A generic virtual reality interaction system and its extensions using the common object request broker architecture (CORBA)
- Rorke, Michael, Bangay, Shaun D
- Authors: Rorke, Michael , Bangay, Shaun D
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432684 , vital:72892 , https://www.cs.ru.ac.za/research/Groups/vrsig/pastprojects/013interaction/paper03.pdf
- Description: The paper describes the design and implementation of an immersive Virtual Reality (VR) interaction system. The system aims to provide a flexible mechanism for programmers to implement interaction in their VR applications, making good use of all accepted practices in the field. The paper further describes how the system was extended to a multi-user system using the CORBA middleware layer.
- Full Text:
- Authors: Rorke, Michael , Bangay, Shaun D
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432684 , vital:72892 , https://www.cs.ru.ac.za/research/Groups/vrsig/pastprojects/013interaction/paper03.pdf
- Description: The paper describes the design and implementation of an immersive Virtual Reality (VR) interaction system. The system aims to provide a flexible mechanism for programmers to implement interaction in their VR applications, making good use of all accepted practices in the field. The paper further describes how the system was extended to a multi-user system using the CORBA middleware layer.
- Full Text:
A Prototyping Environment for Investigating Context Aware Wearable Applications.
- Tsegaye, Melekam, Bangay, Shaun D, Terzoli, Alfredo
- Authors: Tsegaye, Melekam , Bangay, Shaun D , Terzoli, Alfredo
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432783 , vital:72900 , https://www.cs.ru.ac.za/research/g98t4414/static/papers/wearprototsegaye05.pdf
- Description: In this paper we introduce the concept of a contextaware, wearable application prototyping environment, which can be used to support research into new wearable applications. We also present an initial specification for such an environment and show how different types of sensors can be modelled to produce data that describes a given context scenario using our prototyping approach.
- Full Text:
- Authors: Tsegaye, Melekam , Bangay, Shaun D , Terzoli, Alfredo
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432783 , vital:72900 , https://www.cs.ru.ac.za/research/g98t4414/static/papers/wearprototsegaye05.pdf
- Description: In this paper we introduce the concept of a contextaware, wearable application prototyping environment, which can be used to support research into new wearable applications. We also present an initial specification for such an environment and show how different types of sensors can be modelled to produce data that describes a given context scenario using our prototyping approach.
- Full Text:
Adsorptive cathodic stripping voltammetric determination of gold (III) in the presence of yeast mannan
- Lack, Barbara, Duncan, John R, Nyokong, Tebello
- Authors: Lack, Barbara , Duncan, John R , Nyokong, Tebello
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293151 , vital:57060 , xlink:href="https://doi.org/10.1016/S0003-2670(98)00736-3"
- Description: Adsorptive cathodic stripping voltammetric (AdCSV) studies of gold(III) on a glassy carbon electrode and in the presence of yeast mannan are reported. These studies give evidence of the formation of a complex between gold(III) and mannan in acid media as judged by the enhancement in the AdCSV currents and shift in the reduction peak of gold(III) in the presence of mannan. The AdCSV currents were linearly dependent on gold(III) concentrations ranging from 7.0 × 10−7 to 3.0 × 10−4 mol dm−3. A detection limit of 6.0 × 10−8 mol dm−3 was obtained. Interferences of copper(II) were observed in the presence of mannan, but there was no significant interference of silver(I).
- Full Text:
- Authors: Lack, Barbara , Duncan, John R , Nyokong, Tebello
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293151 , vital:57060 , xlink:href="https://doi.org/10.1016/S0003-2670(98)00736-3"
- Description: Adsorptive cathodic stripping voltammetric (AdCSV) studies of gold(III) on a glassy carbon electrode and in the presence of yeast mannan are reported. These studies give evidence of the formation of a complex between gold(III) and mannan in acid media as judged by the enhancement in the AdCSV currents and shift in the reduction peak of gold(III) in the presence of mannan. The AdCSV currents were linearly dependent on gold(III) concentrations ranging from 7.0 × 10−7 to 3.0 × 10−4 mol dm−3. A detection limit of 6.0 × 10−8 mol dm−3 was obtained. Interferences of copper(II) were observed in the presence of mannan, but there was no significant interference of silver(I).
