Energy versus angular momentum in black hole binaries
- Damour, T, Nagar, A, Pollney, D, Reisswig, C
- Authors: Damour, T , Nagar, A , Pollney, D , Reisswig, C
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6792 , http://hdl.handle.net/10962/d1006946
- Description: Using accurate numerical-relativity simulations of (nonspinning) black-hole binaries with mass ratios 1∶1, 2∶1, and 3∶1, we compute the gauge-invariant relation between the (reduced) binding energy E and the (reduced) angular momentum j of the system. We show that the relation E(j) is an accurate diagnostic of the dynamics of a black-hole binary in a highly relativistic regime. By comparing the numerical-relativity ENR(j) curve with the predictions of several analytic approximation schemes, we find that, while the canonically defined, nonresummed post-Newtonian–expanded EPN(j) relation exhibits large and growing deviations from ENR(j), the prediction of the effective one body formalism, based purely on known analytical results (without any calibration to numerical relativity), agrees strikingly well with the numerical-relativity results.
- Full Text:
- Date Issued: 2011
- Authors: Damour, T , Nagar, A , Pollney, D , Reisswig, C
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6792 , http://hdl.handle.net/10962/d1006946
- Description: Using accurate numerical-relativity simulations of (nonspinning) black-hole binaries with mass ratios 1∶1, 2∶1, and 3∶1, we compute the gauge-invariant relation between the (reduced) binding energy E and the (reduced) angular momentum j of the system. We show that the relation E(j) is an accurate diagnostic of the dynamics of a black-hole binary in a highly relativistic regime. By comparing the numerical-relativity ENR(j) curve with the predictions of several analytic approximation schemes, we find that, while the canonically defined, nonresummed post-Newtonian–expanded EPN(j) relation exhibits large and growing deviations from ENR(j), the prediction of the effective one body formalism, based purely on known analytical results (without any calibration to numerical relativity), agrees strikingly well with the numerical-relativity results.
- Full Text:
- Date Issued: 2011
Evaluating the Wald entropy from two-derivative terms in quadratic actions
- Brustein, R, Gorbonos, D, Hadad, M, Medved, A J M
- Authors: Brustein, R , Gorbonos, D , Hadad, M , Medved, A J M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6816 , http://hdl.handle.net/10962/d1004326
- Description: We evaluate the Wald Noether charge entropy for a black hole in generalized theories of gravity. Expanding the Lagrangian to second order in gravitational perturbations, we show that contributions to the entropy density originate only from the coefficients of two-derivative terms. The same considerations are extended to include matter fields and to show that arbitrary powers of matter fields and their symmetrized covariant derivatives cannot contribute to the entropy density. We also explain how to use the linearized gravitational field equation rather than quadratic actions to obtain the same results. Several explicit examples are presented that allow us to clarify subtle points in the derivation and application of our method.
- Full Text:
- Date Issued: 2011
- Authors: Brustein, R , Gorbonos, D , Hadad, M , Medved, A J M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6816 , http://hdl.handle.net/10962/d1004326
- Description: We evaluate the Wald Noether charge entropy for a black hole in generalized theories of gravity. Expanding the Lagrangian to second order in gravitational perturbations, we show that contributions to the entropy density originate only from the coefficients of two-derivative terms. The same considerations are extended to include matter fields and to show that arbitrary powers of matter fields and their symmetrized covariant derivatives cannot contribute to the entropy density. We also explain how to use the linearized gravitational field equation rather than quadratic actions to obtain the same results. Several explicit examples are presented that allow us to clarify subtle points in the derivation and application of our method.
- Full Text:
- Date Issued: 2011
Evaluation of the kinetics and mechanism of drug release from Econazole nitrate nanosponge loaded Carbapol Hydrogel
- Sharma, Renuka, Walker, Roderick B, Pathak, Kamla
- Authors: Sharma, Renuka , Walker, Roderick B , Pathak, Kamla
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6437 , http://hdl.handle.net/10962/d1006614
- Description: The objective of this study was to investigate the mechanism of release of econazole nitrate (EN) nanosponges loaded hydrogel and to compare it with EN hydrogel so as to develop an extended release topical drug delivery system of EN. Nanosponges of EN were prepared using ethyl cellulose and PVA by emulsion solvent evaporation method. On the basis of pharmacotechnical evaluation nanosponges with least particle size of 230.1 nm and good rheological properties were formulated as hydrogel (F1 – F7). In vitro drug release data of EN nanosponges loaded hydrogels in phosphate buffer pH 6.8 and 7.4 when analysed by GraphPad Prism software version 4.0 San Diego, USA best fitted the Makoid-2 Banakar model (R value greater than 0.98). The Korsmeyer-Peppas release exponent (n) ranged between 0.331 – 0.418, which confirmed diffusion as the principle mechanism of drug release. The release mechanism was further confirmed by calculating the ratio of exponents A/B ratio derived from the Kopcha model.
- Full Text:
- Date Issued: 2011
- Authors: Sharma, Renuka , Walker, Roderick B , Pathak, Kamla
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6437 , http://hdl.handle.net/10962/d1006614
- Description: The objective of this study was to investigate the mechanism of release of econazole nitrate (EN) nanosponges loaded hydrogel and to compare it with EN hydrogel so as to develop an extended release topical drug delivery system of EN. Nanosponges of EN were prepared using ethyl cellulose and PVA by emulsion solvent evaporation method. On the basis of pharmacotechnical evaluation nanosponges with least particle size of 230.1 nm and good rheological properties were formulated as hydrogel (F1 – F7). In vitro drug release data of EN nanosponges loaded hydrogels in phosphate buffer pH 6.8 and 7.4 when analysed by GraphPad Prism software version 4.0 San Diego, USA best fitted the Makoid-2 Banakar model (R value greater than 0.98). The Korsmeyer-Peppas release exponent (n) ranged between 0.331 – 0.418, which confirmed diffusion as the principle mechanism of drug release. The release mechanism was further confirmed by calculating the ratio of exponents A/B ratio derived from the Kopcha model.
- Full Text:
- Date Issued: 2011
Good Chemistry
- Authors: Grange, Helen
- Date: 2011
- Subjects: Nyokong, Tebello , Africa-Arab State 2009 Unesco-L'Oreal Award for Women in Science
- Language: English
- Type: Article , text
- Identifier: vital:7185 , http://hdl.handle.net/10962/d1006276 , Nyokong, Tebello , Africa-Arab State 2009 Unesco-L'Oreal Award for Women in Science
- Description: Helen Grange profiles four women who've fearlessly taken on the complex predominantly male-dominated field of science.
