Reproductive and feeding biology of the Natal mountain catfish, Amphilius natalensis (Siluriformes: Amphiliidae)
- Marriott, Michael S, Booth, Anthony J, Skelton, Paul H
- Authors: Marriott, Michael S , Booth, Anthony J , Skelton, Paul H
- Date: 1997
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125837 , vital:35823 , https://doi.10.1023/A:1007361511052
- Description: The family Amphiliidae comprises nine genera and about 60 species. Only five species are found in southern Africa, three of which belong to the genus Amphilius (Skelton 1993). These soft-bodied catlets inhabit clear, fast flowing mountain streams where they live amongst cobbles, feeding predominantly on benthic invertebrates (Crass 1964, Skelton 1993). The Natal mountain catfish, A. natalensis Boulenger, 1917, is a small, nocturnal species with a restricted distribution along the eastern seaboard of southern Africa. It occurs in mountain streams from the Umkomaas River north to the Limpopo system in South Africa. It is also present in the Marozi River, a tributary of the Zambezi River in Zimbabwe and in the Ruo River, Malawi (Skelton 1984, 1993). Skelton (1993) suggested that predation by introduced trout species has led to scarcity of A. natalensis in many streams. In spite of this, no studies on the biology of this catfish species have been published. This study presents the first quantitative information on the biology of an amphiliid catfish, A. natalensis including gametogenesis, spawning seasonality, size-at-maturity, adult sex ratio and diet.
- Full Text:
- Date Issued: 1997
- Authors: Marriott, Michael S , Booth, Anthony J , Skelton, Paul H
- Date: 1997
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125837 , vital:35823 , https://doi.10.1023/A:1007361511052
- Description: The family Amphiliidae comprises nine genera and about 60 species. Only five species are found in southern Africa, three of which belong to the genus Amphilius (Skelton 1993). These soft-bodied catlets inhabit clear, fast flowing mountain streams where they live amongst cobbles, feeding predominantly on benthic invertebrates (Crass 1964, Skelton 1993). The Natal mountain catfish, A. natalensis Boulenger, 1917, is a small, nocturnal species with a restricted distribution along the eastern seaboard of southern Africa. It occurs in mountain streams from the Umkomaas River north to the Limpopo system in South Africa. It is also present in the Marozi River, a tributary of the Zambezi River in Zimbabwe and in the Ruo River, Malawi (Skelton 1984, 1993). Skelton (1993) suggested that predation by introduced trout species has led to scarcity of A. natalensis in many streams. In spite of this, no studies on the biology of this catfish species have been published. This study presents the first quantitative information on the biology of an amphiliid catfish, A. natalensis including gametogenesis, spawning seasonality, size-at-maturity, adult sex ratio and diet.
- Full Text:
- Date Issued: 1997
Feeding, tentacle and gut morphology in five species of southern African intertidal holothuroids (Echinodermata)
- Foster, Gregory G, Hodgson, Alan N
- Authors: Foster, Gregory G , Hodgson, Alan N
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447392 , vital:74621 , https://hdl.handle.net/10520/AJA00445096_757
- Description: Compares the structure of the tentacles and digestive tracts of four species of intertidal dendrochirote, and one species of aspidochirote holothuroid by using light, scanning and transmission electron microscopy. Gut contents were sieved to determine the size of the particulate matter ingested. Concludes that there appears to be a relationship between tentacle morphology and the size and type of food ingested. Gut length, the thickness of the digestive epithelial layer and the number of vesicles present in the enterocyte cells of the digestive epithelium also differ in relation to the food ingested. Illustrates with several photographs.
- Full Text:
- Date Issued: 1996
- Authors: Foster, Gregory G , Hodgson, Alan N
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447392 , vital:74621 , https://hdl.handle.net/10520/AJA00445096_757
- Description: Compares the structure of the tentacles and digestive tracts of four species of intertidal dendrochirote, and one species of aspidochirote holothuroid by using light, scanning and transmission electron microscopy. Gut contents were sieved to determine the size of the particulate matter ingested. Concludes that there appears to be a relationship between tentacle morphology and the size and type of food ingested. Gut length, the thickness of the digestive epithelial layer and the number of vesicles present in the enterocyte cells of the digestive epithelium also differ in relation to the food ingested. Illustrates with several photographs.
- Full Text:
- Date Issued: 1996
Reproductive biology of a riverine cyprinid, Labeo umbratus (Teleostei: Cyprinidae), in small South African reservoirs
- Potts, Warren M, Booth, Anthony J, Hecht, Thomas, Andrew, Timothy G
- Authors: Potts, Warren M , Booth, Anthony J , Hecht, Thomas , Andrew, Timothy G
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125854 , vital:35826 , https://doi.10.2989/16085910509503849
- Description: The reproductive and recruitment characteristics of moggel, Labeo umbratus, populations were examined in four small South African reservoirs. Reproduction, characterised by an extended spawning season, high fecundity, short incubation time and rapid larval development, appears to be ideally suited to the highly variable environment of small reservoirs. Evidence suggested that L. umbratus spawns in the reservoirs. In two reservoirs where samples were conducted monthly, GSI (gonado-somatic index) was positively correlated with both water temperature and day length, whilst the CPUE (catch per unit effort) of juveniles was not related to any environmental variable. The success of moggel spawning appeared to increase when there was early spring and consistent summer rainfall.
