Volcano correlations for the reactivity of surface-confined cobalt N4-macrocyclics for the electrocatalytic oxidation of 2-mercaptoacetate
- Claußen, Jan A, Ochoa, Gonzalo, Páez, Maritza, Costamagno, Juan, Gulppi, Miguel, Nyokong, Tebello, Bedioui, Fethi, Zagal, José H
- Authors: Claußen, Jan A , Ochoa, Gonzalo , Páez, Maritza , Costamagno, Juan , Gulppi, Miguel , Nyokong, Tebello , Bedioui, Fethi , Zagal, José H
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268688 , vital:54222 , xlink:href="https://doi.org/10.1007/s10008-007-0336-y"
- Description: We have investigated the electrocatalytic activity of several substituted and unsubstituted cobalt–phthalocyanines of substituted tetraphenyl porphyrins and of vitamin B12, for the electro-oxidation of 2-mercaptoacetate, with the complexes pre-adsorbed on a pyrolytic graphite electrode. Several N4-macrocyclic were used to have a wide variety of Co(II)/(I) formal potentials. The electrocatalytic activity, measured as current at constant potential, increases with the Co(II)/(I) redox potential for porphyrins as Co–pentafluorotetraphenylporphyrin larger than Co–tetrasulfonatotetraphenylporphyrin larger than Co-2,2′,2″,2‴tetra-aminotetraphenylporphyrin and decreases for cobalt phthalocyanines as Co-3,4-octaethylhexyloxyphthalocyanine > Co–octamethoxyphthalocyanine > Co–tetranitrophthalocyanine Co–tetraaminophthalocyanine > Co–unsubstituted phthalocyanine > Co–tetrasulfonatophthalocyanine > Co–perfluorinated phthalocyanine. Vitamin B12 exhibits the maximum activity. A correlation of log I (at constant potential) versus the Co(II)/(I) formal potential of the catalysts gives a volcano curve. This clearly shows that the search for better catalysts for this reaction point to those N4-macrocyclic complexes with Co(II)/(I) formal potentials close to −0.84 V versus SCE, which correspond to an optimum situation for the interaction of the thiol with the active site.
- Full Text:
- Date Issued: 2008
- Authors: Claußen, Jan A , Ochoa, Gonzalo , Páez, Maritza , Costamagno, Juan , Gulppi, Miguel , Nyokong, Tebello , Bedioui, Fethi , Zagal, José H
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268688 , vital:54222 , xlink:href="https://doi.org/10.1007/s10008-007-0336-y"
- Description: We have investigated the electrocatalytic activity of several substituted and unsubstituted cobalt–phthalocyanines of substituted tetraphenyl porphyrins and of vitamin B12, for the electro-oxidation of 2-mercaptoacetate, with the complexes pre-adsorbed on a pyrolytic graphite electrode. Several N4-macrocyclic were used to have a wide variety of Co(II)/(I) formal potentials. The electrocatalytic activity, measured as current at constant potential, increases with the Co(II)/(I) redox potential for porphyrins as Co–pentafluorotetraphenylporphyrin larger than Co–tetrasulfonatotetraphenylporphyrin larger than Co-2,2′,2″,2‴tetra-aminotetraphenylporphyrin and decreases for cobalt phthalocyanines as Co-3,4-octaethylhexyloxyphthalocyanine > Co–octamethoxyphthalocyanine > Co–tetranitrophthalocyanine Co–tetraaminophthalocyanine > Co–unsubstituted phthalocyanine > Co–tetrasulfonatophthalocyanine > Co–perfluorinated phthalocyanine. Vitamin B12 exhibits the maximum activity. A correlation of log I (at constant potential) versus the Co(II)/(I) formal potential of the catalysts gives a volcano curve. This clearly shows that the search for better catalysts for this reaction point to those N4-macrocyclic complexes with Co(II)/(I) formal potentials close to −0.84 V versus SCE, which correspond to an optimum situation for the interaction of the thiol with the active site.
