates of family functioning and impact evaluations of family-focused social work interventions’ impact on family functioning as areas for future research.
- Full Text:
- Date Issued: 2014
- Authors: Botha, Ferdi , Booysen, Frikkie
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396048 , vital:69146 , xlink:href="https://doi.org/10.1007/s11205-013-0485-6"
- Description: Families form an integral part of society and in fostering individual well-being. Despite the acknowledged importance of family, the association between family functioning and individual well-being outcomes have remained unexplored in the current body of knowledge. This paper explores the association between family functioning and reported levels of life satisfaction and happiness in South Africa. The paper employs the Family Attachment and Changeability Index (FACI8) to measure family functioning, using data from the 2011 South African Social Attitudes Survey. Four measures of family functioning are utilised, namely the aggregate FACI8 scale, the attachment and changeability sub-scales, and family functioning type. Improvements in the level of family functioning as well as in the levels of attachment and changeability are positively associated with life satisfaction and happiness. In addition, individuals living in midrange or balanced family functioning types are more satisfied with life and happier compared to persons living in extremely or moderately dysfunctional families. The findings highlight the importance of supportive intra-family dynamics in fostering greater individual well-being. This in turn places emphasis on the investigation of likely correlates of family functioning and impact evaluations of family-focused social work interventions’ impact on family functioning as areas for future research.
- Full Text:
- Date Issued: 2014
Fish utilization of surf-zones: Are they changing A case study of the sheltered, warm-temperate King’s Beach
- Rishworth, Gavin M, Strydom, Nadine A, Potts, Warren M
- Authors: Rishworth, Gavin M , Strydom, Nadine A , Potts, Warren M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443866 , vital:74167 , https://doi.org/10.1080/15627020.2014.11407616
- Description: Surf-zone fish communities and their shifts over time are generally poorly understood. The aim of this study was to compare the current surf-zone fish assemblage at King's Beach, South Africa, to a similar study conducted three decades ago, before the collapse of many exploited shore fishes in the region. Beach seine nets (mesh sizes of 10 and 50 mm) were used to target juvenile and adult fishes bimonthly from February to August 2011 over the high tide around sunset. A total of 14 species were recorded in both the 30 m and 100 m seine nets. The catch in these seine nets was dominated by Pomadasys olivaceus and Liza richardsonii, and this was significantly different to three decades ago, when P. olivaceus, Sarpa salpa and Diplodus capensis dominated the catch. Important linefish species belonging to the Sparidae and Sciaenidae families were significantly smaller and less abundant in this study. Two sparids, S. salpa and Lithognathus mormyrus, which made a large contribution to the surf-zone catch three decades ago were absent during this study. Reasons for the significant shifts in the surf-zone fish community, including overexploitation of the linefish and potential habitat modification, are discussed.
- Full Text:
- Date Issued: 2014
- Authors: Rishworth, Gavin M , Strydom, Nadine A , Potts, Warren M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443866 , vital:74167 , https://doi.org/10.1080/15627020.2014.11407616
- Description: Surf-zone fish communities and their shifts over time are generally poorly understood. The aim of this study was to compare the current surf-zone fish assemblage at King's Beach, South Africa, to a similar study conducted three decades ago, before the collapse of many exploited shore fishes in the region. Beach seine nets (mesh sizes of 10 and 50 mm) were used to target juvenile and adult fishes bimonthly from February to August 2011 over the high tide around sunset. A total of 14 species were recorded in both the 30 m and 100 m seine nets. The catch in these seine nets was dominated by Pomadasys olivaceus and Liza richardsonii, and this was significantly different to three decades ago, when P. olivaceus, Sarpa salpa and Diplodus capensis dominated the catch. Important linefish species belonging to the Sparidae and Sciaenidae families were significantly smaller and less abundant in this study. Two sparids, S. salpa and Lithognathus mormyrus, which made a large contribution to the surf-zone catch three decades ago were absent during this study. Reasons for the significant shifts in the surf-zone fish community, including overexploitation of the linefish and potential habitat modification, are discussed.
