Pollinator mediated selection in Pelargonium reniforme Curtis (Geraniaceae) : patterns and process
- Authors: De Wet, Leigh-Ann Robynne
- Date: 2013-06-25
- Subjects: Pelargoniums -- Classification , Pelargoniums -- Pollen , Pelargoniums -- Selection
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4255 , http://hdl.handle.net/10962/d1008185 , Pelargoniums -- Classification , Pelargoniums -- Pollen , Pelargoniums -- Selection
- Description: Pelargonium reniforme is currently divided into two subspecies, P. reniforme subsp. reniforme and P. reniforme subsp. velutinum. The species falls into section Reniformia along with the closely-related P. sidoides. Observations of the section showed some discrepancies in the current taxonomy; mainly floral variation that was not recorded in the descriptions of the subspecies of P. reniforme, particularly the differences in hypanthium lengths. Patterns of variability were analysed using both morphometrics and inter simple sequence repeat (ISSR) data for P. reniforme (both subspecies), and P. sidoides. Results showed no support for the current subspecific division of P. reniforme but also no support for the current status of P. sidoides as a separate species. However, both morphometric and ISSR data show some evidence for the existence of two distinctly separate groups within P. reniforl1le subsp. velutinum as two distinct types have been recognized: those with bright pink flowers with long tubes (up to 70mm), and those with pale pink flowers with shorter tubes (as little as 8mm). These two forms have been found in a single population (Grahamstown), where they occur sympatrically, as well as in monomorphic populations. Analyses of the processes thought to be responsible for the observed patterns were conducted on the Grahamstown population. Observations of pollinators suggest that long-tongued insects (Butterflies, Nemestrinid flies) pollinate the long-tubed flowers and short-tongued insects (Bombyliid flies, long-tongued bees) pollinate short-tubed flowers. However, analysis of selection gradients in the population, indicate no directional selection is occurring for hypanthium lengths. The results of this thesis show that selection is occurring within Pelargonium reniforme, but at this time, selection is not strongly directional and floral differences are maintained, even when floral forms occur sympatrically. It is suggested that a review of the taxonomy be undertaken as well as additional pollination and selection studies to confirm suspected taxonomic groupings and relationships between the floral forms respectively. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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A comparison of the vulcanisation of Polyisoprene by a range of Thiuram Diulfides
- Authors: Van Rooyen, Jason Leigh
- Date: 2007
- Subjects: Vulcanization , Vulcanization accelerators
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10399 , http://hdl.handle.net/10948/733 , Vulcanization , Vulcanization accelerators
- Description: This study was initiated in an attempt to investigate dithiocarbamic acid accelerated sulfur vulcanisation. This was, however, found impossible due to the innate instability of dithiocarbamic acids. The focus of the study was then shifted toward thiuram disulfide accelerated sulfur vulcanisation, with emphasis being placed on a rate comparison. Three groups of accelerators were investigated, namely the aromatic, linear aliphatic and cyclic aliphatic thiuram disulfide adducts. The analysis methods that were employed were conventional rubber (cis-1,4-polyisoprene) techniques coupled to model (squalene) compound investigations. The data that was collected consisted of rheometrical torque vs. time data in the rubber system while the data obtained in the model compound study consisted of sulfur and accelerator concentration data as determined by means of high performance liquid chromatography (HPLC). The aromatic accelerators were synthesised in our labs by means of an addition reaction between the aromatic amine and CS2 in basic medium and subsequent oxidation with K3Fe(CN)6, all in a 1:1 molar ratio. The reaction yield was low due to the instability of the dithiocarbamate intermediates and a sluggish oxidation reaction. In the rate constant determination a first order mathematical approach was used for the rubber system as crosslinking is considered to roughly obey first order kinetics. The model compound data was also found to more accurately fit the first order rate law, with an initial slopes method also being applied to the system to determine secondary rate constants and relative rates for the system. The determination of vulcanisation rate constants in the cis-1,4-polyisoprene system was a success, while the rate data determined by means of the squalene model was more related to the rate of accelerator and sulfur consumption as opposed to the rate of crosslinking as is the case with the rubber rate data. The sulfur first order rate data mirrored the rate data derived from the rubber system more closely than the corresponding accelerator rate data, the relative rate data determined by means of initial slopes method, proved that the homolytic cleavage of thiuram disulfides and the subsequent formation of accelerator polysulfides were not limiting steps. This is seen in the similar relative rate data derived from both the raw sulfur and accelerator data in systems that exhibit vastly different vulcanisation rates. Squalene was deemed a suitable model for the cis-1,4-polyisoprene system, although one should consider the extent of charring and solution effects in the individual systems to account for possible incongruities that may be observed between the rubber and simulated system. The lack of agreement between the rubber and model compound rate constant data lies in the fact that the rate of crosslinking is not simplistically related to the rate at which accelerator and sulfur is consumed, this being especially true for the rate at which the accelerator is consumed. Thus the discussion over the acceleratory rates in the various accelerator systems was limited to observations made in the rubber system, with the model compound data was used exclusively to elucidate mechanistic processes. It was discovered that the groups of accelerators examined, namely linear, cyclic and aromatic thiuram disulfide adducts, produced vastly varied rate data. The aromatic thiuram disulfide adducts had only a slight acceleratory effect on the rate of vulcanisation as compared to the unaccelerated sulfur system. The morpholine adduct had a moderately larger rate of acceleration followed by tetramethyl and tetrethylthiuram disulfide, with N’N-dicyclopentamethylenethiuram disulfide having the fastest rate of acceleration.
