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Towards the development of a protocol for the selection of probiotics in marine fish larviculture

  • Authors: Vine, Niall Gordon
  • Date: 2005
  • Subjects: Marine fishes -- Larvae Bacteria Fishes -- Microbiology Fish culture
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5329 , http://hdl.handle.net/10962/d1005175
  • Description: Manipulation or control of the microbiological aquaculture environment has been identified as an important focus area for future hatchery development. Subsequently, alternatives to obtain control of the microbiological environment are being sought of which the field of probiotics appears highly promising. Probiotics are usually selected based on various in vitro characteristics, however, the methods used differ and are sometimes unsuccessful due to poor experimentation. The aim of this work is to contribute towards the development of a protocol for the in vitro screening of bacterial candidate probiotics for marine fish larviculture. To reduce the number of candidate probiotics to be tested in vivo, various in vitro experiments need to be conducted, each screening for a particular mode of action – antagonism towards pathogen through production of antimicrobial compounds, growth and attachment to fish intestinal mucus, and the production of other beneficial compounds such as vitamins, fatty-acids and digestive enzymes. A total of 108 bacteria species were isolated from the digestive tract of the adult common clownfish, Amphiprion percula to screen for potential probiotics to be used in clownfish larval rearing. The antagonistic compounds assay identified twelve isolates which showed antagonism towards two or more aquatic pathogens. This was followed by an in vitro test that involved growing the organisms in fish intestinal mucus and modeling their growth parameters. A ranking index (RI) was developed using the lag period (λ) and doubling time (td) of the organism, where (1over λ x td) x 100. Five candidate probionts (AP1-AP5) with varied growth parameters were used for further in vitro experiments. The attachment to mucus assay introduced a novel tool for quantifying competition for attachment sites between candidate probionts and pathogens on mucus. Candidate probiont Pseudoalteromonas AP5 reduced the attachment ability of Vibrio alginolyticus when added before the pathogen and partially out-competed the pathogen for attachment sites when added second. In vitro screening for the production of beneficial compounds tested the candidate probiotics’ ability to produce digestive enzymes - trypsin, lipase and alkaline phosphatase as well as carotenoids and vitamin C. Candidate probiont Pseudoalteromonas AP5 produced high levels of the enzymes (98.2, 34.1 and 91.3 mU product liberated.ml⁻¹, respectively) and contained carotenoids while Kocuria AP4 contained carotenoids but produced low quantities of enzymes (7.8, 0 and 59 mU product liberated.ml⁻¹, respectively). None of the candidate probiotics produced vitamin C. To eliminate potential pathogenic or toxic candidate probionts, Artemia nauplii were exposed to each candidate probiont and the percentage Artemia mortality after 24-hours was determined. Candidate probiont AP2 caused high mortality of Artemia nauplii (98.4%) and was excluded from further studies. Identification of candidate probionts AP3-AP5 was performed using 16S-rDNA molecular techniques and the bacteria were assigned the names Bacillus AP3, Kocuria AP4 and Pseudoalteromonas AP5, respectively. Two methods of larval probiont delivery were tested – attachment to Artemia, and in-water delivery. Attachment to Artemia was high for both Kocuria AP4 and Pseudoalteromonas AP5 (7.2 x10³ and 2.7x10⁴ bacteria.nauplius⁻¹, respectively) while the in-water viability experiment showed that Kocuria AP4 comprised 23.9% of the total culturable water microflora after 24 hours while Pseudoalteromonas AP5 contributed 100%. To validate the findings from the in vitro experiments, in vivo trials using clownfish larvae were performed. Of the four candidate probiotics tested, only Kocuria AP4 showed potential to increase larval survival. In vitro tests produced a better understanding of the possible mode of action and strategies of competition between bacteria, however, the number of criteria in which a candidate probiont is successful in vitro may not be the best predictor for its effectiveness in vivo. Commercial studies that reduce between-treatment variation are required to test predictions about the most suitable probiont or combinations thereof.
  • Full Text:
  • Date Issued: 2005

