Otoliths versus scales: evaluating the most suitable structure for ageing largemouth bass, Micropterus salmoides, in South Africa
- Taylor, Geraldine C, Weyl, Olaf L F
- Authors: Taylor, Geraldine C , Weyl, Olaf L F
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443907 , vital:74170 , https://doi.org/10.1080/15627020.2012.11407562
- Description: The suitability of scales for ageing Micropterus salmoides was determined by comparing the precision of growth zone counts on scales with those obtained from sectioned sagittal otoliths from a sample of 496 fish collected from Wriggleswade and Mankazana Impoundments in the Eastern Cape, South Africa. Otoliths (1.4% rejected) were more readable than scales (41.7% and 7.5% rejected) for Wriggleswade and Mankazana Impoundments respectively. Otolith readings were more precise (average percentage error (APE) = 13.6%; coefficient of variation (CV) = 15.8%) than scales (APE = 18.0%; CV = 21.9%) for the total sample. Growth zone counts between structures were not symmetrically distributed around the agreed ages (otolith age = scale age) of the fish from Wriggleswade Impoundment (Bowker’s test H2: χ2 = 136, d.f. = 27, P 0.05) and graphical comparison showed that scales tended to underestimate age, particularly for fish older than five years. Scales are therefore not suitable structures for ageing South African M. salmoides which may attain ages of up to 13 years.
- Full Text:
- Date Issued: 2012
- Authors: Taylor, Geraldine C , Weyl, Olaf L F
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443907 , vital:74170 , https://doi.org/10.1080/15627020.2012.11407562
- Description: The suitability of scales for ageing Micropterus salmoides was determined by comparing the precision of growth zone counts on scales with those obtained from sectioned sagittal otoliths from a sample of 496 fish collected from Wriggleswade and Mankazana Impoundments in the Eastern Cape, South Africa. Otoliths (1.4% rejected) were more readable than scales (41.7% and 7.5% rejected) for Wriggleswade and Mankazana Impoundments respectively. Otolith readings were more precise (average percentage error (APE) = 13.6%; coefficient of variation (CV) = 15.8%) than scales (APE = 18.0%; CV = 21.9%) for the total sample. Growth zone counts between structures were not symmetrically distributed around the agreed ages (otolith age = scale age) of the fish from Wriggleswade Impoundment (Bowker’s test H2: χ2 = 136, d.f. = 27, P 0.05) and graphical comparison showed that scales tended to underestimate age, particularly for fish older than five years. Scales are therefore not suitable structures for ageing South African M. salmoides which may attain ages of up to 13 years.
- Full Text:
- Date Issued: 2012
Oxovanadium (IV)-catalysed oxidation of dibenzothiophene and 4, 6-dimethyldibenzothiophene
- Ogunlaja, Adeniyi S, Chidawanyika, Wadzanai J U, Antunes, Edith M, Fernandes, Manuel A, Nyokong, Tebello, Torto, Nelson, Tshentu, Zenixole R
- Authors: Ogunlaja, Adeniyi S , Chidawanyika, Wadzanai J U , Antunes, Edith M , Fernandes, Manuel A , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246025 , vital:51429 , xlink:href="https://doi.org/10.1039/C2DT31433A"
- Description: The reaction between [VIVOSO4] and the tetradentate N2O2-donor Schiff base ligand, N,N-bis(o-hydroxybenzaldehyde)phenylenediamine (sal-HBPD), obtained by the condensation of salicylaldehyde and o-phenylenediamine in a molar ratio of 2 : 1 respectively, resulted in the formation of [VIVO(sal-HBPD)]. The molecular structure of [VIVO(sal-HBPD)] was determined by single crystal X-ray diffraction, and confirmed the distorted square pyramidal geometry of the complex with the N2O2 binding mode of the tetradentate ligand. The formation of the polymer-supported p[VIVO(sal-AHBPD)] proceeded via the nitrosation of sal-HBPD, followed by the reduction with hydrogen to form an amine group that was then linked to Merrifield beads followed by the reaction with [VIVOSO4]. XPS and EPR were used to confirm the presence of oxovanadium(IV) within the beads. The BET surface area and porosity of the heterogeneous catalyst p[VIVO(sal-AHBPD)] were found to be 6.9 m2 g−1 and 180.8 Å respectively. Microanalysis, TG, UV-Vis and FT-IR were used for further characterization of both [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)]. Oxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated using [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)] as catalysts. Progress for oxidation of these model compounds was monitored with a gas chromatograph fitted with a flame ionization detector. The oxidation products were characterized using gas chromatography-mass spectrometry, microanalysis and NMR. Dibenzothiophene sulfone (DBTO2) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO2) were found to be the main products of oxidation. Oxovanadium(IV) Schiff base microspherical beads, p[VIVO(sal-AHBPD)], were able to catalyse the oxidation of sulfur in dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to a tune of 88.0% and 71.8% respectively after 3 h at 40 °C. These oxidation results show promise for potential application of this catalyst in the oxidative desulfurization of crude oils.