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- Date Issued: 2007
A model for adaptive multimodal mobile notification
- Authors: Brander, William
- Date: 2007
- Subjects: Mobile computing , Context-aware computing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10473 , http://hdl.handle.net/10948/699 , Mobile computing , Context-aware computing
- Description: Information is useless unless it is used whilst still applicable. Having a system that notifies the user of important messages using the most appropriate medium and device will benefit users that rely on time critical information. There are several existing systems and models for mobile notification as well as for adaptive mobile notification using context awareness. Current models and systems are typically designed for a specific set of mobile devices, modes and services. Communication however, can take place in many different modes, across many different devices and may originate from many different sources. The aim of this research was to develop a model for adaptive mobile notification using context awareness. An extensive literature study was performed into existing models for adaptive mobile notification systems using context awareness. The literature study identified several potential models but no way to evaluate and compare the models. A set of requirements to evaluate these models was developed and the models were evaluated against these criteria. The model satisfying the most requirements was adapted so as to satisfy the remaining criteria. The proposed model is extensible in terms of the modes, devices and notification sources supported. The proposed model determines the importance of a message, the appropriate device and mode (or modes) of communication based on the user‘s context, and alerts the user of the message using these modes. A prototype was developed as a proof-of-concept of the proposed model and evaluated by conducting an extensive field study. The field study highlighted the fact that most users did not choose the most suitable mode for the context during their initial subscription to the service. The field study also showed that more research needs to be done on an appropriate filtering mechanism for notifications. Users found that the notifications became intrusive and less useful the longer they used them.
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- Date Issued: 2007
An assessment of habitat suitability of the proposed Tyefu community game reserve in Ngqushwa (fomerly Peddie) district, Eastern Cape
- Authors: Mamfengu, Phozisa Faith
- Date: 2007
- Subjects: Game farms -- South Africa -- Eastern Cape -- Management , Habitat (Ecology) , Eastern Cape (South Africa) -- Social conditions
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10653 , http://hdl.handle.net/10948/736 , Game farms -- South Africa -- Eastern Cape -- Management , Habitat (Ecology) , Eastern Cape (South Africa) -- Social conditions
- Description: Land use forms such as cultivation and livestock farming have become less productive and unsustainable in the Tyefu communal villages of Ngqushwa (Formerly Peddie) district, Eastern Cape, South Africa. This is manifest in abandoned and severely degraded cultivation fields as well as transformed vegetation, making it difficult to earn a land based livelihood. Against the backdrop of severe land degradation and poverty levels in these communal villages, game farming has been recommended as an ecologically, economically and socially sustainable form of land use. Tyefu Community Reserve is a project, recommended by the Subtropical Thicket Ecosystem Project (STEP) backed by the Department of Environment Affairs and Tourism (DEAT), for hunting and venison selling. The proposed area has been fenced and animals to be stocked in the reserve have been requested on a loan basis. Such an undertaking requires an understanding of the abundance and condition of vegetation, terrain parameters, and an assessment of potential wildlife species, as well as the carrying capacity of the recommended reserve as a habitat. With the aid of orthophoto maps, Subtropical Thicket Ecosystem Planning (STEP) shapefiles, ASTER satellite imagery and a High Resolution Digital Camera Image, vegetation types were mapped and their condition was assessed. A Digital Elevation Model (DEM) of the area was used to extract terrain parameters such as slope and aspect. The carrying capacity of the proposed reserve was determined using a model originally developed by Boshoff et al. (2001) for estimating potential wildlife and abundance. The proposed reserve is predominantly covered by dense thicket as compared to the adjacent Tyefu communal villages where thicket has been severely degraded. The prominent topographic characteristics such as slope reveal an escarpment ringing the proposed reserve with gentle slopes towards the centre. Slope direction has also influenced the distribution of vegetation in the proposed reserve, as the moist south facing slopes tend to have a greater proportion of dense thicket as opposed to the warm north facing slopes. Vegetation types and topography of the reserve can provide suitable habitat to a variety of wildlife species and are likely to influence the distribution of mammals in the proposed reserve. The carrying capacity model developed has been useful in determining potential species that can be supported by the reserve, and estimating their abundance. Given the small size of the proposed community reserve (about 1800ha), it has been recommended that it should be stretched to link up with the existing Great Fish River Game Complex. It will then fit within the framework as envisaged by STEP (2004), in the form of Fish River Biodiversity Initiative, a conservation corridor bordering the Great Fish River.
