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Item 130000-year-old fossil elephant found near Durban, South-Africa: preliminary-report(Bureau Scientific Publications, 1993-04) Ramsay, PJ; Smith, AM; Lee-Thorp, JC; Vogel, JC; Tyldsley, M; Kidwell, WA modern African elephant tusk was discovered within a late Pleistocene aeolianite at Reunion Rocks, south of Durban. Ionium dating indicates that the tusk is older than 112 kyr BP with stratigraphic control suggesting a date at ca. 130 kyr BP. Preliminary carbon stable-isotopic analyses indicate that the elephant was a grass-grazer. Strontium isotopic analyses indicate a marine signature: this implies that the tusk suffered marine diagenesis or that the elephant accumulated a marine strontium isotope signature by living along the coastline.Item 1910–2010: How infrastructure grew our nation(South African Institution of Civil Engineering, 2010-10) Wall, KOne hundred years ago this year, South Africa was established by an Act of Union. That Act gave us the shape and the texture that defined us as a nation. And it is wonderful that, despite all the exclusions and discriminations since May 1910, we have survived intact as a state and still live within those same, unchanged borders. While articles in the daily press earlier this year discussed political and governance aspects of how far we have travelled as a nation over the last 100 years, the author in this article reflects on infrastructure development and service delivery over the last century. Engineering infrastructure has indeed revolutionised the way we live, work, study, play, dispose of wastes, travel and communicate. Aircraft and the motor car, with improved roads, have revolutionised inter-city travel; the Internet (and Wiki) have revolutionised how learners prepare assignments; computers (and software) have revolutionised data sorting and analysis; aerial photography and satellite imagery have revolutionised map-making – the list could go on.Item 20-year LiDAR observations of stratospheric sudden warming over a mid-latitude site, Observatoire de Haute Provence (44°N, 6°E): Case study and statistical characteristics(Copernicus Publications, 2007-11) Charyulu, DV; Sivakumar, V; Bencherif, H; Kirgis, G; Hauchecorne, A; Rao, DNThe present study delineates the characteristics of Stratospheric Sudden Warming (SSW) events observed over the Observatoire de Haute Provence (OHP: 44°N, 6°E). The study uses 20 years of Rayleigh LiDAR temperature measurements for the 1982-2001 period, which corresponds to 2629 daily temperature profiles. The characteristics of warming events are presented in terms of type of warming (major and minor), magnitude of warming, height of occurrence, day and period of occurrence with emphasis on wave propagation and isentropic transport conditions. The major and minor warming events are classified with respect to temperature increase and reversal in the zonal wind direction in the polar region using National Centre for Environmental Prediction (NCEP) reanalysis data. SSWs occur with a mean frequency of 2.15 events per winter season. The percentages of occurrence of major and minor warming events are found to be ~23 % and ~77 %, respectively. The observed major and minor SSW is associated with descent of stratopause layer by -6 to 6 km range. The height of occurrences of major SSW are distributed between 38 km and 54 km with magnitude in the 12.2-35.7 K temperature range, while the minor SSW appear in 42-54 km range, closer to the usual stratopause layer (~47 km) and with a slightly larger range of temperature magnitude (10.2-32.8 K). The observed major and minor events are examined in connection with Quasi-Biennial Oscillation (QBO) phases and presented.Item 2014 Election forecast - a post-election analysis(Operations Research Society of South Africa (ORSSA), 2017-06) Ittmann, HW; Holloway, Jennifer P; Dudeni-Tlhone, NontembekoGeneral elections are held every five years in South Africa. During the 12 to 24 hour period after the close of the voting booths, the expected final results are of huge interest to the electorate and politicians. In the past, the Council for Scientific and Industrial Research (CSIR) has developed an election forecasting model in order to provide the media and political analysts with forecasts of the final results during this period of peak interest. In formulating this model, which forecasts the election results as the results from voting districts (VDs) become available, some assumptions had to be made. In particular, assumptions were made about the clustering of previous voting patterns as well as the order in which VD results are released. This