- Full Text:
- Date Issued: 2011
- Authors: Grange, Helen
- Date: 2011
- Subjects: Nyokong, Tebello , Africa-Arab State 2009 Unesco-L'Oreal Award for Women in Science
- Language: English
- Type: Article , text
- Identifier: vital:7185 , http://hdl.handle.net/10962/d1006276 , Nyokong, Tebello , Africa-Arab State 2009 Unesco-L'Oreal Award for Women in Science
- Description: Helen Grange profiles four women who've fearlessly taken on the complex predominantly male-dominated field of science.
- Full Text:
- Date Issued: 2011
Has deregulation of non-timber forest product controls and marketing in Orissa state (India) affected local patterns of use and marketing
- Mahapatra, A K, Shackleton, Charlie M
- Authors: Mahapatra, A K , Shackleton, Charlie M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6643 , http://hdl.handle.net/10962/d1006872
- Description: State control of marketing agricultural or forestry products may lead to a trade monopoly and restricted competition, resulting in inequitable returns to producers. Consequently, market deregulation for agriculture and other natural products has been advocated to improve market efficiencies, participation and returns for the producers and local traders. The study examines the impact of deregulation of state marketing controls on collection, sale and returns to extractors and traders from non-timber forest products. It assessed whether deregulation policy resulted in greater benefits to primary extractors and a win–win situation for both producers and traders? Mixed effects were found, with no significant changes in terms of trade, demand, or quantum of consumption; but there was an overall increase in the procurement price for several products following deregulation. The collection and farm gate price of tree based oilseeds and honey increased due to lower transaction costs, and ease of trading with a continued demand for these products. The impact on less valuable products was insignificant. Abolition of monopolistic trading increased competition and had a pull effect on the local market prices of several NTFPs. Although traders paid a higher price to procure products, overall they also benefited being able to sell the purchased products to merchants and manufacturers at a better margin than previously.
- Full Text:
- Date Issued: 2011
- Authors: Mahapatra, A K , Shackleton, Charlie M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6643 , http://hdl.handle.net/10962/d1006872
- Description: State control of marketing agricultural or forestry products may lead to a trade monopoly and restricted competition, resulting in inequitable returns to producers. Consequently, market deregulation for agriculture and other natural products has been advocated to improve market efficiencies, participation and returns for the producers and local traders. The study examines the impact of deregulation of state marketing controls on collection, sale and returns to extractors and traders from non-timber forest products. It assessed whether deregulation policy resulted in greater benefits to primary extractors and a win–win situation for both producers and traders? Mixed effects were found, with no significant changes in terms of trade, demand, or quantum of consumption; but there was an overall increase in the procurement price for several products following deregulation. The collection and farm gate price of tree based oilseeds and honey increased due to lower transaction costs, and ease of trading with a continued demand for these products. The impact on less valuable products was insignificant. Abolition of monopolistic trading increased competition and had a pull effect on the local market prices of several NTFPs. Although traders paid a higher price to procure products, overall they also benefited being able to sell the purchased products to merchants and manufacturers at a better margin than previously.
- Full Text:
- Date Issued: 2011
I love laser : it's my guiding light
- Authors: Nolan, Cathy
- Date: 2011
- Subjects: Nyokong, Tebello
- Language: English
- Type: Article , text
- Identifier: vital:7184 , http://hdl.handle.net/10962/d1006274 , http://unesdoc.unesco.org/images/0019/001906/190645e.pdf#190680 , Nyokong, Tebello
- Description: What is the common thread that could possibly link denim jeans, cancer and pesticides? None is evident. Yet when South African chemist Tebello Nyokong describes her fascinating research, the link that emerges is light. Nyokong, a specialist in nanochemistry, loves laser, and is using it in ways that could have a revolutionary impact on medicine and the environment.
- Full Text:
- Date Issued: 2011
- Authors: Nolan, Cathy
- Date: 2011
- Subjects: Nyokong, Tebello
- Language: English
- Type: Article , text
- Identifier: vital:7184 , http://hdl.handle.net/10962/d1006274 , http://unesdoc.unesco.org/images/0019/001906/190645e.pdf#190680 , Nyokong, Tebello
- Description: What is the common thread that could possibly link denim jeans, cancer and pesticides? None is evident. Yet when South African chemist Tebello Nyokong describes her fascinating research, the link that emerges is light. Nyokong, a specialist in nanochemistry, loves laser, and is using it in ways that could have a revolutionary impact on medicine and the environment.
- Full Text:
- Date Issued: 2011
Ilam's Archival Revitalisation: the past five years at the International Library of African Music
- Authors: Still-Drewett, F
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6983 , http://hdl.handle.net/10962/d1006719
- Description: The International Library for African Music (ILAM) was begun in 1954 by ethnomusicologist Hugh Tracey (1903–1977). Since 2007, an active set of projects in preservation and digitisation of both sound and photographic archives have meant that this highly important archive of traditional African music has been stabilized and conserved. New outreach education projects are helping distribute the wealth of the collection back to the African people. ILAM now has a more secure future and makes seminal contributions in the fields of research, publication and education for African music. French Abstract La Bibliothèque Internationale pour la Musique Africaine (ILAM) a été établie en 1954 par l’ethnomusicologue Hugh Tracey (1903–1977). Depuis 2007, un ensemble de projets actifs dans la préservation et la numérisation des archives sonores et photographiques, a eu comme résultat que ces archives très importantes de la musique traditionnelle africaine ont été stabilisées et conservées. De nouveaux projets d’éducation et de sensibilisation aident à distribuer la richesse de cette collection à la population africaine. ILAM a maintenant un avenir plus sûr et apporte une contribution fondamentale dans les domaines de la recherche, la publication et l’enseignement de la musique africaine. German Abstract Die International Library for African Music (ILAM) wurde im Jahr 1954 durch den Musi kethnolo - gen Hugh Tracey (1903–1977) gegründet. Seit 2007 laufende Projekte zur Bestandssicherung und Digitalisierung des Schall- und Fotoarchivs helfen, dieses überaus wichtige Archiv für traditionelle afrikanische Musik zu erhalten und in seiner Existenz zu stabilisieren. Neue, nach außen wirkende Bildungsprojekte tragen dazu bei, den Reichtum der Sammlung an die afrikanische Bevölkerung zurückzugeben. Durch seine nun gesicherte Zukunft kann ILAM für die afrikanische Musik grundlegende Beiträge in Forschung, Veröffentlichung und Bildung leisten. Afrikaans Abstract Die International Library of African Music (ILAM) is in 1954 deur die etnomusikoloog, Hugh Tracey (1903–1977), gestig. Aktiewe preserverings- en digitaliseringsprojekte van beide klank- en foto-argiewe sedert 2007, het tot gevolg gehad dat hierdie hoogs belangrike argief van tradisionele Afrikamusiek gestabiliseer en bewaar kon word. Nuwe ontwikkelings-uitreikprojekte dra daartoe by dat die rykdom van hierdie versameling teruggeploeg word aan Afrika. ILAM het tans ‘n meer versekerde toekoms en lewer invloedryke bydraes op die gebied van navorsing, publikasie en opleiding in Afrikamusiek. IsiXhosa Abstract Ithala lehlabathi lomculo wase-Afrika, i- International Library for African Music (ILAM) laqalwa ngo- 1954 yingcali yomculo weentlanga ngeentlanga, uHugh Tracey (1903–1977). Ukususela ngo-2007 umsebenzi wokulondoloza nokugcina ngekhompyutha isandi seengoma kwakunye neefoto uthetha ukuba le mbali ibalulekileyo kumculo we-Afrika wemveli iqiniselwe kwaye igcinwe ngononophelo. Iiprojekti ezintsha zokolulela isandla kwabanye abantu ziyanceda ekusasazeni le ndyebo kwabo bantu isuka kubo, ama-Afrika. Ngoku i-ILAM inekamva elingagunqgiyo kwaye inegalelo elibonakalayo kuphando, upapasho nemfundo ngomculo wase-Afrika.