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- Date Issued: 2007
An intelligent user interface model for contact centre operations
- Authors: Singh, Akash
- Date: 2007
- Subjects: User interfaces (Computer systems) , Human-computer interaction , Mobile computing , Customer services -- Management , Call centers -- Customer services
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10475 , http://hdl.handle.net/10948/d1011399 , User interfaces (Computer systems) , Human-computer interaction , Mobile computing , Customer services -- Management , Call centers -- Customer services
- Description: Contact Centres (CCs) are at the forefront of interaction between an organisation and its customers. Currently, 17 percent of all inbound calls are not resolved on the first call by the first agent attending to that call. This is due to the inability of the contact centre agents (CCAs) to diagnose customer queries and find adequate solutions in an effective and efficient manner. The aim of this research is to develop an intelligent user interface (IUI) model to support and improve CC operations. A literature review of existing IUI architectures, modelbased design and existing CC software together with a field study of CCs has resulted in the design of an IUI model for CCs. The proposed IUI model is described in terms of its architecture, component-level design and interface design. An IUI prototype has been developed as a proof of concept of the proposed IUI model. The IUI prototype was evaluated in order to determine to what extent it supports problem identification and query resolution. User testing, incorporating the use of eye tracking and a post-test questionnaire, was used in order to determine the usability and usefulness of the prototype. The results of this evaluation show that the users were highly satisfied with the task support and query resolution assistance provided by the IUI prototype. This research resulted in the design of an IUI model for the domain of CCs. This model can be used to assist the development of CC applications incorporating IUIs. Use of the proposed IUI model is expected to support and enhance the effectiveness and efficiency of CC operations. Further research is needed to conduct a longitudinal study to determine the impact of IUIs in the CC domain.
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- Date Issued: 2007
An investigation into the deployment of IEEE 802.11 networks
- Authors: Janse van Rensburg, Johanna Hendrina
- Date: 2007
- Subjects: Local area networks (Computer networks)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4596 , http://hdl.handle.net/10962/d1004839 , Local area networks (Computer networks)
- Description: Currently, the IEEE 802.11 standard is the leading technology in the Wireless Local Area Network (WLAN) market. It provides flexibility and mobility to users, which in turn, increase productivity. Opposed to traditional fixed Local Area Network (LAN) technologies, WLANs are easier to deploy and have lower installation costs. Unfortunately, there are problems inherent within the technology and standard that inhibits its performance. Technological problems can be attributed to the physical medium of a WLAN, the electromagnetic (EM) wave. Standards based problems include security issues and the MAC layer design. However the impact of these problems can be mitigated with proper planning and design of the WLAN. To do this, an understanding of WLAN issues and the use of WLAN software tools are necessary. This thesis discusses WLAN issues such as security and electromagnetic wave propagation and introduces software that can aid the planning, deployment and maintenance of a WLAN. Furthermore the planning, implementation and auditing phases of a WLAN lifecylce are discussed. The aim being to provide an understanding of the complexities involved to deploy and maintain a secure and reliable WLAN.
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- Date Issued: 2007
An investigation into the introduction of process analytical technology, using near infrared analysis, to selected pharmaceutical processes
- Authors: Naicker, Krishnaveni
- Date: 2007
- Subjects: Near infrared spectroscopy , Pharmaceutical chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10153 , http://hdl.handle.net/10948/577 , http://hdl.handle.net/10948/d1011710 , Near infrared spectroscopy , Pharmaceutical chemistry
- Description: Introduction: Process analytical technologies are systems for the analysis and control of manufacturing processes to assure acceptable end-product quality. This is achieved by timely measurements of critical parameters and performance attributes of raw material and in-process material and processes. The introduction of process analytical technology using near infrared analysis was investigated in three areas, namely incoming raw material analysis, blend uniformity analysis and moisture determination in the fluid bed dryer. Methodology: Incoming raw material identification - The FOSS XDS rapid content analyzer was used for the development of a NIR method for the identification and material qualification of starch maize and lactose monohydrate. Blend uniformity analysis – The SP15 Laboratory Blender fitted with near infrared probe was utilized for the study. Two types of blend experiments were designed to monitor the distribution of magnesium stearate (lubricant) in the blend, namely, a powder blend utilizing lactose monohydrate and a granule blend utilizing Ridaq® granule. Software methods were developed to monitor the standard deviation of the absorbance at the wavelengths that were specific for lactose monohydrate, Ridaq® granule and magnesium stearate. To confirm the prediction of end-point using near infrared, results were verified using an atomic absorption method for magnesium stearate. The blends were sampled at the selected time intervals corresponding to three states of the blend, namely, before end-point, at end-point and after end-point using a sampling plan. An additional six blends were conducted for the granule blend and sampled when the standard deviation had reached a value below 3 x 10-6 at the magnesium stearate wavelength at four consecutive data points (standard deviation value extrapolated from blends carried out to predetermined time intervals). Moisture determination in the fluid bed dryer – Moisture values for two products (Product A and Product B) were retrospectively collected from past production batches. A process capability study was conducted on the moisture values to determine if the current process was in a state of control. Results and Discussion: Incoming raw material identification – The algorithms used for the spectral library were able to distinguish between the raw materials selected. The spectral library positively identified the starch maize and lactose monohydrate samples that were not present in the library. The negative challenge with pregelatinised starch and tablettose demonstrated that the spectral library was able to differentiate between closely related compounds. Blend uniformity analysis – Blends sampled at the predetermined time intervals demonstrated a homogeneous state when the standard deviation of the absorbance was low and a non-homogeneous state when the standard deviation of the absorbance was high, thus near infrared prediction on the state of the blend was confirmed by the standard analytical methods. The series of Ridaq® granule and magnesium stearate blends sampled when the standard deviation was below 3 x 10-6 were homogeneous with the exception of one blend that was marginally out of specification. Blend durations were significantly lower than the standard blend durations used in the facility and ranged from 112 to 198 seconds. Moisture determination in the fluid bed dryer – From the process capability study of the two products it was noted that Product A is stable but can still be optimized while Product B is at a desirable state. The statistical evaluation of the moisture values for Product A and Product B demonstrated that the use of the product temperature to monitor the moisture gave consistent results. The current process is stable and capable of producing repeatable results although near infrared provides a means for continuously monitoring the product moisture and allows one to take action to prevent over-drying or under-drying. Conclusion: From the investigations conducted, it can be seen that there is definitely a niche for process analytical technology at this pharmaceutical company. The implementation is a gradual process of change, which may take time, probably several years (Heinze & Hansen 2005).
