Cytosolic and ER J-domains of mammalian and parasitic origin can functionally interact with DnaK
- Nicoll, W S, Botha, M, McNamara, Caryn, Schlange, M, Pesce, E R, Boshoff, Aileen, Ludewig, M H, Zimmerman, R, Cheetham, M E, Chapple, J P, Blatch, Gregory L
- Authors: Nicoll, W S , Botha, M , McNamara, Caryn , Schlange, M , Pesce, E R , Boshoff, Aileen , Ludewig, M H , Zimmerman, R , Cheetham, M E , Chapple, J P , Blatch, Gregory L
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6484 , http://hdl.handle.net/10962/d1006261 , http://www.sciencedirect.com/science/article/pii/S1357272506003268
- Description: Both prokaryotic and eukaryotic cells contain multiple heat shock protein 40 (Hsp40) and heat shock protein 70 (Hsp70) proteins, which cooperate as molecular chaperones to ensure fidelity at all stages of protein biogenesis. The Hsp40 signature domain, the J-domain, is required for binding of an Hsp40 to a partner Hsp70, and may also play a role in the specificity of the association. Through the creation of chimeric Hsp40 proteins by the replacement of the J-domain of a prokaryotic Hsp40 (DnaJ), we have tested the functional equivalence of J-domains from a number of divergent Hsp40s of mammalian and parasitic origin (malarial Pfj1 and Pfj4, trypanosomal Tcj3, human ERj3, ERj5, and Hsj1, and murine ERj1). An in vivo functional assay was used to test the functionality of the chimeric proteins on the basis of their ability to reverse the thermosensitivity of a dnaJ cbpA mutant Escherichia coli strain (OD259). The Hsp40 chimeras containing J-domains originating from soluble (cytosolic or endoplasmic reticulum (ER)-lumenal) Hsp40s were able to reverse the thermosensitivity of E. coli OD259. In all cases, modified derivatives of these chimeric proteins containing an His to Gln substitution in the HPD motif of the J-domain were unable to reverse the thermosensitivity of E. coli OD259. This suggested that these J-domains exerted their in vivo functionality through a specific interaction with E. coli Hsp70, DnaK. Interestingly, a Hsp40 chimera containing the J-domain of ERj1, an integral membrane-bound ER Hsp40, was unable to reverse the thermosensitivity of E. coli OD259, suggesting that this J-domain was unable to functionally interact with DnaK. Substitutions of conserved amino acid residues and motifs were made in all four helices (I-IV) and the loop regions of the J-domains, and the modified chimeric Hsp40s were tested for functionality using the in vivo assay. Substitution of a highly conserved basic residue in helix II of the J-domain was found to disrupt in vivo functionality for all the J-domains tested. We propose that helix II and the HPD motif of the J-domain represent the fundamental elements of a binding surface required for the interaction of Hsp40s with Hsp70s, and that this surface has been conserved in mammalian, parasitic and bacterial systems.
- Full Text:
- Date Issued: 2007
- Authors: Nicoll, W S , Botha, M , McNamara, Caryn , Schlange, M , Pesce, E R , Boshoff, Aileen , Ludewig, M H , Zimmerman, R , Cheetham, M E , Chapple, J P , Blatch, Gregory L
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6484 , http://hdl.handle.net/10962/d1006261 , http://www.sciencedirect.com/science/article/pii/S1357272506003268
- Description: Both prokaryotic and eukaryotic cells contain multiple heat shock protein 40 (Hsp40) and heat shock protein 70 (Hsp70) proteins, which cooperate as molecular chaperones to ensure fidelity at all stages of protein biogenesis. The Hsp40 signature domain, the J-domain, is required for binding of an Hsp40 to a partner Hsp70, and may also play a role in the specificity of the association. Through the creation of chimeric Hsp40 proteins by the replacement of the J-domain of a prokaryotic Hsp40 (DnaJ), we have tested the functional equivalence of J-domains from a number of divergent Hsp40s of mammalian and parasitic origin (malarial Pfj1 and Pfj4, trypanosomal Tcj3, human ERj3, ERj5, and Hsj1, and murine ERj1). An in vivo functional assay was used to test the functionality of the chimeric proteins on the basis of their ability to reverse the thermosensitivity of a dnaJ cbpA mutant Escherichia coli strain (OD259). The Hsp40 chimeras containing J-domains originating from soluble (cytosolic or endoplasmic reticulum (ER)-lumenal) Hsp40s were able to reverse the thermosensitivity of E. coli OD259. In all cases, modified derivatives of these chimeric proteins containing an His to Gln substitution in the HPD motif of the J-domain were unable to reverse the thermosensitivity of E. coli OD259. This suggested that these J-domains exerted their in vivo functionality through a specific interaction with E. coli Hsp70, DnaK. Interestingly, a Hsp40 chimera containing the J-domain of ERj1, an integral membrane-bound ER Hsp40, was unable to reverse the thermosensitivity of E. coli OD259, suggesting that this J-domain was unable to functionally interact with DnaK. Substitutions of conserved amino acid residues and motifs were made in all four helices (I-IV) and the loop regions of the J-domains, and the modified chimeric Hsp40s were tested for functionality using the in vivo assay. Substitution of a highly conserved basic residue in helix II of the J-domain was found to disrupt in vivo functionality for all the J-domains tested. We propose that helix II and the HPD motif of the J-domain represent the fundamental elements of a binding surface required for the interaction of Hsp40s with Hsp70s, and that this surface has been conserved in mammalian, parasitic and bacterial systems.
- Full Text:
- Date Issued: 2007
D.H. Lawrence around the world: South African perspectives, (Eds.) Jim Phelps and Nigel Bell : book review
- Authors: Van Wyk Smith, Malvern
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6121 , http://hdl.handle.net/10962/d1004702
- Description: The book as a whole provides a scholarly overview of the central position held by the works and ideas of the English writer D. H. Lawrence in the curricula, teaching philosophies and world views of South African university English Departments in the early latter half of the twentieth century. If this suggests something of a resurrectionary enterprise - the informing spirit of the collection, Christina van Heyningen, died some decades ago - it is also true that the names of contributors read like a roll call of those South African and immigrant British academics who from the 1950s to the 1970s made some of our English Departments notable leaders in their field. Essays, old and new, have been carefully chosen and juxtaposed to reveal how and why the teaching of internationally significant literature (in this case the writings of D. H. Lawrence) was in those years deemed to form an essential part of the training of a maturing critical faculty with which to confront not just English literature and cognate academic subjects, but the complex world of adult human experience itself.