- Full Text:
- Date Issued: 2014
Growth metrics and δ15N values of water hyacinth, Eichhornia crassipes, in relation to biological control
- Authors: Hill, Jaclyn M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444744 , vital:74264 , https://www.cabidigitallibrary.org/doi/pdf/10.5555/20173070900
- Description: The success of classical biological control against Eichhornia crassipes (Pontederiaceae) in South Africa has been varied, with failures attributed to numerous factors, predominantly the high levels of eutrophication of many freshwater systems. Studies have shown that increased N-loads are associated with enriched δ15N values of aquatic biota. Stable isotope analyses may therefore help to assess the nutrient status of invaded ecosystems and predict the success of classical biological control. A combination of controlled greenhouse experiments and in-situ observations were used: to quantify the δ15N equilibration rate of E. crassipes leaf tissue (ie the time span of the information on environmental N-loading); to confirm the ability of plant tissue to reflect ecosystem N-loading; and to compare standard water hyacinth growth metrics with δ15N and C/N ratios to evaluate how well they described eutrophication. Using both δ15N values and C/N ratios, it was possible to distinguish clearly between manure-, fertilizer-and control-regimes, and plant tissue provided information on ecosystem N-loading over approximately 16 days. Interpretations were complicated by the plant’s capacity for N storage. Strong correlations between petiole length of E. crassipes and δ15N values indicate that petiole length may be linked to N-loading. Weaker (or a lack of) correlations between δ15N or C/N ratios and remaining growth metrics suggest that generalisations and, or, predictions of eutrophication based on growth metrics should be avoided. A combination approach using plant tissue δ15N and C/N ratios along with maximum petiole length of E. crassipes plants may provide a time-integrated assessment of ecosystem eutrophication and help to identify areas where classical biological control may face significant obstacles in the regulation of water hyacinth populations.
- Full Text:
- Date Issued: 2014
- Authors: Hill, Jaclyn M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444744 , vital:74264 , https://www.cabidigitallibrary.org/doi/pdf/10.5555/20173070900
- Description: The success of classical biological control against Eichhornia crassipes (Pontederiaceae) in South Africa has been varied, with failures attributed to numerous factors, predominantly the high levels of eutrophication of many freshwater systems. Studies have shown that increased N-loads are associated with enriched δ15N values of aquatic biota. Stable isotope analyses may therefore help to assess the nutrient status of invaded ecosystems and predict the success of classical biological control. A combination of controlled greenhouse experiments and in-situ observations were used: to quantify the δ15N equilibration rate of E. crassipes leaf tissue (ie the time span of the information on environmental N-loading); to confirm the ability of plant tissue to reflect ecosystem N-loading; and to compare standard water hyacinth growth metrics with δ15N and C/N ratios to evaluate how well they described eutrophication. Using both δ15N values and C/N ratios, it was possible to distinguish clearly between manure-, fertilizer-and control-regimes, and plant tissue provided information on ecosystem N-loading over approximately 16 days. Interpretations were complicated by the plant’s capacity for N storage. Strong correlations between petiole length of E. crassipes and δ15N values indicate that petiole length may be linked to N-loading. Weaker (or a lack of) correlations between δ15N or C/N ratios and remaining growth metrics suggest that generalisations and, or, predictions of eutrophication based on growth metrics should be avoided. A combination approach using plant tissue δ15N and C/N ratios along with maximum petiole length of E. crassipes plants may provide a time-integrated assessment of ecosystem eutrophication and help to identify areas where classical biological control may face significant obstacles in the regulation of water hyacinth populations.
- Full Text:
- Date Issued: 2014
Guardian of the furnace: mitochondria, TRAP1, ROS and stem cell maintenance
- Kadye, Rose, Kramer, Adam H, Joos-Vandewalle, Julia, Parsons, Michelle, Njengele, Zikhona, Hoppe, Heinrich C, Prinsloo, Earl
- Authors: Kadye, Rose , Kramer, Adam H , Joos-Vandewalle, Julia , Parsons, Michelle , Njengele, Zikhona , Hoppe, Heinrich C , Prinsloo, Earl
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431119 , vital:72745 , xlink:href="https://doi.org/10.1002/iub.1234"
- Description: Mitochondria are key to eukaryotic cell survival and their activity is linked to generation of reactive oxygen species (ROS) which in turn acts as both an intracellular signal and an effective executioner of cells with regards to cellular senescence. The mitochondrial molecular chaperone tumor necrosis factor receptor associated protein 1 (TRAP1) is often termed the cytoprotective chaperone for its role in cancer cell survival and protection from apoptosis. Here, we hypothesize that TRAP1 serves to modulate mitochondrial activity in stem cell maintenance, survival and differentiation.
- Full Text:
- Date Issued: 2014
- Authors: Kadye, Rose , Kramer, Adam H , Joos-Vandewalle, Julia , Parsons, Michelle , Njengele, Zikhona , Hoppe, Heinrich C , Prinsloo, Earl
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431119 , vital:72745 , xlink:href="https://doi.org/10.1002/iub.1234"
- Description: Mitochondria are key to eukaryotic cell survival and their activity is linked to generation of reactive oxygen species (ROS) which in turn acts as both an intracellular signal and an effective executioner of cells with regards to cellular senescence. The mitochondrial molecular chaperone tumor necrosis factor receptor associated protein 1 (TRAP1) is often termed the cytoprotective chaperone for its role in cancer cell survival and protection from apoptosis. Here, we hypothesize that TRAP1 serves to modulate mitochondrial activity in stem cell maintenance, survival and differentiation.