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- Date Issued: 2007
An investigation into the learnability of object-oriented case tools for computing education
- Authors: Scholtz, Brenda Mary
- Date: 2007
- Subjects: Computer science -- Study and teaching , Object-oriented programming (Computer science) , ACSES (Computer system)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10476 , http://hdl.handle.net/10948/694 , Computer science -- Study and teaching , Object-oriented programming (Computer science) , ACSES (Computer system)
- Description: The use of Computer Aided Software Engineering (CASE) tools for teaching object-oriented systems analysis and design (OOSAD) has many potential benefits, but there are also several problems associated with the usage of these tools. A large portion of these problems relate to the usability and learnability of these tools. Learnability is one of the most important attributes of usability and refers to the capability of the system to enable the user to learn its application. The main research question that this study aims to address is “How can the learnability of OO CASE tools for computing education in South Africa be evaluated?”. In order to answer this question several frameworks for evaluating CASE tool usability and learnability were investigated. One of these frameworks, as proposed by Senapathi, was selected as being the most appropriate for evaluating CASE tool learnability for computing education. This framework maintains that the learnability of a CASE tool is dependent on context of use factors such as the tool used, as well as user characteristics such as gender. The primary aim of this research was thus to validate Senapathi's framework for CASE tool learnability in a South African context. A secondary aim of the research was to extend the implementation of the framework in order to enable the comparison of two CASE tools and to support the inclusion of other user characteristics. An experiment was performed at the Nelson Mandela Metropolitan University (NMMU) in 2006. The participants recruited for this experiment were second year computing students at NMMU. During this experiment, the learnability of two OO CASE tools, namely IBM's Rational Software Modeller and Microsoft's Visio, was evaluated and compared. The quantitative and qualitative results supported Senapathi's results and showed that her framework could be used to evaluate CASE tool learnability and could be adapted to evaluate two CASE tools. The results also showed that the majority of the participants rated the learnability of Microsoft Visio higher for both tasks and that the main reasons participants preferred Visio was due to its simplicity, familiarity and recoverability.
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- Date Issued: 2007
Assessing program code through static structural similarity
- Authors: Naude, Kevin Alexander
- Date: 2007
- Subjects: Computer networks -- Security measures , Internet -- Security measures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10478 , http://hdl.handle.net/10948/578 , Computer networks -- Security measures , Internet -- Security measures
- Description: Learning to write software requires much practice and frequent assessment. Consequently, the use of computers to assist in the assessment of computer programs has been important in supporting large classes at universities. The main approaches to the problem are dynamic analysis (testing student programs for expected output) and static analysis (direct analysis of the program code). The former is very sensitive to all kinds of errors in student programs, while the latter has traditionally only been used to assess quality, and not correctness. This research focusses on the application of static analysis, particularly structural similarity, to marking student programs. Existing traditional measures of similarity are limiting in that they are usually only effective on tree structures. In this regard they do not easily support dependencies in program code. Contemporary measures of structural similarity, such as similarity flooding, usually rely on an internal normalisation of scores. The effect is that the scores only have relative meaning, and cannot be interpreted in isolation, ie. they are not meaningful for assessment. The SimRank measure is shown to have the same problem, but not because of normalisation. The problem with the SimRank measure arises from the fact that its scores depend on all possible mappings between the children of vertices being compared. The main contribution of this research is a novel graph similarity measure, the Weighted Assignment Similarity measure. It is related to SimRank, but derives propagation scores from only the locally optimal mapping between child vertices. The resulting similarity scores may be regarded as the percentage of mutual coverage between graphs. The measure is proven to converge for all directed acyclic graphs, and an efficient implementation is outlined for this case. Attributes on graph vertices and edges are often used to capture domain specific information which is not structural in nature. It has been suggested that these should influence the similarity propagation, but no clear method for doing this has been reported. The second important contribution of this research is a general method for incorporating these local attribute similarities into the larger similarity propagation method. An example of attributes in program graphs are identifier names. The choice of identifiers in programs is arbitrary as they are purely symbolic. A problem facing any comparison between programs is that they are unlikely to use the same set of identifiers. This problem indicates that a mapping between the identifier sets is required. The third contribution of this research is a method for applying the structural similarity measure in a two step process to find an optimal identifier mapping. This approach is both novel and valuable as it cleverly reuses the similarity measure as an existing resource. In general, programming assignments allow a large variety of solutions. Assessing student programs through structural similarity is only feasible if the diversity in the solution space can be addressed. This study narrows program diversity through a set of semantic preserving program transformations that convert programs into a normal form. The application of the Weighted Assignment Similarity measure to marking student programs is investigated, and strong correlations are found with the human marker. It is shown that the most accurate assessment requires that programs not only be compared with a set of good solutions, but rather a mixed set of programs of varying levels of correctness. This research represents the first documented successful application of structural similarity to the marking of student programs.