- Full Text:
- Date Issued: 2007
- Authors: Van Wyk Smith, Malvern
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6121 , http://hdl.handle.net/10962/d1004702
- Description: The book as a whole provides a scholarly overview of the central position held by the works and ideas of the English writer D. H. Lawrence in the curricula, teaching philosophies and world views of South African university English Departments in the early latter half of the twentieth century. If this suggests something of a resurrectionary enterprise - the informing spirit of the collection, Christina van Heyningen, died some decades ago - it is also true that the names of contributors read like a roll call of those South African and immigrant British academics who from the 1950s to the 1970s made some of our English Departments notable leaders in their field. Essays, old and new, have been carefully chosen and juxtaposed to reveal how and why the teaching of internationally significant literature (in this case the writings of D. H. Lawrence) was in those years deemed to form an essential part of the training of a maturing critical faculty with which to confront not just English literature and cognate academic subjects, but the complex world of adult human experience itself.
- Full Text:
- Date Issued: 2007
Development of a regional GPS-based ionospheric TEC model for South Africa
- Opperman, Ben D L, Cilliers, Pierre J, McKinnell, Lee-Anne, Haggard, Raymond
- Authors: Opperman, Ben D L , Cilliers, Pierre J , McKinnell, Lee-Anne , Haggard, Raymond
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6799 , http://hdl.handle.net/10962/d1003925
- Description: Advances in South African space physics research and related disciplines require better spatial and time resolution ionospheric information than was previously possible with the existing ionosonde network. A GPS-based, variable degree adjusted spherical harmonic (ASHA) model was developed for near real-time regional ionospheric total electron content (TEC) mapping over South Africa. Slant TEC values along oblique GPS signal paths are quantified from a network of GPS receivers and converted to vertical TEC by means of the single layer mapping function. The ASHA model coefficients and GPS differential biases are estimated from vertical TEC at the ionospheric pierce points and used to interpolate TEC at any location within the region of interest. Diurnal TEC variations with one minute time resolution and time-varying 2D regional TEC maps are constructed. In order to validate the ASHA method, simulations with an IRI ionosphere were performed, while the ASHA results from actual data were compared with two independent GPS-based methodologies and measured ionosonde data.
- Full Text:
- Date Issued: 2007
- Authors: Opperman, Ben D L , Cilliers, Pierre J , McKinnell, Lee-Anne , Haggard, Raymond
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6799 , http://hdl.handle.net/10962/d1003925
- Description: Advances in South African space physics research and related disciplines require better spatial and time resolution ionospheric information than was previously possible with the existing ionosonde network. A GPS-based, variable degree adjusted spherical harmonic (ASHA) model was developed for near real-time regional ionospheric total electron content (TEC) mapping over South Africa. Slant TEC values along oblique GPS signal paths are quantified from a network of GPS receivers and converted to vertical TEC by means of the single layer mapping function. The ASHA model coefficients and GPS differential biases are estimated from vertical TEC at the ionospheric pierce points and used to interpolate TEC at any location within the region of interest. Diurnal TEC variations with one minute time resolution and time-varying 2D regional TEC maps are constructed. In order to validate the ASHA method, simulations with an IRI ionosphere were performed, while the ASHA results from actual data were compared with two independent GPS-based methodologies and measured ionosonde data.
- Full Text:
- Date Issued: 2007
Development of written information for antiretroviral therapy: comprehension in a Tanzanian population
- Mwingira, Betty, Dowse, Roslind
- Authors: Mwingira, Betty , Dowse, Roslind
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6404 , http://hdl.handle.net/10962/d1006477
- Description: Objective To design and develop a simple, easily readable patient information leaflet (PIL) for a commonly used antiretroviral (ARV) regimen and to evaluate its readability and acceptability in a Tanzanian population. Method A PIL incorporating simple text and pictograms was designed for the antiretroviral regimen of stavudine, lamivudine and efavirenz. The PIL was designed according to established good design guidelines, modified during a multi-stage iterative testing process and piloted in a South African Xhosa population. The PIL was made available in both English and Kiswahili. Sixty Tanzanian participants who were not taking ARVs were interviewed. They were asked to read the PIL in the language of their choice and were then asked a series of two-part questions; the first part required participants to locate the information in the PIL, after which they were asked to explain the information in their own words. Acceptability was assessed through close-ended questions and open-ended feedback. The influence of selected patient characteristics on comprehension of the PIL was investigated using one-way ANOVA and t-tests for independent samples with a significance level set at 0.05. Main outcome measure Comprehension of the written information in an overall percentage understanding. Results The overall average percentage comprehension of the PIL was 95%. The target set by the EC guideline that at least 80% of participants correctly locate and understand the information was achieved for 19 of the 20 questions. Five of the six instructions illustrated by pictograms were correctly understood by all participants. The only patient characteristics significantly associated with comprehension were educational level and self-reported ease of reading the PIL. Acceptability of the PIL was high and positive comments were associated with simplicity, good design, easy readability and user-friendliness, the latter enhanced by the inclusion of pictograms. Conclusion The PIL designed for this study was shown to be effective in communicating information about ARVs. Patient characteristics must be taken into account when developing written information, and the final document must be tested for comprehension in the target population.
- Full Text:
- Date Issued: 2007
- Authors: Mwingira, Betty , Dowse, Roslind
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6404 , http://hdl.handle.net/10962/d1006477
- Description: Objective To design and develop a simple, easily readable patient information leaflet (PIL) for a commonly used antiretroviral (ARV) regimen and to evaluate its readability and acceptability in a Tanzanian population. Method A PIL incorporating simple text and pictograms was designed for the antiretroviral regimen of stavudine, lamivudine and efavirenz. The PIL was designed according to established good design guidelines, modified during a multi-stage iterative testing process and piloted in a South African Xhosa population. The PIL was made available in both English and Kiswahili. Sixty Tanzanian participants who were not taking ARVs were interviewed. They were asked to read the PIL in the language of their choice and were then asked a series of two-part questions; the first part required participants to locate the information in the PIL, after which they were asked to explain the information in their own words. Acceptability was assessed through close-ended questions and open-ended feedback. The influence of selected patient characteristics on comprehension of the PIL was investigated using one-way ANOVA and t-tests for independent samples with a significance level set at 0.05. Main outcome measure Comprehension of the written information in an overall percentage understanding. Results The overall average percentage comprehension of the PIL was 95%. The target set by the EC guideline that at least 80% of participants correctly locate and understand the information was achieved for 19 of the 20 questions. Five of the six instructions illustrated by pictograms were correctly understood by all participants. The only patient characteristics significantly associated with comprehension were educational level and self-reported ease of reading the PIL. Acceptability of the PIL was high and positive comments were associated with simplicity, good design, easy readability and user-friendliness, the latter enhanced by the inclusion of pictograms. Conclusion The PIL designed for this study was shown to be effective in communicating information about ARVs. Patient characteristics must be taken into account when developing written information, and the final document must be tested for comprehension in the target population.