- Full Text:
- Date Issued: 2012
- Authors: Ogunlaja, Adeniyi S , Chidawanyika, Wadzanai J U , Antunes, Edith M , Fernandes, Manuel A , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246025 , vital:51429 , xlink:href="https://doi.org/10.1039/C2DT31433A"
- Description: The reaction between [VIVOSO4] and the tetradentate N2O2-donor Schiff base ligand, N,N-bis(o-hydroxybenzaldehyde)phenylenediamine (sal-HBPD), obtained by the condensation of salicylaldehyde and o-phenylenediamine in a molar ratio of 2 : 1 respectively, resulted in the formation of [VIVO(sal-HBPD)]. The molecular structure of [VIVO(sal-HBPD)] was determined by single crystal X-ray diffraction, and confirmed the distorted square pyramidal geometry of the complex with the N2O2 binding mode of the tetradentate ligand. The formation of the polymer-supported p[VIVO(sal-AHBPD)] proceeded via the nitrosation of sal-HBPD, followed by the reduction with hydrogen to form an amine group that was then linked to Merrifield beads followed by the reaction with [VIVOSO4]. XPS and EPR were used to confirm the presence of oxovanadium(IV) within the beads. The BET surface area and porosity of the heterogeneous catalyst p[VIVO(sal-AHBPD)] were found to be 6.9 m2 g−1 and 180.8 Å respectively. Microanalysis, TG, UV-Vis and FT-IR were used for further characterization of both [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)]. Oxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated using [VIVO(sal-HBPD)] and p[VIVO(sal-AHBPD)] as catalysts. Progress for oxidation of these model compounds was monitored with a gas chromatograph fitted with a flame ionization detector. The oxidation products were characterized using gas chromatography-mass spectrometry, microanalysis and NMR. Dibenzothiophene sulfone (DBTO2) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO2) were found to be the main products of oxidation. Oxovanadium(IV) Schiff base microspherical beads, p[VIVO(sal-AHBPD)], were able to catalyse the oxidation of sulfur in dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to a tune of 88.0% and 71.8% respectively after 3 h at 40 °C. These oxidation results show promise for potential application of this catalyst in the oxidative desulfurization of crude oils.
- Full Text:
- Date Issued: 2012
Parameter relationships in high-speed audio networks
- Chigwamba, Nyasha, Foss, Richard, Gurdan, Robby, Klinkradt, Bradley
- Authors: Chigwamba, Nyasha , Foss, Richard , Gurdan, Robby , Klinkradt, Bradley
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427027 , vital:72409 , https://www.aes.org/e-lib/browse.cfm?elib=16211
- Description: When related audio control parameters are distributed in many devices in a high-speed audio network, a means for centralizing remote control and monitoring is required. Changes in one parameter may need to affect other parameters. The XFN protocol enables management of distributed parameters. This paper focuses on how to group related parameters that are physically separated and provides a corresponding implementation using the protocol. A comprehensive grouping theory is presented.
- Full Text:
- Date Issued: 2012
- Authors: Chigwamba, Nyasha , Foss, Richard , Gurdan, Robby , Klinkradt, Bradley
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427027 , vital:72409 , https://www.aes.org/e-lib/browse.cfm?elib=16211
- Description: When related audio control parameters are distributed in many devices in a high-speed audio network, a means for centralizing remote control and monitoring is required. Changes in one parameter may need to affect other parameters. The XFN protocol enables management of distributed parameters. This paper focuses on how to group related parameters that are physically separated and provides a corresponding implementation using the protocol. A comprehensive grouping theory is presented.
- Full Text:
- Date Issued: 2012
Part II Zef/poor white kitsch chique
- Authors: Krueger, Anton
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225745 , vital:49255 , xlink:href="https://doi.org/10.1080/17533171.2012.715484"
- Description: Ninja, who fronts the freak hip-hop band Die Antwoord, might not be quite what Desmond Tutu had in mind when he described South Africans as the “Rainbow People of God,”24 a happy harmonious amalgamation of different races. In his introduction to their seminal comic track “Enter the Ninja,” Ninja presents himself, rather, as a mongrel gutter dog, both embracing and parodying a syncretic fusion of the many different cultures and races of South Africa, celebrating as well as subverting the rainbow nation discourse. As he said in an interview with News24: “South African culture is quite a fucking fruit salad … a fucking fucked rainbow nation. South Africa's totally fucked … but in a cool way.”25 The cool side of being “fucked” in this way is “Zef.” Zef denotes a particular style of vulgar humor (in the usual sense of the word “vulgar,” but also with a nod to its origin in the Latin vulgaris for “mob” or “commoners”), which has been emerging more and more in South Africa during the past decade. It involves a way of presenting a persona in a purposefully degrading way, exaggerating one's appearance and mannerisms as low class, ill bred, and boorish. I would like to consider the recent popularity of “Zef” and examine its connection specifically to popular Afrikaans folk rock culture, a lineage of white poverty, and the feeling of disgrace experienced by many white Afrikaners after the end of apartheid.
- Full Text:
- Date Issued: 2012
- Authors: Krueger, Anton
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225745 , vital:49255 , xlink:href="https://doi.org/10.1080/17533171.2012.715484"
- Description: Ninja, who fronts the freak hip-hop band Die Antwoord, might not be quite what Desmond Tutu had in mind when he described South Africans as the “Rainbow People of God,”24 a happy harmonious amalgamation of different races. In his introduction to their seminal comic track “Enter the Ninja,” Ninja presents himself, rather, as a mongrel gutter dog, both embracing and parodying a syncretic fusion of the many different cultures and races of South Africa, celebrating as well as subverting the rainbow nation discourse. As he said in an interview with News24: “South African culture is quite a fucking fruit salad … a fucking fucked rainbow nation. South Africa's totally fucked … but in a cool way.”25 The cool side of being “fucked” in this way is “Zef.” Zef denotes a particular style of vulgar humor (in the usual sense of the word “vulgar,” but also with a nod to its origin in the Latin vulgaris for “mob” or “commoners”), which has been emerging more and more in South Africa during the past decade. It involves a way of presenting a persona in a purposefully degrading way, exaggerating one's appearance and mannerisms as low class, ill bred, and boorish. I would like to consider the recent popularity of “Zef” and examine its connection specifically to popular Afrikaans folk rock culture, a lineage of white poverty, and the feeling of disgrace experienced by many white Afrikaners after the end of apartheid.