- Full Text:
- Date Issued: 2010
- Authors: Potts, Warren M , Booth, Anthony J , Hecht, Thomas , Andrew, Timothy G
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125854 , vital:35826 , https://doi.10.2989/16085910509503849
- Description: The reproductive and recruitment characteristics of moggel, Labeo umbratus, populations were examined in four small South African reservoirs. Reproduction, characterised by an extended spawning season, high fecundity, short incubation time and rapid larval development, appears to be ideally suited to the highly variable environment of small reservoirs. Evidence suggested that L. umbratus spawns in the reservoirs. In two reservoirs where samples were conducted monthly, GSI (gonado-somatic index) was positively correlated with both water temperature and day length, whilst the CPUE (catch per unit effort) of juveniles was not related to any environmental variable. The success of moggel spawning appeared to increase when there was early spring and consistent summer rainfall.
- Full Text:
- Date Issued: 2010
Deep phylogeographic structure may indicate cryptic species within the Sparid genus Spondyliosoma:
- McKeown, Niall J, Gwilliam, Michael P, Healey, Amy J E, Skujina, Ilze, Potts, Warren M, Sauer, Warwick H H, Shaw, Paul W
- Authors: McKeown, Niall J , Gwilliam, Michael P , Healey, Amy J E , Skujina, Ilze , Potts, Warren M , Sauer, Warwick H H , Shaw, Paul W
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158085 , vital:40147 , DOI: 10.1111/jfb.14316
- Description: Two geographically nonoverlapping species are currently described within the sparid genus Spondyliosoma: Spondyliosoma cantharus (Black Seabream) occurring across Mediterranean and eastern Atlantic waters from NW Europe to Angola and S. emarginatum (Steentjie) considered endemic to southern Africa. To address prominent knowledge gaps this study investigated range‐wide phylogeographic structure across both species. Mitochondrial DNA sequences revealed deep phylogeographic structuring with four regionally partitioned reciprocally monophyletic clades, a Mediterranean clade and three more closely related Atlantic clades [NE Atlantic, Angola and South Africa (corresponding to S. emarginatum)]. Divergence and distribution of the lineages reflects survival in, and expansion from, disjunct glacial refuge areas. Cytonuclear differentiation of S. emarginatum supports its validity as a distinct species endemic to South African waters.
- Full Text:
- Date Issued: 2020
- Authors: McKeown, Niall J , Gwilliam, Michael P , Healey, Amy J E , Skujina, Ilze , Potts, Warren M , Sauer, Warwick H H , Shaw, Paul W
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158085 , vital:40147 , DOI: 10.1111/jfb.14316
- Description: Two geographically nonoverlapping species are currently described within the sparid genus Spondyliosoma: Spondyliosoma cantharus (Black Seabream) occurring across Mediterranean and eastern Atlantic waters from NW Europe to Angola and S. emarginatum (Steentjie) considered endemic to southern Africa. To address prominent knowledge gaps this study investigated range‐wide phylogeographic structure across both species. Mitochondrial DNA sequences revealed deep phylogeographic structuring with four regionally partitioned reciprocally monophyletic clades, a Mediterranean clade and three more closely related Atlantic clades [NE Atlantic, Angola and South Africa (corresponding to S. emarginatum)]. Divergence and distribution of the lineages reflects survival in, and expansion from, disjunct glacial refuge areas. Cytonuclear differentiation of S. emarginatum supports its validity as a distinct species endemic to South African waters.
- Full Text:
- Date Issued: 2020
Recommendations for the future of recreational fisheries to prepare the social‐ecological system to cope with change
- Arlinghaus, Robert, Cooke, Steven J, Sutton, S G, Danylchuk, A J, Potts, Warren M, Freire, K D M, Alós, J, Da Silva, E T, Cowx, Ian G, Van Anrooy, R
- Authors: Arlinghaus, Robert , Cooke, Steven J , Sutton, S G , Danylchuk, A J , Potts, Warren M , Freire, K D M , Alós, J , Da Silva, E T , Cowx, Ian G , Van Anrooy, R
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125810 , vital:35819 , https://doi.10.1111/fme.12191
- Description: This paper presents conclusions and recommendations that emerged from the 7th World Recreational Fishing Conference (WRFC) held in Campinas, Brazil in September 2014. Based on the recognition of the immense social and economic importance of recreational fisheries coupled with weaknesses in robust information about these fisheries in many areas of the world, particularly in many economies in transition, it is recommended to increase effort to build effective governance arrangements and improve monitoring and assessment frameworks in data-poor situations. Moreover, there is a need to increase interdisciplinary studies that will foster a systematic understanding of recreational fisheries as complex adaptive social-ecological systems. To promote sustainable recreational fisheries on a global scale, it is recommended the detailed suggestions for governance and management outlined in the United Nations Food and Agricultural Organization Technical Guidelines for Responsible Fisheries: Recreational Fisheries are followed.
- Full Text:
- Date Issued: 2016
- Authors: Arlinghaus, Robert , Cooke, Steven J , Sutton, S G , Danylchuk, A J , Potts, Warren M , Freire, K D M , Alós, J , Da Silva, E T , Cowx, Ian G , Van Anrooy, R
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125810 , vital:35819 , https://doi.10.1111/fme.12191
- Description: This paper presents conclusions and recommendations that emerged from the 7th World Recreational Fishing Conference (WRFC) held in Campinas, Brazil in September 2014. Based on the recognition of the immense social and economic importance of recreational fisheries coupled with weaknesses in robust information about these fisheries in many areas of the world, particularly in many economies in transition, it is recommended to increase effort to build effective governance arrangements and improve monitoring and assessment frameworks in data-poor situations. Moreover, there is a need to increase interdisciplinary studies that will foster a systematic understanding of recreational fisheries as complex adaptive social-ecological systems. To promote sustainable recreational fisheries on a global scale, it is recommended the detailed suggestions for governance and management outlined in the United Nations Food and Agricultural Organization Technical Guidelines for Responsible Fisheries: Recreational Fisheries are followed.