- Full Text:
- Date Issued: 2011
- Authors: Still-Drewett, F
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6983 , http://hdl.handle.net/10962/d1006719
- Description: The International Library for African Music (ILAM) was begun in 1954 by ethnomusicologist Hugh Tracey (1903–1977). Since 2007, an active set of projects in preservation and digitisation of both sound and photographic archives have meant that this highly important archive of traditional African music has been stabilized and conserved. New outreach education projects are helping distribute the wealth of the collection back to the African people. ILAM now has a more secure future and makes seminal contributions in the fields of research, publication and education for African music. French Abstract La Bibliothèque Internationale pour la Musique Africaine (ILAM) a été établie en 1954 par l’ethnomusicologue Hugh Tracey (1903–1977). Depuis 2007, un ensemble de projets actifs dans la préservation et la numérisation des archives sonores et photographiques, a eu comme résultat que ces archives très importantes de la musique traditionnelle africaine ont été stabilisées et conservées. De nouveaux projets d’éducation et de sensibilisation aident à distribuer la richesse de cette collection à la population africaine. ILAM a maintenant un avenir plus sûr et apporte une contribution fondamentale dans les domaines de la recherche, la publication et l’enseignement de la musique africaine. German Abstract Die International Library for African Music (ILAM) wurde im Jahr 1954 durch den Musi kethnolo - gen Hugh Tracey (1903–1977) gegründet. Seit 2007 laufende Projekte zur Bestandssicherung und Digitalisierung des Schall- und Fotoarchivs helfen, dieses überaus wichtige Archiv für traditionelle afrikanische Musik zu erhalten und in seiner Existenz zu stabilisieren. Neue, nach außen wirkende Bildungsprojekte tragen dazu bei, den Reichtum der Sammlung an die afrikanische Bevölkerung zurückzugeben. Durch seine nun gesicherte Zukunft kann ILAM für die afrikanische Musik grundlegende Beiträge in Forschung, Veröffentlichung und Bildung leisten. Afrikaans Abstract Die International Library of African Music (ILAM) is in 1954 deur die etnomusikoloog, Hugh Tracey (1903–1977), gestig. Aktiewe preserverings- en digitaliseringsprojekte van beide klank- en foto-argiewe sedert 2007, het tot gevolg gehad dat hierdie hoogs belangrike argief van tradisionele Afrikamusiek gestabiliseer en bewaar kon word. Nuwe ontwikkelings-uitreikprojekte dra daartoe by dat die rykdom van hierdie versameling teruggeploeg word aan Afrika. ILAM het tans ‘n meer versekerde toekoms en lewer invloedryke bydraes op die gebied van navorsing, publikasie en opleiding in Afrikamusiek. IsiXhosa Abstract Ithala lehlabathi lomculo wase-Afrika, i- International Library for African Music (ILAM) laqalwa ngo- 1954 yingcali yomculo weentlanga ngeentlanga, uHugh Tracey (1903–1977). Ukususela ngo-2007 umsebenzi wokulondoloza nokugcina ngekhompyutha isandi seengoma kwakunye neefoto uthetha ukuba le mbali ibalulekileyo kumculo we-Afrika wemveli iqiniselwe kwaye igcinwe ngononophelo. Iiprojekti ezintsha zokolulela isandla kwabanye abantu ziyanceda ekusasazeni le ndyebo kwabo bantu isuka kubo, ama-Afrika. Ngoku i-ILAM inekamva elingagunqgiyo kwaye inegalelo elibonakalayo kuphando, upapasho nemfundo ngomculo wase-Afrika.
- Full Text:
- Date Issued: 2011
Incorporation of Ni(II)-dimethylglyoxime ion-imprinted polymer into electrospun polysulphone nanofibre for the determination of Ni(II) ions from aqueous samples
- Rammika, M, Darko, G, Torto, N
- Authors: Rammika, M , Darko, G , Torto, N
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6589 , http://hdl.handle.net/10962/d1004172
- Description: Ni(II)-dimethylglyoxime ion-imprinted polymer (Ni(II)-DMG IIP) was encapsulated in polysulphone and electrospun into nanofibres with diameters ranging from 406 to 854 nm. The structures of the Ni(II)-DMG encapsulated-IIP nanofibre, non-imprinted encapsulated-polymer nanofibre and polysulphone nanofibre mats were observed by scanning electron microscopy and evaluated by infrared spectroscopy. Electrospinning increased the specific surface area of the Ni(II)-DMG encapsulated-IIP nanofibre mats, as was evidenced by the low masses of the Ni(II)-DMG encapsulated-IIP nanofibre mats used. The accuracy of the method was validated by analysing a custom solution of certified reference material (SEP-3); the concentration of Ni(II) obtained was close to the certified one. The limit of detection was found to be 4.0x10-4 μg∙mℓ−1 while the limit of quantification was found to be 1.2x10-3 μg∙mℓ−1. The recovery of Ni(II) achieved using the Ni(II)-DMG imprinted nanofibre mats in water samples was found to range from 83 to 89%, while that of non-imprinted nanofibre mats was found to range from 59 to 65%, and that of polysulphone from 55 to 62%.