Training needs for municipal employees: a case study of Makana Municipality

Trans-oceanic and endemic origins of the small minnow mayflies (Ephemeroptera, Baetidae) of Madagascar

  • Authors: Monaghan, Michael T , Gattolliat, Jean-Luc , Sartori, Michel , Elouard, Jean-Marc , James, Helen , Derleth, Pascale , Glaizot, Olivier , De Moor, Ferdy C , Vogler, Alfried P
  • Date: 2005
  • Language: English
  • Type: Article
  • Identifier: vital:7008 , http://hdl.handle.net/10962/d1008386
  • Description: We investigated the relative importance of dispersal and vicariance in forming the Madagascar insect fauna, sequencing approximately 2300bp from three rRNA gene regions to investigate the phylogeny of Afrotropical small minnow mayflies (Ephemeroptera: Baetidae). Six lineages contained trans-oceanic sister taxa, and variation in genetic divergence between sister taxa revealed relationships that range from very recent dispersal to ancient vicariance. Dispersal was most recent and frequent in species that spend the larval stage in standing water, adding to evidence that these evolutionarily unstable habitats may select for ecological traits that increase dispersal in insects. Ancestral state likelihood analysis suggested at least one Afrotropical lineage had its origin in Madagascar, demonstrating that unidirectional dispersal from a continental source may be too simplistic. We conclude that the Malagasy mayfly fauna should be considered in a biogeographical context that extends beyond Madagascar itself, encompassing trans-oceanic dispersal within multiple lineages.
  • Full Text:
  • Date Issued: 2005

Trans-oceanic and endemic origins of the small minnow mayflies (Ephemeroptera, Baetidae) of Madagascar

  • Authors: Monaghan, M T , Gattolliat, J L , Sartori, Michel , Elouard, J M , Barber-James, Helen M , Derleth, P , Glaizot, Olivier , De Moor, Ferdy C , Vogler, Alfred P
  • Date: 2005
  • Language: English
  • Type: Article
  • Identifier: vital:6957 , http://hdl.handle.net/10962/d1011998
  • Description: We investigated the relative importance of dispersal and vicariance in forming the Madagascar insect fauna, sequencing approximately 2300bp from three rRNA gene regions to investigate the phylogeny of Afrotropical small minnow mayflies (Ephemeroptera: Baetidae). Six lineages contained trans-oceanic sister taxa, and variation in genetic divergence between sister taxa revealed relationships that range from very recent dispersal to ancient vicariance. Dispersal was most recent and frequent in species that spend the larval stage in standing water, adding to evidence that these evolutionarily unstable habitats may select for ecological traits that increase dispersal in insects. Ancestral state likelihood analysis suggested at least one Afrotropical lineage had its origin in Madagascar, demonstrating that unidirectional dispersal from a continental source may be too simplistic. We conclude that the Malagasy mayfly fauna should be considered in a biogeographical context that extends beyond Madagascar itself, encompassing trans-oceanic dispersal within multiple lineages.
  • Full Text:
  • Date Issued: 2005

Transmitting rdf graph deltas for a cheaper semantic web

  • Authors: Cloran, Russell , Irwin, Barry V W
  • Date: 2005
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/428288 , vital:72500
  • Description: The Resoure Description Format is set to become the format to fulfill the vision of the Semantic Web. If RDF is widely to be used as a data representation framework, it would be advantageous to support the transmission differences in RDF graphs, enabling small and therefore possibly more frequent updates. This paper discusses the tools re-quired to enable transmission of graph differences, and the work need-ed to complete this toolset.
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  • Date Issued: 2005