election forecasting model had been used successfully for a number of elections in the past and in these previous elections, with around 5% {10% of the results available, the predictions produced by the model were very close to the final outcome, particularly for the ANC, being the largest party. For the 2014 national election, however, the predictions, with close to 50% of the voting district results known (equivalent to an estimated 40% of the total votes), were still not accurate and varied by more than 1% for both the ANC and the EFF. This paper outlines a post-election analysis to determine the reasons for these discrepancies and how they relate directly to the model assumptions. The aim is to highlight how practical realities can affect the assumptions and consequently their impact on the forecasted results. Reference is made to previous election forecasts and the 2014 post-election analysis is presented.Item 2D numerical model for heat transfer on a laser deposited high entropy alloy baseplate using Comsol Multiphysics(2021-12) Dada, A; Popoola, P; Mathe, Ntombizodwa R; Adeosun, S; Aramide, OIn an optimization study, cracks were observed in the microstructures of laser-deposited HEAs on a steel baseplate from residual stresses, thus, the optimization of crack-free microstructures was achieved by the optimization of the laser parameters by baseplate preheating attributed to the lowering of the thermal gradients of the deposition process. This study reports the finite element analysis on the temperature distribution by the moving laser modelled to achieve process optimization with the necessary boundary conditions. Simulation has been reported as a facilitating tool in predicting the behaviour of materials during process optimization. Comsol Multiphysics 4.4, was used to create a 2D transient heat transfer time-dependent model to simulate the temperature distribution and the laser heating of the A301 steel baseplate surface and determine the effect of temperature on the optimization process of the alloys. Gaussian profiles were used as the heat source distributed per time. The results are presented in terms of thermal fields and Gaussian temperature profiles. Which show the temperature distribution that occurred in the steel baseplate during fabrication and the high cooling rate of the laser additive manufacturing technique restricted thermal stresses, improving adhesion and facilitating the optimization process.Item 3-D breast anthropometry of plus-sized women in South Africa(Taylor & Francis, 2011-09) Pandarum, R; Winnie, Y; Hunter, LawranceExploratory retail studies in South Africa indicate that plus-sized women experience problems and dissatisfaction with poorly fitting bras. The lack of 3-D anthropometric studies for the plus-size women's bra market initiated this research. 3-D body torso measurements were collected from a convenience sample of 176 plus-sized women in South Africa. 3-D breast measurements extracted from the TC(2) NX12-3-D body scanner 'breast module' software were compared with traditional tape measurements. Regression equations show that the two methods of measurement were highly correlated although, on average, the bra cup size determining factor 'bust minus underbust' obtained from the 3-D method is approximately 11% smaller than that of the manual method. It was concluded that the total bust volume correlated with the quadrant volume (r = 0.81), cup length, bust length and bust prominence, should be selected as the overall measure of bust size and not the traditional bust girth and the underbust measurement. Statement of Relevance: This study contributes new data and adds to the knowledge base of anthropometry and consumer ergonomics on bra fit and support, published in this, the Ergonomics Journal, by Chen et al. (2010) on bra fit and White et al. (2009) on breast support during overground running.Item 3-substituted anilines as scaffolds for the construction of glutamine synthetase and DXP-reductoisomerase inhibitors(Taylor & Francis, 2009-01) Mutorwa, M; Salisu, S; Blatch, GL; Kenyon, C; Kaye, PTAccess to a series of truncated ATP analogs, as potential anti-tuberculosis agents, has been explored via alkylation and acylation of 3-aminophenol, whereas chloroacetylation, using chloroacetyl chloride, and subsequent Arbuzov phosphonation of a series of 3-substituted anilines have afforded a series of phosphonate derivatives as potential antimalarial agents.Item 330 mJ single-frequency Ho:YLF slab amplifier(Optical Society of America, 2013-04) Strauss, Hencharl J; Preussler, D; Esser, MJD; Koen, W; Jacobs, Cobus; Collett, OJP; Bollig, CWe report on a double-pass