- Full Text:
Anting in Afrotropical birds: a review
- Authors: Craig, Adrian J F K
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447746 , vital:74671 , https://doi.org/10.1080/00306525.1999.9634237
- Description: Passive anting has been recorded from four non-passerine species in Africa, the Rock Kestrel Falco tinnunculus, the African Finfoot Podica senegalensis, the African Hoopoe Upupa epops and the Whitebacked Mousebird Colius colius. Active or passive anting has been recorded from 21 passerine species in 10 families in the wild, and in captive birds in a further 27 species of 3 families. Although such behaviour may have been overlooked or misinterpreted, the rarity of observations implies that in most species anting is likely to be infrequent. In all cases in which the ants have been identified, they were members of the sub-family Formicinae. It appears unlikely that any single functional explanation can account for the observed occurrences of this behaviour.
- Full Text:
- Authors: Craig, Adrian J F K
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447746 , vital:74671 , https://doi.org/10.1080/00306525.1999.9634237
- Description: Passive anting has been recorded from four non-passerine species in Africa, the Rock Kestrel Falco tinnunculus, the African Finfoot Podica senegalensis, the African Hoopoe Upupa epops and the Whitebacked Mousebird Colius colius. Active or passive anting has been recorded from 21 passerine species in 10 families in the wild, and in captive birds in a further 27 species of 3 families. Although such behaviour may have been overlooked or misinterpreted, the rarity of observations implies that in most species anting is likely to be infrequent. In all cases in which the ants have been identified, they were members of the sub-family Formicinae. It appears unlikely that any single functional explanation can account for the observed occurrences of this behaviour.
- Full Text:
Cicadas (Hemiptera, Homoptera: Cicadoidea) of Mkomazi
- Villet, Martin H, van Noort, Simon, Packer, M
- Authors: Villet, Martin H , van Noort, Simon , Packer, M
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/442756 , vital:74030 , ISBN , https://doi.org/10.1046/j.1472-4642.2001.00094.x
- Description: The cicadas are a group of insects belonging to the order Hemiptera which comprises a diverse range of insects including the bugs, leafhoppers, aphids, scale insects etc. The Hemiptera are characterised by specialised mouth parts that are adapted for piercing and sucking up sap from host plants or animal juices from their prey. All cicadas are plant feeders and can be extremely camouflaged when sitting and feeding on a branch, although the males give themselves away by their persistent, often high pitched calls.
- Full Text:
- Authors: Villet, Martin H , van Noort, Simon , Packer, M
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/442756 , vital:74030 , ISBN , https://doi.org/10.1046/j.1472-4642.2001.00094.x
- Description: The cicadas are a group of insects belonging to the order Hemiptera which comprises a diverse range of insects including the bugs, leafhoppers, aphids, scale insects etc. The Hemiptera are characterised by specialised mouth parts that are adapted for piercing and sucking up sap from host plants or animal juices from their prey. All cicadas are plant feeders and can be extremely camouflaged when sitting and feeding on a branch, although the males give themselves away by their persistent, often high pitched calls.
- Full Text:
Cobalt (II) porphyrazine catalysed reduction of nitrite
- Thamae, Mamothibe, Nyokong, Tebello
- Authors: Thamae, Mamothibe , Nyokong, Tebello
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293162 , vital:57061 , xlink:href="https://doi.org/10.1016/S0022-0728(99)00224-7"
- Description: Studies on the catalytic reduction of nitrite on carbon electrodes modified with Co(II) tetra-2,3-pyridinoporphyrazine (CoTppa, 1), N,N′,N′′,N′′′-tetramethyltetra-2,3-pyridinoporphyrazine ([CoTm-2,3-tppa]4+, 2) and Co(II) N,N′,N′′,N′′′-tetramethyltetra-3,4-pyridinoporphyrazine ([CoTm-3,4-tppa]4+, 3) are reported. There is a close correspondence between the proximity of the methyl groups to the porphyrazine ring and the catalytic activity of the porphyrazine complexes. Bulk electrolysis gave ammonia and hydroxylamine as some of the products. The catalytic activity of the cationic complex, 3, towards the detection of low concentrations of nitrite (less than 10−9 M) in water containing sodium sulfate, was compared with the activities of the anionic cobalt(II) tetrasulfophthalocyanine ([CoTSPc]4−, 4) and the mixed [CoIITm-3,4-tppa]4+·[CoTSPc]4− (5) complexes. Complex 5 showed the best catalytic activity of the three in that large currents were obtained for very low concentrations of nitrite.