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- Date Issued: 2007
Characterisation of Human Hsj1a : an HSP40 molecular chaperone similar to Malarial Pfj4
- Authors: McNamara, Caryn
- Date: 2007
- Subjects: Heat shock proteins , Protein folding , Proteins -- Analysis , Proteins -- Structure , Plasmodium , Malaria , Molecular chaperones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4083 , http://hdl.handle.net/10962/d1007603
- Description: Protein folding, translocation, oligomeric rearrangement and degradation are vital functions to obtain correctly folded proteins in any cell. The constitutive or stress-induced members of each of the heat shock protein (Hsp) families, namely Hsp70 and Hsp40, make up the Hsp70/Hsp40 chaperone system. The Hsp40 J-domain is important for the Hsp70-Hsp40 interaction and hence function. The type-II Hsp40 proteins, Homo sapiens DnaJ 1a (Hsj1a) and Plasmodium falciparum DnaJ 4 (Pfj4), are structurally similar suggesting possible similar roles during malarial infection. This thesis has focussed on identifying whether Hsj1a and Pfj4 are functionally similar in their interaction with potential partner Hsp70 chaperones. Analysis in silico also showed Pfj4 to have a potential chaperone domain, a region resembling a ubiquitin-interacting motif (UIM) corresponding to UIM1 of HsjIa, and another highly conserved region was noted between residues 232-241. The highly conserved regions within the Hsp40 J-domains, and those amino acids therein, are suggested to be responsible for mediating this Hsp70-Hsp40 partner interaction. The thermosensitive dnaJ cbpA Escherichia coli OD259 mutant strain producing type-I Agrobacterium tumefaciens DnaJ (AgtDnaJ) was used as a model heterologous expression system in this study. AgtDnaJ was able to replace the lack of two E coli Hsp40s in vivo, DnaJ and CbpA, whereas AgtDnaJ(H33Q) was unable to. AgtDnaJ-based chimeras containing the swapped J-domains of similar type-II Hsp40 proteins, namely Hsj1Agt and Pfj4Agt, were also able to replace these in E. coli OD259. Conserved J-domain amino acids were identified and were substituted in these chimeras. Of these mutant proteins, Hsj IAgt(L8A), Hsj1Agt(R24A), Hsj1Agt(H31Q), Pfj4Agt(L 11A) and Pfj4Agt(H34Q) were not able to replace the E. coli Hsp40s, whilst Pfj4Agt(Y8A) and Pfj4Agt(R27A) were only able to partially replace them. This shows the leucine of helix I and the histidine of the loop region are key in the in vivo function of both proteins and that the arginine of helix II is key for Hsj1a. The histidine-tagged Hsj1a protein was also successfully purified from the heterologous system. The in vitro stimulated ATPase activity of human Hsp70 by Hsj1a was found to be approximately 14 nmol Pí[subscript]/min/mg, and yet not stimulated by Pfj4, suggesting a possible species-specific interaction is occurring.
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- Date Issued: 2007
Characterisation of InAs-based epilayers by FTIR spectroscopy
- Authors: Baisitse, Tshepiso Revonia
- Date: 2007
- Subjects: Fourier transform infrared spectroscopy , Gallium arsenide semiconductors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10534 , http://hdl.handle.net/10948/474 , Fourier transform infrared spectroscopy , Gallium arsenide semiconductors
- Description: This study focuses on the characterization of InAs and InAs1-xSbx epitaxial layers by infrared reflectance and transmittance spectroscopy and Hall measurements. Reflectance measurements were performed in order to obtain the dielectric parameters and to extract from these information about the electrical properties (mobility and carrier concentration) of this important III-V material system. The transmittance measurements were used to determine the bandgap of InAsSb. Infrared reflectivity and transmittance measurements were performed in the wavelength range 200 – 2000 cm-1 on InAs and InAsSb layers grown on three types of substrates. A classical two oscillator model that takes into account both the free carriers and the lattice, was used to analyse the reflectance data using the BMDP® computer curve fitting software. The dielectric parameters and the electrical properties (carrier concentration and mobility) were extracted from the simulations. Due to the low free carrier concentration in the epitaxial structures, the plasma resonance frequency (ωp) values obtained from the simulations of reflectance spectra measured above 200 cm-1, were in the order of 20-30 cm-1. These low values were confirmed by direct measurements of ωp in reflectance spectra obtained in the range 15-200 cm-1. The simulated carrier concentration and mobility values determined optically were compared to the values determined by Hall measurements at room temperature and previously reported values by other researchers. The simulated values obtained were in reasonable agreement with the Hall values. The simulated and measured carrier concentrations obtained for InAs layers were significantly higher than the intrinsic carrier concentration for InAs at room temperature, indicating notable concentrations of donors resulting from the growth process.
