Double-layer capacitance from the charged surface

A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. 28 October 2016.Energy storage has become an important issue for society, there is a need for affordable and efficient devices that can store energy optimally. Supercapacitors are energy storage devices that can solve society’s energy storage problem. They can store the energy generated by renewable energy systems. In this work approaches will be studied that may be used to estimate capacitance of materials that can be used as the electrode of these devices. These materials must have high energy density, which will address one of the limitations of supercapacitors. To estimate the capacitance of the double layer, the double layer theory and ab initio numerical tools based on density functional theory (DFT) are used. The ab initio tools work with periodic systems, when charging the system one violates the periodicity of the system. This is overcome by using the effective screening medium method, which prevents energy divergent of the system. In this work different configurations of the water molecules are used to average the different orientations of water molecules in the electrolyte. The Pt(111) electrode is used, and electrolyte of sodium ion and water. In different configurations the sodium ion in the electrolyte is located at different positions. The capacitances calculated using two different approaches that we developed in this work are comparable to previously estimated capacitance. This is achieved by using minimal computational efforts. We obtained capacitance within that range. Double layer capacitance can be estimated to a good accuracy with the methods developed in this work. Though there are improvements that can be made on the methods that have been developed in this work to better estimate the double layer capacitance. And also more research has to be done in this field to come up with a theory that will accurately estimate capacitance. At the moment calculating the double layer capacitance is not trivial due to the lack of theory that describe the processes taking place at the surface of the electrode where the capacitance is calculated.LG201

Studies on multiply exposed but persistently HIV-1 seronegative sex workers from KwaZulu/Natal, South Africa

The overall aim of this study was to determine whether host genetic factors are associated with resistance to HIV-1 infection in a group of highly exposed persistently seronegative sex workers from KwaZulu/Natal, South Africa. A cohort of 17 African highly exposed but persistently seronegative (HEPS) commercial sex workers (CSW) were identified who had been in sex work for more than four years (range between 4-26 years). The women had been followed monthly for at least four years as part of HIV-1 prevention programmes (Ramjee, et al., 1998). The overall aim of this study was to identify the frequency of polymorphisms and mutations in chemokine genes, chemokine receptors and chemokine receptor promoter region which ma y be associated with HIV-1 resistance and prolonged disease progression. Secondly, to determine if the chemokine receptors on CD4 T-cells are sufficiently expressed and functional to enable infection. This information will shed light on correlates of immunity as influenced by these polymorphisms and this knowledge will help in the bigger objective of determining factors influencing disease progression as well as the development of an effective HIV-1 vaccine in South Africa

Agronomic and physiological response of maize (Zea mays L.) hybrids to plant density in the dry and wet Middleveld of Eswatini

Received: June 27th, 2022 ; Accepted: December 1st, 2022 ; Published: December 8th, 2022 ; Correspondence: [email protected] of the factors limiting yield of maize in Eswatini is use of non-optimum plant density for the different maturity group of maize hybrids in different agro-ecologies. Thus, an experiment was conducted at Malkerns (wet Middleveld) and Luve (dry Middleveld) in Eswatini to determine the effects of plant density on growth, yield components and grain yield of maize hybrids. Factorial combinations of three maize hybrids [SC 403 (early maturing), SC 621 (medium maturing), SC 719 (late maturing)] and five plant densities (41,667; 44,444; 47,619; 50,000, and 57,143 plants ha-1 ) were evaluated in Randomised Complete Block Design in three replications. The results showed that Malkerns had significantly higher crop growth rate (CGR) between V12 and R6 growth stages, relative growth rate (RGR) between V6 and V12 growth stages, mass of thousand kernels (395.60 g), aboveground dry biomass (22.71 t ha-1 ) and grain yield (7.67 t ha-1 ). Among maize hybrids, SC 719 produced significantly the highest CGR (18.37 g m-2 per day) between V12 and R6, aboveground dry biomass (23.05 t ha-1 ), number of kernels per m2 (2074), and grain yield (7.49 ha-1 ). Moreover, SC 719 grown at Malkerns recorded significantly the highest leaf area index (LAI) at V6, and the highest CGR (31.35 g m-2 per day) between V6 and V12 and the tallest plants. The highest density of 57,143 plants ha-1 produced the highest LAI, aboveground dry biomass (21.53 t ha-1 ) and grain yield (7.17 t ha-1 ). Thus, late maturing maize hybrid SC 719 and plant density of 57,143 plants ha-1 (70 cm × 25 cm) can be used to enhance the productivity of maize in the Middleveld of Eswatini