- Full Text:
- Date Issued: 2016
An RTSP proxy for implementing the IPTV media function using a streaming server
- Shibeshi, Zelalem S, Terzoli, Alfredo, Bradshaw, Karen L
- Authors: Shibeshi, Zelalem S , Terzoli, Alfredo , Bradshaw, Karen L
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429136 , vital:72562 , https://www.informatica.si/index.php/informatica/article/view/383
- Description: Multimedia content delivery in IMS, including IPTV, is handled by a separate unit, the Media Function (MF), made up of media control and media delivery units, which in the case of IPTV are the Media Control Function (MCF) and Media Delivery Function (MDF), respectively. According to the different specifications of an IMS based IPTV architecture, the User Equipment (UE) is expected to use the RTSP protocol as a media control protocol to interact with the MCF, and obtains delivery of media from the MDF using the RTP protocol. This also means that the streaming session needs to be initiated from the media controller on behalf of the user but the delivery of media is sent to the UE from the media deliverer (media server). Due both to the lack of free and open source Media Servers and the availability of free and open source Streaming Servers, the ideal choice for the delivery of multimedia services, including IPTV, by the research community is Streaming Servers. Nevertheless, because of denial of service attacks and other issues, most streaming servers do not allow a different location for the session setup request and the delivery of media in the streaming session. In other words, most streaming servers are not designed to be controlled by some other entity other than the RTSP client that consumes the media. This makes it difficult to have a separate media control unit for IPTV service in IMS if one wanted to use a streaming server as an MDF unit. So, while waiting for streaming servers to work in this manner, it is better to find a work around in order to use streaming servers to develop and test IPTV services in IMS environments. For this purpose we propose another component (an RTSP proxy and relay unit) as part of the IPTV MF and to mediate between the MCF and MDF. This unit correctly relays media control commands from the MCF to the MDF and RTP packets from the MDF to the UE. It also helps in the implementation of other streaming functionalities that are required for IPTV service delivery, but which are not implemented in the current open source streaming servers. Additional services can also be easily implemented with the help of this unit. This will facilitate the development of an IPTV service using readily available open source streaming servers and help researchers to evaluate their proposals on new services they would like to develop. In this paper we show how this RTSP proxy unit can be integrated into the Media Function of the IPTV architecture to ease the media delivery process of an IMS based IPTV service.
- Full Text:
- Date Issued: 2012
- Authors: Shibeshi, Zelalem S , Terzoli, Alfredo , Bradshaw, Karen L
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429136 , vital:72562 , https://www.informatica.si/index.php/informatica/article/view/383
- Description: Multimedia content delivery in IMS, including IPTV, is handled by a separate unit, the Media Function (MF), made up of media control and media delivery units, which in the case of IPTV are the Media Control Function (MCF) and Media Delivery Function (MDF), respectively. According to the different specifications of an IMS based IPTV architecture, the User Equipment (UE) is expected to use the RTSP protocol as a media control protocol to interact with the MCF, and obtains delivery of media from the MDF using the RTP protocol. This also means that the streaming session needs to be initiated from the media controller on behalf of the user but the delivery of media is sent to the UE from the media deliverer (media server). Due both to the lack of free and open source Media Servers and the availability of free and open source Streaming Servers, the ideal choice for the delivery of multimedia services, including IPTV, by the research community is Streaming Servers. Nevertheless, because of denial of service attacks and other issues, most streaming servers do not allow a different location for the session setup request and the delivery of media in the streaming session. In other words, most streaming servers are not designed to be controlled by some other entity other than the RTSP client that consumes the media. This makes it difficult to have a separate media control unit for IPTV service in IMS if one wanted to use a streaming server as an MDF unit. So, while waiting for streaming servers to work in this manner, it is better to find a work around in order to use streaming servers to develop and test IPTV services in IMS environments. For this purpose we propose another component (an RTSP proxy and relay unit) as part of the IPTV MF and to mediate between the MCF and MDF. This unit correctly relays media control commands from the MCF to the MDF and RTP packets from the MDF to the UE. It also helps in the implementation of other streaming functionalities that are required for IPTV service delivery, but which are not implemented in the current open source streaming servers. Additional services can also be easily implemented with the help of this unit. This will facilitate the development of an IPTV service using readily available open source streaming servers and help researchers to evaluate their proposals on new services they would like to develop. In this paper we show how this RTSP proxy unit can be integrated into the Media Function of the IPTV architecture to ease the media delivery process of an IMS based IPTV service.
- Full Text:
- Date Issued: 2012
In-kernel cryptographic executable verification
- Motara, Yusuf, M, Irwin, Barry V W
- Authors: Motara, Yusuf, M , Irwin, Barry V W
- Date: 2005
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429049 , vital:72556 , https://doi.org/10.1007/0-387-31163-7_25
- Description: This paper discusses the problems posed by Trojan horses and unauthorized code, and reviews existing solutions for dealing with them. A technique involving the in-kernel verification of executables is proposed. Its advantages include simplicity, transparency, ease of use and minimal setup time. In addition, the technique has several applications, including assisting with honeypot implementations, incident response and forensic investigations.