- Full Text:
- Date Issued: 2012
Patrick Hayes. JM Coetzee and the Novel: writing and politics after Beckett
- Authors: Marais, Mike
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144220 , vital:38322 , DOI: 10.1093/res/hgs014
- Description: According to Patrick Hayes, J. M. Coetzee's fiction, on a thematic level, ‘repeatedly suggests that the condition of modernity is made up of competing, equally important, and yet incommensurate ways of imagining the good community’ (p. 4). The first of these imaginings is grounded in the Kantian notion that the human individual is a rational and autonomous agent, and that it is precisely his or her rational autonomy, and capacity to direct life through neutral principles that commands the respect and recognition of other individuals. As is evident in its emphasis on rationality, this politic of equal dignity and recognition is universalistic in its claims. In contrast, the second imagining of community is based on the recognition of cultural specificity, and the argument that freedom and equal recognition are only possible through a revision of deleterious cultural stereotypes. In its terms, the good community ‘must be founded on the recognition, and active fostering of cultural particularity’ (p. 12). This politic of difference is highly suspicious of the universalizing claims of the politic of dignity, arguing that its appeal to equal dignity is itself a form of particularism masquerading as universalism.
- Full Text:
- Date Issued: 2012
- Authors: Marais, Mike
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144220 , vital:38322 , DOI: 10.1093/res/hgs014
- Description: According to Patrick Hayes, J. M. Coetzee's fiction, on a thematic level, ‘repeatedly suggests that the condition of modernity is made up of competing, equally important, and yet incommensurate ways of imagining the good community’ (p. 4). The first of these imaginings is grounded in the Kantian notion that the human individual is a rational and autonomous agent, and that it is precisely his or her rational autonomy, and capacity to direct life through neutral principles that commands the respect and recognition of other individuals. As is evident in its emphasis on rationality, this politic of equal dignity and recognition is universalistic in its claims. In contrast, the second imagining of community is based on the recognition of cultural specificity, and the argument that freedom and equal recognition are only possible through a revision of deleterious cultural stereotypes. In its terms, the good community ‘must be founded on the recognition, and active fostering of cultural particularity’ (p. 12). This politic of difference is highly suspicious of the universalizing claims of the politic of dignity, arguing that its appeal to equal dignity is itself a form of particularism masquerading as universalism.
- Full Text:
- Date Issued: 2012
Peat formation in the context of the development of the Mkuze floodplain on the coastal plain of Maputaland, South Africa:
- Ellery, William F N, Grenfell, Suzanne E, Grenfell, Michael C, Humphries, M S, Barnes, K, Dahlberg, S, Kindness, A
- Authors: Ellery, William F N , Grenfell, Suzanne E , Grenfell, Michael C , Humphries, M S , Barnes, K , Dahlberg, S , Kindness, A
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144354 , vital:38338 , DOI: 10.1016/j.geomorph.2011.11.009
- Description: This paper examines the geomorphological and sedimentological development of blocked-valley lakes in the Mkuze floodplain on the coastal plain of Maputaland, northern KwaZulu-Natal, South Africa. Blocked tributary valley lakes north of the floodplain become progressively shorter, broader, and less linear toward the eastern (downstream) end of the east–west oriented Mkuze floodplain. Clastic sediment forms surface sedimentary fill in tributary valleys in the west, while peat predominates tributary valley fill in the east. Two contrasting adjacent tributary valleys were examined, the more western Yengweni dominated by clastic sediment at the surface, and the more eastern Totweni with peat.
- Full Text:
- Date Issued: 2012
- Authors: Ellery, William F N , Grenfell, Suzanne E , Grenfell, Michael C , Humphries, M S , Barnes, K , Dahlberg, S , Kindness, A
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144354 , vital:38338 , DOI: 10.1016/j.geomorph.2011.11.009
- Description: This paper examines the geomorphological and sedimentological development of blocked-valley lakes in the Mkuze floodplain on the coastal plain of Maputaland, northern KwaZulu-Natal, South Africa. Blocked tributary valley lakes north of the floodplain become progressively shorter, broader, and less linear toward the eastern (downstream) end of the east–west oriented Mkuze floodplain. Clastic sediment forms surface sedimentary fill in tributary valleys in the west, while peat predominates tributary valley fill in the east. Two contrasting adjacent tributary valleys were examined, the more western Yengweni dominated by clastic sediment at the surface, and the more eastern Totweni with peat.
- Full Text:
- Date Issued: 2012
PhDs by publications
- Niven, Penelope, Grant, Carolyn
- Authors: Niven, Penelope , Grant, Carolyn
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281108 , vital:55693 , xlink:href="https://doi.org/10.1080/13562517.2012.640086"
- Description: PhDs by publications are a relatively new model for doctoral research, especially in the context of the Humanities or Education. This paper describes two writers’ experiences of conducting doctoral studies in this genre and in these faculties. Each discover alternative ways of employing a body of published research papers in development of an overarching thesis. The writers argue that whilst it can be a pragmatic choice for some, PhDs by publications are more likely to be highly complex meta-narratives and that an overview of past research is fraught with theoretical, conceptual and epistemological challenges in the quest for coherence. They claim that the nomenclature ‘PhDs by publications’ or ‘through publications’ is misleading: in the epistemological space of Humanities or Education studies, this mode of doctoral research is more accurately represented as a ‘PhD with or alongside publications’. They conclude that the particular affordance of the model is that it privileges accounts of the process of knowledge building and of descriptions of the gradual emergence of ‘doctoralness’ in the person of the researcher.