- Full Text:
- Date Issued: 2007
Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?
- Teske, Peter R, Lockyear, Jaqueline F, Hecht, Thomas, Kaiser, Horst
- Authors: Teske, Peter R , Lockyear, Jaqueline F , Hecht, Thomas , Kaiser, Horst
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6775 , http://hdl.handle.net/10962/d1008082
- Description: The Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South African estuaries. Its abundance within these systems is low and distributions are patchy. Consequently, monitoring population sizes is labour-intensive. The aim of this study was to establish if Knynsa seahorses are associated with specific regions within the estuaries, on which conservation efforts could concentrate. The relationship of Knysna seahorses with aquatic vegetation was analysed in the Knysna Estuary (the largest of the three estuarine systems inhabited by H. capensis) to determine whether this species shows a preference for a particular plant species, vegetation density or vegetation height. Seahorses were associated with five dominant aquatic plants: Zostera capensis, Caulerpa filiformis, Codium extricatum, Halophila ovalis and Ruppia cirrhosa. Together, these comprised 96% of the submerged objects with which seahorses were associated. The relative abundance of plant species changed along the estuary, but seahorses were present throughout the system, except at the estuary mouth, which was characterized by low plant densities and strong currents. No significant difference was found between the proportion of plant species present in a particular region of the estuary and the proportion of plants that seahorses used as holdfasts. However, when Z. capensis and C. filiformis were present at the same sites, adult seahorses preferred C. filiformis as holdfast. Adult seahorse density (individuals/m²) was significantly correlated with percentage vegetation cover and with holdfast length, but juvenile seahorse density was not. Nonetheless, significantly more adult and juvenile seahorses were found at sites characterized by high vegetation cover (>75%) than at sites with lower cover. Our results indicate that although there is some evidence that Knynsa seahorses prefer certain plant species over others, they are likely to be encountered anywhere in the estuary where aquatic plants are present. Conservation efforts in the Knysna Estuary should thus concentrate on such vegetated areas, which comprise approximately 11% of the total submerged surface area.
- Full Text:
- Date Issued: 2007
- Authors: Teske, Peter R , Lockyear, Jaqueline F , Hecht, Thomas , Kaiser, Horst
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6775 , http://hdl.handle.net/10962/d1008082
- Description: The Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South African estuaries. Its abundance within these systems is low and distributions are patchy. Consequently, monitoring population sizes is labour-intensive. The aim of this study was to establish if Knynsa seahorses are associated with specific regions within the estuaries, on which conservation efforts could concentrate. The relationship of Knysna seahorses with aquatic vegetation was analysed in the Knysna Estuary (the largest of the three estuarine systems inhabited by H. capensis) to determine whether this species shows a preference for a particular plant species, vegetation density or vegetation height. Seahorses were associated with five dominant aquatic plants: Zostera capensis, Caulerpa filiformis, Codium extricatum, Halophila ovalis and Ruppia cirrhosa. Together, these comprised 96% of the submerged objects with which seahorses were associated. The relative abundance of plant species changed along the estuary, but seahorses were present throughout the system, except at the estuary mouth, which was characterized by low plant densities and strong currents. No significant difference was found between the proportion of plant species present in a particular region of the estuary and the proportion of plants that seahorses used as holdfasts. However, when Z. capensis and C. filiformis were present at the same sites, adult seahorses preferred C. filiformis as holdfast. Adult seahorse density (individuals/m²) was significantly correlated with percentage vegetation cover and with holdfast length, but juvenile seahorse density was not. Nonetheless, significantly more adult and juvenile seahorses were found at sites characterized by high vegetation cover (>75%) than at sites with lower cover. Our results indicate that although there is some evidence that Knynsa seahorses prefer certain plant species over others, they are likely to be encountered anywhere in the estuary where aquatic plants are present. Conservation efforts in the Knysna Estuary should thus concentrate on such vegetated areas, which comprise approximately 11% of the total submerged surface area.
- Full Text:
- Date Issued: 2007
Dog Latin, Norman Morrissey : book review
- Authors: Beard, Margot
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6115 , http://hdl.handle.net/10962/d1003828
- Description: I have only seen one earlier collection of Morrissey's - his slim volume Seasons (1999). Therein he revealed his enjoyment and interest in haiku. Even the two longer poems in that volume were haiku-like, being brief self-contained stanzas grouped under a single title. His new volume, Dog Latin, consists of sixty short poems primarily concerned with man and nature. A number of these are haiku-like in their brevity ("Edgar on Inclusive Fitness," "Setting Ratbane," "Adam Again"), although they too often do not amount to more than post-it like notes. ("This habit / of holding habits to the wind / -me" is the sum total of the poem "Adam Again.") The epigraph to the whole collection is the final stanza of Robert Frost's "The Need of Being Versed in Country Things," which suggests both Morrissey's interest in the apparently unconsidered minutiae of natural objects and beings, and, it would seem, an admiration of Frost's deceptively plain, unmannered style.
- Full Text:
- Date Issued: 2007
- Authors: Beard, Margot
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6115 , http://hdl.handle.net/10962/d1003828
- Description: I have only seen one earlier collection of Morrissey's - his slim volume Seasons (1999). Therein he revealed his enjoyment and interest in haiku. Even the two longer poems in that volume were haiku-like, being brief self-contained stanzas grouped under a single title. His new volume, Dog Latin, consists of sixty short poems primarily concerned with man and nature. A number of these are haiku-like in their brevity ("Edgar on Inclusive Fitness," "Setting Ratbane," "Adam Again"), although they too often do not amount to more than post-it like notes. ("This habit / of holding habits to the wind / -me" is the sum total of the poem "Adam Again.") The epigraph to the whole collection is the final stanza of Robert Frost's "The Need of Being Versed in Country Things," which suggests both Morrissey's interest in the apparently unconsidered minutiae of natural objects and beings, and, it would seem, an admiration of Frost's deceptively plain, unmannered style.
- Full Text:
- Date Issued: 2007
Education is a spring… it bubbles
- Authors: Berger, Guy
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6333 , http://hdl.handle.net/10962/d1008478
- Description: [From the introduction]: Asians, Americans, Australians. A handful of Africans and a couple of Arabs. A sprinkling of Canadians, Mexicans, Finns. An Israeli, a Chilean and quite a few others. In total, 450 people from some 50 countries. In common: they’re all lecturers and trainers. Busy swopping notes in Singapore at the first-ever World Journalism Education Congress [WJEC] in July. It’s a resource-rich pool of ideas and experiences.