- Full Text:
- Date Issued: 2011
- Authors: Rammika, M , Darko, G , Torto, N
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6589 , http://hdl.handle.net/10962/d1004172
- Description: Ni(II)-dimethylglyoxime ion-imprinted polymer (Ni(II)-DMG IIP) was encapsulated in polysulphone and electrospun into nanofibres with diameters ranging from 406 to 854 nm. The structures of the Ni(II)-DMG encapsulated-IIP nanofibre, non-imprinted encapsulated-polymer nanofibre and polysulphone nanofibre mats were observed by scanning electron microscopy and evaluated by infrared spectroscopy. Electrospinning increased the specific surface area of the Ni(II)-DMG encapsulated-IIP nanofibre mats, as was evidenced by the low masses of the Ni(II)-DMG encapsulated-IIP nanofibre mats used. The accuracy of the method was validated by analysing a custom solution of certified reference material (SEP-3); the concentration of Ni(II) obtained was close to the certified one. The limit of detection was found to be 4.0x10-4 μg∙mℓ−1 while the limit of quantification was found to be 1.2x10-3 μg∙mℓ−1. The recovery of Ni(II) achieved using the Ni(II)-DMG imprinted nanofibre mats in water samples was found to range from 83 to 89%, while that of non-imprinted nanofibre mats was found to range from 59 to 65%, and that of polysulphone from 55 to 62%.
- Full Text:
- Date Issued: 2011
Late Quaternary environmental phases in the Eastern Cape and adjacent Plettenberg Bay-Knysna region and Little Karoo, South Africa
- Authors: Lewis, Colin A
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6712 , http://hdl.handle.net/10962/d1006749
- Description: Four major climato-environmental phases have been identified in the Eastern Cape, Plettenberg Bay-Knysna region and Little Karoo between somewhat before ~ 40 000 cal. a BP and the present: the Birnam Interstadial from before 40 000 cal. a BP until ~ 24 000 cal. a BP; the Bottelnek Stadial (apparently equating with the Last Glacial Maximum) from ~24 000 cal. a BP until before ~ 18 350 cal. a BP; the Aliwal North (apparently equating with the Late Glacial) from before ~ 18 350 cal. a BP until ~ 11 000 cal. a BP; the Dinorben (apparently equating with the Holocene) from ~ 11 000 cal. a BP until the present. The evidence for, and the characteristics of, these phases is briefly described.
- Full Text:
- Date Issued: 2011
- Authors: Lewis, Colin A
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6712 , http://hdl.handle.net/10962/d1006749
- Description: Four major climato-environmental phases have been identified in the Eastern Cape, Plettenberg Bay-Knysna region and Little Karoo between somewhat before ~ 40 000 cal. a BP and the present: the Birnam Interstadial from before 40 000 cal. a BP until ~ 24 000 cal. a BP; the Bottelnek Stadial (apparently equating with the Last Glacial Maximum) from ~24 000 cal. a BP until before ~ 18 350 cal. a BP; the Aliwal North (apparently equating with the Late Glacial) from before ~ 18 350 cal. a BP until ~ 11 000 cal. a BP; the Dinorben (apparently equating with the Holocene) from ~ 11 000 cal. a BP until the present. The evidence for, and the characteristics of, these phases is briefly described.
- Full Text:
- Date Issued: 2011
Molecular systematics of the African snake family Lamprophiidae Fitzinger, 1843 (Serpentes: Elapoidea), with particular focus on the genera Lamprophis Fitzinger 1843 and Mehelya Csiki 1903
- Kelly, Christopher M R, Branch, William R, Broadley, Donald G, Barker, Nigel P, Villet, Martin H
- Authors: Kelly, Christopher M R , Branch, William R , Broadley, Donald G , Barker, Nigel P , Villet, Martin H
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6861 , http://hdl.handle.net/10962/d1011151
- Description: The snake family Lamprophiidae Fitzinger (Serpentes: Elapoidea) is a putatively Late Eocene radiation of nocturnal snakes endemic to the African continent. It incorporates many of the most characteristic and prolific of Africa's non-venomous snake species, including the widespread type genus Lamprophis Fitzinger, 1843 (house snakes). We used approximately 2500 bases of mitochondrial and nuclear DNA sequence data from 28 (41%) of the approximately 68 recognised lamprophiid species in nine of the eleven genera to investigate phylogenetic structure in the family and to inform taxonomy at the generic level. Cytochrome b, ND4 and tRNA gene sequences (mitochondrial) and c-mos sequences (nuclear) were analysed using Maximum Likelihood, Bayesian Inference and Maximum Parsimony methods. The genus Mehelya Csiki, 1903 was paraphyletic with respect to Gonionotophis Boulenger, 1893. To address this, the concept of Gonionotophis is expanded to include all current Mehelya species. The genus Lamprophis emerged polyphyletic: the enigmatic Lamprophis swazicus was sister to Hormonotus modestus from West Africa, and not closely related to its nominal congeners. It is moved to a new monotypic genus (Inyoka gen. nov.). The remaining Lamprophis species occur in three early-diverging lineages. (1) Lamprophis virgatus and the widely distributed Lamprophis fuliginosus species complex (which also includes Lamprophis lineatus and Lamprophis olivaceus) formed a clade for which the generic name Boaedon Duméril, Bibron & Duméril, 1854 is resurrected. (2) The water snakes (Lycodonomorphus) were nested within Lamprophis (sensu lato), sister to Lamprophis inornatus. We transfer this species to the genus Lycodonomorphus Fitzinger, 1843. (3) We restrict Lamprophis (sensu strictissimo) to a small clade of four species endemic to southern Africa: the type species of Lamprophis Fitzinger, 1843 (Lamprophis aurora) plus Lamprophis fiskii, Lamprophis fuscus and Lamprophis guttatus.