Trauma, imagery and the therapeutic relationship : Langu's story

  • Authors: Karpelowsky, B , Edwards, David J A
  • Date: 2005
  • Language: English
  • Type: Article
  • Identifier: vital:6268 , http://hdl.handle.net/10962/d1008267
  • Description: This paper, a phenomenological case study, describes the psychotherapy of Langu (pseudonym), a 21-year-old student, who presented with Acute Stress Disorder following a series of motor accidents that affected him and his family. Langu's most distressing experience was having to identify his brother's mutilated and severely burned body. Because of the intensity of the intrusive re-experiencing of traumatic imagery and the degree of dissociative numbing, Langu participated in four intensive guided imagery sessions, which involved reliving the incident, and imaginal dialogues with his dead brother. Session records and supervision notes from the therapy process that unfolded over 22 sessions served as the basis for a thematically selective case narrative. Additional material was obtained from several research interviews with Langu over the following months. The narrative highlights the impact of the imagery work as well as relational aspects of the therapy. The case narrative provides a source for examining many aspects of the psychological impact of trauma and the path to healing, as well as the dilemmas and challenges faced by therapists working with traumatised individuals.
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  • Date Issued: 2005

Trauma, resilience and vulnerability to PTSD : a review and clinical case analysis

  • Authors: Edwards, David J A , Sakasa, P , Van Wyk, G
  • Date: 2005
  • Language: English
  • Type: Article
  • Identifier: vital:6230 , http://hdl.handle.net/10962/d1007780
  • Description: This article begins with two case examples of a girl and an adolescent who were raped and developed chronic PTSD. These are used as a basis for understanding the role of a range of factors that are associated with resilience and vulnerability in the face of traumatic events. A literature review examines the proportion of individuals who develop PTSD following trauma and the factors associated with vulnerability and resilience. These include gender, developmental factors, social support and personality factors. Psychological factors associated with maintenance of chronic PTSD are also briefly reviewed. This material is used as a basis for reconsidering the case examples. Each case is formulated within a framework based on sources of vulnerability and qualities of resilience. Approaches to intervention are suggested that could address the range of factors making the individuals vulnerable to chronic psychological problems and support resiliency and recovery.
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  • Date Issued: 2005

Treating PTSD in South African contexts : a theoretical framework and a model for developing evidence-based practice

  • Authors: Edwards, David J A
  • Date: 2005
  • Language: English
  • Type: Article
  • Identifier: vital:6231 , http://hdl.handle.net/10962/d1007781
  • Description: Several psychological factors contribute to the development and maintenance of post-traumatic stress disorder (PTSD) because they interfere with the emotional processing of the traumatic event. These include problematic and painful emotions such as anxiety, shame, guilt and grief, distorted or dysfunctional cognitions, and cognitive, emotional, and behavioural avoidance mechanisms. Analysis of these maintaining factors provides the basis for current approaches to treatment which support traumatised individuals in facing emotional pain, working to resolve shame, grief and guilt, and expanding existing schemas to accommodate the traumatic event(s). Randomised controlled trials (RCTs) are reviewed in which the efficacy of some of these treatments have been evaluated. While many South African practitioners are familiar with current evidence-based approaches and are skilled at adapting them to local cultural and contextual conditions, a great deal still needs to be done to build a sound research base for local practice in the treatment of PTSD and disseminating that research to practitioners in the field. It is recommended that a case-based evaluation strategy be used to complement the findings of international RCT studies in order to build a foundation of locally contextualised and applicable scientific knowledge.
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  • Date Issued: 2005

Trust on the Web

  • Authors: Cloran, Russell , Irwin, Barry V W
  • Date: 2005
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/428900 , vital:72544 , https://digifors.cs.up.ac.za/issa/2005/Proceedings/Full/025_Article.pdf
  • Description: This paper forms a backdrop for work investigating trust on the semantic web. With the mass of information currently available on the web, and the low barrier to entry for the publication of information on the web, it can be difficult to classify the au-thority of information found on the web. We use a case study of a suspected phish-ing scam in South Africa to examine the methods an advanced user may use to veri-fy the authenticity of a web site and the information it published. From this case study, we see that a website which is legitimate may easily appear to be a scam, because of the manner in which information is presented and the failure to use es-tablished industry best practices. We discuss a number of ways in which doubt may have been eliminated. We then discuss how a distributed trust system, as favoured by many researchers in trust on the semantic web, may have been implemented in this case to prove the authenticity of the site without the traditional means involv-ing the high cost of a digital certificate from a recognised Certificate Authority.
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  • Date Issued: 2005