- Full Text:
- Authors: Thamae, Mamothibe , Nyokong, Tebello
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293162 , vital:57061 , xlink:href="https://doi.org/10.1016/S0022-0728(99)00224-7"
- Description: Studies on the catalytic reduction of nitrite on carbon electrodes modified with Co(II) tetra-2,3-pyridinoporphyrazine (CoTppa, 1), N,N′,N′′,N′′′-tetramethyltetra-2,3-pyridinoporphyrazine ([CoTm-2,3-tppa]4+, 2) and Co(II) N,N′,N′′,N′′′-tetramethyltetra-3,4-pyridinoporphyrazine ([CoTm-3,4-tppa]4+, 3) are reported. There is a close correspondence between the proximity of the methyl groups to the porphyrazine ring and the catalytic activity of the porphyrazine complexes. Bulk electrolysis gave ammonia and hydroxylamine as some of the products. The catalytic activity of the cationic complex, 3, towards the detection of low concentrations of nitrite (less than 10−9 M) in water containing sodium sulfate, was compared with the activities of the anionic cobalt(II) tetrasulfophthalocyanine ([CoTSPc]4−, 4) and the mixed [CoIITm-3,4-tppa]4+·[CoTSPc]4− (5) complexes. Complex 5 showed the best catalytic activity of the three in that large currents were obtained for very low concentrations of nitrite.
- Full Text:
Common Property Models of Sea Tenure: A Case Study from the Roviana and Vonavona Lagoons, New Georgia, Solomon Islands
- Authors: Shankar, Aswani
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/439865 , vital:73715 , xlink:href="https://doi.org/10.1023/A:1018727607651"
- Description: In recent decades, Pacific Region indigenous sea tenure regimes have received considerable attention from social scientists who believe thatmarine-localized common entitlements and fishing practices can aid modern littoral fisheries management. The endorsement of sea tenure institutions as managerial tools, however, has proceeded without adequate consideration of their vulnerability to social and economic changes. The general view held by researchers is that Pacific Island Sea tenure regimes are generally undermined by the influence of exogenous forces resulting in an open-access commons. In this article, it is argued that the contemporary transformation of sea tenure regimes emerges not only from exogenous agency, but from a complex set of autochthonous processes. A case study from New Georgia, Solomon Islands, is presented to show how sea tenure regimes can vary within an ethnically and culturally homogeneous region. Three tenure models are presented to show how different pre- and post-European contact regional settlement patterns, localized processes of political expansion and contraction, and dynamic indigenous sociocultural principles have resulted in institutional differences between each sea tenure model. The effect of the market economy on the organizational structure and managerial outcomes of each model also is discussed.
- Full Text:
- Authors: Shankar, Aswani
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/439865 , vital:73715 , xlink:href="https://doi.org/10.1023/A:1018727607651"
- Description: In recent decades, Pacific Region indigenous sea tenure regimes have received considerable attention from social scientists who believe thatmarine-localized common entitlements and fishing practices can aid modern littoral fisheries management. The endorsement of sea tenure institutions as managerial tools, however, has proceeded without adequate consideration of their vulnerability to social and economic changes. The general view held by researchers is that Pacific Island Sea tenure regimes are generally undermined by the influence of exogenous forces resulting in an open-access commons. In this article, it is argued that the contemporary transformation of sea tenure regimes emerges not only from exogenous agency, but from a complex set of autochthonous processes. A case study from New Georgia, Solomon Islands, is presented to show how sea tenure regimes can vary within an ethnically and culturally homogeneous region. Three tenure models are presented to show how different pre- and post-European contact regional settlement patterns, localized processes of political expansion and contraction, and dynamic indigenous sociocultural principles have resulted in institutional differences between each sea tenure model. The effect of the market economy on the organizational structure and managerial outcomes of each model also is discussed.
- Full Text:
Creating a Web-based Spatiotemporal GIS using Java and VRML
- Clayton, Peter G, Wells, George C, Preston, Michael
- Authors: Clayton, Peter G , Wells, George C , Preston, Michael
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433413 , vital:72968 , https://www.learntechlib.org/p/7417/
- Description: This paper presents our approach towards creating a Web-based Spatiotemporal Geographic Information System, in particular, the creation of the spatial data set and the component interaction. It explores the possibility of rendering Virtual GIS Worlds in near real time across the WWW using a standard Web browser as the user interface. A" proof of concept" Web-based VGIS application was developed to investigate methods for the efficient transfer of high-bandwidth multimedia GIS content over the WWW, as well as providing a suitable development environment for research into Web-based Temporal GIS. This paper describes how VRML and Java were used to provide the visualisation of virtual worlds, interaction with individual objects inside the virtual world, and the query tools for adding, deleting, selecting or manipulating these objects or their associated attribute data.
