Browsing Faculty of Natural Sciences by Title
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Adesemowo, A. Kayode; Tucker, William D. (Telkom, 2003)[more][less]
Abstract: As mobile devices and networks become more data-centric, text messaging requires an extension of co-presence capabilities for better interactive discussion between input/output handicapped handheld users and their free form desktop counterparts. Given some degree of co-presence (online presence and awareness) in text-based Instant Messaging, we hope to increase this co-presence on a handheld with fast-track feedback (FF) mechanisms. These are user-defined gestures, such as emoticons, and prioritised messages. We are building a system that facilitates gesture input within an interactive text-based chat over a wireless network running Session Initiation Protocol (SIP). The chat bridges a robust desktop environment and a small number of handhelds. This work in progress looks into the SIP Instant Messaging and Presence Leveraging Extensions as a platform to provide fast-track interactive and co-presence feedback. The aim is to rubberise a hitherto plastic and limited instant messaging conversation. We shall measure co-presence levels between FF and standard IM environments in and without desktop and handhelds by engaging two groups of users in chats session. We expect to demonstrate that there exists high co-presence notion in open (work by Sun Research Awarenex Group and AT&T Hubbubme in similar domain were in closed systems) FF text messaging open environment as we would like to show that this higher presence brings a much more enhanced interactive discourse. The envisaged results are intended to extrapolate to online aware co-presence in the up and coming smart phones on 3G packet networks. URI: http://hdl.handle.net/10566/539 Files in this item: 1
AdesemowoTuckerMobileDevices2003.pdf (180.9Kb) -
Sjoling, Sara; Cowan, Donald A. (Springer Verlag, 2003)[more][less]
Abstract: The microbial diversity in maritime meltwater pond sediments from Bratina Island, Ross Sea, Antarctica was investigated by 16S rDNA-dependent molecular phylogeny. Investigations of the vertical distribution, phylogenetic composition, and spatial variability of Bacteria and Archaea in the sediment were carried out. Results revealed the presence of a highly diverse bacterial population and a significantly depthrelated composition. Assessment of 173 partial 16S rDNA clones analyzed by amplified rDNA restriction analysis (ARDRA) using tetrameric restriction enzymes (HinP1I 5'GVCGC3'and Msp I. 5'CVGG3', BioLabs) revealed 153 different bacterial OTUs (operational taxonomic units). However, only seven archaeal OTUs were detected, indicating low archaeal diversity. Based on ARDRA results, 30 bacterial clones were selected for sequencing and the sequenced clones fell into seven major lineages of the domain Bacteria; the a, c, and d subdivisions of Proteobacteria, the Cytophaga–Flavobacterium– Bacteroides, the Spirochaetaceae, and the Actinobacteria. All of the archaeal clones sequenced belonged to the group Crenarchaeota and phylogenetic analysis revealed close relationships with members of the deep-branching Group 1 Marine Archaea. URI: http://hdl.handle.net/10566/148 Files in this item: 1
Sjoling16SrDNA.pdf (543.4Kb) -
Sparks, Conrad, A.J.; Gibbons, Mark J. (Taylor & Francis and NISC, 2003)[more][less]
Abstract: A total of 242 zooplankton samples from the upper 100 m of the water column was collected discontinuously from March 1997 to January 1999 off the Orange River mouth on the west coast of southern Africa. Six species of hydromedusae were recovered at generally low abundance, of which Euphysa aurata, Leuckartia octona and Proboscidactyla menoni were dominant. E. aurata and L. octona showed evidence of seasonality in abundance. The low diversity of the fauna was remarkable and it is hypothesized that this might be attributable in part to sedimentation from the Orange River, and in part to locally weak circulation and the wide extent of the continental shelf. URI: http://hdl.handle.net/10566/380 Files in this item: 1
SparksHydromedusaeOrangeRiver2003.pdf (57.50Kb) -
Ngara, Rudo; Ndimba, Roya; Borch-Jensen, Jonas; Jensen, Ole Nørregaard; Ndimba, Bongani (Elsevier, 2012)[more][less]