- Full Text:
- Date Issued: 2005
- Authors: Motara, Yusuf, M , Irwin, Barry V W
- Date: 2005
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429049 , vital:72556 , https://doi.org/10.1007/0-387-31163-7_25
- Description: This paper discusses the problems posed by Trojan horses and unauthorized code, and reviews existing solutions for dealing with them. A technique involving the in-kernel verification of executables is proposed. Its advantages include simplicity, transparency, ease of use and minimal setup time. In addition, the technique has several applications, including assisting with honeypot implementations, incident response and forensic investigations.
- Full Text:
- Date Issued: 2005
Mapping the most significant computer hacking events to a temporal computer attack model
- Van Heerden, Renier, Pieterse, Heloise, Irwin, Barry V W
- Authors: Van Heerden, Renier , Pieterse, Heloise , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429950 , vital:72654 , https://doi.org/10.1007/978-3-642-33332-3_21
- Description: This paper presents eight of the most significant computer hacking events (also known as computer attacks). These events were selected because of their unique impact, methodology, or other properties. A temporal computer attack model is presented that can be used to model computer based attacks. This model consists of the following stages: Target Identification, Reconnaissance, Attack, and Post-Attack Recon-naissance stages. The Attack stage is separated into: Ramp-up, Dam-age and Residue. This paper demonstrates how our eight significant hacking events are mapped to the temporal computer attack model. The temporal computer attack model becomes a valuable asset in the protection of critical infrastructure by being able to detect similar attacks earlier.
- Full Text:
- Date Issued: 2012
- Authors: Van Heerden, Renier , Pieterse, Heloise , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429950 , vital:72654 , https://doi.org/10.1007/978-3-642-33332-3_21
- Description: This paper presents eight of the most significant computer hacking events (also known as computer attacks). These events were selected because of their unique impact, methodology, or other properties. A temporal computer attack model is presented that can be used to model computer based attacks. This model consists of the following stages: Target Identification, Reconnaissance, Attack, and Post-Attack Recon-naissance stages. The Attack stage is separated into: Ramp-up, Dam-age and Residue. This paper demonstrates how our eight significant hacking events are mapped to the temporal computer attack model. The temporal computer attack model becomes a valuable asset in the protection of critical infrastructure by being able to detect similar attacks earlier.
- Full Text:
- Date Issued: 2012
In-kernel cryptographic executable verification
- Motara, Yusuf, M, Irwin, Barry V W
- Authors: Motara, Yusuf, M , Irwin, Barry V W
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429937 , vital:72653 , https://doi.org/10.1007/0-387-31163-7_25
- Description: This paper discusses the problems posed by Trojan horses and unau-thorized code, and reviews existing solutions for dealing with them. A technique involving the in-kernel verification of executables is pro-posed. Its advantages include simplicity, transparency, ease of use and minimal setup time. In addition, the technique has several applications, including assisting with honeypot implementations, incident response and forensic investigations.
- Full Text:
- Date Issued: 2005
- Authors: Motara, Yusuf, M , Irwin, Barry V W
- Date: 2005
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429937 , vital:72653 , https://doi.org/10.1007/0-387-31163-7_25
- Description: This paper discusses the problems posed by Trojan horses and unau-thorized code, and reviews existing solutions for dealing with them. A technique involving the in-kernel verification of executables is pro-posed. Its advantages include simplicity, transparency, ease of use and minimal setup time. In addition, the technique has several applications, including assisting with honeypot implementations, incident response and forensic investigations.
- Full Text:
- Date Issued: 2005
An approach to the evaluation of microcomputer operating systems with respect to real-time issues
- Authors: Wells, George C
- Date: 1991
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430484 , vital:72694 , https://doi.org/10.1016/0165-6074(91)90014-K
- Description: This paper gives an overview of the approach used for the assessment of several operating systems for microcomputers. The operating systems are all commercial products and cover a spectrum ranging from general purpose operating systems to small, real-time operating systems. The criteria used for the evaluation are discussed and the approach used is discussed in detail. The results of the evaluation are not discussed in this paper.
- Full Text:
- Date Issued: 1991
- Authors: Wells, George C
- Date: 1991
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430484 , vital:72694 , https://doi.org/10.1016/0165-6074(91)90014-K
- Description: This paper gives an overview of the approach used for the assessment of several operating systems for microcomputers. The operating systems are all commercial products and cover a spectrum ranging from general purpose operating systems to small, real-time operating systems. The criteria used for the evaluation are discussed and the approach used is discussed in detail. The results of the evaluation are not discussed in this paper.
- Full Text:
- Date Issued: 1991
Bioavailability and activity of 0.1% amcinonide preparations: comparison with proprietary topical corticosteroid formulations of differing potencies
- Authors: Woodford, R , Haigh, John M
- Date: 1979
- Language: English
- Type: text , Article
- Identifier: vital:6447 , http://hdl.handle.net/10962/d1006634
- Description: The activity of a 0.1% amcinonide cream was compared with those of selected proprietary topical corticosteroid formulations of potencies differing according to the United Kingdom (U.K.) MIMS classification (very potent, potent and moderately potent) using a standard six hour vasoconstrictor assay with multiple reading times. Statistical analysis indicated that 0.1% amcinonide cream feU within the category of a very potent preparation. Three 0.1% amcinonide formulations (cream, combination cream and combination ointment, the last two containing anti-infective agents) were equipotent in the skin-blanching test.
- Full Text:
- Date Issued: 1979
- Authors: Woodford, R , Haigh, John M
- Date: 1979
- Language: English
- Type: text , Article
- Identifier: vital:6447 , http://hdl.handle.net/10962/d1006634
- Description: The activity of a 0.1% amcinonide cream was compared with those of selected proprietary topical corticosteroid formulations of potencies differing according to the United Kingdom (U.K.) MIMS classification (very potent, potent and moderately potent) using a standard six hour vasoconstrictor assay with multiple reading times. Statistical analysis indicated that 0.1% amcinonide cream feU within the category of a very potent preparation. Three 0.1% amcinonide formulations (cream, combination cream and combination ointment, the last two containing anti-infective agents) were equipotent in the skin-blanching test.