- Full Text:
- Authors: Clayton, Peter G , Wells, George C , Preston, Michael
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433413 , vital:72968 , https://www.learntechlib.org/p/7417/
- Description: This paper presents our approach towards creating a Web-based Spatiotemporal Geographic Information System, in particular, the creation of the spatial data set and the component interaction. It explores the possibility of rendering Virtual GIS Worlds in near real time across the WWW using a standard Web browser as the user interface. A" proof of concept" Web-based VGIS application was developed to investigate methods for the efficient transfer of high-bandwidth multimedia GIS content over the WWW, as well as providing a suitable development environment for research into Web-based Temporal GIS. This paper describes how VRML and Java were used to provide the visualisation of virtual worlds, interaction with individual objects inside the virtual world, and the query tools for adding, deleting, selecting or manipulating these objects or their associated attribute data.
- Full Text:
Description of adult and larva of Ichnestoma pringlei n. sp. (Coleoptera: Scarabaeidae Cetoniinae), with notes on its biology and ecology
- Perissinotto, Renzo, Smith, Tamara J, Stobbia, P
- Authors: Perissinotto, Renzo , Smith, Tamara J , Stobbia, P
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/453815 , vital:75289 , https://doi.org/10.1080/03946975.1999.10539390
- Description: There are at present 10 described species in the primitive genus Ichnestoma Gory and Percheron 1833. These are all phylogenetic and geographic relicts of high evolutionary and conservation interest. The discovery of a new species, I. pringlei n. sp., and the first description of a larva (third instar) of this genus are reported here. New information is also presented on their life-cycle and on the dependence of their activities on rainfall patterns, particularly in the semi-arid region of the Karoo. In this region, larvae seem to take 2 years to complete growth and metamorphosis since they feed only after major rainfall events, while remaining inactive and deep underground during dry periods. Adults emerge from their cocoons only after summer rains of at least 15 mm. They lack functional mouth parts and are unable to feed. Their life span is only 3–5 days. Because females are completely flightless and unable to disperse, species of the genus are extremely vulnerable to environmental degradation. It seems likely that they may play a key role in the decomposition of dead plant matter, especially in dry and clay-rich soils where other primary decomposers are scarce.
- Full Text:
- Authors: Perissinotto, Renzo , Smith, Tamara J , Stobbia, P
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/453815 , vital:75289 , https://doi.org/10.1080/03946975.1999.10539390
- Description: There are at present 10 described species in the primitive genus Ichnestoma Gory and Percheron 1833. These are all phylogenetic and geographic relicts of high evolutionary and conservation interest. The discovery of a new species, I. pringlei n. sp., and the first description of a larva (third instar) of this genus are reported here. New information is also presented on their life-cycle and on the dependence of their activities on rainfall patterns, particularly in the semi-arid region of the Karoo. In this region, larvae seem to take 2 years to complete growth and metamorphosis since they feed only after major rainfall events, while remaining inactive and deep underground during dry periods. Adults emerge from their cocoons only after summer rains of at least 15 mm. They lack functional mouth parts and are unable to feed. Their life span is only 3–5 days. Because females are completely flightless and unable to disperse, species of the genus are extremely vulnerable to environmental degradation. It seems likely that they may play a key role in the decomposition of dead plant matter, especially in dry and clay-rich soils where other primary decomposers are scarce.
- Full Text:
DSC screening of potential prochlorperazine-excipient interactions in preformulation studies
- Brown, Michael E, Antunes, Edith M, Glass, Beverley M, Lebete, Mosimotsana L, Walker, Roderick B
- Authors: Brown, Michael E , Antunes, Edith M , Glass, Beverley M , Lebete, Mosimotsana L , Walker, Roderick B
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184367 , vital:44212 , xlink:href="https://doi.org/10.1023/A:1010150305542"
- Description: Differential scanning calorimetry was used to examine the thermal behaviour of mixtures of the drug prochlorperazine with standard excipients, to assess potential interactions, and of mixtures with cyclodextrins, to investigate inclusion complexation which could increase the photostability of the drug. For most of the excipients (magnesium stearate, stearic acid, Explotab®, Ac-Di-Sol®, Encompress® and Ludipress®, lactose and Starch 1500) disappearance or broadening of the melting endotherm of the drug indicated interactions. Lubritab® was the only 'inert' excipient tested. Mixtures of prochlorperazine and the cyclodextrins gave incomplete inclusion complexation as shown by only partial disappearance of the melting endotherm of the drug.