- Full Text:
- Date Issued: 2012
- Authors: Niven, Penelope , Grant, Carolyn
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281108 , vital:55693 , xlink:href="https://doi.org/10.1080/13562517.2012.640086"
- Description: PhDs by publications are a relatively new model for doctoral research, especially in the context of the Humanities or Education. This paper describes two writers’ experiences of conducting doctoral studies in this genre and in these faculties. Each discover alternative ways of employing a body of published research papers in development of an overarching thesis. The writers argue that whilst it can be a pragmatic choice for some, PhDs by publications are more likely to be highly complex meta-narratives and that an overview of past research is fraught with theoretical, conceptual and epistemological challenges in the quest for coherence. They claim that the nomenclature ‘PhDs by publications’ or ‘through publications’ is misleading: in the epistemological space of Humanities or Education studies, this mode of doctoral research is more accurately represented as a ‘PhD with or alongside publications’. They conclude that the particular affordance of the model is that it privileges accounts of the process of knowledge building and of descriptions of the gradual emergence of ‘doctoralness’ in the person of the researcher.
- Full Text:
- Date Issued: 2012
Photooxidation of 4-chlorophenol sensitized by lutetium tetraphenoxy phthalocyanine anchored on electrospun polystyrene polymer fiber
- Zugle, Ruphino, Antunes, Edith M, Khene, Samson M, Nyokong, Tebello
- Authors: Zugle, Ruphino , Antunes, Edith M , Khene, Samson M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245787 , vital:51405 , xlink:href="https://doi.org/10.1016/j.poly.2011.11.005"
- Description: An electrospun polystyrene (PS) fiber incorporating tetraphenoxy phthalocyanine complex of lutetium (LuTPPc/PS) as a photosensitizer was applied for the degradation of 4-chlorophenol in aqueous solution in the presence of visible light. The photocatalytic activity of the LuTPPc in the fiber was compared to that of zinc phthalocyanine (ZnPc) incorporated into the PS fiber, and the former showed higher activity. UV–Vis spectral changes of sample solutions indicated transformation of the analyte with first order kinetics and half-lives that are within one and half hours for LuTPPc/PS. Products identified from the spectral changes and gas chromatography were benzoquinone, hydroquinone and 4,4′-dihydroxydiphenol suggesting that the photodegradation of 4-chlorophenol was through both Types I and II mechanisms.
- Full Text:
- Date Issued: 2012
- Authors: Zugle, Ruphino , Antunes, Edith M , Khene, Samson M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245787 , vital:51405 , xlink:href="https://doi.org/10.1016/j.poly.2011.11.005"
- Description: An electrospun polystyrene (PS) fiber incorporating tetraphenoxy phthalocyanine complex of lutetium (LuTPPc/PS) as a photosensitizer was applied for the degradation of 4-chlorophenol in aqueous solution in the presence of visible light. The photocatalytic activity of the LuTPPc in the fiber was compared to that of zinc phthalocyanine (ZnPc) incorporated into the PS fiber, and the former showed higher activity. UV–Vis spectral changes of sample solutions indicated transformation of the analyte with first order kinetics and half-lives that are within one and half hours for LuTPPc/PS. Products identified from the spectral changes and gas chromatography were benzoquinone, hydroquinone and 4,4′-dihydroxydiphenol suggesting that the photodegradation of 4-chlorophenol was through both Types I and II mechanisms.
- Full Text:
- Date Issued: 2012
Photophysical and photochemical properties of novel phthalocyanines bearing non-peripherally substituted mercaptoquinoline moiety
- Yaşa, Göknur, Erdoğmuş, Ali, Uğur, Ahmet Lütf, Şener, M Kasım, Avcıata, Ulvi, Nyokong, Tebello
- Authors: Yaşa, Göknur , Erdoğmuş, Ali , Uğur, Ahmet Lütf , Şener, M Kasım , Avcıata, Ulvi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244360 , vital:51250 , xlink:href="https://doi.org/10.1142/S1088424612500940"
- Description: The synthesis, photophysical and photochemical properties of nonperipherally (a) mercaptoquinoline substituted Zn(II), TiO(IV) and Mg(II) and quaternized Zn(II) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1 H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 4 and 5 have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. Complex 3 showed very good solubility in water as well as DMSO and DMF. General trends are described for singlet oxygen, photodegradation and fluorescence quantum yields of these complexes in DMSO and DMF. While complex 2 has higher singlet oxygen and fluorescence quantum yields than 3, 4 and 5, complex 4 has higher fluorescence quantum yields in DMF and DMSO than 2, 3 and 5. The effect of the solvents and metal on the photophysical and photochemical parameters of the metallophthalocyanines are also reported.
- Full Text:
- Date Issued: 2012
- Authors: Yaşa, Göknur , Erdoğmuş, Ali , Uğur, Ahmet Lütf , Şener, M Kasım , Avcıata, Ulvi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244360 , vital:51250 , xlink:href="https://doi.org/10.1142/S1088424612500940"
- Description: The synthesis, photophysical and photochemical properties of nonperipherally (a) mercaptoquinoline substituted Zn(II), TiO(IV) and Mg(II) and quaternized Zn(II) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1 H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 4 and 5 have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. Complex 3 showed very good solubility in water as well as DMSO and DMF. General trends are described for singlet oxygen, photodegradation and fluorescence quantum yields of these complexes in DMSO and DMF. While complex 2 has higher singlet oxygen and fluorescence quantum yields than 3, 4 and 5, complex 4 has higher fluorescence quantum yields in DMF and DMSO than 2, 3 and 5. The effect of the solvents and metal on the photophysical and photochemical parameters of the metallophthalocyanines are also reported.