- Full Text:
- Date Issued: 2014
Happiness, socioeconomic status, and family functioning in South African households
- Botha, Ferdie, Booysen, Frikkie
- Authors: Botha, Ferdie , Booysen, Frikkie
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396075 , vital:69148 , xlink:href="https://doi.org/10.1007/s11205-013-0485-6"
- Description: This paper examines how SES relates to individual happiness, while also controlling for family functioning; the latter measured by the Family Attachment and Changeability Index 8 (FACI8). An individual-, household-, and subjective SES index are developed via multiple correspondence analyses (MCA). Using data from the 2012 South African Social Attitudes Survey (SASAS), the paper employs structural equation modelling (SEM) to explore the relationship between happiness, SES, and family functioning. Multiple-group SEM (MGSEM) is employed to examine the association between happiness and family functioning across quartiles of the three SES indices. The results reveal that higher SES is significantly related to greater happiness, with the role of household- and subjective SES being stronger than individual SES. Furthermore, improved levels of family changeability are positively associated with happiness, whereas there is no relationship between happiness and family attachment. Overall, levels of family changeability and individual happiness are likely to benefit from improvements in socioeconomic status.
- Full Text:
- Date Issued: 2014
- Authors: Botha, Ferdie , Booysen, Frikkie
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/396075 , vital:69148 , xlink:href="https://doi.org/10.1007/s11205-013-0485-6"
- Description: This paper examines how SES relates to individual happiness, while also controlling for family functioning; the latter measured by the Family Attachment and Changeability Index 8 (FACI8). An individual-, household-, and subjective SES index are developed via multiple correspondence analyses (MCA). Using data from the 2012 South African Social Attitudes Survey (SASAS), the paper employs structural equation modelling (SEM) to explore the relationship between happiness, SES, and family functioning. Multiple-group SEM (MGSEM) is employed to examine the association between happiness and family functioning across quartiles of the three SES indices. The results reveal that higher SES is significantly related to greater happiness, with the role of household- and subjective SES being stronger than individual SES. Furthermore, improved levels of family changeability are positively associated with happiness, whereas there is no relationship between happiness and family attachment. Overall, levels of family changeability and individual happiness are likely to benefit from improvements in socioeconomic status.
- Full Text:
- Date Issued: 2014
Higher education studies as a field of research
- Authors: McKenna, Sioux
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187405 , vital:44631 , xlink:href="https://hdl.handle.net/10520/EJC161436"
- Description: The field of Higher Education Studies is a rapidly growing one in South Africa and abroad but there has been little systematic review of the form this growth is taking. This article presents a case study of higher education research by considering a newly formed Higher Education Studies doctoral programme. The programme comprises 29 PhD scholars in 2014, all engaged in research on some aspect of higher education. The description of the PhD programme, the PhD scholars and what their research topics are, reveals a picture of the broad range of concerns within the field of Higher Education Studies and suggests that the field is a region, in Bernstein's terms. This means that it draws on multiple disciplines and looks both to the values and structures of those disciplines and to the professional world of work. It is argued that the strengthening of the epistemological base of Higher Education Studies is necessary for higher education research to move forwards with enhanced relational and positional autonomy.
- Full Text:
- Date Issued: 2014
- Authors: McKenna, Sioux
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187405 , vital:44631 , xlink:href="https://hdl.handle.net/10520/EJC161436"
- Description: The field of Higher Education Studies is a rapidly growing one in South Africa and abroad but there has been little systematic review of the form this growth is taking. This article presents a case study of higher education research by considering a newly formed Higher Education Studies doctoral programme. The programme comprises 29 PhD scholars in 2014, all engaged in research on some aspect of higher education. The description of the PhD programme, the PhD scholars and what their research topics are, reveals a picture of the broad range of concerns within the field of Higher Education Studies and suggests that the field is a region, in Bernstein's terms. This means that it draws on multiple disciplines and looks both to the values and structures of those disciplines and to the professional world of work. It is argued that the strengthening of the epistemological base of Higher Education Studies is necessary for higher education research to move forwards with enhanced relational and positional autonomy.
- Full Text:
- Date Issued: 2014
Histological confirmation of epizootic ulcerative syndrome in two cyprinid species from Lake Liambezi, Zambezi Region, Namibia
- McHugh, Kyle J, Smit, Nico J, Christison, Kevin W, Weyl, Olaf L F
- Authors: McHugh, Kyle J , Smit, Nico J , Christison, Kevin W , Weyl, Olaf L F
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443354 , vital:74110 , https://hdl.handle.net/10520/EJC160489
- Description: Epizootic ulcerative syndrome (EUS) is a fish disease caused by an infection of the oomycete, Aphanomyces invadans. During a fish biodiversity assessment of Lake Liambezi, Zambezi Region, Namibia, in August 2011, two Barbus haasianus and three Barbus unitaeniatus with circular ulcerative skin lesions were collected. Lake Liambezi receives inflow from the Zambezi, Chobe and Linyanti rivers. The presence of EUS in the two species was confirmed histologically by: a loss of epidermis at the site of the lesion; hyphae visible deep into the muscle layer with an associated granulomatous inflammatory reaction; and muscle fibre degeneration visible with associated penetrating hyphae. This paper provides further histological confirmation of EUS from Lake Liambezi and the first record of the disease in B. haasianus.