Gender in Planning and Urban Development

Gender-sensitive urban planningThere is increasing evidence that women and men experience cities in different ways. Therefore gender-sensitive urban planning is needed. However, like other built environment occupations, the planning profession has traditionally been ‘gender blind’. The Commonwealth Association of Planners (CAP) has been a strong advocate for ‘reinventing planning’ (Farmer et al. 2006). CAP argues for ‘planning as an inclusive process ... rooted in concerns for equity’ (CAP 2008). Gender equality is one dimension of this kind of inclusive planning. This position, which was endorsed by the UN-Habitat World Urban Forum in 2006, also reflects the Commonwealth’s strong commitment to gender equality. So why does gender matter in urban planning? And, what might ‘gendered planning practice’ hope to achieve?Commonwealth Secretaria

Basin analysis of the Soutpansberg and Tuli Coalfields, Limpopo Province of South Africa

The Soutpansberg and Tuli Coalfields are both hosted in the Karoo Basin, Limpopo Province of South Africa. The Soutpansberg Coalfield is situated north of the Soutpansberg Mountain Range and has a strike length of about 200 km and width of about 80 km which is fault controlled and extends from Waterpoort in the west to the Kruger National Park in the east. The Tuli Coalfield occurs in a small intracratonic, east-west trending fault-controlled sedimentary basin with a preserved width of 80 km and length of 120 km. The east to west trend of the Tuli Coalfield parallels that of the Soutpansberg Coalfield further east, and the two coalfields link up with the north-south trending Lebombo Basin. The Tuli Coalfield occurs in the Tuli Basin, while the Soutpansberg Coalfield occurs in the Soutpansberg Basin. The two basins preserve a heterogeneous succession of the Upper Paleozoic to Lower Mesozoic sedimentary and volcanic rocks of the Karoo Supergroup. Because the area is largely covered by the Quaternary Kalahari Group sands, the stratigraphy of the succession is not as well understood as the Main Karoo Basin in South Africa. This study deals with the intra-basinal stratigraphic correlation, facies and depositional environments, petrography, geochemistry, provenance, geophysics, structural geology, diagenesis of sandstone, subsidence history and coal quality in the Soutpansberg and Tuli Coalfields. Based on the field work and detailed sedimentological analyses of over 2000 borehole data, seven facies associations (FAs) comprising sixteen major lithofacies were identified. The facies associations are: Glacial diamictite and sandstone (FA 1), Clast supported conglomerate and sandstone (FA 2), Tabular cross-bedded sandstone (FA 3), Trough and planar cross-bedded sandstone (FA 4), Fine calcareous and micaceous siltstone and mudstone (FA 5), Sandy shale/mudstone (FA 6), Laminated or thin-bedded Carbonaceous shale/mudstone and coal (FA 7). The facies associations (FA 1 to FA 7) correspond to the lithostratigraphic sub-divisions of the Tshidzi, Madzaringwe and Mikambeni Formations. The Madzaringwe Formation in this study is informally sub-divided into the Lower, Middle and Upper Members while the Mikambeni Formation is informally sub-divided into the Lower and Upper Members. Sedimentological characteristics of the identified facies associations indicate the following depositional environments: Fluvioglacial (braided streams) depositional environment (FA 1, Tshidzi Diamictite Formation); Floodplain ponds, lakes, marshes and backswamps (FA 6 and FA 7, Lower Member of the Madzaringwe Formation); Meandering and braided channels, crevasse splays, levees and crevasse channels (FA 2, FA 3, FA 4 and FA 5, Middle Member of the Madzaringwe Formation); Floodplain ponds, lakes and backswamps (FA 6 and FA 7, Upper Member of the Madzaringwe Formation); Meandering and braided channels, crevasse splays, swamps and shallow lakes (FA 5, FA 6 and FA 7, Lower Member of the Mikambeni Formation) and lastly braided channels, meandering channels, levees and crevasse channels (FA 2, FA 3, FA 4 and FA 5, Upper Member of the Mikambeni Formation). Paleocurrent directions were measured using directional structures (cross-bedding and asymmetric ripple marks). The paleocurrent analysis shows that the direction of the channels was from south-west to north-east in both coalfields. Based on the structural study and geophysical interpretations, the structural and tectonic