- Full Text:
- Date Issued: 2012
Photophysical and photochemical studies of sulfur containing phthalocyanine derivatives in the presence of folic acid
- Nombona, Nolwazi, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
Photophysics and photochemistry of octaglucosylated zinc phthalocyanine derivatives
- Iqbal, Zafar, Ogunsipe, Abimbola, Nyokong, Tebello, Lyubimtsev, Alexey, Hanack, Michael, Ziegler, Thomas
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
Physico-chemical properties of lutetium phthalocyanine complexes in solution and in solid polystyrene polymer fibers and their application in photoconversion of 4-nitrophenol
- Zugle, Ruphino, Nyokong, Tebello
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243520 , vital:51160 , xlink:href="https://doi.org/10.1016/j.molcata.2012.02.010"
- Description: The photophysical and photochemical behavior of two phthalocyanine complexes of lutetium peripherally substituted with tetraphenoxy and tetra-2-pyridiloxy groups were studied in solution and when dispersed in polystyrene polymer fiber. The phthalocyanines were found not to fluoresce significantly in solution and not at all within the fiber matrix as compared with standard unsubstituted zinc phthalocyanine. They showed very promising photoactivity in solution with high singlet oxygen quantum yields. Their photoactivity within the polymer fiber matrix was also demonstrated with the photoconversion of 4-nitrophenol, a water pollutant. The photodegradation process with both phthalocyanines follows first order kinetics similar to that observed for the zinc phthalocyanine and the photo-products were found to be hydroquinone, benzoquinone and 4-nitrocatechol.
- Full Text:
- Date Issued: 2012
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243520 , vital:51160 , xlink:href="https://doi.org/10.1016/j.molcata.2012.02.010"
- Description: The photophysical and photochemical behavior of two phthalocyanine complexes of lutetium peripherally substituted with tetraphenoxy and tetra-2-pyridiloxy groups were studied in solution and when dispersed in polystyrene polymer fiber. The phthalocyanines were found not to fluoresce significantly in solution and not at all within the fiber matrix as compared with standard unsubstituted zinc phthalocyanine. They showed very promising photoactivity in solution with high singlet oxygen quantum yields. Their photoactivity within the polymer fiber matrix was also demonstrated with the photoconversion of 4-nitrophenol, a water pollutant. The photodegradation process with both phthalocyanines follows first order kinetics similar to that observed for the zinc phthalocyanine and the photo-products were found to be hydroquinone, benzoquinone and 4-nitrocatechol.
- Full Text:
- Date Issued: 2012
Quality of life in Grahamstown, East London and Mdantsane: preliminary result
- Helliker, Kirk D, Bekker, Simon, Lambie, Eileen
- Authors: Helliker, Kirk D , Bekker, Simon , Lambie, Eileen
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144756 , vital:38376 , DOI: 10.1080/02580144.1981.10428933
- Description: A quality of life survey amongst residents of three Eastern Cape towns, viz. Grahamstown, East London, and Mdantsane, shows that the attitudes to home and neighbourhood which urban residents in the Eastern Cape develop, are fashioned in large part by both the residential “group area” in which these urban dwellers live, and by their socio-economic status. White residents, overwhelmingly, are satisfied with their diets, their municipality, their homes. They feel safe in their homes and are satisfied that police protection is available if needed. For black residents fear of poverty and unemployment, of physical violence, and dissatisfaction with an inadequate diet is widespread. Indian and coloured urban residents who are generally perceived as minorities in Grahamstown and East London, occupy an intermediate position. Their residential areas are sited close to predominantly low income black residential areas. Higher income Indian and coloured households show lower rates of dissatisfaction with diet, housing, and municipal services than the black community.
- Full Text:
- Date Issued: 2012
- Authors: Helliker, Kirk D , Bekker, Simon , Lambie, Eileen
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144756 , vital:38376 , DOI: 10.1080/02580144.1981.10428933
- Description: A quality of life survey amongst residents of three Eastern Cape towns, viz. Grahamstown, East London, and Mdantsane, shows that the attitudes to home and neighbourhood which urban residents in the Eastern Cape develop, are fashioned in large part by both the residential “group area” in which these urban dwellers live, and by their socio-economic status. White residents, overwhelmingly, are satisfied with their diets, their municipality, their homes. They feel safe in their homes and are satisfied that police protection is available if needed. For black residents fear of poverty and unemployment, of physical violence, and dissatisfaction with an inadequate diet is widespread. Indian and coloured urban residents who are generally perceived as minorities in Grahamstown and East London, occupy an intermediate position. Their residential areas are sited close to predominantly low income black residential areas. Higher income Indian and coloured households show lower rates of dissatisfaction with diet, housing, and municipal services than the black community.
- Full Text:
- Date Issued: 2012
Quinones and halogenated monoterpenes of algal origin show anti-proliferative effects against breast cancer cells in vitro:
- de la Mare, Jo-Anne, Lawson, Jessica C, Chiwakata, Maynard T, Beukes, Denzil R, Blatch, Gregory L, Edkins, Adrienne L
- Authors: de la Mare, Jo-Anne , Lawson, Jessica C , Chiwakata, Maynard T , Beukes, Denzil R , Blatch, Gregory L , Edkins, Adrienne L
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/165165 , vital:41214 , DOI: 10.1007/s10637-011-9788-0
- Description: Red and brown algae have been shown to produce a variety of compounds with chemotherapeutic potential. A recent report described the isolation of a range of novel polyhalogenated monoterpene compounds from the red algae Plocamium corallorhiza and Plocamium cornutum collected off the coast of South Africa, together with the previously described tetraprenylquinone, sargaquinoic acid (SQA), from the brown algae Sargassum heterophyllum. In our study, the algal compounds were screened for anti-proliferative activity against metastatic MDA-MB-231 breast cancer cells revealing that a number of compounds displayed anti-cancer activity with IC50 values in the micromolar range. A subset of the compounds was tested for differential toxicity in the MCF-7/MCF12A system and five of these, including sargaquinoic acid, were found to be at least three times more toxic to the breast cancer than the non-malignant cell line.