- Full Text:
- Date Issued: 2014
- Authors: McHugh, Kyle J , Smit, Nico J , Christison, Kevin W , Weyl, Olaf L F
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443354 , vital:74110 , https://hdl.handle.net/10520/EJC160489
- Description: Epizootic ulcerative syndrome (EUS) is a fish disease caused by an infection of the oomycete, Aphanomyces invadans. During a fish biodiversity assessment of Lake Liambezi, Zambezi Region, Namibia, in August 2011, two Barbus haasianus and three Barbus unitaeniatus with circular ulcerative skin lesions were collected. Lake Liambezi receives inflow from the Zambezi, Chobe and Linyanti rivers. The presence of EUS in the two species was confirmed histologically by: a loss of epidermis at the site of the lesion; hyphae visible deep into the muscle layer with an associated granulomatous inflammatory reaction; and muscle fibre degeneration visible with associated penetrating hyphae. This paper provides further histological confirmation of EUS from Lake Liambezi and the first record of the disease in B. haasianus.
- Full Text:
- Date Issued: 2014
Homestead greening is widespread amongst the urban poor in three medium-sized South African towns
- Kaoma, Humphrey, Shackleton, Charlie M
- Authors: Kaoma, Humphrey , Shackleton, Charlie M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398291 , vital:69398 , xlink:href="https://doi.org/10.1007/s11252-014-0362-3"
- Description: Trees in urban areas are important sources of ecosystem services and benefits. In most towns the bulk of urban biodiversity, and trees specifically, are found in homestead gardens. But there is only limited understanding of the tree holdings in such gardens, and how they vary within and between towns, especially for developing countries where rapid urbanisation and high poverty influence the use of and reliance on land and local resources. We report on the nature of tree holdings in private gardens of poorer suburbs in three medium-sized towns along a gradient of decreasing mean annual rainfall in northern South Africa. A total of 3 217 trees were enumerated across 450 randomly selected homesteads. Most (90 %) households had at least one tree on their homestead, with an average of 7.7 ± 6.1 trees. Most householders had planted the trees themselves. The density of trees declined along the moisture gradient. Within towns, tree density was positively related to garden size, which in turn was related to relative affluence and age of the suburb. Newer and poorer suburbs had the fewest trees per household. Sixty-two tree species were recorded, which were dominated by alien species, especially fruit trees. There was no relationship between the moisture gradient and tree species richness per household, but within towns there was a difference between suburbs, being lowest in the newest suburbs. Numbers of trees and species per household was positively related to age of the household head.
- Full Text:
- Date Issued: 2014
- Authors: Kaoma, Humphrey , Shackleton, Charlie M
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398291 , vital:69398 , xlink:href="https://doi.org/10.1007/s11252-014-0362-3"
- Description: Trees in urban areas are important sources of ecosystem services and benefits. In most towns the bulk of urban biodiversity, and trees specifically, are found in homestead gardens. But there is only limited understanding of the tree holdings in such gardens, and how they vary within and between towns, especially for developing countries where rapid urbanisation and high poverty influence the use of and reliance on land and local resources. We report on the nature of tree holdings in private gardens of poorer suburbs in three medium-sized towns along a gradient of decreasing mean annual rainfall in northern South Africa. A total of 3 217 trees were enumerated across 450 randomly selected homesteads. Most (90 %) households had at least one tree on their homestead, with an average of 7.7 ± 6.1 trees. Most householders had planted the trees themselves. The density of trees declined along the moisture gradient. Within towns, tree density was positively related to garden size, which in turn was related to relative affluence and age of the suburb. Newer and poorer suburbs had the fewest trees per household. Sixty-two tree species were recorded, which were dominated by alien species, especially fruit trees. There was no relationship between the moisture gradient and tree species richness per household, but within towns there was a difference between suburbs, being lowest in the newest suburbs. Numbers of trees and species per household was positively related to age of the household head.
- Full Text:
- Date Issued: 2014
HPLC method for simultaneous analysis of ranitidine and metronidazole in dosage forms
- King'ori, Loti D, Walker, Roderick B
- Authors: King'ori, Loti D , Walker, Roderick B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184790 , vital:44272 , xlink:href="https://doi.org/10.14233/ajchem.2014.15432"
- Description: A simple, rapid, precise and accurate stability indicating HPLC method for the simultaneous analysis of metronidazole and ranitidine in dosage forms has been developed and validated. Calibration curves for metronidazole and ranitidine exhibited linearity (R2 = 0.9995 for both compounds) over the concentration ranges investigated. The method was sensitive, selective and accurate for both compounds. Both drugs were found to be stable following acid hydrolysis studies. However, following alkali hydrolysis degradation of both compounds was observed. Furthermore metronidazole appeared to be stable following oxidative studies however ranitidine underwent complete degradation under these conditions. Both drugs were well resolved from the degradation products. The stability indicating chromatographic method has the necessary precision and accuracy for the simultaneous analysis of metronidazole and ranitidine in dosage forms.