Unconscious influences on discourses about consciousness : ideology, state-specific science and unformulated experience

  • Authors: Edwards, D J A
  • Date: 2005
  • Language: English
  • Type: Article
  • Identifier: vital:6226 , http://hdl.handle.net/10962/d1007776
  • Description: Discussions about consciousness are complicated by the fact that participants do not share a common underlying “ordinary” consciousness. Everyday experience is founded on what Teasdale calls implicational cognition, much of which is not verbally formulated. An unacknowledged aspect of debate is individuals’ attempts to negotiate the expression of their unformulated experience. This is further complicated by the way in which a discourse, based on particular ontological assumptions, exercises an ideological control which limits what underlying aspects of experience can be formulated at all. Tart’s concept of state specific sciences provides a framework within which the role of unformulated experience can be acknowledged and taken into account. Unless this is done, debates will be vitiated by participants engaging in ideological struggles and talking at cross-purposes.
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  • Date Issued: 2005

Understanding editorial independence and public accountability issues in public broadcasting service: a study of the editorial policies at the South African Broadcasting Corporation (SABC)

  • Authors: Jjuuko, Denis Charles
  • Date: 2005
  • Subjects: South African Broadcasting Corporation , South African Broadcasting Corporation -- Law and legislation , Broadcasting -- Social aspects -- South Africa , Mass media -- Social aspects -- South Africa , Broadcasting policy -- South Africa
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3437 , http://hdl.handle.net/10962/d1002891 , South African Broadcasting Corporation , South African Broadcasting Corporation -- Law and legislation , Broadcasting -- Social aspects -- South Africa , Mass media -- Social aspects -- South Africa , Broadcasting policy -- South Africa
  • Description: The concepts of editorial independence and public accountability are necessary in public broadcasting service as they help make a distinction between a public service broadcaster, a government and a commercial service broadcaster. This is because public service broadcasters are tasked with the responsibility of serving the interests of the general public. To do this, the above mentioned concepts have to be in place. This study examines these issues (editorial independence and public accountability) with reference to a case study of the editorial policies of the South African Broadcasting Corporation (SABC). Using public broadcasting theory, policy theory and qualitative research methods, the study examines the genesis of these editorial policies in 2003/2004 and how they provide the SABC with a means of balancing the tensions of editorial independence and public accountability. In analysing the SABC’s editorial policies, the study deals only with those policies whose principles are directly related to editorial independence and public accountability. Although some of these policies are found to be in line with public broadcasting service trends, others are found lacking. Various recommendations are made. The case study demonstrates the importance of an integrated and elaborated policy perspective in setting out how a public service broadcaster can manage editorial independence and public accountability. It also highlights the importance of using international ‘role models’ in ways that are appropriately adapted for the specific country concerned.
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  • Date Issued: 2005

Unlocking the armour: enabling intrusion detection and analysis of encrypted traffic streams

  • Authors: Irwin, Barry V W
  • Date: 2005
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/428845 , vital:72540
  • Description: In the interests of maintaining end to end security, increasing volumes of information are being encrypted while in transit. Many organisations and users will make use of secure encrypted protocols for information interchange given an option. The very security that is provided by these transport protocols, such as IPSEC, HTTPS and SSH also acts against the security monitoring of an organisation’s traffic. Intrusion detection systems are no longer easily able to inspect the payload of encrypted protocols. Similarly these protocols can potentially be difficult for securi-ty and network administrators to debug, validate and analyse. This pa-per discusses the need for a means of a trusted third party being able to unpack encrypted data traversing a network and a proposes an ar-chitecture which would enable this to be achieved through the extrac-tion and sharing of the appropriate encipherment tokens, based on the assumption that an organisation has legitimate access to one side of a communication entering or exiting its network. This problem also has particular relevance to honey-net research and for investigators trying to perform real-time monitoring of an intruder which is making use of such a protected protocol. A proof of concept implementation of the proposed architecture is also discussed.
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  • Date Issued: 2005