- Full Text:
- Date Issued: 2012
- Authors: de la Mare, Jo-Anne , Lawson, Jessica C , Chiwakata, Maynard T , Beukes, Denzil R , Blatch, Gregory L , Edkins, Adrienne L
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/165165 , vital:41214 , DOI: 10.1007/s10637-011-9788-0
- Description: Red and brown algae have been shown to produce a variety of compounds with chemotherapeutic potential. A recent report described the isolation of a range of novel polyhalogenated monoterpene compounds from the red algae Plocamium corallorhiza and Plocamium cornutum collected off the coast of South Africa, together with the previously described tetraprenylquinone, sargaquinoic acid (SQA), from the brown algae Sargassum heterophyllum. In our study, the algal compounds were screened for anti-proliferative activity against metastatic MDA-MB-231 breast cancer cells revealing that a number of compounds displayed anti-cancer activity with IC50 values in the micromolar range. A subset of the compounds was tested for differential toxicity in the MCF-7/MCF12A system and five of these, including sargaquinoic acid, were found to be at least three times more toxic to the breast cancer than the non-malignant cell line.
- Full Text:
- Date Issued: 2012
Radical thinking in South Africa’s age of retreat
- Helliker, Kirk D, Vale, Peter C J
- Authors: Helliker, Kirk D , Vale, Peter C J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71214 , vital:29818 , https://doi.org/10.1177/0021909612442654
- Description: This article traces the rise and fall of radical praxis in South Africa and offers a critique of the prevailing practices of former Marxists under post-apartheid conditions. Western Marxism emerged in the 1970s in South Africa and Marxist activists became deeply involved in the liberation movements. With the unravelling of apartheid, the main liberation forces made a social pact with capitalist forces and former Marxists embraced a statist project. In the context of the rise of ‘new’ social movements, radical thinking of a more Libertarian kind is emerging in contemporary South Africa.
- Full Text: false
- Date Issued: 2012
- Authors: Helliker, Kirk D , Vale, Peter C J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71214 , vital:29818 , https://doi.org/10.1177/0021909612442654
- Description: This article traces the rise and fall of radical praxis in South Africa and offers a critique of the prevailing practices of former Marxists under post-apartheid conditions. Western Marxism emerged in the 1970s in South Africa and Marxist activists became deeply involved in the liberation movements. With the unravelling of apartheid, the main liberation forces made a social pact with capitalist forces and former Marxists embraced a statist project. In the context of the rise of ‘new’ social movements, radical thinking of a more Libertarian kind is emerging in contemporary South Africa.
- Full Text: false
- Date Issued: 2012
Regular moult-breeding overlap in the Pale-winged Starling Onychognathus nabouroup
- Authors: Craig, Adrian J F K
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/449518 , vital:74827 , https://www.tandfonline.com/doi/pdf/10.2989/00306525.2012.737149
- Description: In an earlier publication, with a sample consisting entirely of dated museum specimens, I concluded that, at the population level, moult-breeding overlap occurred in the Pale-winged Starling Onychognathus nabouroup, and in two other southern African Sturnidae, for which both museum skins and ringing records were available (Craig 1983). Subsequently, additional Pale-winged Starling specimens were examined in a reassessment of the subspecies that had been described, but no further analysis of the moult was undertaken (Craig 1988a). As part of a current behavioural study of this species, 58 Pale-winged Starlings were captured and colour-ringed at Augrabies Falls National Park during October 2011, and moult data were recorded for each bird following the standard scoring system for primary wing-feathers (de Beer et al. 2001). This prompted a re-examination of my earlier data, including the application of the Underhill-Zucchini model (Underhill and Zucchini 1988) to the available material.
- Full Text:
- Date Issued: 2012
- Authors: Craig, Adrian J F K
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/449518 , vital:74827 , https://www.tandfonline.com/doi/pdf/10.2989/00306525.2012.737149
- Description: In an earlier publication, with a sample consisting entirely of dated museum specimens, I concluded that, at the population level, moult-breeding overlap occurred in the Pale-winged Starling Onychognathus nabouroup, and in two other southern African Sturnidae, for which both museum skins and ringing records were available (Craig 1983). Subsequently, additional Pale-winged Starling specimens were examined in a reassessment of the subspecies that had been described, but no further analysis of the moult was undertaken (Craig 1988a). As part of a current behavioural study of this species, 58 Pale-winged Starlings were captured and colour-ringed at Augrabies Falls National Park during October 2011, and moult data were recorded for each bird following the standard scoring system for primary wing-feathers (de Beer et al. 2001). This prompted a re-examination of my earlier data, including the application of the Underhill-Zucchini model (Underhill and Zucchini 1988) to the available material.