- Full Text:
- Date Issued: 2014
- Authors: King'ori, Loti D , Walker, Roderick B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184790 , vital:44272 , xlink:href="https://doi.org/10.14233/ajchem.2014.15432"
- Description: A simple, rapid, precise and accurate stability indicating HPLC method for the simultaneous analysis of metronidazole and ranitidine in dosage forms has been developed and validated. Calibration curves for metronidazole and ranitidine exhibited linearity (R2 = 0.9995 for both compounds) over the concentration ranges investigated. The method was sensitive, selective and accurate for both compounds. Both drugs were found to be stable following acid hydrolysis studies. However, following alkali hydrolysis degradation of both compounds was observed. Furthermore metronidazole appeared to be stable following oxidative studies however ranitidine underwent complete degradation under these conditions. Both drugs were well resolved from the degradation products. The stability indicating chromatographic method has the necessary precision and accuracy for the simultaneous analysis of metronidazole and ranitidine in dosage forms.
- Full Text:
- Date Issued: 2014
Hsp90 binds directly to fibronectin (FN) and inhibition reduces the extracellular fibronectin matrix in breast cancer cells
- Hunter, Morgan C, O’Hagan, Kyle L, Kenyon, Amy, Dhanani, Karim C H, Prinsloo, Earl, Edkins, Adrienne L
- Authors: Hunter, Morgan C , O’Hagan, Kyle L , Kenyon, Amy , Dhanani, Karim C H , Prinsloo, Earl , Edkins, Adrienne L
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431143 , vital:72748 , xlink:href="https://doi.org/10.1371/journal.pone.0086842"
- Description: Heat shock protein 90 (Hsp90) has been identified in the extracellular space and has been shown to chaperone a finite number of extracellular proteins involved in cell migration and invasion. We used chemical cross-linking and immunoprecipitation followed by tandem mass spectrometry (MS/MS) to isolate a complex containing Hsp90 and the matrix protein fibronectin (FN) from breast cancer cells. Further analysis showed direct binding of Hsp90 to FN using an in vitro co-immunoprecipitation assay, a solid phase binding assay and surface plasmon resonance (SPR) spectroscopy. Confocal microscopy showed regions of co-localisation of Hsp90 and FN in breast cancer cell lines. Exogenous Hsp90β was shown to increase the formation of extracellular FN matrix in the Hs578T cell line, whilst knockdown or inhibition of Hsp90 led to a reduction in the levels of both soluble and insoluble FN and could be partially rescued by addition of exogenous Hsp90β. Treatment of cells with novobiocin led to internalization of FN into vesicles that were positive for the presence of the lysosomal marker, LAMP-1. Taken together, the direct interaction between FN and Hsp90, as well as the decreased levels of both soluble and insoluble FN upon Hsp90 inhibition or knockdown, suggested that FN may be a new client protein for Hsp90 and that Hsp90 was involved in FN matrix assembly and/or stability. The identification of FN as a putative client protein of Hsp90 suggests a role for Hsp90 in FN matrix stability, which is important for a number of fundamental cellular processes including embryogenesis, wound healing, cell migration and metastasis.
- Full Text:
- Date Issued: 2014
- Authors: Hunter, Morgan C , O’Hagan, Kyle L , Kenyon, Amy , Dhanani, Karim C H , Prinsloo, Earl , Edkins, Adrienne L
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431143 , vital:72748 , xlink:href="https://doi.org/10.1371/journal.pone.0086842"
- Description: Heat shock protein 90 (Hsp90) has been identified in the extracellular space and has been shown to chaperone a finite number of extracellular proteins involved in cell migration and invasion. We used chemical cross-linking and immunoprecipitation followed by tandem mass spectrometry (MS/MS) to isolate a complex containing Hsp90 and the matrix protein fibronectin (FN) from breast cancer cells. Further analysis showed direct binding of Hsp90 to FN using an in vitro co-immunoprecipitation assay, a solid phase binding assay and surface plasmon resonance (SPR) spectroscopy. Confocal microscopy showed regions of co-localisation of Hsp90 and FN in breast cancer cell lines. Exogenous Hsp90β was shown to increase the formation of extracellular FN matrix in the Hs578T cell line, whilst knockdown or inhibition of Hsp90 led to a reduction in the levels of both soluble and insoluble FN and could be partially rescued by addition of exogenous Hsp90β. Treatment of cells with novobiocin led to internalization of FN into vesicles that were positive for the presence of the lysosomal marker, LAMP-1. Taken together, the direct interaction between FN and Hsp90, as well as the decreased levels of both soluble and insoluble FN upon Hsp90 inhibition or knockdown, suggested that FN may be a new client protein for Hsp90 and that Hsp90 was involved in FN matrix assembly and/or stability. The identification of FN as a putative client protein of Hsp90 suggests a role for Hsp90 in FN matrix stability, which is important for a number of fundamental cellular processes including embryogenesis, wound healing, cell migration and metastasis.