Using a FreeBSD "cluster" to provide network services

  • Authors: Siebörger, David
  • Date: 2005
  • Language: English
  • Type: Conference paper
  • Identifier: vital:6611 , http://hdl.handle.net/10962/d1009524
  • Description: A presentation on how FreeBSD might be used in a load-balancing cluster, using work done at Rhodes University as a case study. Presented to a community of higher education IT practitioners in September 2005.
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  • Date Issued: 2005

Using aspects of game theory for enhanced stakeholder participation perspectives in integrated water resource management: a Kat River Valley case study

  • Authors: Mbatha, Cyril
  • Date: 2005
  • Subjects: Water resources development -- Case studies , Water-supply -- South Africa -- Kat River Valley -- Management , Economic development -- Case studies , Water-supply -- Government policy -- South Africa , Economic development -- South Africa -- Kat River Valley , Game theory
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:971 , http://hdl.handle.net/10962/d1002705 , Water resources development -- Case studies , Water-supply -- South Africa -- Kat River Valley -- Management , Economic development -- Case studies , Water-supply -- Government policy -- South Africa , Economic development -- South Africa -- Kat River Valley , Game theory
  • Description: South Africa is a water poor region and yet, like in many other developing countries, water resources are a valuable production input in socially important industries such as agriculture and mining (Nieuwoudt et al., 2004:162-182). With a mean annual rainfall and runoff of 502mm and 42mm (420m³ per hectare per annum) respectively, Briers and Powell (1993:1) speculate that water shortages will limit South Africa’s economic development in the twenty-first century. In response to the challenges of water resource scarcity and socio-economic inequalities, in 1997 the South African Department of Water Affairs and Forestry (DWAF), following international trends, formulated a National Water Policy (NWP) based on Integrated Water Resource Management (IWRM) principles (Palmer et al., 2003). The main objectives of the NWP (1997) are to protect national water resources from degradation, provide economically disadvantaged communities with access to water resources and promote economic development, through the devolution of water management responsibilities to locally established water institutions (NWP, 1997). The pursuit of these objectives requires a thorough investigation of biophysical, sociopolitical and economic characteristics of the demarcated water areas. For such an investigation to provide accurate and locally relevant results, broad stakeholder participation is of paramount importance. The thesis discusses economic measures required in pursuing enhanced stakeholder participation levels at local levels. A socio-economic survey investigation describing major participation trends against reported property rights and Willingness to Pay values was conducted in the Kat River Valley, Eastern Cape province. From the investigation, observed participation trends driven by economic interests were identified and used in recommendations proposed for the policy implementation process. Using game theoretic arguments as guidelines in soliciting cooperative behaviour in the use and consumption of common resources (Ostrom, 1990), the thesis proposes the introduction of water related public works projects as employment creating vehicles for individuals and communities targeted for economic empowerment and participation in the water policy. However, for sustainable stakeholder participation levels, it is argued that the employment positions created through the projects need to be designed in a manner that would encourage an evolution of long-term relationships between stakeholders and the water management institutions.
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  • Date Issued: 2005

Virtuous living towards an African theology of wisdom in the context of the African renaissance