- Full Text:
- Date Issued: 2007
- Authors: Berger, Guy
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6333 , http://hdl.handle.net/10962/d1008478
- Description: [From the introduction]: Asians, Americans, Australians. A handful of Africans and a couple of Arabs. A sprinkling of Canadians, Mexicans, Finns. An Israeli, a Chilean and quite a few others. In total, 450 people from some 50 countries. In common: they’re all lecturers and trainers. Busy swopping notes in Singapore at the first-ever World Journalism Education Congress [WJEC] in July. It’s a resource-rich pool of ideas and experiences.
- Full Text:
- Date Issued: 2007
Effects of substituents on the photochemical and photophysical properties of main group metal phthalocyanines
- Authors: Nyokong, Tebello
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6581 , http://hdl.handle.net/10962/d1004146
- Description: The review focuses on the photochemical (singlet oxygen and photobleaching quantum yields) and photophysical (triplet quantum yields and lifetimes and fluorescence lifetimes) properties of metallophthalocyanine complexes containing main group metals (Zn, Al, Ge, Si, Sn, Ga and In) and some unmetallated phthalocyanine complexes. Five tables containing photophysical and photochemical data for sulfonated phthalocyanines, tetra-, octa-substituted and unsubstituted phthalocyanines in a variety of solvents, are included in the review.
- Full Text:
- Date Issued: 2007
- Authors: Nyokong, Tebello
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6581 , http://hdl.handle.net/10962/d1004146
- Description: The review focuses on the photochemical (singlet oxygen and photobleaching quantum yields) and photophysical (triplet quantum yields and lifetimes and fluorescence lifetimes) properties of metallophthalocyanine complexes containing main group metals (Zn, Al, Ge, Si, Sn, Ga and In) and some unmetallated phthalocyanine complexes. Five tables containing photophysical and photochemical data for sulfonated phthalocyanines, tetra-, octa-substituted and unsubstituted phthalocyanines in a variety of solvents, are included in the review.
- Full Text:
- Date Issued: 2007
Electrochemical characterisation of tetra- and octa-substituted oxo(phthalocyaninato)titanium(IV) complexes
- Tau, Prudence Lerato, Nyokong, Tebello
- Authors: Tau, Prudence Lerato , Nyokong, Tebello
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6598 , http://hdl.handle.net/10962/d1004347
- Description: The synthesis and electrochemical characterisation of the following oxotitanium tetra-substituted phthalocyanines are reported: 1,(4)-(tetrabenzyloxyphthalocyaninato)titanium(IV) oxide (5a); 1,(4)- {tetrakis[4-(benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide (5b); 2,(3)- (tetrabenzyloxyphthalocyaninato)titanium(IV) oxide (6a) and 2,(3)-{tetrakis[4- (benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide (6b). The electrochemical characterisation of complexes octa-substituted with 4-(benzyloxy)phenoxy (9b), phenoxy (9c) and tert -butylphenoxy (9d) groups is also reported. The cyclic voltammograms of the complexes exhibit reversible couples I–III and couple IV is quasi-reversible for complexes 5a, 5b, 6a and 6b. The first two reductions are metal-based processes, confirmed by spectroelectrochemistry to be due to Ti IV Pc 2 − /Ti III Pc 2 − and Ti III Pc 2 − /Ti II Pc 2 − redox processes and the last two reductions are ring-based processes due to Ti II Pc 2 − /Ti II Pc 3 − and Ti II Pc 3 − /Ti II Pc 4 − . Chronocoulometry confirmed a one-electron transfer at each reduction step. The electrochemistry of the above complexes is also compared to the previously reported 5c, 5d, 6c and 6d.
- Full Text:
- Date Issued: 2007
- Authors: Tau, Prudence Lerato , Nyokong, Tebello
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6598 , http://hdl.handle.net/10962/d1004347
- Description: The synthesis and electrochemical characterisation of the following oxotitanium tetra-substituted phthalocyanines are reported: 1,(4)-(tetrabenzyloxyphthalocyaninato)titanium(IV) oxide (5a); 1,(4)- {tetrakis[4-(benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide (5b); 2,(3)- (tetrabenzyloxyphthalocyaninato)titanium(IV) oxide (6a) and 2,(3)-{tetrakis[4- (benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide (6b). The electrochemical characterisation of complexes octa-substituted with 4-(benzyloxy)phenoxy (9b), phenoxy (9c) and tert -butylphenoxy (9d) groups is also reported. The cyclic voltammograms of the complexes exhibit reversible couples I–III and couple IV is quasi-reversible for complexes 5a, 5b, 6a and 6b. The first two reductions are metal-based processes, confirmed by spectroelectrochemistry to be due to Ti IV Pc 2 − /Ti III Pc 2 − and Ti III Pc 2 − /Ti II Pc 2 − redox processes and the last two reductions are ring-based processes due to Ti II Pc 2 − /Ti II Pc 3 − and Ti II Pc 3 − /Ti II Pc 4 − . Chronocoulometry confirmed a one-electron transfer at each reduction step. The electrochemistry of the above complexes is also compared to the previously reported 5c, 5d, 6c and 6d.
- Full Text:
- Date Issued: 2007
Enlarged arguments in Bantu : evidence from Chichewa
- Authors: Simango, Silvester Ron
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6140 , http://hdl.handle.net/10962/d1011592
- Description: This paper re-examines two types of constructions that have featured in the discussion of possessor ascension in Bantu: one type – an applicative construction – is associated with alienable possession, and the other – non-applicative – is associated with inalienable possession. The study shows that the former expresses affectedness, and that the possessor reading arises only by construal; whereas the latter expresses a part–whole relationship. The paper argues that the two constructions differ in more significant ways than has previously been acknowledged; and that their distinct derivations cannot be captured by traditional possessor ascension (PA) analyses. The putative “alienable” possessor constructions belong to the class of (benefactive) applicative constructions and should be analyzed as such. The paper proposes that the so-called “inalienable” possessor constructions can best be accounted for by positing the existence of “enlarged arguments” wherein the possessum functions as a nominal predicate which more narrowly pinpoints the locus of the action described by the verb.
- Full Text:
- Date Issued: 2007
- Authors: Simango, Silvester Ron
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6140 , http://hdl.handle.net/10962/d1011592
- Description: This paper re-examines two types of constructions that have featured in the discussion of possessor ascension in Bantu: one type – an applicative construction – is associated with alienable possession, and the other – non-applicative – is associated with inalienable possession. The study shows that the former expresses affectedness, and that the possessor reading arises only by construal; whereas the latter expresses a part–whole relationship. The paper argues that the two constructions differ in more significant ways than has previously been acknowledged; and that their distinct derivations cannot be captured by traditional possessor ascension (PA) analyses. The putative “alienable” possessor constructions belong to the class of (benefactive) applicative constructions and should be analyzed as such. The paper proposes that the so-called “inalienable” possessor constructions can best be accounted for by positing the existence of “enlarged arguments” wherein the possessum functions as a nominal predicate which more narrowly pinpoints the locus of the action described by the verb.