- Full Text:
- Date Issued: 2011
- Authors: Kelly, Christopher M R , Branch, William R , Broadley, Donald G , Barker, Nigel P , Villet, Martin H
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6861 , http://hdl.handle.net/10962/d1011151
- Description: The snake family Lamprophiidae Fitzinger (Serpentes: Elapoidea) is a putatively Late Eocene radiation of nocturnal snakes endemic to the African continent. It incorporates many of the most characteristic and prolific of Africa's non-venomous snake species, including the widespread type genus Lamprophis Fitzinger, 1843 (house snakes). We used approximately 2500 bases of mitochondrial and nuclear DNA sequence data from 28 (41%) of the approximately 68 recognised lamprophiid species in nine of the eleven genera to investigate phylogenetic structure in the family and to inform taxonomy at the generic level. Cytochrome b, ND4 and tRNA gene sequences (mitochondrial) and c-mos sequences (nuclear) were analysed using Maximum Likelihood, Bayesian Inference and Maximum Parsimony methods. The genus Mehelya Csiki, 1903 was paraphyletic with respect to Gonionotophis Boulenger, 1893. To address this, the concept of Gonionotophis is expanded to include all current Mehelya species. The genus Lamprophis emerged polyphyletic: the enigmatic Lamprophis swazicus was sister to Hormonotus modestus from West Africa, and not closely related to its nominal congeners. It is moved to a new monotypic genus (Inyoka gen. nov.). The remaining Lamprophis species occur in three early-diverging lineages. (1) Lamprophis virgatus and the widely distributed Lamprophis fuliginosus species complex (which also includes Lamprophis lineatus and Lamprophis olivaceus) formed a clade for which the generic name Boaedon Duméril, Bibron & Duméril, 1854 is resurrected. (2) The water snakes (Lycodonomorphus) were nested within Lamprophis (sensu lato), sister to Lamprophis inornatus. We transfer this species to the genus Lycodonomorphus Fitzinger, 1843. (3) We restrict Lamprophis (sensu strictissimo) to a small clade of four species endemic to southern Africa: the type species of Lamprophis Fitzinger, 1843 (Lamprophis aurora) plus Lamprophis fiskii, Lamprophis fuscus and Lamprophis guttatus.
- Full Text:
- Date Issued: 2011
Non-perturbative unitarity constraints on the ratio of shear viscosity to entropy density in ultraviolet-complete theories with a gravity dual
- Authors: Brustein, R , Medved, A J M
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6817 , http://hdl.handle.net/10962/d1004327
- Description: We reconsider, from a novel perspective, how unitarity constrains the corrections to the ratio of shear viscosity η to entropy density s. We start with higher-derivative extensions of Einstein gravity in asymptotically anti-de Sitter spacetimes. It is assumed that these theories are derived from string theory and thus have a unitary UV completion that is dual to a unitary, UV-complete boundary gauge theory. We then propose that the gravitational perturbations about a solution of the UV-complete theory are described by an effective theory whose linearized equations of motion have at most two time derivatives. Our proposal leads to a concrete prescription for the calculation of η/s for theories of gravity with arbitrary higher-derivative corrections. The resulting ratio can take on values above or below 1/4π and is consistent with all the previous calculations, even though our reasoning is substantially different. For the purpose of calculating η/s, our proposal also leads to only two possible candidates for the effective two-derivative theory: Einstein and Gauss-Bonnet gravity. The distinction between the two is that Einstein gravity satisfies the equivalence principle, and so its graviton correlation functions are polarization-independent, whereas the Gauss-Bonnet theory has polarization-dependent correlation functions. We discuss the graviton three-point functions in this context and explain how these can provide additional information on the value of η/s.
- Full Text:
- Date Issued: 2011
- Authors: Brustein, R , Medved, A J M
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6817 , http://hdl.handle.net/10962/d1004327
- Description: We reconsider, from a novel perspective, how unitarity constrains the corrections to the ratio of shear viscosity η to entropy density s. We start with higher-derivative extensions of Einstein gravity in asymptotically anti-de Sitter spacetimes. It is assumed that these theories are derived from string theory and thus have a unitary UV completion that is dual to a unitary, UV-complete boundary gauge theory. We then propose that the gravitational perturbations about a solution of the UV-complete theory are described by an effective theory whose linearized equations of motion have at most two time derivatives. Our proposal leads to a concrete prescription for the calculation of η/s for theories of gravity with arbitrary higher-derivative corrections. The resulting ratio can take on values above or below 1/4π and is consistent with all the previous calculations, even though our reasoning is substantially different. For the purpose of calculating η/s, our proposal also leads to only two possible candidates for the effective two-derivative theory: Einstein and Gauss-Bonnet gravity. The distinction between the two is that Einstein gravity satisfies the equivalence principle, and so its graviton correlation functions are polarization-independent, whereas the Gauss-Bonnet theory has polarization-dependent correlation functions. We discuss the graviton three-point functions in this context and explain how these can provide additional information on the value of η/s.
- Full Text:
- Date Issued: 2011
Pet stores, aquarists and the internet trade as modes of introduction and spread of invasive macrophytes in South Africa
- Martin, Grant D, Coetzee, Julie A
- Authors: Martin, Grant D , Coetzee, Julie A
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6843 , http://hdl.handle.net/10962/d1011045
- Description: Submerged aquatic invasive plant species are increasingly being recognised as a major threat to South African water ways. Pet stores, aquarists and the internet-mediated trade were investigated as pathways for submerged invasive macrophyte introductions into South Africa. Online and manually distributed surveys were used to determine the extent of movement of invasive as well as indigenous submerged plant species in South Africa. Sixty-four stores and twenty-three aquarists were surveyed. Four areas of risk were identified in this study. Firstly, and most importantly, a variety of invasive and/or prohibited plants are sold by pet stores. Secondly, there is a lack of knowledge regarding identification as well as regulation of submerged species, which may then result in the unintentional trade of potentially invasive species. It seems that, in many cases, the pet stores are ignorant or misinformed of the potential dangers, rather than intentionally attempting to breach the legislation. Thirdly, aquarists own, trade and move plants in and around the country, which makes it very difficult to monitor which species are being moved around South Africa and to what extent. Finally, the internet is a pathway of potential concern, but it is difficult to quantify its contribution to the trade of invasive species in South Africa.
- Full Text:
- Date Issued: 2011
- Authors: Martin, Grant D , Coetzee, Julie A
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6843 , http://hdl.handle.net/10962/d1011045
- Description: Submerged aquatic invasive plant species are increasingly being recognised as a major threat to South African water ways. Pet stores, aquarists and the internet-mediated trade were investigated as pathways for submerged invasive macrophyte introductions into South Africa. Online and manually distributed surveys were used to determine the extent of movement of invasive as well as indigenous submerged plant species in South Africa. Sixty-four stores and twenty-three aquarists were surveyed. Four areas of risk were identified in this study. Firstly, and most importantly, a variety of invasive and/or prohibited plants are sold by pet stores. Secondly, there is a lack of knowledge regarding identification as well as regulation of submerged species, which may then result in the unintentional trade of potentially invasive species. It seems that, in many cases, the pet stores are ignorant or misinformed of the potential dangers, rather than intentionally attempting to breach the legislation. Thirdly, aquarists own, trade and move plants in and around the country, which makes it very difficult to monitor which species are being moved around South Africa and to what extent. Finally, the internet is a pathway of potential concern, but it is difficult to quantify its contribution to the trade of invasive species in South Africa.