  • Authors: Nkesiga, Reverend Solomon Basabose
  • Date: 2005
  • Subjects: Wisdom -- Religious aspects , Ethics -- Africa -- Religious aspects , Black theology
  • Language: English
  • Type: Thesis , Doctoral , DPhil
  • Identifier: vital:8414 , http://hdl.handle.net/10948/454 , http://hdl.handle.net/10948/d1011900 , Wisdom -- Religious aspects , Ethics -- Africa -- Religious aspects , Black theology
  • Description: The structure of this study is a complex inter-relationship of a variety of sources in a theological work, namely, personal experience, African social and politico-economic context, philosophical reflection, wisdom traditions and Christian theology. These sources form a coherent inter-relationship which is foundational for an African theology of wisdom. The introduction gives an overview of my moral and theological formation. This is intended to provide a perspective through which the issue of moral orientation in African context has been approached. It is therefore entitled: Moral formation and the shaping of a theological mind. The first chapter answers the question: Why is Africa in need of a wisdom theology that addresses the issue of moral regeneration? This question is posed in the broader context of the current African Renaissance debates. The links between the Italian (European) and African Renaissance indicate that moral regeneration is a crucial part of the socio-political, intellectual and economic re-birth of Africa. This “socio-historical” source gives the context and urgency of a wisdom theology. It is therefore entitled: A contextual analysis: The European and African Renaissance. The second chapter re-asserts the rise of virtue ethics as an alternative ethical theory to the predominant deontological and utilitarian traditions. This is achieved through analysing Alisdair MacIntyre’s earlier work, After Virtue: A Study in Moral Theory (1981), set in the context of Iris Murdoch and Elizabeth Anscombe, the modern initiators of a virtue ethic. This “philosophical” source gives the theoretical framework that addresses the question of moral formation. It is therefore entitled: A philosophical analysis: The rise of virtue ethics as alternative ethical theory. The third chapter is devoted to two related “wisdom” themes: Firstly, the seven traditional virtues are briefly described highlighting the virtue of wisdom as foundational. Secondly, the idea of wisdom is further developed via three wisdom traditions, namely: wisdom in the Hellenistic, Judeo-Christian and African traditions. This “sapiential” source gives this African theology of wisdom its most important building blocks. This chapter is therefore entitled: A sapiential analysis: Wisdom as foundation for virtue ethics in Africa. The last chapter brings the previous sources together under a specific theological perspective. It draws on aspects of recent African theologians’ work, notably: Kwame Gyekye and Benezet Bujo who engage with and bring together Western and African theological traditions. I answer a pertinent question, “What does such a ‘theological’ perspective entail?” I draw on Scripture and its Trinitarian tradition to demonstrate how African wisdom, reinforced by the framework of virtue theory, and developed in the context of present-day Africa by an African student of theology, has the potential to contribute to the moral transformation of Africa. This more overt “theological” source is the distinctive Christian enterprise of an African wisdom theology. The chapter title is aligned with the overall title of this study: A theological analysis: Toward an African virtue ethics? To this end, this study achieves its attempt to construct an inter-related framework from which an African theology of wisdom may emerge.
  • Full Text:
  • Date Issued: 2005

Web usage mining of organisational web sites

  • Authors: Oosthuizen, Craig Peter
  • Date: 2005
  • Subjects: Web usage mining -- South Africa , Internet users -- South Africa , Information visualization
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:9595 , http://hdl.handle.net/10948/399 , Web usage mining -- South Africa , Internet users -- South Africa , Information visualization
  • Description: Web Usage Mining (WUM) can be used to determine whether the information architecture of a web site is structured correctly. Existing WUM tools however, do not indicate which web usage mining algorithms are used or provide effective graphical visualisations of the results obtained. WUM techniques can be used to determine typical navigation patterns of the users of organisational web sites. An organisational web site can be described as a site which has a high level of content. The Computer Science & Information Systems (CS&IS) web site at the Nelson Mandela Metropolitan University (NMMU) is an example of such a web site. The process of combining WUM and information visualisation techniques in order to discover useful information about web usage patterns is called visual web mining. The goal of this research is to discuss the development of a WUM model and a prototype, called WebPatterns, which allows the user to effectively visualise web usage patterns of an organisational web site. This will facilitate determining whether the information architecture of the CS&IS web site is structured correctly. The WUM algorithms used in WebPatterns are association rule mining and sequence analysis. The purpose of association rule mining is to discover relationships between different web pages within a web site. Sequence analysis is used to determine the longest time ordered paths that satisfy a user specified minimum frequency. A radial tree layout is used in WebPatterns to visualise the static structure of the organisational web site. The structure of the web site is laid out radially, with the home page in the middle and other pages positioned in circles at various levels around it. Colour and other visual cues are used to show the results of the WUM algorithms. User testing was used to determine the effectiveness and usefulness of WebPatterns for visualising web usage patterns. The results of the user testing clearly show that the participants were highly satisfied with the visual design and information provided by WebPatterns. All the participants also indicated that they would like to use WebPatterns in the future. Analysis of the web usage patterns presented by WebPatterns was used to determine that the information architecture of the CS&IS web site can be restructured to better facilitate information retrieval. Changes to the CS&IS web site web were suggested, included placing embedded hyperlinks on the home page to the frequently accessed sections of the web site.
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  • Date Issued: 2005

Wedwa mama

Wireless communication for previously disadvantaged secondary schools in Grahamstown, South Africa.