Abstract: Sorghum bicolor, a drought tolerant cereal crop, is not only an important food source in the semi arid/arid regions but also a potential model for studying and gaining a better understanding of the molecular mechanisms of drought and salt stress tolerance in cereals. In this study, seeds of a sweet sorghumvariety, MN1618, were planted and grown on solid MS growth medium with or without 100mM NaCl. Heat shock protein expression immunoblotting assays demonstrated that this salt treatment induced stress within natural physiological parameters for our experimental material. 2D PAGE in combination with MS/MS proteomics techniques were used to separate, visualise and identify salinity stress responsive proteins in young sorghum leaves. Out of 281 Coomassie stainable spots, 118 showed statistically significant responses (p<0.05) to salt stress treatments. Of the 118 spots, 79 were selected for tandem mass spectrometric identification, owing to their good resolution and abundance levels, and of these, 55 were positively identified. Identified proteins were divided into six functional categories including both known and novel/putative stress responsive proteins. Molecular and physiological functions of some of our proteins of interest are currently under investigation via bioinformatic and molecular biology approaches. URI: http://hdl.handle.net/10566/543 Files in this item: 1
NdimbaSweetSorghum2012.pdf (765.8Kb) -
Adesemowo, A. Kayode; Tucker, William D. (Telkom, 2004)[more][less]
Abstract: A text only Instant Messaging (IM) built on the IETF open standard SIP/SIMPLE has been developed in line with our proposed introduction of a user-defined text Hotkey feature. These act as an on-click Affective Gesture (AG): in similitude to Face-to-Face (F2F) expressive gesture-like abilities. Given that text communication possesses expressive discourse with some presence level, we seek to show that one-click text-gesture fast-tracking enhances text communication further. For this study, we are taking a hybrid quantitative and qualitative approach. Initial Pre-trial results have shown that an AG approach is more likely to improve IM chat spontaneity/response rate. Further experimental trials are being undertaken. Mobile devices and networks are becoming more data-centric (evident in Japanese I-mode) even as mobile network voice Average Revenue Per User (ARPU) are declining, new stream of data services are required which must take cognisance of handhelds features albeit their small screen estate and input/output limitation. Given that IM is entrenched in the social space, especially among teenagers and gaining wide adoption in the business place, we believe extensions are required for IM steep uptake in the mobile world, much as SMS has gained prominence. Enhanced input mechanisms for handheld IM system are expected to increase co-presence between handheld users and their desktop-based counterparts while in a synchronous discussion. URI: http://hdl.handle.net/10566/548 Files in this item: 1
AdesemowoTuckerInstantMessaging2004.pdf (165.2Kb) -
Adesemowo, A. Kayode; Tucker, William D. (SAICSIT in association with ACM, 2005)[more][less]
Abstract: Text communication can be perceived as lacking in chat spontaneity, or plastic, due to medium limitations during interaction. A form of text messaging, Instant Messaging (IM), is now on the uptake, even on mobile handhelds. This paper presents results of using affective gesture to rubberise IM chat in order to improve synchronous communication spontaneity. The experimental design makes use of a text-only IM tool, running on handhelds, built with the Session Initiation Protocol (SIP) and the SIP Instant Messaging and Presence Leveraging Extensions (SIMPLE). The tool was developed with a novel user-defined hotkey – a one-click context menu that fast-tracks the creation and transmission of text-gestures and emoticons. A hybrid quantitative and qualitative approach was taken in order to enable data triangulation. Data collected from user trials affirms that the affective gesture hotkey facility improves chat responsiveness, thus enhancing chat spontaneity. URI: http://hdl.handle.net/10566/464 Files in this item: 1
AdesemowoTuckerInstantMessaging2005.pdf (364.4Kb) -
Cowan, Donald A. (UWC, 2010)[more][less]
Abstract: The IMBM Brochure (2009) provides a summary of the staffing, activities and outputs of the Institute for the 2009 academic year Description: Institute for Microbial Biotechnology and Metagenomics brochure for 2009 URI: http://hdl.handle.net/10566/127 Files in this item: 1
IMBMbrochure2009.pdf (1.295Mb) -
Naidoo, Vaughn; Tucker, William D. (Telkom, 2000)[more][less]