- Full Text:
- Date Issued: 2011
Prof Nyokong receives another Science award
- Authors: Matiwana, Zamuxolo
- Date: 2011
- Subjects: Nyokong, Tebello , International Conference on Frontiers of Polymers and Advanced Materiel (ICFPAM)
- Language: English
- Type: Article , text
- Identifier: vital:7182 , http://hdl.handle.net/10962/d1006267 , Nyokong, Tebello
- Description: The Rhodes University professor of Medicinal Chemistry and Nanotechnology, Tebello Nyokong, says the Award for her Scientific Achievements by the International Conference on Frontiers of Polymers and Advanced Materiel (ICFPAM) is an honour, especially since it is awarded in memory of the centenary of the first Nobel Prize in Chemistry awarded to a woman: Marie Curie.
- Full Text:
- Date Issued: 2011
- Authors: Matiwana, Zamuxolo
- Date: 2011
- Subjects: Nyokong, Tebello , International Conference on Frontiers of Polymers and Advanced Materiel (ICFPAM)
- Language: English
- Type: Article , text
- Identifier: vital:7182 , http://hdl.handle.net/10962/d1006267 , Nyokong, Tebello
- Description: The Rhodes University professor of Medicinal Chemistry and Nanotechnology, Tebello Nyokong, says the Award for her Scientific Achievements by the International Conference on Frontiers of Polymers and Advanced Materiel (ICFPAM) is an honour, especially since it is awarded in memory of the centenary of the first Nobel Prize in Chemistry awarded to a woman: Marie Curie.
- Full Text:
- Date Issued: 2011
Psoralea margaretiflora (Psoraleeae, Fabaceae): a new species from the Sneeuberg Centre of Floristic Endemism, Eastern Cape, South Africa
- Stirton, Charles H, Clark, Vincent Ralph, Barker, Nigel P, Muasya, A Muthama
- Authors: Stirton, Charles H , Clark, Vincent Ralph , Barker, Nigel P , Muasya, A Muthama
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6543 , http://hdl.handle.net/10962/d1005999
- Description: A new species of Psoralea is described. Psoralea margaretiflora C.H. Stirton & V.R. Clark is endemic to the Sneeuberg Centre of Floristic Endemism, Eastern Cape, South Africa. This resprouter is characterised by its small greenish-white flowers with a small trifid purple nectar patch and translucent veins; 5(–7)-pinnate leaflets; multi-branching erect short seasonal flowering shoots; and tall habit of many stiff bare stems with the seasonal shoots massed at the apex. It is most similar to P. oligophylla Eckl. & Zeyh., a widespread species found in the Eastern Cape. The reseeder P. oligophylla differs in its lax virgate spreading habit with numerous long glaucous seasonal shoots; single stem, 1(–3)- glaucous leaflets; more numerous white flowers; and standard petals with a purple ring surrounding a bright yellow nectar patch.
- Full Text:
- Date Issued: 2011
- Authors: Stirton, Charles H , Clark, Vincent Ralph , Barker, Nigel P , Muasya, A Muthama
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6543 , http://hdl.handle.net/10962/d1005999
- Description: A new species of Psoralea is described. Psoralea margaretiflora C.H. Stirton & V.R. Clark is endemic to the Sneeuberg Centre of Floristic Endemism, Eastern Cape, South Africa. This resprouter is characterised by its small greenish-white flowers with a small trifid purple nectar patch and translucent veins; 5(–7)-pinnate leaflets; multi-branching erect short seasonal flowering shoots; and tall habit of many stiff bare stems with the seasonal shoots massed at the apex. It is most similar to P. oligophylla Eckl. & Zeyh., a widespread species found in the Eastern Cape. The reseeder P. oligophylla differs in its lax virgate spreading habit with numerous long glaucous seasonal shoots; single stem, 1(–3)- glaucous leaflets; more numerous white flowers; and standard petals with a purple ring surrounding a bright yellow nectar patch.
- Full Text:
- Date Issued: 2011
Publicising chemistry in a multicultural society through chemistry outreach
- Harrison, T G, Shallcross, D E, Norman, N C, Sewry, Joyce D, Davies-Coleman, Michael T
- Authors: Harrison, T G , Shallcross, D E , Norman, N C , Sewry, Joyce D , Davies-Coleman, Michael T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6573 , http://hdl.handle.net/10962/d1004136
- Description: Given the emphasis in Higher Education on community engagement in South Africa and the importance of international collaboration, we discuss a joint approach to chemistry outreach in two countries on two continents with widely differing target school audiences. We describe the history of the partnership between the chemistry departments at Rhodes University and the University of Bristol and provide an outline of the chemistry content of their outreach initiatives, the modes of delivery, the advantages to both departments and their students for involvement in various levels of outreach, the challenges they still face and additional opportunities that such work facilitated. The lecture demonstration 'A Pollutant's Tale' was presented to thousands of learners all over the world, including learners at resource-deprived schools in South Africa. Challenges to extend outreach activities in South Africa include long travelling distances, as well as a lack of facilities (such as school halls and electricity) at schools. Outreach activities not only impacted on the target audience of young learners, they also impacted upon the postgraduate and other chemistry students taking part in these initiatives. This collaboration strengthened both institutions and their outreach work and may also lead to chemistry research collaborations between the academics involved.
- Full Text:
- Date Issued: 2011
- Authors: Harrison, T G , Shallcross, D E , Norman, N C , Sewry, Joyce D , Davies-Coleman, Michael T
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6573 , http://hdl.handle.net/10962/d1004136
- Description: Given the emphasis in Higher Education on community engagement in South Africa and the importance of international collaboration, we discuss a joint approach to chemistry outreach in two countries on two continents with widely differing target school audiences. We describe the history of the partnership between the chemistry departments at Rhodes University and the University of Bristol and provide an outline of the chemistry content of their outreach initiatives, the modes of delivery, the advantages to both departments and their students for involvement in various levels of outreach, the challenges they still face and additional opportunities that such work facilitated. The lecture demonstration 'A Pollutant's Tale' was presented to thousands of learners all over the world, including learners at resource-deprived schools in South Africa. Challenges to extend outreach activities in South Africa include long travelling distances, as well as a lack of facilities (such as school halls and electricity) at schools. Outreach activities not only impacted on the target audience of young learners, they also impacted upon the postgraduate and other chemistry students taking part in these initiatives. This collaboration strengthened both institutions and their outreach work and may also lead to chemistry research collaborations between the academics involved.