Ho:YLF slab amplifier which delivered 350 ns long single-frequency pulses of up to 330 mJ at 2064 nm, with a maximum M(sup2) of 1.5 at 50 Hz. It was end pumped with a diode-pumped Tm:YLF slab laser and seeded with up to 50 mJ of single-frequency pulses.Item 3D edge detection seismic attributes used to map potential conduits for water and methane in deep gold mines in the Witwatersrand basin, South Africa(Society of Exploration Geophysicists, 2012-09) Manzi, MSD; Durrheim, RJ; Hein, KAA; King, NInrushes of ground water and the ignition of flammable gases pose risks to workers in deep South African gold mines. Large volumes of water may be stored in solution cavities in dolomitic rocks that overlie the Black Reef (BLR) Formation, while there are several possible sources for methane, namely, coal seams, kerogen found in some gold ore bodies, or methane introduced by igneous intrusions. Potential conduits that may transport water and methane to underground workings were mapped using 3D reflection seismic data. Edge detection attributes successfully identified many faults, some with displacements as small as 10 m. Faults that displace the Ventersdorp Contact Reef (VCR) and the BLR horizons were of special interest, as known occurrences of fissure water and methane in underground workings show a good correlation with faults that were imaged on the VCR and BLR horizons. Because there are uncertainties in determining the linkage of faults with aquifers and methane sources, it is considered prudent to assume that all structures that displace the VCR and BLR horizons are potential conduits.Item 3D evaluation of fine-scale normalised DSMs in urban settings(2020-09) Breytenbach, AndreHumankind often needs to accurately model, identify and spatially quantify aboveground phenomena on the Earth’s surface for informed decision-making. Height data derived from digital elevation models (DEMs) is often used to achieve this. This study conducted a deterministic assessment of three normalised digital surface models (nDSMs) of different spatial resolutions, namely 2m, 4m and 12m, derived from VHR digital stereo aerial photography, tri-stereo Pléiades imagery and Tandem-X InSAR data, respectively. Covering a predominantly built-up area within a city landscape, the nDSMs were vertically and volumetrically compared to assess their quality and fit-for-use. In each case a consistent systematic evaluation was accomplished against a lidar derived reference surface at matching spatial resolutions (co-registered) using a semi-automated GIS routine. The relative height and volumetric errors were statistically analysed and described, including those computed individually over nine urban land cover/land use (LCLU) classes and several selected large buildings. Higher vertical accuracies were reported across single storey structures and areas with no to little or short vegetation, as apposed to substantially lower accuracies obtained over multi-levelled buildings and tall (dense) woody vegetation. Here significant underestimations of volumes exacerbated by lower spatial resolutions were also observed across each nDSM. Conversely, notable volume overestimations were found over predominantly grass-covered areas in especially the finer-scaled nDSMs. VHR elevation data is recommended to model and quantify aboveground elements spatially in 3D (e.g. buildings, earthworks and woody vegetation) in urban landscapes, but a sensitivity test beforehand remains critical to ensure more reliable outcomes for users and stakeholders alike.Item 5G: the convergence of wireless communications(Springerlink, 2015-03) Chavez-Santiago, R; Szydelko, M; Kliks, A; Foukalas, F; Haddad, Y; Nolan, KE; Kelly, MY; Masonta, Moshe T; Balasingham, IAs the rollout of 4G mobile communication networks takes place, representatives of industry and academia have started to look into the technological developments toward the next generation (5G). Several research projects involving key international mobile network operators, infrastructure manufacturers, and academic institutions, have been launched recently to set the technological foundations of 5G. However, the architecture of future 5G systems, their performance, and mobile services to be provided have not been clearly defined. In this paper, we put forth the vision for 5G as the convergence of evolved versions of current cellular networks with other complementary radio access technologies. Therefore, 5G may not be a single radio access interface but rather a ”network of networks”. Evidently, the seamless integration of a variety of air interfaces, protocols, and frequency bands, requires paradigm shifts in the way