- Full Text:
- Date Issued: 2014
Human perception of the measurement of a network attack taxonomy in near real-time
- Van Heerden, Renier, Malan, Mercia M, Mouton, Francois, Irwin, Barry V W
- Authors: Van Heerden, Renier , Malan, Mercia M , Mouton, Francois , Irwin, Barry V W
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429924 , vital:72652 , https://doi.org/10.1007/978-3-662-44208-1_23
- Description: This paper investigates how the measurement of a network attack taxonomy can be related to human perception. Network attacks do not have a time limitation, but the earlier its detected, the more damage can be prevented and the more preventative actions can be taken. This paper evaluate how elements of network attacks can be measured in near real-time(60 seconds). The taxonomy we use was developed by van Heerden et al (2012) with over 100 classes. These classes present the attack and defenders point of view. The degree to which each class can be quantified or measured is determined by investigating the accuracy of various assessment methods. We classify each class as either defined, high, low or not quantifiable. For example, it may not be possible to determine the instigator of an attack (Aggressor), but only that the attack has been launched by a Hacker (Actor). Some classes can only be quantified with a low confidence or not at all in a sort (near real-time) time. The IP address of an attack can easily be faked thus reducing the confidence in the information obtained from it, and thus determining the origin of an attack with a low confidence. This determination itself is subjective. All the evaluations of the classes in this paper is subjective, but due to the very basic grouping (High, Low or Not Quantifiable) a subjective value can be used. The complexity of the taxonomy can be significantly reduced if classes with only a high perceptive accuracy is used.
- Full Text:
- Date Issued: 2014
- Authors: Van Heerden, Renier , Malan, Mercia M , Mouton, Francois , Irwin, Barry V W
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429924 , vital:72652 , https://doi.org/10.1007/978-3-662-44208-1_23
- Description: This paper investigates how the measurement of a network attack taxonomy can be related to human perception. Network attacks do not have a time limitation, but the earlier its detected, the more damage can be prevented and the more preventative actions can be taken. This paper evaluate how elements of network attacks can be measured in near real-time(60 seconds). The taxonomy we use was developed by van Heerden et al (2012) with over 100 classes. These classes present the attack and defenders point of view. The degree to which each class can be quantified or measured is determined by investigating the accuracy of various assessment methods. We classify each class as either defined, high, low or not quantifiable. For example, it may not be possible to determine the instigator of an attack (Aggressor), but only that the attack has been launched by a Hacker (Actor). Some classes can only be quantified with a low confidence or not at all in a sort (near real-time) time. The IP address of an attack can easily be faked thus reducing the confidence in the information obtained from it, and thus determining the origin of an attack with a low confidence. This determination itself is subjective. All the evaluations of the classes in this paper is subjective, but due to the very basic grouping (High, Low or Not Quantifiable) a subjective value can be used. The complexity of the taxonomy can be significantly reduced if classes with only a high perceptive accuracy is used.
- Full Text:
- Date Issued: 2014
Improved l-cysteine electrocatalysis through a sequential drop dry technique using multi-walled carbon nanotubes and cobalt tetraaminophthalocyanine conjugates
- Nyoni, Stephen, Mugadza, Tawanda, Nyokong, Tebello
- Authors: Nyoni, Stephen , Mugadza, Tawanda , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193813 , vital:45398 , xlink:href="https://doi.org/10.1016/j.electacta.2013.10.023"
- Description: Voltammetry, chronoamperometry, scanning electrochemical microscopy and electrochemical impedance spectroscopy methods are used for characterization of a glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNTs)–cobalt tetraaminophthalocyanine (CoTAPc) mixture or sequential drop dry modification technique whereby the MWCNTs are first placed on to the electrode followed by CoTAPc. The sequential drop dry CoTAPc–MWCNTs modified surface gave better catalytic responses with a catalytic rate constant of 2.2 × 105 M−1 s−1, apparent electron transfer rate constant of 0.073 cm s−1, and a limit of detection of 2.8 × 10−7 M. Scanning electrochemical microscopy (SECM) surface characterization (topography and reactivity) further gave proof the better catalytic perfomance of the sequential drop dry CoTAPc–MWCNTs modified surface.