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- Date Issued: 2007
Combined and additive effects of assembly tasks and constrained body postures
- Authors: Skelton, Sarah Anne
- Date: 2007
- Subjects: Musculoskeletal system -- Diseases , Human engineering , Posture , Posture disorders , Work -- Physiological aspects , Occupational diseases , Manual work , Job stress
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5107 , http://hdl.handle.net/10962/d1005185 , Musculoskeletal system -- Diseases , Human engineering , Posture , Posture disorders , Work -- Physiological aspects , Occupational diseases , Manual work , Job stress
- Description: Despite extensive research into musculoskeletal disorders (MSDs) they continue to plague workers. Manual materials handling (MMH), in particular the concurrence of load manipulation and awkward body posture, has been identified as a key factor in the onset of MSDs. Only a few studies have looked at the interaction between manipulation tasks and working posture during assembly tasks and as a result their relationship has not been widely explored. Assessing the stresses resulting from individual task factors and body posture in isolation and adding them together may be too simplified to estimate an overall risk profile, since this does not take into account that there may be a non-linear interaction in strain responses when manipulation task and body posture interact. Therefore, the present study investigated biophysical, physiological and psychophysical responses to combined tasks, rather than individual tasks of body posture and manipulative tasks. The objective of the research was to establish the interactive effects of constrained body postures and manipulative tasks and to identify whether a cumulative or compensatory reaction occurs during this interaction. Nine conditions were assessed in a laboratory setting, which included combinations of three working postures (standing, sitting and stooping) and three assembly tasks (torque wrenching, precision and no task). Thirty-six subjects were required to complete all nine conditions, with each condition lasting ninety seconds. Muscle activity was recorded for seven muscles from the upper extremity, trunk and lower extremity regions and was complemented by physiological (heart rate, tidal volume, minute ventilation, oxygen consumption, energy expenditure and breathing frequency) and psychophysical (body discomfort) data. At the completion of all nine conditions subjects completed a retrospective psychophysical rating questionnaire pertaining to discomfort felt during the conditions. Responses obtained for the different task and posture combinations revealed compensatory reactions (additive > combined) for most of the conditions assessed for the biomechanical and physiological responses. In the majority of cases for muscle activity, no significant differences were found between the combined and the additive effects (p < 0.05), while for the physiological responses there were mostly significant differences observed. Psychophysical responses indicated that there was a significant difference overall between the additive and combined effects. The results of this study demonstrate that in order to identify risk areas, manipulation tasks and constrained working postures may be considered either in isolation and added together (additive) or as a combined task, since there were very few significant differences observed between these two effects. Further studies are required, however, to provide conclusive evidence.
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- Date Issued: 2007
Conservation incentives for private commercial farmers in the thicket biome, Eastern Cape, South Africa
- Authors: Cumming, Tracey Lyn
- Date: 2007
- Subjects: Landowners -- South Africa -- Eastern Cape , Invasive plants -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4745 , http://hdl.handle.net/10962/d1006953 , Landowners -- South Africa -- Eastern Cape , Invasive plants -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa -- Eastern Cape
- Description: This study sought opportunities to mitigate the pressures of land transformation and alien invader plants on commercial farm land in the thicket biome in the lower reaches of the Fish Kowie Corridor. It had two aims. Firstly, to determine the role incentives could play in mitigating these pressures. Secondly, to determine the characteristics of an incentive programme that would most effectively achieve this. In order to do this, an understanding of landowner activities, needs, opinions and barriers to behaviour; the nature of the pressures on thicket and the nature of the required behaviour to reduce these pressures; and current and past institutional arrangements needed to be achieved. This was done predominantly through a current literature review and personal interviews with landowners and key informants. These findings were used to make recommendations for an effective incentive programme. Landowners showed a preference towards tangible incentives, in particular management assistance, financial compensation and law enforcement. They indicated an aversion to an incentive programme implemented by a government agency, particularly district and provincial government. Rather, landowners showed a propensity towards a nongovernment organisation (NGO) or a farmers group implementing an incentive programme. It was recommended that the two major pressures, namely land transformation and alien invader plants, required different interventions by different agencies in order to be mitigated. The pressure of land transformation required a stewardship model response, with the primary drive being a non-contractual environmental extension service to landowners. The extension service should focus on promoting pro-conservation practises, raising awareness and disseminating information. It should also build a relationship of trust between landowners and the implementing agency. The pressure of alien invader plants would be most effectively addressed through the Working for Water programme. Tangible incentives must be provided to the landowner to induce the costly exercise of alien invader plant control. In particular, the high cost of labour must be addressed. The regulatory incentive of applying laws requiring landowners to control alien invader plants on their land should also be enforced.
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- Date Issued: 2007
Consistent testing for lag length in cointegrated relationships
- Authors: Liu, Limin
- Date: 2007
- Subjects: Cointegration -- South Africa , Econometrics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10575 , http://hdl.handle.net/10948/547 , http://hdl.handle.net/10948/d1011715 , Cointegration -- South Africa , Econometrics
- Description: In the past few decades the theory of cointegration has been widely used in the empirical analysis of economic data. The reason is that, it captures the economic notion of a long-run economic relation. One of the problems experienced when applying cointegrated techniques to econometric modelling is the determination of lag lengths for the modelled variables. Applied studies have resulted in contradictory choices for lag length selection. This study reviews and compares some of the well-known information criteria using simulation techniques for bivariate models.