networks cooperate and complement each other to deliver data rates of several Gigabits per second with end-to-end latency of a few milliseconds. We provide an overview of the key radio technologies that will play a key role in the realization of this vision for the next generation of mobile communication networks. We also introduce some of the research challenges that need to be addressed.Item A 6-bit, 500-MS/s current-steering DAC in SiGe BiCMOS technology and considerations for SFDR performance(Elsevier, 2015-04) Reddy, Reeshen; Sinha, SThis paper presents a six-bit current-steering digital-to-analogue converter (DAC), which optimises the spurious free dynamic range (SFDR) performance of high-speed binary weighted architectures by lowering current switch distortion and reducing the clock feedthrough effect. A novel current source cell is implemented that comprises heterojunction bipolar transistor current switches, negative-channel metal-oxide semiconductor (NMOS) cascode and NMOS current source to overcome distortion by specifically enhancing the SFDR for high-speed DACs. The DAC is implemented using silicon¿germanium (SiGe) BiCMOS 130 nm technology and achieves a better than 21.96 dBc SFDR across the Nyquist band for a sampling rate of 500 MS/s with a core size of 0.1 mm2 and dissipates just 4 mW compared to other BiCMOS DACs that achieve similar SFDR performance with higher output voltages, resulting in a much larger power dissipation.Item 99mTc-MDP as an imaging tool to evaluate the in vivo biodistribution of solid lipid nanoparticles(Elsevier, 2018-11) Mandiwana, Vusani; Kalombo, Lonji; Grobler, A; Zeevaart, JRThe aim of this study was to establish the in vivo uptake and tissue distribution of (sup)99mTc-MDP-encapsulated Solid Lipid Nanoparticles (SLNs) post administration. Radioactive (sup)99mTc-MDP encapsulated into SLNs was administered to rats to trace their biodistribution through imaging and ex vivo studies. As expected IV injected (sup)99mTc-MDP exhibited predominant visual bone uptake and a high localisation of particles in the kidneys (3.87%ID/g) followed by bone (2.66%ID/g). IV administered 99mTc-MDP encapsulated by SLN showed similar uptake than (sup)99mTc-MDP. Orally administrated (sup)99mTc-MDP showed no uptake in any organs except the GI-tract while orally administered (sup)99mTc-MDP-SLN showed distinct transfer of (sup)99mTc-MDP from the GI tract with measurable levels in the kidneys and bone.Item a-MnO2 nanorod/onion-like carbon composite cathode material for aqueous zinc-ion battery(Elsevier, 2019-05) Palaniyandy, Nithyadharseni; Kebede, Mesfin A; Raju, Kumar; Ozoemena, KI; Le Roux, Lukas; Mathe, Mahlanyane K; Jayaprakasam, ROnion-like carbon (OLC) integrated a-MnO2 nanorods (a-MnO2/OLC) composite has been studied as a viable cathode material for potential development of high-performance zinc-ion batteries (ZIBs). XRD results revealed the tetragonal phase of the a-MnO2 materials, and the FE-SEM and HR-TEM images show nano-sized rod-shaped morphology with an average diameter of 30 nm. The BET surface area of the a-MnO2/OLC composite was almost 6 times (247.22 m2/g) higher than that of the pristine (42.48 m2/g) material and the thermogravimetric investigation was exposed 50% of MnO2 and 50% OLC is presented in the composite. The electrochemical performance of the cells was evaluated by galvanostatic cycling (GC), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using 1 M ZnSO4 plus 0.1 M MnSO4 additive as electrolyte and Zn foil as the anode. Cycling results indicate that a-MnO2/OLC composite exhibits a stable and high reversible capacity of 168 mAh g-1 (93% capacity retention) compared to the a-MnO2 material with a capacity of 104 mAh g-1 (81% capacity retention) after 100 cycles.Item AAC services for multilingual populations: South African service provider perspectives(Elsevier, 2018-06) Tönsing, KM; Van Niekerk, K; Schlunz, Georg I; Wilken, IlanaBACKGROUND: In South Africa, many persons in need of augmentative and alternative communication (AAC) come from multilingual backgrounds. There is as yet a limited evidence base (locally and internationally) for the provision of AAC services to multilingual populations. The perspectives of service providers can assist in gaining an understanding of current practices and the factors that influence these. AIMS: The study aimed to obtain the perspectives of AAC service providers about practices in providing AAC systems and AAC intervention to clients from multilingual backgrounds. METHODS & PROCEDURES: Fifteen AAC service providers were purposefully chosen to participate in one of three focus groups - two face-to-face and one