- Full Text:
- Date Issued: 1979
Infrared evidence for the transmission of electronic effects through a metal atom in a series of new cadmium complexes
- Haigh, John M, Van Dam, M A, Thornton, D A
- Authors: Haigh, John M , Van Dam, M A , Thornton, D A
- Date: 1967
- Language: English
- Type: text , Article
- Identifier: vital:6371 , http://hdl.handle.net/10962/d1006073
- Description: A series of novel cadmium complexes has been synthesized from the reaction of cadmium chloride, bromide and iodide with primary aromatic amines. The complexes are either mononuclear or polynuclear according to the nature of the halide and amine employed. A possible mechanism for their formation is proposed. The N - H stretching and bending frequencies are linearly related to the electronegativity of the co-ordinated halogen, indicating that the electron withdrawing capacity of the halogen is transmitted through the cadmium atom.
- Full Text:
- Date Issued: 1967
- Authors: Haigh, John M , Van Dam, M A , Thornton, D A
- Date: 1967
- Language: English
- Type: text , Article
- Identifier: vital:6371 , http://hdl.handle.net/10962/d1006073
- Description: A series of novel cadmium complexes has been synthesized from the reaction of cadmium chloride, bromide and iodide with primary aromatic amines. The complexes are either mononuclear or polynuclear according to the nature of the halide and amine employed. A possible mechanism for their formation is proposed. The N - H stretching and bending frequencies are linearly related to the electronegativity of the co-ordinated halogen, indicating that the electron withdrawing capacity of the halogen is transmitted through the cadmium atom.
- Full Text:
- Date Issued: 1967
Institutions and economic research: a case of location externalities on agricultural resource allocation in the Kat River basin, South Africa. A Rejoinder
- Mbatha, Cyril N, Antrobus, Geoffrey G
- Authors: Mbatha, Cyril N , Antrobus, Geoffrey G
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143002 , vital:38184 , https://0-doi.org.wam.seals.ac.za/10.1080/03031853.2013.798069
- Description: In Mbatha and Antrobus (2008), an argument was put forward against an importation or adoption of universal models or general theorems to explain locally prevailing socio-economic conditions and predict outcomes in varied geographical contexts such as in the Kat River basin. In response to this argument a comment in this edition argues that our “results are caused by, metaphorically speaking, comparing apples and oranges. If, however, all of the relevant information is taken into account, a simple economic model may suffice to depict the situation within the KRV.” Here we illustrate that the comment comes from a misreading of basic details in the original discussion and in its construction and presentation of an alternative model of the KRV conditions the comment reiterates our original argument that general models and theorems are likely to fail to explain local intricacies primarily because they are not founded on local historical institutions.
- Full Text:
- Date Issued: 2013
- Authors: Mbatha, Cyril N , Antrobus, Geoffrey G
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143002 , vital:38184 , https://0-doi.org.wam.seals.ac.za/10.1080/03031853.2013.798069
- Description: In Mbatha and Antrobus (2008), an argument was put forward against an importation or adoption of universal models or general theorems to explain locally prevailing socio-economic conditions and predict outcomes in varied geographical contexts such as in the Kat River basin. In response to this argument a comment in this edition argues that our “results are caused by, metaphorically speaking, comparing apples and oranges. If, however, all of the relevant information is taken into account, a simple economic model may suffice to depict the situation within the KRV.” Here we illustrate that the comment comes from a misreading of basic details in the original discussion and in its construction and presentation of an alternative model of the KRV conditions the comment reiterates our original argument that general models and theorems are likely to fail to explain local intricacies primarily because they are not founded on local historical institutions.
- Full Text:
- Date Issued: 2013
Characterization and Analysis of NTP Amplifier Traffic
- Rudman, Lauren, Irwin, Barry V W
- Authors: Rudman, Lauren , Irwin, Barry V W
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429482 , vital:72616 , 10.23919/SAIEE.2016.8531542
- Description: Network Time Protocol based DDoS attacks saw a lot of popularity throughout 2014. This paper shows the characterization and analysis of two large datasets containing packets from NTP based DDoS attacks captured in South Africa. Using a series of Python based tools, the dataset is analysed according to specific parts of the packet headers. These include the source IP address and Time-to-Live (TTL) values. The analysis found the top source addresses and looked at the TTL values observed for each address. These TTL values can be used to calculate the probable operating system or DDoS attack tool used by an attacker. We found that each TTL value seen for an address can indicate the number of hosts attacking the address or indicate minor routing changes. The Time-to-Live values are then analysed as a whole to find the total number used throughout each attack. The most frequent TTL values are then found and show that the majority of them indicate the attackers are using an initial TTL of 255. This value can indicate the use of a certain DDoS tool that creates packets with that exact initial TTL. The TTL values are then put into groups that can show the number of IP addresses a group of hosts are targeting. The paper discusses our work with two brief case studies correlating observed data to real-world attacks, and the observable impact thereof.