Abstract: With QoS available on IP-dominant NGNs, Policy-based Network Management (PBNM) is an effective mechanism for managing services as opposed to actual devices. IP is ubiquitous, and any NGN must contend with legacy devices that do not support emerging PBNM protocols. This Work in Progress uses the common Internet notion of a proxy to enforce policies on legacy equipment. We use VoIP as a mechanism to test the validity of our intended solution. URI: http://hdl.handle.net/10566/449 Files in this item: 1
NaidooTuckerVoIP2000.pdf (53.16Kb) -
Kobo, Hlabishi Isaac; Tucker, William D.; Norman, Michael (Telkom, 2010)[more][less]
Abstract: This paper discusses a way of offering voice instant messaging based on Internet Protocol using Session Initiation Protocol. The purpose of this investigation is to enhance the modern social communication amongst the people of South Africa who are already accustomed to text-based instant messaging. The proposed application aims to implement the traditional Push-to-Talk technology using Internet Protocol. Thus the proposed IP-based Push-to-Talk is a new approach to voice communication which emulates a walkie-talkie system. On the mobile phone IP-Push-to-Talk herein referred to as Push-to-Talk over a cell phone can be viewed as a voice SMS. The adoption of a Push-to-Talk service was inspired by the fact that it applies half-duplex communication. This enhances the primary objective of offering a cheap voice instant messaging. In half-duplex communication, only one person can talk at a time, thereby avoiding bidirectional charging. The project was implemented on two platforms, a PC and a mobile phone. The PC Push-to-Talk was implemented through client server approach whilst the mobile Push-to-Talk through a peer-to-peer approach. Several software engineering strategies were used for user requirements gathering as well for testing. Six users participated in the test and the results were gathered through questionnaires. The results showed that, half-duplex communication is efficient and yet very economical as it makes less usage of system resources. URI: http://hdl.handle.net/10566/623 Files in this item: 1
KoboNormanTucker-SATNAC2010.pdf (532.1Kb) -
Jeffries, Michael; Tucker, William D. (Telkom, 2001)[more][less]
Abstract: The Session Initiation Protocol and H.323 dominate the Voice over IP world. These signaling protocols are responsible for call setup and call tear down by IP telephony solutions. This project analyses and discusses the underlying H.323 and SIP interoperability issues and intends to build a scalable solution for the interoperability of these protocols. The gateway maps the call sequences between the two protocols. A test scenario establishes a barrage of call setup and tear down requests to test the scalability of any H.323/SIP interoperability solution. URI: http://hdl.handle.net/10566/465 Files in this item: 1
JeffriesTuckerSIP2001.pdf (65.32Kb) -
Jeffries, Michael; Tucker, William D. (Telkom, 2000)[more][less]
Abstract: Current VoIP signaling protocols are interoperable with the PSTN SS7 via H.323-to-SS7 or SIP-to-SS7 gateways. As we move toward the Next Generation Network, the PSTN falls away and we work toward carrier-grade VoIP interoperability between H.323, SIP, and other future VoIP signaling protocols. This paper present a Work in Progress to design and implement a solution based on the Internet Protocol itself. URI: http://hdl.handle.net/10566/425 Files in this item: 1
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Vuza, Xolisa; Tucker, William D. (Telkom, 2004)[more][less]
Abstract: We intend adding video messaging and conferencing to Multimodal Telemedicine Intecommunicator (MuTI), a previous system that has already been in place in the target environment. This is to allow a semi-synchronous communication to occur over the Internet Protocol. Videoconferencing can be used to communicate synchronously and video messaging in a store and forward fashion can be used to communicate asynchronously. MuTI supports store and forward of still images, voicemail and text. The system also supports real time communication by means of audio. The aim of this research is to learn how to bridge the digital divide by building applications that are useful and relevant to the users we build for. We are developing this application together with the users of the application in an iterative fashion where we build the prototypes and show the users at each cycle. The feedback that we get from the users plays an important role in building a prototype for the next cycle. The software will be instrumented to provide statistics about the system usage. We are also going to get data from the users by using questionnaires and compare this data with the statistics about software usage to see how much the system has been used and which features in the system do the users like. We are using a rural South African context in conducting this research. We hope to bring about guidelines and recommendations on how to develop applications to bridge the digital divide in a developing world context. URI: http://hdl.handle.net/10566/435 Files in this item: 1