online focus group. Data from the face-to-face focus groups was transcribed verbatim. Thematic analysis was used to identify themes and subthemes in the data. OUTCOMES & RESULTS: Four overarching themes were identified, namely (a) current practices, (b) factors influencing current practices, (c) service provides' orientation towards different language options in AAC intervention, and (d) needs and desired developments regarding AAC technology. This paper reports on the first three themes. Service providers reported their practices to range from a focus on L1 exclusively, L2 exclusively, to a multilingual (sequential or simultaneous) approach. The South African language context, family language preferences and choices, service provider skill and knowledge, as well as AAC technology were identified as factors influencing their practices. Although many viewed access to multiple languages through AAC as positive, they also expressed concerns and reservations about providing multilingual AAC services. CONCLUSIONS & IMPLICATIONS: Although service providers in general saw the need to give clients from multilingual backgrounds access to multiple languages using AAC, this did not always translate into multilingual AAC practices. Both extrinsic factors (e.g. the lack of appropriate AAC devices, software and apps giving access to non-English languages) and intrinsic factors (service providers' language competency and their beliefs about the cognitive demands of multilingual AAC systems) influenced their practices and choices. Appropriate AAC service delivery to multilingual populations in South Africa would require not only appropriate AAC technology developments, but also research evidence to establish the efficacy of multilingual AAC interventions for clients with a variety of characteristics.Item Ab initio calculation of the voltage profile for LiC6(Elsevier Science BV, 2003-03) Kganyago, KR; Ngoepe, PE; Catlow, CRAEnergetics of the anode system LiC6 compared to metallic lithium is calculated within the framework of local-density functional theory (LDA-DFT) techniques. Our results suggest that the energy of anode intercalation results in a small change to the cell voltage.Item Ab initio studies of vacancies in (8,0) and (8,8) single-walled carbon and boron nitride nanotubes(American Scientific Publishers, 2012-09) Mashapa, MG; Chetty, N; Ray, Suprakas SA systematic study of vacancies in single-walled carbon nanotubes and boron nitride nanotubes was carried out. First principles calculations within the framework of density functional theory using the CASTEP code are used to optimize fully the geometries of the systems. The generalized gradient approximation is used for the exchange-correlation functional. We find that the pristine single-walled carbon nanotubes have lower heats of formation compared with the boron nitride nanotubes, consistent with other findings. The zig-zag (8,0) carbon nnaotube has a slightly lower (-3.32 eV) heat of formation compared to the armchair (8,8) configuration (-3.25 eV). Comparison of the heats of formation of the vacancy systems is made and we draw conclusions about the relative stability of these defects. The heats of formation and atomic relaxations of the vacancies are explained as resulting from the tendency of the affected ions to recover the lost electronic coordination. For the boron nitride nanotube, we find that the vacancies on the nitrogen and boron site, namely VN, and VB, are respectively the more stable vacancies in the B- and N-rich environments. The electronic structure of the single vacancies also depends on the nanotube chirality.Item Above ground perennial plant biomass across an altitudinal and land-use gradient in Namaqualand, South Africa(Elsevier, 2010-08) Anderson, PML; Hoffman, MT; O'Farrell, Patrick JThis study set out to generate estimates of the standing perennial biomass for six different vegetation types, and associated upland and lowland habitats, across the altitudinal gradient presented by the Kamiesberg mountain range in the Namaqualand region of the Northern Cape Province of South Africa. Volume-biomass regressions, established for 94 perennial species accounting for 70–80% of the plant cover, were used to generate these estimations. Comparisons to other studies give similar findings, corroborating the method adopted. Biomass was found to vary significantly in relation to the altitudinal, and associated rainfall, gradient, as well as by habitat type where the rocky uplands have considerably more biomass that the sandy lowland habitats. An examination of the impact of sustained heavy grazing associated with a communal rangeland on this