- Full Text:
- Date Issued: 2016
- Authors: Rudman, Lauren , Irwin, Barry V W
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429482 , vital:72616 , 10.23919/SAIEE.2016.8531542
- Description: Network Time Protocol based DDoS attacks saw a lot of popularity throughout 2014. This paper shows the characterization and analysis of two large datasets containing packets from NTP based DDoS attacks captured in South Africa. Using a series of Python based tools, the dataset is analysed according to specific parts of the packet headers. These include the source IP address and Time-to-Live (TTL) values. The analysis found the top source addresses and looked at the TTL values observed for each address. These TTL values can be used to calculate the probable operating system or DDoS attack tool used by an attacker. We found that each TTL value seen for an address can indicate the number of hosts attacking the address or indicate minor routing changes. The Time-to-Live values are then analysed as a whole to find the total number used throughout each attack. The most frequent TTL values are then found and show that the majority of them indicate the attackers are using an initial TTL of 255. This value can indicate the use of a certain DDoS tool that creates packets with that exact initial TTL. The TTL values are then put into groups that can show the number of IP addresses a group of hosts are targeting. The paper discusses our work with two brief case studies correlating observed data to real-world attacks, and the observable impact thereof.
- Full Text:
- Date Issued: 2016
Exploration and design of a synchronous message passing framework for a CPU-NPU heterogeneous architecture
- Pennefather, Sean, Bradshaw, Karen L, Irwin, Barry V W
- Authors: Pennefather, Sean , Bradshaw, Karen L , Irwin, Barry V W
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429537 , vital:72620 , https://ieeexplore.ieee.org/abstract/document/8425384
- Description: In this paper we present the development of a framework for communication between an NPU (network processing unit) and CPU through synchronous message passing that is compliant with the synchronous communication events of the CSP formalisms. This framework is designed to be used for passing generic information between application components operating on both architectures and is intended to operate in conjunction with existing datapaths present on the NPU which in turn are responsible for network traffic transmission. An investigation of different message passing topologies is covered before the proposed message passing fabric is presented. As a proof of concept, an initial implementation of the fabric is developed and tested to determine its viability and correctness. Through testing it is shown that the implemented framework operates as intended. However, it is noted the throughput of the exploratory implementation is not considered suitable for high-performance applications and further evaluation is required.
- Full Text:
- Date Issued: 2018
- Authors: Pennefather, Sean , Bradshaw, Karen L , Irwin, Barry V W
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429537 , vital:72620 , https://ieeexplore.ieee.org/abstract/document/8425384
- Description: In this paper we present the development of a framework for communication between an NPU (network processing unit) and CPU through synchronous message passing that is compliant with the synchronous communication events of the CSP formalisms. This framework is designed to be used for passing generic information between application components operating on both architectures and is intended to operate in conjunction with existing datapaths present on the NPU which in turn are responsible for network traffic transmission. An investigation of different message passing topologies is covered before the proposed message passing fabric is presented. As a proof of concept, an initial implementation of the fabric is developed and tested to determine its viability and correctness. Through testing it is shown that the implemented framework operates as intended. However, it is noted the throughput of the exploratory implementation is not considered suitable for high-performance applications and further evaluation is required.
- Full Text:
- Date Issued: 2018
Investigating multi-thread utilization as a software defence mechanism against side channel attacks
- Frieslaar, Ibraheem, Irwin, Barry V W
- Authors: Frieslaar, Ibraheem , Irwin, Barry V W
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430190 , vital:72672 , https://doi.org/10.1145/3015166.3015176
- Description: A state-of-the-art software countermeasure to defend against side channel attacks is investigated in this work. The implementation of this novel approach consists of using multi-threads and a task scheduler on a microcontroller to purposefully leak out information at critical points in the cryptographic algorithm and confuse the attacker. This research demonstrates it is capable of outperforming the known countermeasure of hiding and shuffling in terms of preventing the secret information from being leaked out. Furthermore, the proposed countermeasure mitigates the side channel attacks, such as correlation power analysis and template attacks.
- Full Text:
- Date Issued: 2016
- Authors: Frieslaar, Ibraheem , Irwin, Barry V W
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430190 , vital:72672 , https://doi.org/10.1145/3015166.3015176
- Description: A state-of-the-art software countermeasure to defend against side channel attacks is investigated in this work. The implementation of this novel approach consists of using multi-threads and a task scheduler on a microcontroller to purposefully leak out information at critical points in the cryptographic algorithm and confuse the attacker. This research demonstrates it is capable of outperforming the known countermeasure of hiding and shuffling in terms of preventing the secret information from being leaked out. Furthermore, the proposed countermeasure mitigates the side channel attacks, such as correlation power analysis and template attacks.
- Full Text:
- Date Issued: 2016
Technology solutions to strengthen the integration of marginalized communities into the global knowledge society
- Hlungulu, Bulumko, Kunjuzwa, Dumani, Ndlovu, Nyankiso, Samalenge, Jimmy, Sikhumbuzo, Ngwenya, Thinyane, Mamello, Terzoli, Alfredo
- Authors: Hlungulu, Bulumko , Kunjuzwa, Dumani , Ndlovu, Nyankiso , Samalenge, Jimmy , Sikhumbuzo, Ngwenya , Thinyane, Mamello , Terzoli, Alfredo
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430769 , vital:72714 , https://ieeexplore.ieee.org/abstract/document/5753005
- Description: Information and Communication Technology (ICT) has made it possible to explore novel and innovative mechanisms to leap-frog socio-economic development in rural and marginalized communities. An ICT for development intervention called Siyakhula Living Lab (SLL) has been underway in Dwesa, a rural community in the Eastern Cape Prov-ince, for the past four years. The living lab methodology, which enables user-driven innovation within a multi-stakeholder relationship of aca-demia, user communities, government and private industry, has facili-tated greater integration of the Dwesa community into the digital ecolo-gy and subsequently the knowledge society. This paper introduces the SLL intervention, discusses the SLL's supporting technical infrastruc-ture and the interventions that are undertaken towards long-term sus-tainability of the project. The developed eServices are also discussed, with a view to highlighting the key characteristics that contribute to in-creased context-sensitivity, ownership, and buy-in from the community.