- Full Text:
- Date Issued: 2008
What future subordinates will value in their leaders
- Cox, A, Amos, Trevor L, Baxter, Jeremy
- Authors: Cox, A , Amos, Trevor L , Baxter, Jeremy
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270992 , vital:54499 , xlink:href="https://hdl.handle.net/10520/EJC51031"
- Description: Leaders should not randomly choose a leadership style. To be effective, leaders need to ensure that their leadership style is congruent with what subordinates value. The focus of this study is on what the future South African graduate workforce will value in a leader. The female and male respondents in this study emphasise similar leadership values, indicating that there is no distinct set of competencies that will be valued separately by males and females. The same was found for respondents of different cultures, namely African, Coloured, Indian, White and other. With respect to both gender and culture, the respondents emphasise a mixture of African and Western leadership values. This supports the idea that to be effective in South Africa, leaders need to understand the prevailing national cultural values before simply applying ''foreign'' leadership models and theories based upon cultural values found in the West. This research finds that irrespective of gender and culture in the South African workplace, to be effective, leaders need to be loyal and inspirational, have vision and integrity and must be open and honest with their subordinates. Leaders should avoid being autocratic, strict, religious, ritualistic and traditional. They should also avoid using consensus and perceived external control.
- Full Text:
- Date Issued: 2008
- Authors: Cox, A , Amos, Trevor L , Baxter, Jeremy
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270992 , vital:54499 , xlink:href="https://hdl.handle.net/10520/EJC51031"
- Description: Leaders should not randomly choose a leadership style. To be effective, leaders need to ensure that their leadership style is congruent with what subordinates value. The focus of this study is on what the future South African graduate workforce will value in a leader. The female and male respondents in this study emphasise similar leadership values, indicating that there is no distinct set of competencies that will be valued separately by males and females. The same was found for respondents of different cultures, namely African, Coloured, Indian, White and other. With respect to both gender and culture, the respondents emphasise a mixture of African and Western leadership values. This supports the idea that to be effective in South Africa, leaders need to understand the prevailing national cultural values before simply applying ''foreign'' leadership models and theories based upon cultural values found in the West. This research finds that irrespective of gender and culture in the South African workplace, to be effective, leaders need to be loyal and inspirational, have vision and integrity and must be open and honest with their subordinates. Leaders should avoid being autocratic, strict, religious, ritualistic and traditional. They should also avoid using consensus and perceived external control.
- Full Text:
- Date Issued: 2008
When commercial can also be community:
- Authors: du Toit, Peter , Rau, Asta
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159322 , vital:40287 , https://hdl.handle.net/10520/EJC140094
- Description: Questions of ownership, control and profit distribution are widely used to distinguish between commercial and community media ventures, but an over-reliance on such distinctions may eclipse other important considerations in a way that impacts negatively on media diversity.
- Full Text:
- Date Issued: 2008
- Authors: du Toit, Peter , Rau, Asta
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159322 , vital:40287 , https://hdl.handle.net/10520/EJC140094
- Description: Questions of ownership, control and profit distribution are widely used to distinguish between commercial and community media ventures, but an over-reliance on such distinctions may eclipse other important considerations in a way that impacts negatively on media diversity.
- Full Text:
- Date Issued: 2008
Women’s rights get a dressing down: mini skirt attacks in South Africa
- Authors: Vincent, Louise
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141888 , vital:38013 , DOI: 10.18848/1447-9508/cgp/v06i06/42462
- Description: On Sunday the 17th of February 2008 25-year old Nwabisa Ngcukana was stripped, paraded naked while more than 100 onlookers jeered and laughed, doused in alcohol and sexually assaulted by taxi drivers and hawkers at the Noord Street taxi rank in Johannesburg1 (The Star 2008: 2). She was the fourth woman to be assaulted in this way at the rank on that evening. Three other women were stripped and sexually assaulted at the same taxi rank on the previous day. In each of these cases the fact that the women were wearing mini skirts was cited as the reason for the attack.