  • Authors: Brandt, Ingrid , Terzoli, Alfredo , Hodgkinson-Williams, Cheryl
  • Date: 2005
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/427615 , vital:72451 , https://citeseerx.ist.psu.edu/document?repid=rep1andtype=pdfanddoi=2520d49f684e821c84350ae8c504572f35186d2f
  • Description: With an alarmingly low teledensity in South Africa, less than 5% in some rural areas, and not much hope of further wired infrastructure, as the costs incurred are high compared to potential revenue, wireless connec-tivity could be a great asset and service in South Africa. This paper looks at how wireless communication technologies, 802.11, WiMAX and VSAT, can be used to allow broadband connectivity of schools to the Internet, with special reference to experimental work that is being done in Grahamstown schools.
  • Full Text:
  • Date Issued: 2005

Wireless Network Visualization Using Radio Propagation Modelling

  • Authors: Janse van Rensburg, Johanna , Irwin, Barry V W
  • Date: 2005
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/428859 , vital:72541 , https://d1wqtxts1xzle7.cloudfront.net/81589186/Papers_5CJanse_van_Rensburg_Wireless_Radio_Prop-libre.pdf?1646243170=esponse-content-disposi-tion=inline%3B+filename%3DWireless_Network_Visualization_Using_Rad.pdfExpires=1714748958Signature=OF69CzUsXIaE9WuVUQ~p01LV8Fdm4EOpX1eudE3qomWEWQ9jngy36AuZ38dZEAfIhWWFgO7byMtmx8hOUE3uYjjqLLGziqWV05r~K2n~DdSHAO1x2omrK53ew3lSW2AJ677zsqOIcRb-yVr7kE2PbAw1QolptUWQVI2YpAHEKdg5EQXm2iAW~FrQ7ljJxuwZTKaVLoubxj4HRLwJxTPIS9iN9nHn3sNKyIojfG6duWnCQ0dpkIKiKWTY6HVioBQCiN1vSdLUagXnTeRthoOFGyfo2kd3XG1Pi3tttIwFviPCh5H1297BCpMruY-h6XjSnPBGgAG33dOnkClBFnyAKg__Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA
  • Description: Wireless technologies have had an enormous impact on networking in re-cent years. It can create new business oppurtunities and allow users to communicate and share data in a new fashion. Wireless Networks de-crease installation costs, reduce the deployment time of a network and overcome physical barrier problems inherent in wiring. Unfortunately this flexibility comes at a price. The deployment, installation and setup of a WLAN is not a simple task and a number of factors need to be considered. Wireless Networks are notorious for being insecure due to signal spill, ad-hoc unauthorized access points and varying encryption strengths and standards. RF (Radio Frequency) interference and physical barriers sup-press a signal. In addition the channel frequencies each access point will be using in order to provide maximum roaming but minimum inter access point interference need to be considered. It is a complex balancing act to take these factors into account while still maintaining coverage, perfor-mance and security requirements. In this paper the benefits and feasibility of a model will be discussed that will enable the network administrator to visualize the coverage footprint of their wireless network when the above factors are taken into consideration. The program will be able to predict the strength, propagation and unwanted spill of signals which could compro-mise the security of an organisation prior to the deployment of a WLAN. In addition the model will provide functionality to visualize a signal from audit data once the WLAN is operational. The end result will be a program that can aid in the configuration, installation and management of a secure WLAN.
  • Full Text:
  • Date Issued: 2005

Woman doing Ngqokola

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