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- Date Issued: 2007
Constructing a low-cost, open-source, VoiceXML
- Authors: King, Adam
- Date: 2007 , 2013-07-01
- Subjects: VoiceXML (Document markup language) , Asterisk (Computer file) , Internet telephony , Open source software
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4585 , http://hdl.handle.net/10962/d1004735 , VoiceXML (Document markup language) , Asterisk (Computer file) , Internet telephony , Open source software
- Description: Voice-enabled applications, applications that interact with a user via an audio channel, are used extensively today. Their use is growing as speech related technologies improve, as speech is one of the most natural methods of interaction. They can provide customer support as IVRs, can be used as an assistive technology, or can become an aural interface to the Internet. Given that the telephone is used extensively throughout the globe, the number of potential users of voice-enabled applications is very high. VoiceXML is a popular, open, high-level, standard means of creating voice-enabled applications which was designed to bring the benefits of web based development to services. While VoiceXML is an ideal language for creating these applications, VoiceXML gateways, the hardware and software responsible for interpreting VoiceXML applications and interfacing with the PSTN, are still expensive and so there is a need for a low-cost gateway. Asterisk, and open-source, TDM/VoIP telephony platform, can be used as a low-cost PSTN interface. This thesis investigates adding a VoiceXML service to Asterisk, creating a low-cost VoiceXML prototype gateway which is able to render voice-enabled applications. Following the Component-Based Software Engineering (CBSE) paradigm, the VoiceXML gateway is divided into a set of components which are sourced from the open-source community, and integrated to create the gateway. The browser requires a VoiceXML interpreter (OpenVXI), a Text-To-Speech engine (Festival) and a speech recognition engine (Sphinx 4). The integration of the components results in a low-cost, open-source VoiceXML gateway. System tests show that the integration of the components was successful, and that the system can handle concurrent calls. A fully compliant version of the gateway can be used in the real world to render voice-enabled applications at a low cost. , KMBT_363 , Adobe Acrobat 9.55 Paper Capture Plug-in
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- Date Issued: 2007
Cytokine properties of CD23 on human Eosinophilic cells
- Authors: Ferreira, Lauren
- Date: 2007
- Subjects: Cytokines , CD23 antigen , Eosinophil
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10333 , http://hdl.handle.net/10948/503 , http://hdl.handle.net/10948/d1012001 , Cytokines , CD23 antigen , Eosinophil
- Description: CD23, the low affinity IgE receptor, is expressed by various cell types and has numerous functions depending on the form of the protein, its interaction with various ligands and the type of cell involved. CD23 is pivotal in the regulation of IgE, with the soluble form involved in up-regulation, while the membrane bound form is involved in the down-regulation. It is clear why it is believed to be a central molecule in allergic responses, and a therapeutic target for the treatment of allergic disease. In this study a recombinant form of the entire extracellular domain of the protein, exCD23, was produced by PCR cloning and expressed in E. coli. His•Tag™s were introduced onto the C-terminus and N-terminus, respectively, in order to simplify the purification procedure. After renaturation and purification, the recombinant exCD23 bound IgE, indicating its activity. From the IgE binding studies it was established that the position of the tag did not influence the binding. GST•Tagged™ exCD23 was also produced in an attempt to increase the solubility of the recombinant protein, but this proved unsuccessful. Butyrate differentiated EoL-1 cells were treated with the Nterminal His•Tagged™ exCD23, and the protein appeared to suppress the secretion of the constitutively expressed cytokines, especially IL-8 and IFN- , when compared to untreated cells. In addition, treatment of the EoL-1 cells with exCD23 had a significant proliferative effect, but could not induce differentiation of this cell line into mature eosinophilic-like cells.
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- Date Issued: 2007
Depressive disorders and chronic comorbid disease states: a pharmacoepidemiological evaluation
- Authors: Kritiotis, Lia Costas
- Date: 2007
- Subjects: Depression, Mental , Child psychopathology , Adolescent psychopathology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10151 , http://hdl.handle.net/10948/653 , Depression, Mental , Child psychopathology , Adolescent psychopathology
- Description: The treatment of Depressive Disorders in patients with chronic comorbid disease states warrants careful consideration of the risk-benefit ratio pertaining to the pharmacokinetic and pharmacodynamic characteristics of the antidepressant being considered, against the physiological susceptibilities of the patient; potential drug-drug interactions and depressive symptoms. The primary aim of this study was to investigate the relationship between Depressive Disorders and the most frequently diagnosed chronic comorbid disease states in a depressed South African study population; and to comment on the appropriateness of antidepressants prescribed to these patients. This retrospective drug utilisation study consisted of two parts: the first part focused on the prevalence of the most frequently diagnosed chronic comorbidities in a depressed South African population (N = 21 171). The three most prevalent chronic comorbid disease states were Hypertension (52.87 percent), Lipid Disorders (20.40 percent) and Arthritis (16.70 percent). The second part of the study included an assessment of the antidepressants prescribed to depressed patients in 2004 (N = 6 150). Emphasis was placed on the suitability of antidepressants selected for depressed adult patients (18 years of age and older) with comorbid Hypertension, Lipid Disorders or Arthritis. SSRIs were prescribed most frequently to the depressed patients during 2004 (59.67 percent). SSRIs are the suggested first-line treatments for depressed patients with multiple chronic comorbid disease states. However, of the SSRIs, fluoxetine has the least favourable pharmacokinetic profile and was found to be the antidepressant prescribed most often. Amitriptyline, which was the TCA prescribed most frequently, produces the greatest degree of anticholinergic, sedative and hypotensive effects, relative to other agents in the same antidepressant class. Thus, it is not recommended as a first-line antidepressant, especially in depressed patients with comorbidities. This study identifies potential areas of intervention regarding antidepressant prescribing in depressed individuals with chronic comorbid disease states and offers recommendations to promote the selection of optimal, individualised drug treatment strategies for these patients.