- Full Text:
- Date Issued: 2012
Remote fingerprinting and multisensor data fusion
- Hunter, Samuel O, Stalmans, Etienne, Irwin, Barry V W, Richter, John
- Authors: Hunter, Samuel O , Stalmans, Etienne , Irwin, Barry V W , Richter, John
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429813 , vital:72641 , 10.1109/ISSA.2012.6320449
- Description: Network fingerprinting is the technique by which a device or service is enumerated in order to determine the hardware, software or application characteristics of a targeted attribute. Although fingerprinting can be achieved by a variety of means, the most common technique is the extraction of characteristics from an entity and the correlation thereof against known signatures for verification. In this paper we identify multiple host-defining metrics and propose a process of unique host tracking through the use of two novel fingerprinting techniques. We then illustrate the application of host fingerprinting and tracking for increasing situational awareness of potentially malicious hosts. In order to achieve this we provide an outline of an adapted multisensor data fusion model with the goal of increasing situational awareness through observation of unsolicited network traffic.
- Full Text:
- Date Issued: 2012
- Authors: Hunter, Samuel O , Stalmans, Etienne , Irwin, Barry V W , Richter, John
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429813 , vital:72641 , 10.1109/ISSA.2012.6320449
- Description: Network fingerprinting is the technique by which a device or service is enumerated in order to determine the hardware, software or application characteristics of a targeted attribute. Although fingerprinting can be achieved by a variety of means, the most common technique is the extraction of characteristics from an entity and the correlation thereof against known signatures for verification. In this paper we identify multiple host-defining metrics and propose a process of unique host tracking through the use of two novel fingerprinting techniques. We then illustrate the application of host fingerprinting and tracking for increasing situational awareness of potentially malicious hosts. In order to achieve this we provide an outline of an adapted multisensor data fusion model with the goal of increasing situational awareness through observation of unsolicited network traffic.
- Full Text:
- Date Issued: 2012
Representations of the subject ‘woman’ and the politics of abortion: an analysis of South African newspaper articles from 1978 to 2005
- Macleod, Catriona I, Feltham-King, Tracey
- Authors: Macleod, Catriona I , Feltham-King, Tracey
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/446286 , vital:74487 , xlink:href="https://doi.org/10.1080/13691058.2012.685760"
- Description: A key element in cultural and gender power relations surrounding abortion is how women who undergo an abortion are represented in public talk. We analyse how women were named and positioned, and the attendant constructions of abortion, in South African newspaper articles on abortion from 1978 to 2005, a period during which there were radical political and legislative shifts. The name ‘woman’ was the most frequently used (70% of articles) followed by ‘girl/teenager/child’ (25%), ‘mother’ (25%), ‘patient’ (11%) and ‘minor’ (6%). The subject positionings enabled by these names were dynamic and complex and were interwoven with the localised, historical politics of abortion. The ‘innocent mother’ and the bifurcated ‘patient’ (woman/foetus) positionings were invoked in earlier epochs to promote abortion under medical conditions. The ‘dangerous mother’ and woman as ‘patient’ positionings were used more frequently under liberal abortion legislation to oppose and to advocate for abortion, respectively. The positioning of the ‘girl/teenager/child’ as dependent and vulnerable was used in contradictory ways, both to oppose abortion and to argue for a liberalisation of restrictive legislation, depending on the attendant construction of abortion. The neutral naming of ‘woman’ was, at times, linked to the liberal imaginary of ‘choice’.
- Full Text:
- Date Issued: 2012
- Authors: Macleod, Catriona I , Feltham-King, Tracey
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/446286 , vital:74487 , xlink:href="https://doi.org/10.1080/13691058.2012.685760"
- Description: A key element in cultural and gender power relations surrounding abortion is how women who undergo an abortion are represented in public talk. We analyse how women were named and positioned, and the attendant constructions of abortion, in South African newspaper articles on abortion from 1978 to 2005, a period during which there were radical political and legislative shifts. The name ‘woman’ was the most frequently used (70% of articles) followed by ‘girl/teenager/child’ (25%), ‘mother’ (25%), ‘patient’ (11%) and ‘minor’ (6%). The subject positionings enabled by these names were dynamic and complex and were interwoven with the localised, historical politics of abortion. The ‘innocent mother’ and the bifurcated ‘patient’ (woman/foetus) positionings were invoked in earlier epochs to promote abortion under medical conditions. The ‘dangerous mother’ and woman as ‘patient’ positionings were used more frequently under liberal abortion legislation to oppose and to advocate for abortion, respectively. The positioning of the ‘girl/teenager/child’ as dependent and vulnerable was used in contradictory ways, both to oppose abortion and to argue for a liberalisation of restrictive legislation, depending on the attendant construction of abortion. The neutral naming of ‘woman’ was, at times, linked to the liberal imaginary of ‘choice’.
- Full Text:
- Date Issued: 2012
Research Testbed Networks: Practical Tools for Service Delivery?
- Wertlen, Ronald R, Siebörger, Ingrid, Tsietsi, Mosiuoa, Shibeshi, Zelalem S, Terzoli, Alfredo
- Authors: Wertlen, Ronald R , Siebörger, Ingrid , Tsietsi, Mosiuoa , Shibeshi, Zelalem S , Terzoli, Alfredo
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429204 , vital:72567 , https://doi.org/10.1002/j.1681-4835.2012.tb00351.x
- Description: The Telkom Centre of Excellence (CoE) at Rhodes University, housed in the Computer Science department was opened in 1997. The CoE's focus on Distributed multimedia service platforms soon showed that the technology being researched could be applied in the disadvantaged peri‐urban communities. The CoE has thus concentrated its research on building a testbed network that delivers real services to real users. In 2007, the testbed was extended to include a marginalised rural area in the Siyakhula Living Lab. The greatest factor in the sustainability of the CoE testbed network has been maintaining usefulness to all the stakeholders over the last 12 years. Industrial funding, University outreach goals and research goals could all be harmonised, while sustaining the delivery of high quality informatics services in the community. This paper presents a brief case study of the communications network testbed and how it was applied to the Development Informatics space. It analyses the roles played by stakeholders in either assisting and sustaining or obstructing the service delivery. It makes key recommendations on best practices for research networks that can also bring informatics to disadvantaged communities. It shows how testbeds for the research of new technologies can be designed so as to allow Development Informatics work to take place on such networks.