- Full Text:
- Date Issued: 2011
Selective removal of chromium (VI) from sulphates and other metal anions using an ion-imprinted polymer
- Pakade, V, Cukrowska, E, Darkwa, J, Torto, N, Chimuka, L
- Authors: Pakade, V , Cukrowska, E , Darkwa, J , Torto, N , Chimuka, L
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6588 , http://hdl.handle.net/10962/d1004171
- Description: A linear copolymer was prepared from 4-vinylpyridine and styrene. An ion-imprinted polymer (IIP) specific for Cr (VI) adsorption was prepared by copolymerisation of the quaternised linear copolymer (quaternised with 1,4-chlorobutane), 2-vinylpyridine functional monomer and ethylene glycol dimethacrylate (EGDMA), as the cross-linking monomer, in the presence of 1,1’-azobis(cyclohexanecarbonitrile) as initiator. Ammonium dichromate and aqueous methanol were used as a template and porogenic solvent, respectively. Leaching of the chromate template from the polymer particles was achieved with successive stirring of the ion-imprinted polymer (IIP) particles in 4 M HNO3 solutions to obtain leached materials, which were then used for selective rebinding of Cr (VI) ions from aqueous solutions. Similarly, the non-imprinted polymer/ control polymer (NIP/CP) material was also prepared under exactly the same conditions as the IIP but without the chromate anion template. Various parameters, such as solution pH, initial concentration, aqueous phase volume, sorbent dosage, contact time and leaching solution volumes, were investigated. Scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, BET surface area and pore size analysis were used for the characterisation of IIP (both unleached and leached) and CP materials. Optimal parameters were as follows: solution pH, 3; contact time, 120 min; eluent, 20 mℓ of 0.1 M NaOH; and sorbent amount, 125 mg. Maximum retention capacity of IIP and CP was 37.58 and 25.44 mg∙g-1, respectively. The extraction efficiencies of the IIP and CP were compared using a batch and SPE mode of extraction. In the absence of high concentrations of ions, especially sulphate ions, both CP and IIP demonstrated no differences in binding of Cr (VI), which was almost 100%. However, in the presence of high concentrations of sulphate ions, the selectivity on the CP completely collapsed. The study clearly demonstrates the suitably of the developed IIP for selective extraction of Cr (VI) in complex samples such as those from acid mine drainage. The selectivity was also compared by direct injection of the real-world sample, both spiked and non-spiked, into that obtained after IIP selective extraction. Despite the method’s very low detection limits for direct injection (below 1 μg∙ℓ-1), no Cr (VI) was obtained. However, after IIP selective extraction, spiked Cr (VI) was detected in the spiked sample.
- Full Text:
- Date Issued: 2011
- Authors: Pakade, V , Cukrowska, E , Darkwa, J , Torto, N , Chimuka, L
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6588 , http://hdl.handle.net/10962/d1004171
- Description: A linear copolymer was prepared from 4-vinylpyridine and styrene. An ion-imprinted polymer (IIP) specific for Cr (VI) adsorption was prepared by copolymerisation of the quaternised linear copolymer (quaternised with 1,4-chlorobutane), 2-vinylpyridine functional monomer and ethylene glycol dimethacrylate (EGDMA), as the cross-linking monomer, in the presence of 1,1’-azobis(cyclohexanecarbonitrile) as initiator. Ammonium dichromate and aqueous methanol were used as a template and porogenic solvent, respectively. Leaching of the chromate template from the polymer particles was achieved with successive stirring of the ion-imprinted polymer (IIP) particles in 4 M HNO3 solutions to obtain leached materials, which were then used for selective rebinding of Cr (VI) ions from aqueous solutions. Similarly, the non-imprinted polymer/ control polymer (NIP/CP) material was also prepared under exactly the same conditions as the IIP but without the chromate anion template. Various parameters, such as solution pH, initial concentration, aqueous phase volume, sorbent dosage, contact time and leaching solution volumes, were investigated. Scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, BET surface area and pore size analysis were used for the characterisation of IIP (both unleached and leached) and CP materials. Optimal parameters were as follows: solution pH, 3; contact time, 120 min; eluent, 20 mℓ of 0.1 M NaOH; and sorbent amount, 125 mg. Maximum retention capacity of IIP and CP was 37.58 and 25.44 mg∙g-1, respectively. The extraction efficiencies of the IIP and CP were compared using a batch and SPE mode of extraction. In the absence of high concentrations of ions, especially sulphate ions, both CP and IIP demonstrated no differences in binding of Cr (VI), which was almost 100%. However, in the presence of high concentrations of sulphate ions, the selectivity on the CP completely collapsed. The study clearly demonstrates the suitably of the developed IIP for selective extraction of Cr (VI) in complex samples such as those from acid mine drainage. The selectivity was also compared by direct injection of the real-world sample, both spiked and non-spiked, into that obtained after IIP selective extraction. Despite the method’s very low detection limits for direct injection (below 1 μg∙ℓ-1), no Cr (VI) was obtained. However, after IIP selective extraction, spiked Cr (VI) was detected in the spiked sample.
- Full Text:
- Date Issued: 2011
Tebello Nyokong "As chemists, we are designers"
- Authors: Nolan, Cathy
- Date: 2011
- Language: English
- Type: Article , text
- Identifier: vital:7201 , http://hdl.handle.net/10962/d1006385
- Description: What is the common thread running through denim jeans, cancer and pesticides? None springs to mind, yet when chemist Tebello Nyokong describes her fascinating research, a link begins to emerge: light. A specialist in nanochemistry, Nyokong is using laser in ways that could revolutionize not only the diagnosis and treatment of cancer but also water purification.
- Full Text:
- Date Issued: 2011
- Authors: Nolan, Cathy
- Date: 2011
- Language: English
- Type: Article , text
- Identifier: vital:7201 , http://hdl.handle.net/10962/d1006385
- Description: What is the common thread running through denim jeans, cancer and pesticides? None springs to mind, yet when chemist Tebello Nyokong describes her fascinating research, a link begins to emerge: light. A specialist in nanochemistry, Nyokong is using laser in ways that could revolutionize not only the diagnosis and treatment of cancer but also water purification.