settings of the two coalfields have been revealed, both coalfields are normal fault-bounded. The geological evolution of the Karoo strata, at least since the Upper Carboniferous, essentially follows the type model for passive continental margin terrain. Paleostress inversion techniques have been employed to interpret the stress regime of the two coalfields. The Soutpansberg Basin is characterised by W-E to ENE-WSW extension and N-S to NNW-SSE compression. The Tuli Basin is characterised by N-S to NNW-SSE compression and W-E to ENE-WSE extension. This stress field reflects the established structural trend of the two shear belts (the Tshipise and Siloam shear zones) bounding the Central Zone of the Limpopo Mobile Belt. The geophysical interpretations were focused on outlining structures, contacts and on the delineation of gravity, magnetic and radiometric signatures in areas defined as anomalous. The magnetic, gravity and radiometric data showed low amplitudes in the sedimentary strata compared to the surrounding and basement geological bodies. The E-N-E fault system has a notable signature, defining two magnetic domains on both southern and northern sides of the Soutpansberg Coalfield. The intrusive emplacements are mainly fault controlled and they trend in the same direction as the two fault systems. Jurassic volcanics (Letaba and Jozini Formations) follow a SW-NE trend, outcropping in the east (Soutpansberg Basin), producing a strong magnetic response in this area, and partly buried in the west, where magnetic intensity tends to be reduced. Petrographic and geochemical analyses of the Soutpansberg sandstones revealed immature sub-litharenite, sub-arkose and minor arkosic arenites in nature, dominated by sub-angular to rounded detrital grains, sourced from recycled orogens, craton interior to transitional continental. The sandstones of the Tuli Coalfield are classified as sub-arkoses and minor sub-litharenites and sourced from the craton interior and recycled orogen provenances. Both petrographic and geochemical results suggest a passive continental margin source. Petrographic and geochemical results of the samples of the Soutpansberg Coalfield suggest uplifted basement source areas dominated by sedimentary rocks with minor granite-gneiss rocks. The petrography and geochemistry of the Tuli sandstones suggest source areas dominantly composed of plutonic (granites) and metamorphic (gneisses and schists) rocks with a component from a sedimentary (quartz-arenites, quartzites, shales, arkoses and meta-arkoses) rocks. Diagenetic features of Mikambeni and Madzaringwe sandstones are subdivided into early, middle and late stages. Time is relative with the earliest diagenetic event occurring shortly after deposition and the latest occurring up until present time. The main diagenetic processes that have affected the sandstones include mechanical compaction, cementation and the dissolution of framework grains and cements. Early diagenetic processes include mechanical compaction, silica and calcite cementation, clay minerals (pore lining and pore-filling kaolinite, illite and smectite), feldspar authigenesis and the formation of hematite cements and coatings. Late diagenesis includes quartz and feldspar overgrowths, seritisation, chlorite alteration, grain deformation, pressure-solution and fracturing and albitisation. The subsidence of the basins is believed to be initiated and thermally controlled by tectonics (i.e. faults of basements blocks) rather than sedimentary burial. The subsidence within the basins supports the primary graben system which must have been centered within the present basins, and later became a region of major faulting. This gave way to the Late Carboniferous rapid subsidence, with areas of greater extension subsiding more rapidly. The Early Permian (last phase) is characterised by a slow subsidence representing the post-rift thermal subsidence. The rift flanks were gradually uplifted and, and then generally subsided as a results of thermal contraction after the extension terminated. Based on the coal analysis, both coalfields are characterised by coking bituminous coal. The study has revealed that the eastern Soutpansberg Coalfield is likely to present better opportunities for identification of potentially exploitable coal deposits as compared to the Tuli Coalfield

Protected area management and environmental decision-making : the case of Dlinza Forest Nature Reserve, KwaZulu-Natal.