- Full Text:
- Date Issued: 2012
- Authors: Wertlen, Ronald R , Siebörger, Ingrid , Tsietsi, Mosiuoa , Shibeshi, Zelalem S , Terzoli, Alfredo
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429204 , vital:72567 , https://doi.org/10.1002/j.1681-4835.2012.tb00351.x
- Description: The Telkom Centre of Excellence (CoE) at Rhodes University, housed in the Computer Science department was opened in 1997. The CoE's focus on Distributed multimedia service platforms soon showed that the technology being researched could be applied in the disadvantaged peri‐urban communities. The CoE has thus concentrated its research on building a testbed network that delivers real services to real users. In 2007, the testbed was extended to include a marginalised rural area in the Siyakhula Living Lab. The greatest factor in the sustainability of the CoE testbed network has been maintaining usefulness to all the stakeholders over the last 12 years. Industrial funding, University outreach goals and research goals could all be harmonised, while sustaining the delivery of high quality informatics services in the community. This paper presents a brief case study of the communications network testbed and how it was applied to the Development Informatics space. It analyses the roles played by stakeholders in either assisting and sustaining or obstructing the service delivery. It makes key recommendations on best practices for research networks that can also bring informatics to disadvantaged communities. It shows how testbeds for the research of new technologies can be designed so as to allow Development Informatics work to take place on such networks.
- Full Text:
- Date Issued: 2012
Reverse saturation absorption spectra and optical limiting properties of chlorinated tetrasubstituted phthalocyanines containing different metals
- Tuhl, Ahmad, Manaa, Hacene, Makhseed, Saad, Al-Awadi, Nouria, Matthew, Jacob, Ibrahim, Hamada Mohamed, Nyokong, Tebello, Behbehani, Haider
- Authors: Tuhl, Ahmad , Manaa, Hacene , Makhseed, Saad , Al-Awadi, Nouria , Matthew, Jacob , Ibrahim, Hamada Mohamed , Nyokong, Tebello , Behbehani, Haider
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243498 , vital:51158 , xlink:href="https://doi.org/10.1016/j.optmat.2012.05.018"
- Description: A highly non-aggregated series of peripherally tetra(2,6-diisopropylphenoxy) substituted phthalocyanines (Pcs) containing different metals (Al, Ga, In and Zn) were prepared and their nonlinear optical properties (NLO), including the optical limiting behavior were investigated. This study explores the effect of the implanted metals along with the peripheral chlorine atoms on the NLO of the prepared complexes, thereby improving their optical limiting performance. The best wavelength at which the Pc complex exhibits the strongest nonlinear effect was determined over the low absorption window region (420–590 nm) comprised between the Q and B bands using a nanosecond pulsed laser with the aid of a Z-scan technique. The excited state absorption cross sections (σeff) have been found to be wavelength dependent with common double peaks at 505 nm and around 485 nm and the highest value was calculated for Pc1–In (1.1 × 10−16 cm2). The figure of merit spectra show different spectral structure when compared to the excited state absorption spectra and the largest figure of merit value was found to be around 107 for Pc1–In derivative. In full agreement with reverse saturation results, the optical limiting measurements, carried out at 485 nm and 532 nm for each derivative, show very low optical limiting thresholds at the former wavelength. In the continuous wave excitation regime, the Z-scan measurements, which were carried out at 632.8 and 532 nm, showed strong refractive and absorptive nonlinear effects.
- Full Text:
- Date Issued: 2012
- Authors: Tuhl, Ahmad , Manaa, Hacene , Makhseed, Saad , Al-Awadi, Nouria , Matthew, Jacob , Ibrahim, Hamada Mohamed , Nyokong, Tebello , Behbehani, Haider
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243498 , vital:51158 , xlink:href="https://doi.org/10.1016/j.optmat.2012.05.018"
- Description: A highly non-aggregated series of peripherally tetra(2,6-diisopropylphenoxy) substituted phthalocyanines (Pcs) containing different metals (Al, Ga, In and Zn) were prepared and their nonlinear optical properties (NLO), including the optical limiting behavior were investigated. This study explores the effect of the implanted metals along with the peripheral chlorine atoms on the NLO of the prepared complexes, thereby improving their optical limiting performance. The best wavelength at which the Pc complex exhibits the strongest nonlinear effect was determined over the low absorption window region (420–590 nm) comprised between the Q and B bands using a nanosecond pulsed laser with the aid of a Z-scan technique. The excited state absorption cross sections (σeff) have been found to be wavelength dependent with common double peaks at 505 nm and around 485 nm and the highest value was calculated for Pc1–In (1.1 × 10−16 cm2). The figure of merit spectra show different spectral structure when compared to the excited state absorption spectra and the largest figure of merit value was found to be around 107 for Pc1–In derivative. In full agreement with reverse saturation results, the optical limiting measurements, carried out at 485 nm and 532 nm for each derivative, show very low optical limiting thresholds at the former wavelength. In the continuous wave excitation regime, the Z-scan measurements, which were carried out at 632.8 and 532 nm, showed strong refractive and absorptive nonlinear effects.
- Full Text:
- Date Issued: 2012