- Full Text:
- Date Issued: 2008
- Authors: Vincent, Louise
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141888 , vital:38013 , DOI: 10.18848/1447-9508/cgp/v06i06/42462
- Description: On Sunday the 17th of February 2008 25-year old Nwabisa Ngcukana was stripped, paraded naked while more than 100 onlookers jeered and laughed, doused in alcohol and sexually assaulted by taxi drivers and hawkers at the Noord Street taxi rank in Johannesburg1 (The Star 2008: 2). She was the fourth woman to be assaulted in this way at the rank on that evening. Three other women were stripped and sexually assaulted at the same taxi rank on the previous day. In each of these cases the fact that the women were wearing mini skirts was cited as the reason for the attack.
- Full Text:
- Date Issued: 2008
‘Boys will be boys’: traditional Xhosa male circumcision, HIV and sexual socialisation in contemporary South Africa
- Authors: Vincent, Louise
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141500 , vital:37980 , DOI: 10.1080/13691050701861447
- Description: Ritual male circumcision is among the most secretive and sacred of rites practiced by the Xhosa of South Africa. Recently, the alarming rate of death and injury among initiates has led to the spotlight of media attention and government regulation being focused on traditional circumcision. While many of the physical components of the ritual have been little altered by the centuries, its cultural and social meanings have not remained unchanged. This paper attempts to understand how some of these cultural and social meanings have shifted, particularly with respect to attitudes towards sex and the role that circumcision schools traditionally played in the sexual.
- Full Text:
- Date Issued: 2008
- Authors: Vincent, Louise
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141500 , vital:37980 , DOI: 10.1080/13691050701861447
- Description: Ritual male circumcision is among the most secretive and sacred of rites practiced by the Xhosa of South Africa. Recently, the alarming rate of death and injury among initiates has led to the spotlight of media attention and government regulation being focused on traditional circumcision. While many of the physical components of the ritual have been little altered by the centuries, its cultural and social meanings have not remained unchanged. This paper attempts to understand how some of these cultural and social meanings have shifted, particularly with respect to attitudes towards sex and the role that circumcision schools traditionally played in the sexual.
- Full Text:
- Date Issued: 2008
Evaluating parts-of-speech taggers for use in a text-to-scene conversion system
- Glass, Kevin R, Bangay, Shaun D
- Authors: Glass, Kevin R , Bangay, Shaun D
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432654 , vital:72890 , https://www.cs.ru.ac.za/research/groups/vrsig/currentprojects/053texttoscene/paper01.pdf
- Description: This paper presents parts-of-speech tagging as a first step towards an autonomous text-to-scene conversion system. It categorizes some freely available taggers, according to the techniques used by each in order to automatically identify word-classes. In addition, the performance of each identified tagger is verified experimentally. The SUSANNE corpus is used for testing and reveals the complexity of working with different tagsets, resulting in substantially lower accuracies in our tests than in those reported by the developers of each tagger. The taggers are then grouped to form a voting system to attempt to raise accuracies, but in no cases do the combined results improve upon the individual accuracies. Additionally a new metric, agreement, is tentatively proposed as an indication of confidence in the output of a group of taggers where such output cannot be validated.
- Full Text:
- Date Issued: 2005
- Authors: Glass, Kevin R , Bangay, Shaun D
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432654 , vital:72890 , https://www.cs.ru.ac.za/research/groups/vrsig/currentprojects/053texttoscene/paper01.pdf
- Description: This paper presents parts-of-speech tagging as a first step towards an autonomous text-to-scene conversion system. It categorizes some freely available taggers, according to the techniques used by each in order to automatically identify word-classes. In addition, the performance of each identified tagger is verified experimentally. The SUSANNE corpus is used for testing and reveals the complexity of working with different tagsets, resulting in substantially lower accuracies in our tests than in those reported by the developers of each tagger. The taggers are then grouped to form a voting system to attempt to raise accuracies, but in no cases do the combined results improve upon the individual accuracies. Additionally a new metric, agreement, is tentatively proposed as an indication of confidence in the output of a group of taggers where such output cannot be validated.
- Full Text:
- Date Issued: 2005