- Full Text:
- Date Issued: 2010
- Authors: Hlungulu, Bulumko , Kunjuzwa, Dumani , Ndlovu, Nyankiso , Samalenge, Jimmy , Sikhumbuzo, Ngwenya , Thinyane, Mamello , Terzoli, Alfredo
- Date: 2010
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430769 , vital:72714 , https://ieeexplore.ieee.org/abstract/document/5753005
- Description: Information and Communication Technology (ICT) has made it possible to explore novel and innovative mechanisms to leap-frog socio-economic development in rural and marginalized communities. An ICT for development intervention called Siyakhula Living Lab (SLL) has been underway in Dwesa, a rural community in the Eastern Cape Prov-ince, for the past four years. The living lab methodology, which enables user-driven innovation within a multi-stakeholder relationship of aca-demia, user communities, government and private industry, has facili-tated greater integration of the Dwesa community into the digital ecolo-gy and subsequently the knowledge society. This paper introduces the SLL intervention, discusses the SLL's supporting technical infrastruc-ture and the interventions that are undertaken towards long-term sus-tainability of the project. The developed eServices are also discussed, with a view to highlighting the key characteristics that contribute to in-creased context-sensitivity, ownership, and buy-in from the community.
- Full Text:
- Date Issued: 2010
An exploration of Work-Integrated Learning for a professional public service. The co-creation of the public servant of the future.
- Authors: Draai, Enaleen
- Subjects: Public Service, Work-Integrated Learning , Public Service, Public servant of the future
- Language: English
- Type: text , PDF , Lectures
- Identifier: http://hdl.handle.net/10948/66482 , vital:75534
- Description: In its quest for growth and development, society is continually met with new and emerging phenomena that seek co-existence with perennial issues. Society is thus defined by a myriad of complex socioeconomic, governance, political, and technological challenges requiring problem-solving for change. Human capital development informed by requisite knowledge, competence, and skills becomes crucial. However, graduate employability has drawn substantial attention from employers and the world of work, citing a mismatch between the curriculum pursued in higher education and the work readiness of graduates. In this discussion, higher education refers to universities. The implication is that these graduates do not hold the attributes and aptitudes required and expected by the world of work. Graduates lack the requisite aptitude to transfer the knowledge acquired (Breedenkamp, Botma and Nyoni 2023:36; Mseleku 2022:775). These assertions are particular where regulation and professional registration are not a requirement of the qualification and occupation. Studies have also shown that students cite a mismatch between the curriculum pursued, which is focused chiefly on theoretical foundations with little emphasis on practical linkage and their ability to secure employment, thus compounding the transition from studentship to employee. (Harry, Chinyamurindi and Mjoli: 2018:2; Mncayi 2021). Furthermore, the qualifications pursued by graduates are cited as not meeting labour demands where a scarce skills gap exists. In addition, under-employment is also evident when individuals assume employment in areas that do not develop their expertise in the qualifications pursued. Similarly, the individuals also pursue continuous temporary and short-term contractual employment unrelated to their disciplinary focus acquired (Basson, du Plessis and Brink 2023:119). The ability to secure employment draws attention to the individual and the attributes held for employability.
- Full Text:
- Authors: Draai, Enaleen
- Subjects: Public Service, Work-Integrated Learning , Public Service, Public servant of the future
- Language: English
- Type: text , PDF , Lectures
- Identifier: http://hdl.handle.net/10948/66482 , vital:75534
- Description: In its quest for growth and development, society is continually met with new and emerging phenomena that seek co-existence with perennial issues. Society is thus defined by a myriad of complex socioeconomic, governance, political, and technological challenges requiring problem-solving for change. Human capital development informed by requisite knowledge, competence, and skills becomes crucial. However, graduate employability has drawn substantial attention from employers and the world of work, citing a mismatch between the curriculum pursued in higher education and the work readiness of graduates. In this discussion, higher education refers to universities. The implication is that these graduates do not hold the attributes and aptitudes required and expected by the world of work. Graduates lack the requisite aptitude to transfer the knowledge acquired (Breedenkamp, Botma and Nyoni 2023:36; Mseleku 2022:775). These assertions are particular where regulation and professional registration are not a requirement of the qualification and occupation. Studies have also shown that students cite a mismatch between the curriculum pursued, which is focused chiefly on theoretical foundations with little emphasis on practical linkage and their ability to secure employment, thus compounding the transition from studentship to employee. (Harry, Chinyamurindi and Mjoli: 2018:2; Mncayi 2021). Furthermore, the qualifications pursued by graduates are cited as not meeting labour demands where a scarce skills gap exists. In addition, under-employment is also evident when individuals assume employment in areas that do not develop their expertise in the qualifications pursued. Similarly, the individuals also pursue continuous temporary and short-term contractual employment unrelated to their disciplinary focus acquired (Basson, du Plessis and Brink 2023:119). The ability to secure employment draws attention to the individual and the attributes held for employability.