- Full Text: false
- Authors: Brown, Michael E , Antunes, Edith M , Glass, Beverley M , Lebete, Mosimotsana L , Walker, Roderick B
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184367 , vital:44212 , xlink:href="https://doi.org/10.1023/A:1010150305542"
- Description: Differential scanning calorimetry was used to examine the thermal behaviour of mixtures of the drug prochlorperazine with standard excipients, to assess potential interactions, and of mixtures with cyclodextrins, to investigate inclusion complexation which could increase the photostability of the drug. For most of the excipients (magnesium stearate, stearic acid, Explotab®, Ac-Di-Sol®, Encompress® and Ludipress®, lactose and Starch 1500) disappearance or broadening of the melting endotherm of the drug indicated interactions. Lubritab® was the only 'inert' excipient tested. Mixtures of prochlorperazine and the cyclodextrins gave incomplete inclusion complexation as shown by only partial disappearance of the melting endotherm of the drug.
- Full Text: false
Honeybees, Apis mellifera Linnaeus (Hymenoptera: Apidae), of equatorial Africa
- Radloff, Sarah E, Hepburn, H Randall
- Authors: Radloff, Sarah E , Hepburn, H Randall
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451885 , vital:75083 , https://hdl.handle.net/10520/AJA10213589_364
- Description: Morphometric and flight dimensional characters of worker honeybees, Apis mellifera Linnaeus, from equatorial Gabon were analysed by multivariate methods to characterize the population. A single morphocluster and a single flight dimension cluster were obtained. When these bees were grouped together with those of other countries of the region, again a single morphoduster and flight cluster were obtained. All of the outlier samples were previously designated as Apis mellifera adansonii Latreille and completely surround the Gabon samples, establishing the same subspecies membership for the latter. The bees of Gabon are morphometrically more homogeneous than in any other area of Africa.
- Full Text:
- Authors: Radloff, Sarah E , Hepburn, H Randall
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451885 , vital:75083 , https://hdl.handle.net/10520/AJA10213589_364
- Description: Morphometric and flight dimensional characters of worker honeybees, Apis mellifera Linnaeus, from equatorial Gabon were analysed by multivariate methods to characterize the population. A single morphocluster and a single flight dimension cluster were obtained. When these bees were grouped together with those of other countries of the region, again a single morphoduster and flight cluster were obtained. All of the outlier samples were previously designated as Apis mellifera adansonii Latreille and completely surround the Gabon samples, establishing the same subspecies membership for the latter. The bees of Gabon are morphometrically more homogeneous than in any other area of Africa.
- Full Text:
Integrating the development of academic literacy into mainstream teaching and learning
- Authors: Amos, Trevor L
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270891 , vital:54489 , xlink:href="https://hdl.handle.net/10520/AJA10113487_947"
- Description: Higher education is challenged to develop effective and independent learners of students who experience learning difficulties. These students are however, (potentially) able to engage in and do not necessarily lack the the inherent bstract cognitive capability necessary for academic success. The aim of this article is to be done in practice to integrate the development of academic literacy into mainstream teaching and learning.
- Full Text:
- Authors: Amos, Trevor L
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270891 , vital:54489 , xlink:href="https://hdl.handle.net/10520/AJA10113487_947"
- Description: Higher education is challenged to develop effective and independent learners of students who experience learning difficulties. These students are however, (potentially) able to engage in and do not necessarily lack the the inherent bstract cognitive capability necessary for academic success. The aim of this article is to be done in practice to integrate the development of academic literacy into mainstream teaching and learning.
- Full Text:
Interactions of cobalt (II) tetrasulfophthalocyanine with nitrite in the presence of nitrate and perchlorate ions
- Chebotareva, Natalia, Nyokong, Tebello
- Authors: Chebotareva, Natalia , Nyokong, Tebello
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293257 , vital:57069 , xlink:href="https://doi.org/10.1080/00958979908054907"
- Description: Spectroscopic changes observed on addition of nitrite to solutions of cobalt(II) tetra-sulfophthalocyanine ([Co(II)TSPc]4-) in the presence of N− 3 or ClO− 4 are reported. There is spectroscopic evidence for the oxidation of [Co(II)TSPc]4- to a [Co(III)TSPc]3- species in the presence of nitrite ions. Equilibrium and kinetic studies for the interaction between [Co(II)TSPc]4- and NO− 2 are reported. The rate was found to be first order in both [Co(II)TSPc]4- and NO− 2. The rate constant for the forward reaction, k f=1.6 × 10−4 dm3mol−1s−1 was determined at 20°C for the interaction between nitrite ions and [Co(II)TSPc]4- in the presence of NO3 − or ClO4 − ions.