Thesis (M.Sc.)-University of Natal, Durban, 2004.Colonial conservation emerged as colonial conservationists perceived the threat of deforestation, climatic change and famine. The sense that there were limits to nature's capacity to meet human demands, led to colonial conservationism which portrayed nature as separated from human life. Protected areas (PA's), both forest and game reserves, were created that excluded local people in terms of both access and management. In South Africa the National Forests Act 84 of 1998 has created new conditions in which there is a greater opportunity for communities to benefit from indigenous forests, which apart from their other uses are a valuable resource from the point of view of ecotourism. This study thus seeks to assess moves from exclusivist to community based forms of environmental decision-making (EDM) at Dlinza Forest Nature Reserve. This study provides an example of an ecotourism project started during the democratic period in South Africa and at the height of the global move to community conservation. First however it traces the management history of the forest in order to assess change in the management style over time. The study investigates rural people's attitudes towards the forest and it was found that although the forest was preserved for many years, the rural people still feel much attached to it as a result of the beliefs they have about it. The study contrasts different visions of the forest in terms of competing use and non-use values, and demonstrates that each group exercised its will and attempted to display "ownership" of the forest through a number of activities undertaken at the forest. An analysis of the public participation followed in terms of the ecotourism project was undertaken to determine the extent to which the rural community was involved. Theoretical models of environmental decision-making were applied in order to identify the mode of decisionmaking used historically and in the present. The results of the study show that poor rural people are still marginalized in EDM despite the new philosophies of PA management and the democratising shifts taking place in the country. Resistance to the policies and regulations of the reserve has been observed and this may lead to severe degradation of the resources that the reserve is meant to protect. The study thus recommends strengthening locally based EDM via partnerships as partnerships do not only provide relief for the consequences of conflict, they also strive for a win-win situation. The study concluded that greater involvement of the rural community requires a change in the mindset of conservation authorities, in particular with regard to the issue of representivity in EDM

Beyond master planning? New approaches to spatial planning in Ekurhuleni, South Africa

Traditional master planning has been criticised, but continues in various forms. This paper critically assesses an initiative by a South Africa metropolitan municipality to develop ‘local spatial developmen tframeworks’: comprehensive integrated plans dealing with 22 sectors, for some 103 areas, to guide land us edecisions and to provide a frame work for development. The paper concludes that despite some innovative aspects, several elements of traditional master planning were evident. New approaches to spatial planning were being shaped by older thinking, but also by the impact of a traditional land use management system.The findings point to the need for greater attention to debating alternative forms of spatial planning and their appro-priateness in various contexts.

Medium-modified DGLAP evolution of fragmentation functions from large to small x

The unified description of fragmentation function evolution from large to small x which was developed for the vacuum in previous publications is now generalized to the medium, and is studied for the case in which the complete contribution from the largest class of soft gluon logarithms, the double logarithms, are accounted for and with the fixed order part calculated to leading order. In this approach it proves possible to choose the remaining degrees of freedom related to the medium such that the distribution of produced hadrons is suppressed at large momenta while the production of soft radiation-induced charged hadrons at small momenta is enhanced, in agreement with experiment. Just as for the vacuum, our approach does not require further assumptions concerning fragmentation and is more complete than previous computations of evolution in the medium

Medium-modified average multiplicity and multiplicity fluctuations in jets

The energy evolution of average multiplicities and multiplicity fluctuations in jets produced in heavy-ion collisions is investigated from a toy QCD-inspired model. In this model, we use modified splitting functions accounting for medium-enhanced radiation of gluons by a fast parton which propagates through the quark gluon plasma. The leading contribution of the standard production of soft hadrons is enhanced by a factor $\sqrt{N_s}$ while next-to-leading order (NLO) corrections are suppressed by $1/\sqrt{N_s}$, where the parameter $N_s>1$ accounts for the induced-soft gluons in the medium. Our results for such global observables are cross-checked and compared with their limits in the vacuum.Comment: 8 pages and 4 figures. Version to be published in EPJ