- Full Text:
- Date Issued: 2011
Tebello Nyokong 'As chemists, we are designers'
- Authors: Nolan, Cathy
- Date: 2011
- Subjects: Nyokong, Tebello , L’Oreal–UNESCO Awards for Women in Science
- Language: English
- Type: Article , text
- Identifier: vital:7183 , http://hdl.handle.net/10962/d1006272 , Nyokong, Tebello , L’Oreal–UNESCO Awards for Women in Science
- Description: What is the common thread running through denim jeans, cancer and pesticides? None springs to mind, yet when chemist Tebello Nyokong describes her fascinating research, a link begins to emerge: light. A specialist in nanochemistry, Nyokong is using laser in ways that could revolutionize not only the diagnosis and treatment of cancer but also water purification. Born in Lesotho, Tebello Nyokong is Professor of Medicinal Chemistry and Nanotechnology at Rhodes University in South Africa and Director of the Nanotechnology Innovation Centre for Sensors (Mintek). In 2009, she was one of the five Laureates of the 2009 L’Oreal–UNESCO Awards for Women in Science.
- Full Text:
- Date Issued: 2011
- Authors: Nolan, Cathy
- Date: 2011
- Subjects: Nyokong, Tebello , L’Oreal–UNESCO Awards for Women in Science
- Language: English
- Type: Article , text
- Identifier: vital:7183 , http://hdl.handle.net/10962/d1006272 , Nyokong, Tebello , L’Oreal–UNESCO Awards for Women in Science
- Description: What is the common thread running through denim jeans, cancer and pesticides? None springs to mind, yet when chemist Tebello Nyokong describes her fascinating research, a link begins to emerge: light. A specialist in nanochemistry, Nyokong is using laser in ways that could revolutionize not only the diagnosis and treatment of cancer but also water purification. Born in Lesotho, Tebello Nyokong is Professor of Medicinal Chemistry and Nanotechnology at Rhodes University in South Africa and Director of the Nanotechnology Innovation Centre for Sensors (Mintek). In 2009, she was one of the five Laureates of the 2009 L’Oreal–UNESCO Awards for Women in Science.
- Full Text:
- Date Issued: 2011
The distribution, abundance and composition of street trees in selected towns of the Eastern Cape, South Africa
- Kuruneri-Chitepo, C, Shackleton, Charlie M
- Authors: Kuruneri-Chitepo, C , Shackleton, Charlie M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6639 , http://hdl.handle.net/10962/d1006865
- Description: Street trees are an important component of the urban forest as they provide critical ecosystem services which contribute to human health and environmental quality. However, little is known about the distribution, diversity and density of street trees, particularly in the developing world where urbanisation is most rapid. Thus, the aim of this paper was to assess the distribution, composition and abundance of street trees across three towns along an environmental gradient in the Eastern Cape of South Africa, and identify the key challenges faced by local officials concerned with the provision of street trees. In each town, streets were randomly sampled in the commercial, affluent residential, township settlement and low cost housing areas under the Reconstruction and Development Program (RDP). Attributes recorded per tree were species, circumference, height and health, while semi-structured interviews were conducted with the municipal officials involved in the establishment and maintenance of street trees. A total of 1,485 trees were encountered, comprising 61 species. The majority (56%) of trees were alien species. Noticeable differences in tree density and species richness were evident across suburbs, being highest in the more affluent suburbs and poorly represented in the low income township and RDP areas. There was a decreasing mean tree height and health score along the environmental gradient from the coastal town to the inland town. Although awareness of the benefits of street trees was high, as was the need to reduce the proportion of alien species, the primary constraint to establishment and maintenance of street trees in the three towns was limited budget and human resources.
- Full Text:
- Date Issued: 2011
- Authors: Kuruneri-Chitepo, C , Shackleton, Charlie M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6639 , http://hdl.handle.net/10962/d1006865
- Description: Street trees are an important component of the urban forest as they provide critical ecosystem services which contribute to human health and environmental quality. However, little is known about the distribution, diversity and density of street trees, particularly in the developing world where urbanisation is most rapid. Thus, the aim of this paper was to assess the distribution, composition and abundance of street trees across three towns along an environmental gradient in the Eastern Cape of South Africa, and identify the key challenges faced by local officials concerned with the provision of street trees. In each town, streets were randomly sampled in the commercial, affluent residential, township settlement and low cost housing areas under the Reconstruction and Development Program (RDP). Attributes recorded per tree were species, circumference, height and health, while semi-structured interviews were conducted with the municipal officials involved in the establishment and maintenance of street trees. A total of 1,485 trees were encountered, comprising 61 species. The majority (56%) of trees were alien species. Noticeable differences in tree density and species richness were evident across suburbs, being highest in the more affluent suburbs and poorly represented in the low income township and RDP areas. There was a decreasing mean tree height and health score along the environmental gradient from the coastal town to the inland town. Although awareness of the benefits of street trees was high, as was the need to reduce the proportion of alien species, the primary constraint to establishment and maintenance of street trees in the three towns was limited budget and human resources.
- Full Text:
- Date Issued: 2011
The identity of Albuca caudata Jacq. (Hyacinthaceae) and a description of a new related species : A. bakeri
- Martinez-Azorin, Mario, Cresbo, Manuel B, Dold, Anthony P, Barker, Nigel P
- Authors: Martinez-Azorin, Mario , Cresbo, Manuel B , Dold, Anthony P , Barker, Nigel P
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6528 , http://hdl.handle.net/10962/d1005969
- Description: The name Albuca caudata Jacq. has been widely misunderstood or even ignored since its description in 1791. After studying herbarium specimens and living populations in South Africa, plants fitting Jacquin´s concept of that species are found to be widely distributed in the Eastern Cape, mainly in the Albany centre of Endemism. Furthermore, some divergent specimens matching Baker´s concept of Albuca caudata are described as a new related species: Albuca bakeri. Data on typification, morphology, ecology, and distribution are reported for both taxa. Affinities and divergences with other close allies are also discussed.
- Full Text:
- Date Issued: 2011
- Authors: Martinez-Azorin, Mario , Cresbo, Manuel B , Dold, Anthony P , Barker, Nigel P
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6528 , http://hdl.handle.net/10962/d1005969
- Description: The name Albuca caudata Jacq. has been widely misunderstood or even ignored since its description in 1791. After studying herbarium specimens and living populations in South Africa, plants fitting Jacquin´s concept of that species are found to be widely distributed in the Eastern Cape, mainly in the Albany centre of Endemism. Furthermore, some divergent specimens matching Baker´s concept of Albuca caudata are described as a new related species: Albuca bakeri. Data on typification, morphology, ecology, and distribution are reported for both taxa. Affinities and divergences with other close allies are also discussed.
- Full Text:
- Date Issued: 2011