- Full Text:
- Date Issued: 2007
Ethnicity and nationalism in urban colonial Zimbabwe : Bulawayo, 1950 to 1963
- Authors: Msindo, Enocent
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6149 , http://hdl.handle.net/10962/d1006813 , http://dx.doi.org/10.1017/S0021853707002538
- Description: Zimbabwean historians have not yet fully assessed the interaction of two problematic identities, ethnicity and nationalism, to determine whether the two can work as partners and successfully co-exist. This essay argues that, in Bulawayo during the period studied, ethnicity co-existed with and complemented nationalism rather than the two working as polar opposite identities. Ethnic groups provided both the required leaders who became prominent nationalist figures and the precolonial history, personalities and monuments that sparked the nationalist imagination. From the 1950s, ethnic groups expanded their horizons and provided platforms from which emerging African nationalists launched their agenda. Understanding these interrelationships will reshape our understanding of the workings of these two identities in a cosmopolitan town.
- Full Text:
- Date Issued: 2007
- Authors: Msindo, Enocent
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6149 , http://hdl.handle.net/10962/d1006813 , http://dx.doi.org/10.1017/S0021853707002538
- Description: Zimbabwean historians have not yet fully assessed the interaction of two problematic identities, ethnicity and nationalism, to determine whether the two can work as partners and successfully co-exist. This essay argues that, in Bulawayo during the period studied, ethnicity co-existed with and complemented nationalism rather than the two working as polar opposite identities. Ethnic groups provided both the required leaders who became prominent nationalist figures and the precolonial history, personalities and monuments that sparked the nationalist imagination. From the 1950s, ethnic groups expanded their horizons and provided platforms from which emerging African nationalists launched their agenda. Understanding these interrelationships will reshape our understanding of the workings of these two identities in a cosmopolitan town.
- Full Text:
- Date Issued: 2007
Evaluating the impact of the Institutional Repository, or positioning innovation between a rock and a hard place
- Authors: Thomas, G M E
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6988 , http://hdl.handle.net/10962/d1012411
- Description: Repositories remain an innovative but marginalized technology largely because there is no consensus about an agreed set of Performance Indicators (PIs) that demonstrate their overall impact on the research enterprise of our universities. A successful Institutional Repository should be evaluated in terms of the extent to which the open access repository builds a critical mass of scholarly content which is sustained and available through active university community engagement and ongoing scholarly contributions (faculty, researchers & students) that, when managed efficiently and effectively, ultimately strengthen, promote and give visibility to the research enterprise of the institution, and bring benefit to broader society. However, librarians are grappling with what and how best to demonstrate ‘institutional good’ but without clear evidence, assessment is fed by perception based on limited information which leads to diminished impact and value of the facility, a tyranny described as being caught between a rock and a hard place. Using Illuminative Evaluation to design a series of quantitative and qualitative metrics, it is proposed that a distinction be made between significant and secondary Performance Indicators where the former gather evidence to demonstrate the overall effect or impact of the IR on the individual and collective research community.
- Full Text:
- Date Issued: 2007
- Authors: Thomas, G M E
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6988 , http://hdl.handle.net/10962/d1012411
- Description: Repositories remain an innovative but marginalized technology largely because there is no consensus about an agreed set of Performance Indicators (PIs) that demonstrate their overall impact on the research enterprise of our universities. A successful Institutional Repository should be evaluated in terms of the extent to which the open access repository builds a critical mass of scholarly content which is sustained and available through active university community engagement and ongoing scholarly contributions (faculty, researchers & students) that, when managed efficiently and effectively, ultimately strengthen, promote and give visibility to the research enterprise of the institution, and bring benefit to broader society. However, librarians are grappling with what and how best to demonstrate ‘institutional good’ but without clear evidence, assessment is fed by perception based on limited information which leads to diminished impact and value of the facility, a tyranny described as being caught between a rock and a hard place. Using Illuminative Evaluation to design a series of quantitative and qualitative metrics, it is proposed that a distinction be made between significant and secondary Performance Indicators where the former gather evidence to demonstrate the overall effect or impact of the IR on the individual and collective research community.
- Full Text:
- Date Issued: 2007
Factors affecting ethical judgement of South African chartered accountants
- Maree, Kevin W, Radloff, Sarah E
- Authors: Maree, Kevin W , Radloff, Sarah E
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: Article
- Identifier: vital:6073 , http://hdl.handle.net/10962/d1001647 , ISSN 1022-2529 , http://0-dx.doi.org.wam.seals.ac.za/10.1108/10222529200700001
- Description: The start of the twenty-first century was marred by a spate of company collapses that involved fraudulent accounting activity. In many cases, company executives, many of whom belonged to the accounting profession, perpetrated the fraud. As a result, internationally, the accounting profession has suffered an enormous loss of goodwill, and its reputation as a profession with integrity has been severely harmed. Accounting professionals are no longer accorded the high regard they commanded in the past. The consequences for the profession have been far-reaching: accounting now faces a long, uphill battle to restore its reputation and to regain the trust of the international business community. This study replicates two famous international studies in the South African context. The focus of the study was to establish whether factors such as the Code of Professional Conduct of the South African Institute of Chartered Accountants (SAICA), the corporate ethical environment and their age influence the ethical judgement of individual accountants. The first such study was conducted in the United States of America (USA), and it was followed by similar research in Turkey. The results of these two studies suggested very different factors that could influence accountants' ethical judgement. The study reported in this article investigated South African chartered accountants; and its results were similar to those obtained in the US study.
- Full Text:
- Date Issued: 2007
- Authors: Maree, Kevin W , Radloff, Sarah E
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: Article
- Identifier: vital:6073 , http://hdl.handle.net/10962/d1001647 , ISSN 1022-2529 , http://0-dx.doi.org.wam.seals.ac.za/10.1108/10222529200700001
- Description: The start of the twenty-first century was marred by a spate of company collapses that involved fraudulent accounting activity. In many cases, company executives, many of whom belonged to the accounting profession, perpetrated the fraud. As a result, internationally, the accounting profession has suffered an enormous loss of goodwill, and its reputation as a profession with integrity has been severely harmed. Accounting professionals are no longer accorded the high regard they commanded in the past. The consequences for the profession have been far-reaching: accounting now faces a long, uphill battle to restore its reputation and to regain the trust of the international business community. This study replicates two famous international studies in the South African context. The focus of the study was to establish whether factors such as the Code of Professional Conduct of the South African Institute of Chartered Accountants (SAICA), the corporate ethical environment and their age influence the ethical judgement of individual accountants. The first such study was conducted in the United States of America (USA), and it was followed by similar research in Turkey. The results of these two studies suggested very different factors that could influence accountants' ethical judgement. The study reported in this article investigated South African chartered accountants; and its results were similar to those obtained in the US study.