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Yi, Long; Connan, James (Association for Computing Machinery, 2007)[more][less]
Abstract: Self-tuning has been an elusive goal for operating systems and is becoming a pressing issue for modern operating systems. Well-trained system administrators are able to tune an operating system to achieve better system performance for a specific system class. Unfortunately, the system class can change when the running applications change. Our model for self-tuning operating system is based on a monitor-classify-adjust loop. The idea of this loop is to continuously monitor certain performance metrics, and whenever these change, the system determines the new system class and dynamically adjusts tuning parameters for this new class. This paper describes KernTune, a prototype tool that identifies the system class and improves system performance automatically. A key aspect of KernTune is the notion of Artificial Intelligence (AI) oriented performance tuning. It uses a support vector machine (SVM) to identify the system class, and tunes the operating system for that specific system class. This paper presents design and implementation details for KernTune. It shows how KernTune identifies a system class and tunes the operating system for improved performance. URI: http://hdl.handle.net/10566/53 Files in this item: 1
Yi_KernTune(2007).pdf (262.3Kb) -
Yi, Long; Tucker, William D. (Telkom, 2008)[more][less]
Abstract: This paper describes Kiara, an open source SIPbased communication system that provides the building blocks to enable Deaf relay services. We have implemented a prototype that provides real-time text, voice and video to a variety of end user devices over a variety of networks. The work-in-progress concerns the addition of relay services for the Deaf. URI: http://hdl.handle.net/10566/523 Files in this item: 1
YiTuckerKiara2008.pdf (173.6Kb) -
Babajide, Omotola; Leslie, Petrik; Amigun, Bamikole; Ameer, Farouk (MDPI, 2009)[more][less]
Abstract: Biodiesel has attracted increasing interest and has proved to be a good substitute for fossil-based fuels due to its environmental advantages and availability from renewable resources such as refined and waste vegetable oils. Several studies have shown that biodiesel is a better fuel than the fossil-derived diesel in terms of engine performance, emissions reduction, lubricity and environmental benefits. The increasing popularity of biodiesel has generated great demand for its commercial production methods, which in turn calls for the development of technically and economically sound process technologies. This paper explores the applicability of ultrasound in the optimization of low-cost feedstock – in this case waste cooking oil – in the transesterification conversion to biodiesel. It was found that the conversion efficiency of the waste oil using ultrasound was higher than with the mechanical stirring method. The optimized variables of 6:1 methanol/oil ratio at a reaction temperature of 30 °C and a reaction time of 30 min and 0.75% KOH (wt/wt) catalyst concentration was obtained for the transesterification of the waste oil via the use of ultrasound. URI: http://hdl.handle.net/10566/573 Files in this item: 1
BabajideBiodiesel2009.pdf (248.8Kb) -
Cowan, Donald A.; Stafford, William (ASM Press, 2007)[more][less]
URI: http://hdl.handle.net/10566/126 Files in this item: 1
CowanMetagenomicMethods2007.pdf (432.7Kb) -
Cowan, Donald A.; Arslanoglu, A.; Burton, Stephanie; Cameron, Rory A.; Baker, Gillian; Smith, Jacques J.; Meyer, Quinton (Portland Press, 2004)[more][less]