- Full Text:
- Authors: Chebotareva, Natalia , Nyokong, Tebello
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293257 , vital:57069 , xlink:href="https://doi.org/10.1080/00958979908054907"
- Description: Spectroscopic changes observed on addition of nitrite to solutions of cobalt(II) tetra-sulfophthalocyanine ([Co(II)TSPc]4-) in the presence of N− 3 or ClO− 4 are reported. There is spectroscopic evidence for the oxidation of [Co(II)TSPc]4- to a [Co(III)TSPc]3- species in the presence of nitrite ions. Equilibrium and kinetic studies for the interaction between [Co(II)TSPc]4- and NO− 2 are reported. The rate was found to be first order in both [Co(II)TSPc]4- and NO− 2. The rate constant for the forward reaction, k f=1.6 × 10−4 dm3mol−1s−1 was determined at 20°C for the interaction between nitrite ions and [Co(II)TSPc]4- in the presence of NO3 − or ClO4 − ions.
- Full Text:
Lack of a response of the sub-tropical rodent (Saccostomus campestris) to a secondary plant compound, 6-methoxybenzoxazolinone—consequences for reproductive strategy
- White, Rehema M, Bernard, Ric T F
- Authors: White, Rehema M , Bernard, Ric T F
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447273 , vital:74601 , https://www.ajol.info/index.php/az/article/view/154795
- Description: A potential strategy for southern African small mammals to maximise reproductive success is to cue breeding activity to rainfall and subsequent vegetative growth via a secondary plant compound such as 6-methoxybenzoxazolinone (6MBOA). This study investigated whether the sub-tropical rodent Saccostomus campestris utilised this compound to enhance reproductive activity. 6MBOA or control vehicle were injected into adult females and into peri-pubertal females under long day (LD) and short day (SD) photoperiods (adults n= 6 to 8: peri-pubertals n= 5 to 10/treatment). There was no significant effect of 6MBOA or photoperiod on uterine or ovarian masses nor on ovarian development in sacrificed animals, nor on age at vaginal opening of peri-pubertals It was concluded that 6MBOA is not a major stimulant of reproduction in this species. Rather, we propose that seasonal breeding occurs in response to multiple environmental cues. This reproductive strategy and omnivory permit.
- Full Text:
- Authors: White, Rehema M , Bernard, Ric T F
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447273 , vital:74601 , https://www.ajol.info/index.php/az/article/view/154795
- Description: A potential strategy for southern African small mammals to maximise reproductive success is to cue breeding activity to rainfall and subsequent vegetative growth via a secondary plant compound such as 6-methoxybenzoxazolinone (6MBOA). This study investigated whether the sub-tropical rodent Saccostomus campestris utilised this compound to enhance reproductive activity. 6MBOA or control vehicle were injected into adult females and into peri-pubertal females under long day (LD) and short day (SD) photoperiods (adults n= 6 to 8: peri-pubertals n= 5 to 10/treatment). There was no significant effect of 6MBOA or photoperiod on uterine or ovarian masses nor on ovarian development in sacrificed animals, nor on age at vaginal opening of peri-pubertals It was concluded that 6MBOA is not a major stimulant of reproduction in this species. Rather, we propose that seasonal breeding occurs in response to multiple environmental cues. This reproductive strategy and omnivory permit.
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Phoretic association of blackflies (Oiptera: Simuliidae) with heptageniid mayflies (Ephemeroptera: Heptageniidae) in South Africa
- Authors: de Moor, Ferdy C
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452172 , vital:75109 , https://journals.co.za/doi/pdf/10.10520/AJA10213589_400
- Description: The phoretic or epizoitic association of blackfly (Diptera: Simuliidae) larvae and pupae with other aquatic arthropods has been documented for a number of tropical African species (Grenier and Mouchet 1959; Corbet 1961, 1962; Germain et al. 1966; Disney 1969, 1971a-d, 1973; also references in Crosskey 1990). The significance of these associations has led to much speculation, although no scientific conclusions regarding the origin and purposes of the associations have been reached (Corbet 1961; Crosskey 1990).