- Full Text:
- Date Issued: 2007
First evidence for the Cenomanian-Turonian oceanic anoxic event (OAE2, Bonarelli event) from the Ionian Zone, western continental Greece
- Karakitsios, V, Tsikos, Harilaos, Van Breugel, Y, Koletti, L, Sinninghe Damsté, J S, Jenkyns, H C
- Authors: Karakitsios, V , Tsikos, Harilaos , Van Breugel, Y , Koletti, L , Sinninghe Damsté, J S , Jenkyns, H C
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6735 , http://hdl.handle.net/10962/d1007547
- Description: Integrated biostratigraphic (planktonic foraminifera, calcareous nannofossils), chemostratigraphic (bulk C and O isotopes) and compound-specific organic geochemical studies of a mid-Cretaceous pelagic carbonate—black shale succession of the Ionian Zone (western Greece), provide the first evidence for the Cenomanian–Turonian oceanic anoxic event (OAE2, ‘Bonarelli’ event) in mainland Greece. The event is manifested by the occurrence of a relatively thin (35 cm), yet exceptionally organic carbon-rich (44.5 wt% TOC), carbonate-free black shale, near the Cenomanian–Turonian boundary within the Vigla limestone formation (Berriasian–Turonian). Compared to the ‘Bonarelli’ black-shale interval from the type locality of OAE2 in Marche–Umbria, Italy, this black shale exhibits greatly reduced stratigraphic thickness, coupled with a considerable relative enrichment in TOC. Isotopically, enriched δ[superscript 13]C values for both bulk organic matter (−22.2‰) and specific organic compounds are up to 5‰ higher than those of underlying organic-rich strata of the Aptian-lower Albian Vigla Shale member, and thus compare very well with similar values of Cenomanian–Turonian black shale occurrences elsewhere. The relative predominance of bacterial hopanoids in the saturated, apolar lipid fraction of the OAE2 black shale of the Ionian Zone supports recent findings suggesting the abundance of N[subscript 2]-fixing cyanobacteria in Cretaceous oceans during the Cenomanian–Turonian and early Aptian oceanic anoxic events.
- Full Text:
- Date Issued: 2007
- Authors: Karakitsios, V , Tsikos, Harilaos , Van Breugel, Y , Koletti, L , Sinninghe Damsté, J S , Jenkyns, H C
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6735 , http://hdl.handle.net/10962/d1007547
- Description: Integrated biostratigraphic (planktonic foraminifera, calcareous nannofossils), chemostratigraphic (bulk C and O isotopes) and compound-specific organic geochemical studies of a mid-Cretaceous pelagic carbonate—black shale succession of the Ionian Zone (western Greece), provide the first evidence for the Cenomanian–Turonian oceanic anoxic event (OAE2, ‘Bonarelli’ event) in mainland Greece. The event is manifested by the occurrence of a relatively thin (35 cm), yet exceptionally organic carbon-rich (44.5 wt% TOC), carbonate-free black shale, near the Cenomanian–Turonian boundary within the Vigla limestone formation (Berriasian–Turonian). Compared to the ‘Bonarelli’ black-shale interval from the type locality of OAE2 in Marche–Umbria, Italy, this black shale exhibits greatly reduced stratigraphic thickness, coupled with a considerable relative enrichment in TOC. Isotopically, enriched δ[superscript 13]C values for both bulk organic matter (−22.2‰) and specific organic compounds are up to 5‰ higher than those of underlying organic-rich strata of the Aptian-lower Albian Vigla Shale member, and thus compare very well with similar values of Cenomanian–Turonian black shale occurrences elsewhere. The relative predominance of bacterial hopanoids in the saturated, apolar lipid fraction of the OAE2 black shale of the Ionian Zone supports recent findings suggesting the abundance of N[subscript 2]-fixing cyanobacteria in Cretaceous oceans during the Cenomanian–Turonian and early Aptian oceanic anoxic events.
- Full Text:
- Date Issued: 2007
Freshwater invertebrate fauna of the Tristan da Cunha islands (South Atlantic Ocean), with new records for Inaccessible and Nightingale Islands
- Authors: Barber-James, Helen M
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:7001 , http://hdl.handle.net/10962/d1008360
- Description: As part of a multidisciplinary floristic-faunistic study, a three week survey of the invertebrate fauna of Inaccessible Island (South Atlantic Ocean) was carried out in October / November 1989. In addition, one day of collecting was done on Nightingale Island. This paper deals only with the fauna associated with freshwater ecosystems from these islands, some of which are usually associated with marine or brackish conditions. On Inaccessible Island, five distinct types of freshwater body were identified - pH neutral streams, acidic streams (pH 5), an open pool of standing water (pH 6), areas of acidic bog, and seepages down rock faces. The survey, the most comprehensive for Inaccessible Island to date, has resulted in the discovery of 19 aquatic invertebrate species previously unrecorded on Inaccessible Island, two new to Nightingale Island, and 14 of which are new to the Tristan da Cunha archipelago. Many of the species are known from other parts of the world, indicating a low degree of endemicity within the freshwater invertebrate community. Recolonisation from the source populations, preventing an isolated gene pool, may account for the low endemicity. Several of the species have a degree of salinity tolerance, enabling them to withstand transportation across tracts of ocean, and others have marine origins.
- Full Text:
- Date Issued: 2007
- Authors: Barber-James, Helen M
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:7001 , http://hdl.handle.net/10962/d1008360
- Description: As part of a multidisciplinary floristic-faunistic study, a three week survey of the invertebrate fauna of Inaccessible Island (South Atlantic Ocean) was carried out in October / November 1989. In addition, one day of collecting was done on Nightingale Island. This paper deals only with the fauna associated with freshwater ecosystems from these islands, some of which are usually associated with marine or brackish conditions. On Inaccessible Island, five distinct types of freshwater body were identified - pH neutral streams, acidic streams (pH 5), an open pool of standing water (pH 6), areas of acidic bog, and seepages down rock faces. The survey, the most comprehensive for Inaccessible Island to date, has resulted in the discovery of 19 aquatic invertebrate species previously unrecorded on Inaccessible Island, two new to Nightingale Island, and 14 of which are new to the Tristan da Cunha archipelago. Many of the species are known from other parts of the world, indicating a low degree of endemicity within the freshwater invertebrate community. Recolonisation from the source populations, preventing an isolated gene pool, may account for the low endemicity. Several of the species have a degree of salinity tolerance, enabling them to withstand transportation across tracts of ocean, and others have marine origins.