Abstract: With the rapid development of powerful protein evolution and enzyme-screening technologies, there is a growing belief that optimum conditions for biotransformation processes can be established without the constraints of the properties of the biocatalyst. These technologies can then be applied to find the ‘ideal biocatalyst’ for the process. In identifying the ideal biocatalyst, the processes of gene discovery and enzyme evolution play major roles. However, in order to expand the pool genes for in vitro evolution, new technologies, which circumvent the limitations of microbial culturability, must be applied. These technologies, which currently include metagenomic library screening, gene-specific amplification methods and even full metagenomic sequencing, provide access to a volume of ‘sequence space’ that is not addressed by traditional screening. URI: http://hdl.handle.net/10566/142 Files in this item: 1
CowanMetagenomicsGeneDiscovery2004.pdf (575.0Kb) -
Neethling, Simone; Channing, Alan; Gershwin, Lisa-Ann; Gibbons, Mark J. (Cambridge University Press, 2011)[more][less]
Abstract: A new record of Crambionella stuhlmanni is reported from the east coast of South Africa. The material is described using quantitative morphological data, and mitochondrial (CO1) and nuclear (ITS-1) sequence data. The species can be diagnosed by a combination of morphological features including the presence of conical projections on velar lappets, the absence of orbicular appendages among mouthlets and the short length of the terminal club on the oral arm. Mitochondrial sequence data unambiguously delineate C. stuhlmanni as a separate species from C. orsini, and phylogenetic analyses support its placement within the monophyletic genus, Crambionella URI: http://hdl.handle.net/10566/249 Files in this item: 1
Neethling et al 2011.pdf (481.9Kb) -
Mugabo, Pierre; Els, Ilse; Smith, Johan; Rabie, Helena; Smith, Peter; Mirochnick, Mark; Steyn, Wilhelm; Hall, David; Madsen, Richard; Cotton, Mark F (Health & Medical Publishing Group, 2011)[more][less]
Abstract: Background. No pharmacokinetic data exist for premature infants receiving single-dose nevirapine (sd NVP) for prevention of mother-to-child transmission (MTCT) of HIV. Aim. To describe NVP decay pharmacokinetics in two groups of premature infants - those whose mothers either received or did not receive NVP during labour. Methods. Infants less than 37 weeks' gestation were prospectively enrolled. Mothers received sd NVP during labour if time allowed. Infants received sd NVP and zidovudine. Blood was collected on specified days after birth and NVP concentrations were determined by liquid chromatography-mass spectrometry. Results. Data were obtained from 81 infants, 58 born to mothers who received sd NVP during labour (group I) and 23 to mothers who did not receive NVP (group II). Of the infants 29.6% were small for gestational age (SGA). Median (range) maximum concentration (Cmax), time to reach maximum concentration (Tmax), area under the plasma concentration-time curve (AUC) and halflife (T) were 1 438 (350-3 832) ng/ml, 25h50 (9h40-83h45), 174 134 (22 308-546 408) ng×h/ml and 59.0 (15.4-532.6) hours for group I and 1 535 (635-4 218) ng/ml, 17h35 (7h40-29h), 168 576 (20 268-476 712) ng×h/ml and 69.0 (22.12-172.3) hours for group II. For group II, the median (range) volume of distribution (Vd) and body clearance (Cl) were 1 702.6 (623.7-6 189.8) ml and 34.9 (6.2-163.8) ml/h. The AUC was higher (p=0.006) and Cl lower (p<0.0001) in SGA infants. Plasma concentrations exceeding 100 ng/ml were achieved over 8 days in 78% infants in group I and 70.0% in group II. The MTCT rate was 4.8%. Conclusion. Women in preterm labour often deliver with little advance warning. Our study suggests that NVP dosing of preterm infants as soon as possible after birth without maternal intrapartum dosing may be as effective as combined maternal and infant dosing. URI: http://hdl.handle.net/10566/405 Files in this item: 1
MugaboPrematureMTCT.pdf (503.0Kb) -
Buecher, Emmanuelle; Gibbons, Mark J. (NISC (Pty) Ltd and Taylor& Francis, 2003)[more][less]
Abstract: Diel vertical migration (DVM) of six common species of hydromedusae was investigated during two drogue studies conducted in St Helena Bay on the west coast of South Africa in February 1995. Clytia spp., Obelia spp. and Bougainvillia macloviana, were largely confined to surface waters and did not appear to display any DVM. By contrast, Leuckartiara octona and Euphysa aurata displayed clear DVM and, like Proboscidactyla menoni, were found at greater depths than the other species. The depth distribution and amplitude of migration varied between surveys for most species, so definitive interpretations of patterns could not be made. URI: http://hdl.handle.net/10566/377 Files in this item: 1
BuecherDielVerticalMigration2003.pdf (121.3Kb)