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- Authors: de Moor, Ferdy C
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452172 , vital:75109 , https://journals.co.za/doi/pdf/10.10520/AJA10213589_400
- Description: The phoretic or epizoitic association of blackfly (Diptera: Simuliidae) larvae and pupae with other aquatic arthropods has been documented for a number of tropical African species (Grenier and Mouchet 1959; Corbet 1961, 1962; Germain et al. 1966; Disney 1969, 1971a-d, 1973; also references in Crosskey 1990). The significance of these associations has led to much speculation, although no scientific conclusions regarding the origin and purposes of the associations have been reached (Corbet 1961; Crosskey 1990).
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Re-evaluation of Ashton’s types of African cicadas (Homoptera Cicadidae).
- Authors: Villet, Martin H
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/453840 , vital:75291 , https://doi.org/10.1080/03946975.1999.10539389
- Description: ASHTON (1914) described three species of cicada from Africa which were soon placed in synonymy with other species. Re-examination of the type material lead to the following revisions: Platypleura nigromarginata Ashton 1914 is removed from synonymy with Oxypleura quadraticollis (Butler 1874) and placed in the genus Strumoseura n. gen.; P. sikumba Ashton 1914 is confirmed as a junior synonym of Manza basimacula (Walker 1850) along with M. parva Villet 1989 n. syn.; and P. longirostris Ashton 1914 is removed from the synonymy of P. divisa Germar 1834.
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- Authors: Villet, Martin H
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/453840 , vital:75291 , https://doi.org/10.1080/03946975.1999.10539389
- Description: ASHTON (1914) described three species of cicada from Africa which were soon placed in synonymy with other species. Re-examination of the type material lead to the following revisions: Platypleura nigromarginata Ashton 1914 is removed from synonymy with Oxypleura quadraticollis (Butler 1874) and placed in the genus Strumoseura n. gen.; P. sikumba Ashton 1914 is confirmed as a junior synonym of Manza basimacula (Walker 1850) along with M. parva Villet 1989 n. syn.; and P. longirostris Ashton 1914 is removed from the synonymy of P. divisa Germar 1834.
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Song sharing by neighbourhood groups of territorial male Blackeyed Bulbuls
- Lloyd, Penn, Hulley, Patrick E, Craig, Adrian J F K
- Authors: Lloyd, Penn , Hulley, Patrick E , Craig, Adrian J F K
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447841 , vital:74678 , https://doi.org/10.1080/00306525.1999.9634238
- Description: The territorial song of the Blackeyed Bulbul Pycnonotus barbatus is described for a population followed over two breeding seasons in suburban Grahamstown, South Africa. The Blackeyed Bulbul has a discrete and highly structured system of phrase sharing by neighbourhood groups of males. The most common repertoire size is five phrases (mean 5.5; range 2–9). In a temporally-stable song population, individual phrases are shared independently by discrete clusters of males. Neighbours show a strong tendency to share phrase types (but rarely whole repertoires), with overall song similarity decreasing rapidly with increasing distance between birds. This species is an ideal candidate for testing hypotheses concerning the adaptive value of song sharing by neighbourhood groups.
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- Authors: Lloyd, Penn , Hulley, Patrick E , Craig, Adrian J F K
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447841 , vital:74678 , https://doi.org/10.1080/00306525.1999.9634238
- Description: The territorial song of the Blackeyed Bulbul Pycnonotus barbatus is described for a population followed over two breeding seasons in suburban Grahamstown, South Africa. The Blackeyed Bulbul has a discrete and highly structured system of phrase sharing by neighbourhood groups of males. The most common repertoire size is five phrases (mean 5.5; range 2–9). In a temporally-stable song population, individual phrases are shared independently by discrete clusters of males. Neighbours show a strong tendency to share phrase types (but rarely whole repertoires), with overall song similarity decreasing rapidly with increasing distance between birds. This species is an ideal candidate for testing hypotheses concerning the adaptive value of song sharing by neighbourhood groups.
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The cicada genus Nyara n. gen. (Homoptera Cicadidae) systematics, behaviour and conservation status
- Authors: Villet, Martin H
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/453870 , vital:75295 , https://doi.org/10.1080/03946975.1999.10539385
- Description: The cicada genus Nyara n. gen. and its sole species N. thanatotica n. sp. are described and diagnosed. This species is very peculiar because it often feigns death when disturbed. This is the first time such behaviour has been described in a cicada. Nyara is the third endemic cicada genus described from a South African forest. Its distribution along the subtropical Eastern Cape coast, which is threatened by strip mining and housing developments, highlights the need for conservation of these under-researched habitats.