- Full Text:
- Date Issued: 2014
- Authors: Nyoni, Stephen , Mugadza, Tawanda , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193813 , vital:45398 , xlink:href="https://doi.org/10.1016/j.electacta.2013.10.023"
- Description: Voltammetry, chronoamperometry, scanning electrochemical microscopy and electrochemical impedance spectroscopy methods are used for characterization of a glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNTs)–cobalt tetraaminophthalocyanine (CoTAPc) mixture or sequential drop dry modification technique whereby the MWCNTs are first placed on to the electrode followed by CoTAPc. The sequential drop dry CoTAPc–MWCNTs modified surface gave better catalytic responses with a catalytic rate constant of 2.2 × 105 M−1 s−1, apparent electron transfer rate constant of 0.073 cm s−1, and a limit of detection of 2.8 × 10−7 M. Scanning electrochemical microscopy (SECM) surface characterization (topography and reactivity) further gave proof the better catalytic perfomance of the sequential drop dry CoTAPc–MWCNTs modified surface.
- Full Text:
- Date Issued: 2014
Indium phthalocyanine–CdSe/ZnS quantum dots nanocomposites showing size dependent and near ideal optical limiting behaviour
- Sanusi, Kayode, Nyokong, Tebello
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189921 , vital:44947 , xlink:href="https://doi.org/10.1016/j.optmat.2014.09.021"
- Description: Indium phthalocyanine–CdSe/ZnS quantum dots (QDs) nanocomposites (InPc–CdSe/ZnS) of three sizes (5.57, 8.12 and 8.75 nm) were synthesized according to known procedures. The particle size of the CdSe/ZnS QDs alone are 3.95, 6.02, and 6.66 nm, and are denoted as QD1, QD2 and QD3 respectively. The nonlinear absorption (NLA) properties of the nanoconjugates (InPc–CdSe/ZnS) were investigated with nanosecond laser radiation at 532 nm wavelength. Enhanced NLA properties compared to the InPc alone were observed in the conjugates. The NLA was found to increase with the size of the CdSe/ZnS particles attached to the phthalocyanine. The observed increase was due to the availability of more free-carrier ions in the larger QDs, thus giving rise to the enhanced free-carrier absorption. The measured free-carrier absorption cross-sections (σFCA) are 1.10, 1.65 and 1.95 (×10−19 cm2) for InPc-QD1, InPc-QD2 and InPc-QD3 respectively. The nanoconjugates (InPc–CdSe/ZnS) showed a much lower threshold for optical limiting together with a much lower transmission at high fluences, than the previously reported nanocomposite limiters.
- Full Text:
- Date Issued: 2014
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189921 , vital:44947 , xlink:href="https://doi.org/10.1016/j.optmat.2014.09.021"
- Description: Indium phthalocyanine–CdSe/ZnS quantum dots (QDs) nanocomposites (InPc–CdSe/ZnS) of three sizes (5.57, 8.12 and 8.75 nm) were synthesized according to known procedures. The particle size of the CdSe/ZnS QDs alone are 3.95, 6.02, and 6.66 nm, and are denoted as QD1, QD2 and QD3 respectively. The nonlinear absorption (NLA) properties of the nanoconjugates (InPc–CdSe/ZnS) were investigated with nanosecond laser radiation at 532 nm wavelength. Enhanced NLA properties compared to the InPc alone were observed in the conjugates. The NLA was found to increase with the size of the CdSe/ZnS particles attached to the phthalocyanine. The observed increase was due to the availability of more free-carrier ions in the larger QDs, thus giving rise to the enhanced free-carrier absorption. The measured free-carrier absorption cross-sections (σFCA) are 1.10, 1.65 and 1.95 (×10−19 cm2) for InPc-QD1, InPc-QD2 and InPc-QD3 respectively. The nanoconjugates (InPc–CdSe/ZnS) showed a much lower threshold for optical limiting together with a much lower transmission at high fluences, than the previously reported nanocomposite limiters.
- Full Text:
- Date Issued: 2014
Invasive alien species as drivers in socio-ecological systems: Local adaptations towards use of Lantana in Southern India
- Kannan, Ramesh, Shackleton, Charlie M, Shaanker, Ramanan U
- Authors: Kannan, Ramesh , Shackleton, Charlie M , Shaanker, Ramanan U
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180932 , vital:43671 , xlink:href="https://doi.org/10.1007/s10668-013-9500-y"
- Description: Lantana camara. L (hereafter Lantana) was first introduced by the British into India in 1807 as an ornamental plant. Since then the species has spread across the length and breadth of the country. Attempts to control Lantana in India have not been successful. In this study, we analysed the use of Lantana by local communities in southern India and identified the possible causes and consequences of its use through the use of a household survey of the socio-economic profile of the user and nonuser households and an analysis of the ecological history of the communities. Communities have been using Lantana for over 25–30 years and apparently such use was not prompted by external agencies. The characteristics of user and nonuser households were similar, except that Lantana users were more literate and had a greater number of occupations per household than nonusers. Per capita income was similar between user and nonuser groups. For nonuser groups, their main income sources were from trading (44 %), wage labour (32 %) and forest resources (23 %). In contrast, the Lantana user groups substituted their loss of income from forest resources (7 %) by income from Lantana (46 %). The ecological history revealed that Lantana was adopted as a resource at a time when it was increasing in the landscape and traditional bamboo resources were in decline because of overuse by commercial enterprises and mast flowering. This change in ecological resource availability prompted a major shift in livelihoods for some in the area.