- Full Text:
- Date Issued: 2007
Freshwater invertebrate fauna of the Tristan da Cunha islands (South Atlantic Ocean), with new records for Inaccessible and Nightingale Islands
- Barber-James, Helen Margaret
- Authors: Barber-James, Helen Margaret
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6940 , http://hdl.handle.net/10962/d1011964
- Description: As part of a multidisciplinary floristic-faunistic study, a three week survey of the invertebrate fauna of Inaccessible Island (South Atlantic Ocean) was carried out in October / November 1989. In addition, one day of collecting was done on Nightingale Island. This paper deals only with the fauna associated with freshwater ecosystems from these islands, some of which are usually associated with marine or brackish conditions. On Inaccessible Island, five distinct types of freshwater body were identified - pH neutral streams, acidic streams (pH 5), an open pool of standing water (pH 6), areas of acidic bog, and seepages down rock faces. The survey, the most comprehensive for Inaccessible Island to date, has resulted in the discovery of 19 aquatic invertebrate species previously unrecorded on Inaccessible Island, two new to Nightingale Island, and 14 of which are new to the Tristan da Cunha archipelago. Many of the species are known from other parts of the world, indicating a low degree of endemicity within the freshwater invertebrate community. Recolonisation from the source populations, preventing an isolated gene pool, may account for the low endemicity. Several of the species have a degree of salinity tolerance, enabling them to withstand transportation across tracts of ocean, and others have marine origins.
- Full Text:
- Date Issued: 2007
- Authors: Barber-James, Helen Margaret
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6940 , http://hdl.handle.net/10962/d1011964
- Description: As part of a multidisciplinary floristic-faunistic study, a three week survey of the invertebrate fauna of Inaccessible Island (South Atlantic Ocean) was carried out in October / November 1989. In addition, one day of collecting was done on Nightingale Island. This paper deals only with the fauna associated with freshwater ecosystems from these islands, some of which are usually associated with marine or brackish conditions. On Inaccessible Island, five distinct types of freshwater body were identified - pH neutral streams, acidic streams (pH 5), an open pool of standing water (pH 6), areas of acidic bog, and seepages down rock faces. The survey, the most comprehensive for Inaccessible Island to date, has resulted in the discovery of 19 aquatic invertebrate species previously unrecorded on Inaccessible Island, two new to Nightingale Island, and 14 of which are new to the Tristan da Cunha archipelago. Many of the species are known from other parts of the world, indicating a low degree of endemicity within the freshwater invertebrate community. Recolonisation from the source populations, preventing an isolated gene pool, may account for the low endemicity. Several of the species have a degree of salinity tolerance, enabling them to withstand transportation across tracts of ocean, and others have marine origins.
- Full Text:
- Date Issued: 2007
Global diversity of mayflies (Ephemeroptera, Insecta) in freshwater
- Barber-James, Helen M, Gattolliat, Jean-Luc, Sartori, Michel, Hubbard, Michael D
- Authors: Barber-James, Helen M , Gattolliat, Jean-Luc , Sartori, Michel , Hubbard, Michael D
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:7002 , http://hdl.handle.net/10962/d1008361
- Description: The extant global Ephemeroptera fauna is represented by over 3,000 described species in 42 families and more than 400 genera. The highest generic diversity occurs in the Neotropics, with a correspondingly high species diversity, while the Palaearctic has the lowest generic diversity, but a high species diversity. Such distribution patterns may relate to how long evolutionary processes have been carrying on in isolation in a bioregion. Over an extended period, there may be extinction of species, but evolution of more genera. Dramatic extinction events such as the K-T mass extinction have affected current mayfly diversity and distribution. Climatic history plays an important role in the rate of speciation in an area, with regions which have been climatically stable over long periods having fewer species per genus, when compared to regions subjected to climatic stresses, such as glaciation. A total of 13 families are endemic to specific bioregions, with eight among them being monospecific. Most of these have restricted distributions which may be the result of them being the relict of a previously more diverse, but presently almost completely extinct family, or may be the consequence of vicariance events, resulting from evolution due to long-term isolation.
- Full Text:
- Date Issued: 2007
- Authors: Barber-James, Helen M , Gattolliat, Jean-Luc , Sartori, Michel , Hubbard, Michael D
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:7002 , http://hdl.handle.net/10962/d1008361
- Description: The extant global Ephemeroptera fauna is represented by over 3,000 described species in 42 families and more than 400 genera. The highest generic diversity occurs in the Neotropics, with a correspondingly high species diversity, while the Palaearctic has the lowest generic diversity, but a high species diversity. Such distribution patterns may relate to how long evolutionary processes have been carrying on in isolation in a bioregion. Over an extended period, there may be extinction of species, but evolution of more genera. Dramatic extinction events such as the K-T mass extinction have affected current mayfly diversity and distribution. Climatic history plays an important role in the rate of speciation in an area, with regions which have been climatically stable over long periods having fewer species per genus, when compared to regions subjected to climatic stresses, such as glaciation. A total of 13 families are endemic to specific bioregions, with eight among them being monospecific. Most of these have restricted distributions which may be the result of them being the relict of a previously more diverse, but presently almost completely extinct family, or may be the consequence of vicariance events, resulting from evolution due to long-term isolation.
- Full Text:
- Date Issued: 2007
Gowin's Knowledge Vee and the integration of philosophy and methodology : a case study
- Authors: Fox, Roddy C
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6682 , http://hdl.handle.net/10962/d1006677
- Description: Universities with a strong research tradition commonly have courses or modules examining the tradition’s philosophies and methodologies to prepare their students to undertake research programmes. Recently, however, authors have called for wider debate concerning how we teach these courses and this paper is intended, in part, to make a contribution to this debate. The Research Philosophy and Methodology module examined here makes an intriguing case study because of a number of distinctive characteristics. The teaching philosophy of the module is social constructivist and it uses Gowin’s Knowledge Vee as its main heuristic device. This facilitates the construction of knowledge about philosophy and methodology in an integrated manner. The module has also been designed for both physical and human geography students at the introductory post-graduate level. There is, therefore, a second element of integration in the curriculum. Lastly, the module is predominantly web-based, being taken by distance students through the exchange agreement between Rhodes University, South Africa, and the University of Trollhättan-Uddevalla, Sweden. Evidence from reflective exercises shows that the learners’ understanding of research and the research process has deepened considerably through using Gowin’s Vee. Furthermore, using the Knowledge Vee in the web-based context has facilitated the integrative aspects of the module.