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- Date Issued: 2007
Determination of the botanical composition of black rhinoceros (Diceros bicornis) dung using the rbcL gene as a molecular marker, and analysis of antioxidant and phenolic content of its browse
- Authors: Bulani, Siyavuya Ishmael
- Date: 2007 , 2013-06-25
- Subjects: Black rhinoceros -- Food , Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- Analysis -- South Africa -- Eastern Cape , Plant ecology -- South Africa -- Eastern Cape , Genetic markers , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4070 , http://hdl.handle.net/10962/d1006468 , Black rhinoceros -- Food , Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- Analysis -- South Africa -- Eastern Cape , Plant ecology -- South Africa -- Eastern Cape , Genetic markers , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants
- Description: The black rhinoceros remains one of the world's extremely endangered species despite a variety of policies to protect it. The black rhinoceros population at the Great Fish River Reserve (GFRR) in the Eastern Cape in South Africa has increased steadily since their re-introduction in 1986. This megaherbivore is a browser, with a diet obtained largely from the short and medium succulent thicket of the GFRR. Knowledge of the preferential diet of the black rhinoceros on the reserve is an important factor for the effective management of the land and the herbivores that compete for its resources. The dietary preferences of the black rhinoceros at the reserve have been established using backtracking methods. In this study the rbcL gene was used to establish an rbcL gene database of the plants from the GFRR and determine the botanical composition of the black rhinoceros dung from the GFRR. Due to the limited number of rbcL gene plant sequences from the GFRR deposited in the GenBank database, 18 plant species from the GFRR were sequenced. Sequence analyses between the partial rbcL gene sequences generated were able to distinguish between plants down to species level. Plant species from the family Euphorbiaceae and Fabaceae showed sequence variation at intra-specific level compared to those of Tiliaceae which were more conserved. The generated rbcL gene sequences from seasonal dung samples were compared to the rbcL gene sequenced from 18 plant species obtained from the GFRR and those from the GenBank database. A wide range of plant species were identified from the dung samples. There were no major differences in botanical composition between the dung samples, except that Grewia spp. were found to dominate in almost all seasons. The results obtained on the free radical scavenging activity of the extracts against 2,2-Diphenyl-l-picrylhydrazyl (DPPH) increased in the order of methanol > ethyl acetate > chloroform. The DPPH free radical scavenging activity of the methanol plant extracts increased in the order Brachylaena elliptica > Plumbago auriculata > Grewia robusta > Azima tetracantha. Methanol extracts on the TLC plate sprayed with Fe³⁺-2,4,6-Tri-2-pyridyl-s-triazine (TPTZ) showed that the compounds present in the extracts react differently to ferric ion, with most compounds unable to reduce ferric ion. Furthermore the methanol extracts were able to exhibit reduction potentials vs. Ag/AgCl at low concentrations. The compounds in the extracts were shown to be phenolic acids and flavonoid glycosides.
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- Date Issued: 2007
Development and assessment of an oxytocin parenteral dosage form prepared using pluronic ® F127
- Authors: Chaibva, Faith Anesu
- Date: 2007
- Subjects: Oxytocin -- Therapeutic use , Drugs -- Dosage forms , Pregnancy -- Complications -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3747 , http://hdl.handle.net/10962/d1003225 , Oxytocin -- Therapeutic use , Drugs -- Dosage forms , Pregnancy -- Complications -- Management
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- Date Issued: 2007
Development of an antiretroviral solid dosage form using multivariate analysis
- Authors: Nqabeni, Luxolo
- Date: 2007
- Subjects: Analysis of variance , Experimental design , Multivariate analysis , Antiretroviral agents -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10145 , http://hdl.handle.net/10948/705 , Analysis of variance , Experimental design , Multivariate analysis , Antiretroviral agents -- South Africa
- Description: The aim of pharmaceutical development is to design a quality product and the manufacturing process to deliver the product in a reproducible manner. The development of a new and generic formulation is based on a large number of experiments. Statistics provides many tools for studying the conditions of formulations and processes and enables us to optimize the same while being able to minimize our experimentation. The purpose of this study was to apply experimental design methodology (DOE) and multivariate analysis to the development and optimization of tablet formulations containing 150 mg lamivudine manufactured by direct compression.
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- Date Issued: 2007