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- Authors: Villet, Martin H
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/453870 , vital:75295 , https://doi.org/10.1080/03946975.1999.10539385
- Description: The cicada genus Nyara n. gen. and its sole species N. thanatotica n. sp. are described and diagnosed. This species is very peculiar because it often feigns death when disturbed. This is the first time such behaviour has been described in a cicada. Nyara is the third endemic cicada genus described from a South African forest. Its distribution along the subtropical Eastern Cape coast, which is threatened by strip mining and housing developments, highlights the need for conservation of these under-researched habitats.
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The Development of a Generic Framework for the Implementation of Cheap, Component-Based Virtual Video-Conferencing System
- Panagou, Soteri, Bangay, Shaun D
- Authors: Panagou, Soteri , Bangay, Shaun D
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432824 , vital:72903 , https://www.cs.ru.ac.za/research/Groups/vrsig/pastprojects/014humanmodelling/paper03.pdf
- Description: We address the problem of virtual-videoconferencing. The proposed solution is effected in terms of a generic framework based on an in-house Virtual Reality system. The framework is composed of a number of distinct components: model acquisition, head tracking, expression analysis, network transmission and avatar reconstruction. The framework promises to provide a unique, cheap, and fast system for avatar construction, transmission and animation. This approach affords a conversion from the traditional video stream approach to the management of an avatar remotely and consequently makes minimal demands on network resources.
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- Authors: Panagou, Soteri , Bangay, Shaun D
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432824 , vital:72903 , https://www.cs.ru.ac.za/research/Groups/vrsig/pastprojects/014humanmodelling/paper03.pdf
- Description: We address the problem of virtual-videoconferencing. The proposed solution is effected in terms of a generic framework based on an in-house Virtual Reality system. The framework is composed of a number of distinct components: model acquisition, head tracking, expression analysis, network transmission and avatar reconstruction. The framework promises to provide a unique, cheap, and fast system for avatar construction, transmission and animation. This approach affords a conversion from the traditional video stream approach to the management of an avatar remotely and consequently makes minimal demands on network resources.
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The Virtual Remote Control-An Extensible, Virtual Reality, User Interface Device
- Rorke, Michael, Bangay, Shaun D
- Authors: Rorke, Michael , Bangay, Shaun D
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432743 , vital:72896 , https://www.cs.ru.ac.za/research/Groups/vrsig/pastprojects/013interaction/paper02.pdf
- Description: Immersive virtual reality (VR) places the user inside of the computing envi-ronment, blurring the distinction between the environment itself and the user interface to access that environment non-obvious. This lack of distinction between environment and interface makes it difficult to place menus and other interface elements where the user is both able to access them easily and where they do not obscure large parts of the users field of view. We propose a system called the 'Virtual Remote Control' (VRC). The VRC con-sists of a physical device (a small touchpad tracked using a Polhemus In-sideTrak magnetic tracker) which the user is able to hold and for which there is a representation in the virtual environment. The VRC is represented in the environment by a virtual menu. The user is able to make selections from the virtual menu by moving their finger around the touch pad part of the VRC and 'tapping' on the required action. Additionally, the user is able to select an object for the action to be applied on, by 'pointing' the representa-tion of the VRC at the object-as one would point a remote control at a Hi-fi of TV set.
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- Authors: Rorke, Michael , Bangay, Shaun D
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432743 , vital:72896 , https://www.cs.ru.ac.za/research/Groups/vrsig/pastprojects/013interaction/paper02.pdf
- Description: Immersive virtual reality (VR) places the user inside of the computing envi-ronment, blurring the distinction between the environment itself and the user interface to access that environment non-obvious. This lack of distinction between environment and interface makes it difficult to place menus and other interface elements where the user is both able to access them easily and where they do not obscure large parts of the users field of view. We propose a system called the 'Virtual Remote Control' (VRC). The VRC con-sists of a physical device (a small touchpad tracked using a Polhemus In-sideTrak magnetic tracker) which the user is able to hold and for which there is a representation in the virtual environment. The VRC is represented in the environment by a virtual menu. The user is able to make selections from the virtual menu by moving their finger around the touch pad part of the VRC and 'tapping' on the required action. Additionally, the user is able to select an object for the action to be applied on, by 'pointing' the representa-tion of the VRC at the object-as one would point a remote control at a Hi-fi of TV set.
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