standing perennial biomass, showed a significant decrease in on the lowland habitats. This loss in biomass is principally of palatable species, with no evidence of a response in terms of perennial biomass. These findings point to degradation on the lowland habitats of the communal rangeland, with negative consequences for livestock farmers in the region.Item An above-ground biomass map of African savannahs and woodlands at 25m resolution derived from ALOS PALSAR(Elsevier, 2018-03) Bouvet, A; Mermoz, S; Le Toan, T; Villard, L; Mathieu, Renaud SA; Naidoo, Laven; Asner, GPSavannahs and woodlands are among the most important biomes in Africa: they cover half of sub-Saharan Africa, provide vital ecosystem services to the rural communities, and play a major part in the carbon budget. Despite their importance and their fragility, they are much less studied than other ecosystems like rainforests. In particular, the distribution and amount of the above-ground woody biomass (AGB) is largely unknown. In this paper, we produce the first continental map of the AGB of African savannahs and woodlands at a resolution of 25 m. The map is built from the 2010 L-band PALSAR mosaic produced by JAXA, along the following steps: a) stratification into wet/dry season areas in order to account for seasonal effects, b) development of a direct model relating the PALSAR backscatter to AGB, with the help of in situ and ancillary data, c) Bayesian inversion of the direct model. A value of AGB and its uncertainty has been assigned to each pixel. This approach allows estimating AGB until 85 Mg·ha- 1 approximately, while dense forests and non-vegetated areas are masked out using the ESA CCI Land Cover dataset. The resulting map is visually compared with existing AGB maps and is validated using a cross-validation approach and a comparison with AGB estimates obtained from LiDAR datasets, leading to an RMSD of 8 to 17 Mg·ha- 1. Finally, carbon stocks for savannahs in Africa and in 50 countries are estimated and compared with estimates by FAO and from AGB maps available over Africa.Item Aboveground biomass density models for NASA’s Global Ecosystem Dynamics Investigation (GEDI) lidar mission(2022-03) Duncanson, L; Kellner, JR; Armston, J; Dubayah, R; Minora, DM; Hancock, S; Healey, SP; Patterson, PL; Main, Russell S; Naidoo, LavenNASA’s Global Ecosystem Dynamics Investigation (GEDI) is collecting spaceborne full waveform lidar data with a primary science goal of producing accurate estimates of forest aboveground biomass density (AGBD). This paper presents the development of the models used to create GEDI’s footprint-level (~25 m) AGBD (GEDI04_A) product, including a description of the datasets used and the procedure for final model selection. The data used to fit our models are from a compilation of globally distributed spatially and temporally coincident field and airborne lidar datasets, whereby we simulated GEDI-like waveforms from airborne lidar to build a calibration database. We used this database to expand the geographic extent of past waveform lidar studies, and divided the globe into four broad strata by Plant Functional Type (PFT) and six geographic regions. GEDI’s waveform-to-biomass models take the form of parametric Ordinary Least Squares (OLS) models with simulated Relative Height (RH) metrics as predictor variables. From an exhaustive set of candidate models, we selected the best input predictor variables, and data transformations for each geographic stratum in the GEDI domain to produce a set of comprehensive predictive footprint-level models. We found that model selection frequently favored combinations of RH metrics at the 98th, 90th, 50th, and 10th height above ground-level percentiles (RH98, RH90, RH50, and RH10, respectively), but that inclusion of lower RH metrics (e.g. RH10) did not markedly improve model performance. Second, forced inclusion of RH98 in all models was important and did not degrade model performance, and the best performing models were parsimonious, typically having only 1-3 predictors. Third, stratification by geographic domain (PFT, geographic region) improved model performance in comparison to global models without stratification. Fourth, for the vast majority of strata, the best performing models were fit using square root transformation of field AGBD and/or height metrics. There was considerable variability in model performance across geographic strata, and areas with sparse training data and/or high AGBD values had the poorest performance. These models are used to produce global predictions of AGBD, but will be improved in the future as more and better training data become available.