- Full Text:
Colonisation and community structure of benthic diatoms on artificial substrates following a major flood event: a case of the Kowie River (Eastern Cape, South Africa)
- Dalu, Tatenda, Froneman, P William, Chari, Lenin D, Richoux, Nicole B
- Authors: Dalu, Tatenda , Froneman, P William , Chari, Lenin D , Richoux, Nicole B
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143357 , vital:38239 , http://dx.doi.org/10.4314/wsa.v40i3.10
- Description: A major flooding event that occurred during October–November 2012 caused major changes in the Kowie River hydromorphology and aquatic communities. The aim of our study was to identify the environmental variables that structure riverine benthic diatom communities at upstream and downstream locations 25 km apart on the Kowie River, South Africa. This was undertaken using tiles as artificial substrates so that we could study how the communities developed after the flood disturbance. The diatom community structure was assessed over a 28-day period following a flood event in October 2012. The Mann Whitney test indicated that there was a statistically significant difference (p 0.05) in total dissolved solids, salinity, pH and oxygen reduction potential between the two sites. In total, 58 diatom species belonging to 30 genera were identified over the 28-day study.
- Full Text:
- Date Issued: 2014
- Authors: Dalu, Tatenda , Froneman, P William , Chari, Lenin D , Richoux, Nicole B
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143357 , vital:38239 , http://dx.doi.org/10.4314/wsa.v40i3.10
- Description: A major flooding event that occurred during October–November 2012 caused major changes in the Kowie River hydromorphology and aquatic communities. The aim of our study was to identify the environmental variables that structure riverine benthic diatom communities at upstream and downstream locations 25 km apart on the Kowie River, South Africa. This was undertaken using tiles as artificial substrates so that we could study how the communities developed after the flood disturbance. The diatom community structure was assessed over a 28-day period following a flood event in October 2012. The Mann Whitney test indicated that there was a statistically significant difference (p 0.05) in total dissolved solids, salinity, pH and oxygen reduction potential between the two sites. In total, 58 diatom species belonging to 30 genera were identified over the 28-day study.
- Full Text:
- Date Issued: 2014
Can δ15N and δ13C stable isotopes and fatty acid signatures indicate changes in phytobenthos composition on an artificial substrate?
- Dalu, Tatenda, Froneman, P William
- Authors: Dalu, Tatenda , Froneman, P William
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68086 , vital:29197 , https://doi.org/10.2989/16085914.2014.974018
- Description: Publisher version , Temporal changes in fatty acid composition and δ15N, δ13C stable isotope values of the phytobenthos growing on artificial clay substrates under natural conditions over a 28-day period at an upstream and a downstream site in the Kowie River near Grahamstown were investigated in 2012. High concentrations of diatom markers 16:1ω7 and 20:5ω3 fatty acids were recorded, especially at the downstream site, reflecting the importance of diatoms in contributing to the phytobenthos communities at that station. After day 7 at the downstream site the average δ15N value of the phytobenthos was lighter, gradually increasing by ∼2‰ and ∼5‰ overall to heavier values on day 28. At the upstream site there were no significant changes (<1‰ increase) in δ15N values of the phytobenthos over time. Stable nitrogen (δ15N) and carbon (δ13C) signatures in the phytobenthos communities were significantly different between sites (one-way ANOVA; p < 0.001). The stable isotope values and fatty acid concentrations of phytobenthos at the downstream site were different to those of the phytobenthos at the upstream site, and they changed concurrently with changes in the phytobenthos community structure. At the downstream site there was a strong correlation of the δ15N of phytobenthos with nitrates (R = 0.56) and time (weeks; R = 0.81). However, the fatty acids were not specific enough to characterise the composition of phytobenthos communities. Other biomarker methods, such as stable isotopes and microscopic examination of the communities, were found to be useful. The results from this relatively small-scale tile experiment indicate the complexity of changes in fatty acid composition and δ15N, δ13C stable isotope values of a phytobenthos community. Stable isotope and fatty acid composition can be successfully used to map changes in phytobenthos composition and carbon and nitrogen flow patterns along a river continuum.
- Full Text: false
- Date Issued: 2014
- Authors: Dalu, Tatenda , Froneman, P William
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68086 , vital:29197 , https://doi.org/10.2989/16085914.2014.974018
- Description: Publisher version , Temporal changes in fatty acid composition and δ15N, δ13C stable isotope values of the phytobenthos growing on artificial clay substrates under natural conditions over a 28-day period at an upstream and a downstream site in the Kowie River near Grahamstown were investigated in 2012. High concentrations of diatom markers 16:1ω7 and 20:5ω3 fatty acids were recorded, especially at the downstream site, reflecting the importance of diatoms in contributing to the phytobenthos communities at that station. After day 7 at the downstream site the average δ15N value of the phytobenthos was lighter, gradually increasing by ∼2‰ and ∼5‰ overall to heavier values on day 28. At the upstream site there were no significant changes (<1‰ increase) in δ15N values of the phytobenthos over time. Stable nitrogen (δ15N) and carbon (δ13C) signatures in the phytobenthos communities were significantly different between sites (one-way ANOVA; p < 0.001). The stable isotope values and fatty acid concentrations of phytobenthos at the downstream site were different to those of the phytobenthos at the upstream site, and they changed concurrently with changes in the phytobenthos community structure. At the downstream site there was a strong correlation of the δ15N of phytobenthos with nitrates (R = 0.56) and time (weeks; R = 0.81). However, the fatty acids were not specific enough to characterise the composition of phytobenthos communities. Other biomarker methods, such as stable isotopes and microscopic examination of the communities, were found to be useful. The results from this relatively small-scale tile experiment indicate the complexity of changes in fatty acid composition and δ15N, δ13C stable isotope values of a phytobenthos community. Stable isotope and fatty acid composition can be successfully used to map changes in phytobenthos composition and carbon and nitrogen flow patterns along a river continuum.
- Full Text: false
- Date Issued: 2014