- Full Text:
- Date Issued: 2014
- Authors: Kannan, Ramesh , Shackleton, Charlie M , Shaanker, Ramanan U
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/180932 , vital:43671 , xlink:href="https://doi.org/10.1007/s10668-013-9500-y"
- Description: Lantana camara. L (hereafter Lantana) was first introduced by the British into India in 1807 as an ornamental plant. Since then the species has spread across the length and breadth of the country. Attempts to control Lantana in India have not been successful. In this study, we analysed the use of Lantana by local communities in southern India and identified the possible causes and consequences of its use through the use of a household survey of the socio-economic profile of the user and nonuser households and an analysis of the ecological history of the communities. Communities have been using Lantana for over 25–30 years and apparently such use was not prompted by external agencies. The characteristics of user and nonuser households were similar, except that Lantana users were more literate and had a greater number of occupations per household than nonusers. Per capita income was similar between user and nonuser groups. For nonuser groups, their main income sources were from trading (44 %), wage labour (32 %) and forest resources (23 %). In contrast, the Lantana user groups substituted their loss of income from forest resources (7 %) by income from Lantana (46 %). The ecological history revealed that Lantana was adopted as a resource at a time when it was increasing in the landscape and traditional bamboo resources were in decline because of overuse by commercial enterprises and mast flowering. This change in ecological resource availability prompted a major shift in livelihoods for some in the area.
- Full Text:
- Date Issued: 2014
Investigating the chaperone properties of a novel heat shock protein, Hsp70. c, from Trypanosoma brucei
- Burger, Adélle, Ludewig, Michael H, Boshoff, Aileen
- Authors: Burger, Adélle , Ludewig, Michael H , Boshoff, Aileen
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431155 , vital:72749 , xlink:href="https://doi.org/10.1155/2014/172582"
- Description: The neglected tropical disease, African Trypanosomiasis, is fatal and has a crippling impact on economic development. Heat shock protein 70 (Hsp70) is an important molecular chaperone that is expressed in response to stress and Hsp40 acts as its co-chaperone. These proteins play a wide range of roles in the cell and they are required to assist the parasite as it moves from a cold blooded insect vector to a warm blooded mammalian host. A novel cytosolic Hsp70, from Trypanosoma brucei, TbHsp70.c, contains an acidic substrate binding domain and lacks the C-terminal EEVD motif.The ability of a cytosolic Hsp40 from Trypanosoma brucei J protein 2, Tbj2, to function as a co-chaperone of TbHsp70.c was investigated.The main objective was to functionally characterize TbHsp70.c to further expand our knowledge of parasite biology. TbHsp70.c and Tbj2 were heterologously expressed and purified and both proteins displayed the ability to suppress aggregation of thermolabile MDH and chemically denatured rhodanese. ATPase assays revealed a 2.8-fold stimulation of the ATPase activity of TbHsp70.c by Tbj2. TbHsp70.c and Tbj2 both demonstrated chaperone activity and Tbj2 functions as a co-chaperone of TbHsp70.c.In vivo heat stress experiments indicated upregulation of the expression levels of TbHsp70.c.
- Full Text:
- Date Issued: 2014
- Authors: Burger, Adélle , Ludewig, Michael H , Boshoff, Aileen
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431155 , vital:72749 , xlink:href="https://doi.org/10.1155/2014/172582"
- Description: The neglected tropical disease, African Trypanosomiasis, is fatal and has a crippling impact on economic development. Heat shock protein 70 (Hsp70) is an important molecular chaperone that is expressed in response to stress and Hsp40 acts as its co-chaperone. These proteins play a wide range of roles in the cell and they are required to assist the parasite as it moves from a cold blooded insect vector to a warm blooded mammalian host. A novel cytosolic Hsp70, from Trypanosoma brucei, TbHsp70.c, contains an acidic substrate binding domain and lacks the C-terminal EEVD motif.The ability of a cytosolic Hsp40 from Trypanosoma brucei J protein 2, Tbj2, to function as a co-chaperone of TbHsp70.c was investigated.The main objective was to functionally characterize TbHsp70.c to further expand our knowledge of parasite biology. TbHsp70.c and Tbj2 were heterologously expressed and purified and both proteins displayed the ability to suppress aggregation of thermolabile MDH and chemically denatured rhodanese. ATPase assays revealed a 2.8-fold stimulation of the ATPase activity of TbHsp70.c by Tbj2. TbHsp70.c and Tbj2 both demonstrated chaperone activity and Tbj2 functions as a co-chaperone of TbHsp70.c.In vivo heat stress experiments indicated upregulation of the expression levels of TbHsp70.c.
- Full Text:
- Date Issued: 2014