- Full Text:
- Date Issued: 2007
- Authors: Fox, Roddy C
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6682 , http://hdl.handle.net/10962/d1006677
- Description: Universities with a strong research tradition commonly have courses or modules examining the tradition’s philosophies and methodologies to prepare their students to undertake research programmes. Recently, however, authors have called for wider debate concerning how we teach these courses and this paper is intended, in part, to make a contribution to this debate. The Research Philosophy and Methodology module examined here makes an intriguing case study because of a number of distinctive characteristics. The teaching philosophy of the module is social constructivist and it uses Gowin’s Knowledge Vee as its main heuristic device. This facilitates the construction of knowledge about philosophy and methodology in an integrated manner. The module has also been designed for both physical and human geography students at the introductory post-graduate level. There is, therefore, a second element of integration in the curriculum. Lastly, the module is predominantly web-based, being taken by distance students through the exchange agreement between Rhodes University, South Africa, and the University of Trollhättan-Uddevalla, Sweden. Evidence from reflective exercises shows that the learners’ understanding of research and the research process has deepened considerably through using Gowin’s Vee. Furthermore, using the Knowledge Vee in the web-based context has facilitated the integrative aspects of the module.
- Full Text:
- Date Issued: 2007
GPS TEC and ionosonde TEC over Grahamstown, South Africa: first comparisons
- McKinnell, Lee-Anne, Opperman, Ben D L, Cilliers, Pierre J
- Authors: McKinnell, Lee-Anne , Opperman, Ben D L , Cilliers, Pierre J
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6800 , http://hdl.handle.net/10962/d1004163
- Description: The Grahamstown, South Africa (33.3°S, 26.5°E) ionospheric field station operates a UMass Lowell digital pulse ionospheric sounder (Digisonde) and an Ashtech geodetic grade dual frequency GPS receiver. The GPS receiver is owned by Chief Directorate Surveys and Mapping (CDSM) in Cape Town, forms part of the national TrigNet network and was installed in February 2005. The sampling rates of the GPS receiver and Digisonde were set to 1 s and 15 min, respectively. Data from four continuous months, March–June 2005 inclusive, were considered in this initial investigation. Data available from the Grahamstown GPS receiver was limited, and, therefore, only these 4 months have been considered. Total Electron Content (TEC) values were determined from GPS measurements obtained from satellites passing near vertical (within an 80° elevation) to the station. TEC values were obtained from ionograms recorded at times within 5 min of the near vertical GPS measurement. The GPS derived TEC values are referred to as GTEC and the ionogram derived TEC values as ITEC. Comparisons of GTEC and ITEC values are presented in this paper. The differential clock biases of the GPS satellites and receivers are taken into account. The plasmaspheric contribution to the TEC can be inferred from the results, and confirm findings obtained by other groups. This paper describes the groundwork for a procedure that will allow the validation of GPS derived ionospheric information with ionosonde data. This work will be of interest to the International Reference Ionosphere (IRI) community since GPS receivers are becoming recognised as another source for ionospheric information.
- Full Text:
- Date Issued: 2007
- Authors: McKinnell, Lee-Anne , Opperman, Ben D L , Cilliers, Pierre J
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6800 , http://hdl.handle.net/10962/d1004163
- Description: The Grahamstown, South Africa (33.3°S, 26.5°E) ionospheric field station operates a UMass Lowell digital pulse ionospheric sounder (Digisonde) and an Ashtech geodetic grade dual frequency GPS receiver. The GPS receiver is owned by Chief Directorate Surveys and Mapping (CDSM) in Cape Town, forms part of the national TrigNet network and was installed in February 2005. The sampling rates of the GPS receiver and Digisonde were set to 1 s and 15 min, respectively. Data from four continuous months, March–June 2005 inclusive, were considered in this initial investigation. Data available from the Grahamstown GPS receiver was limited, and, therefore, only these 4 months have been considered. Total Electron Content (TEC) values were determined from GPS measurements obtained from satellites passing near vertical (within an 80° elevation) to the station. TEC values were obtained from ionograms recorded at times within 5 min of the near vertical GPS measurement. The GPS derived TEC values are referred to as GTEC and the ionogram derived TEC values as ITEC. Comparisons of GTEC and ITEC values are presented in this paper. The differential clock biases of the GPS satellites and receivers are taken into account. The plasmaspheric contribution to the TEC can be inferred from the results, and confirm findings obtained by other groups. This paper describes the groundwork for a procedure that will allow the validation of GPS derived ionospheric information with ionosonde data. This work will be of interest to the International Reference Ionosphere (IRI) community since GPS receivers are becoming recognised as another source for ionospheric information.
- Full Text:
- Date Issued: 2007
Growth of Aloe ferox Mill. at selected sites in the Makana region of the Eastern Cape
- Shackleton, Charlie M, Gambiza, James
- Authors: Shackleton, Charlie M , Gambiza, James
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6654 , http://hdl.handle.net/10962/d1007068
- Description: There is widespread harvesting of the leaves of Aloe ferox to supply bitters and gel for cosmetic and health products. Government and private agencies are interested in expanding the industry as a means of providing income for poor rural communities. With the growing interest in the commercial use of A. ferox it is important that harvesting programmes are based on an adequate understanding of the ecology and productivity of the species, which will underpin estimates of possible sustainable yields. In this paper we report mean annual growth rates of 283 A. ferox plants (at six sites) during the 2005/2006 season. Growth was variable across sites and plant height. In terms of sites, the mean height growth ranged between 1.7 cm per plant per year at site 4 and 4.6 cm at site 2. The mean height increment across all sites and plants was 2.8 ± 0.2 cm. Plant height had a strong effect on annual increment with small plants (< 6 cm) more than doubling their height in the 12 month period, whereas plants taller than 2 m grew by approximately 1% over the year. Across the five unburnt sites, the mean standing stock of leaves grew by two per plant. The proportion of plants flowering increased progressively with plant height. Most (90%) of the plants that flowered in 2005 did so again in 2006.
- Full Text:
- Date Issued: 2007
- Authors: Shackleton, Charlie M , Gambiza, James
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6654 , http://hdl.handle.net/10962/d1007068
- Description: There is widespread harvesting of the leaves of Aloe ferox to supply bitters and gel for cosmetic and health products. Government and private agencies are interested in expanding the industry as a means of providing income for poor rural communities. With the growing interest in the commercial use of A. ferox it is important that harvesting programmes are based on an adequate understanding of the ecology and productivity of the species, which will underpin estimates of possible sustainable yields. In this paper we report mean annual growth rates of 283 A. ferox plants (at six sites) during the 2005/2006 season. Growth was variable across sites and plant height. In terms of sites, the mean height growth ranged between 1.7 cm per plant per year at site 4 and 4.6 cm at site 2. The mean height increment across all sites and plants was 2.8 ± 0.2 cm. Plant height had a strong effect on annual increment with small plants (< 6 cm) more than doubling their height in the 12 month period, whereas plants taller than 2 m grew by approximately 1% over the year. Across the five unburnt sites, the mean standing stock of leaves grew by two per plant. The proportion of plants flowering increased progressively with plant height. Most (90%) of the plants that flowered in 2005 did so again in 2006.
- Full Text:
- Date Issued: 2007