Journal Articles

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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, W
A 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.
1910–2010: How infrastructure grew our nation
(South African Institution of Civil Engineering, 2010-10) Wall, K
One 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.
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, DN
The 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.
2014 Election forecast - a post-election analysis
(Operations Research Society of South Africa (ORSSA), 2017-06) Ittmann, HW; Holloway, Jennifer P; Dudeni-Tlhone, Nontembeko
General 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.
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, O
In 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.
3-D breast anthropometry of plus-sized women in South Africa
(Taylor & Francis, 2011-09) Pandarum, R; Winnie, Y; Hunter, Lawrance
Exploratory 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.
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, PT
Access 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.
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, C
We 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.
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, N
Inrushes 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.
3D evaluation of fine-scale normalised DSMs in urban settings
(2020-09) Breytenbach, Andre
Humankind 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.
3D printed microfluidic chip design for diagnostic studies
(2024-12) Sekhwama, Masindi; Mpofu, Kelvin T; Mcoyi, Michael P; Sivarasu, S
In this study, additive manufacturing (3D printing) is utilised to fabricate lateral flow microfluidic chips (LFMC). Our chips were designed using Autodesk design software and printed using a Formlabs 3D printer. They are printed using Formlabs V4 resin polymer. In this work, the design process is highlighted in detail and shows an LFMC design that is made for potential applications in diagnostics studies. Our study also tested the performance of one of the chip designs in actual diagnostics experiment on an optical transmittance setup with a peristaltic pump. The LFMC was integrated onto a custom-built transmittance optical biosensor to measure the transmission intensity. A real-time kinetic study was conducted using an HIV-1 oligonucleotide probe. The study involved performing real-time transmittance analysis by pumping the HIV-1 oligonucleotide probe at different flow rates, ranging from 9. 5 μm/min to 13 μm/min with intervals of 0.5 μm/min. During the experiment, transmission intensity or transmitted light was measured in real time as the oligonucleotide HIV probe bound to neutravidin immobilised on the Au metal surface. These measurements were recorded using a USB400 spectrometer, with a broad- band UV light source that emits wavelengths ranging from 400 to 800 nm. The study underscored the significance of microfluidic chips as devices capable of enhancing the performance of biosensors as well as the use of 3D printing in the design and manufacture of these microfluidic chips.
5G RedCap enhancement towards Improved Cellular LPWAN/5G-IoT for Smart Cities and Industrial IoT using genetic algorithm-based neural network
(2024-06) Ogbodo, EU; Abu-Mahfouz, Adnan MI; Kurien, AA
Abstract: Background: The low power wide area networks (LPWANs) technologies significantly impact numerous IoT deployment use cases, especially in the smart cities' scenario. LPWAN is used to support low data rate use cases. Unfortunately, medium data rate (up to 50 Mbps and more) IoT applications are not operational by LPWAN. Hence, a 5G reduced capability (RedCap) new ra dio (NR) device was provided to address this limitation. However, the 5G RedCap suffers a cover age loss due to the reduction of the physical layer complexity of the 5G legacy user equipment (UE). Therefore, 5G RedCap enhancements require coverage loss compensation. Objective: This paper aims to improve the performance of 5G RedCap in terms of coverage, energy efficiency, and throughput for Smart Cities and Industrial IoT (IIoT) using a genetic algorithm based neural network (GA-NN) model. Method: The method involves using a GA-NN model for a two-fold enhancement of the 5G Red Cap. This enhancement includes a specialized-enhancement RedCap (se-RedCap) for low data rates and an enhanced RedCap (eRedCap) for high data rates (up to 300 Mbps) support. The GA NN model has been implemented and assessed in MATLAB Global Optimization and 5G Toolbox. Furthermore, an introduced and modified parametric rectified linear unit (ePReLU) activation func tion fA evaluates the final summation data parameters trained with a specific threshold for the best performance. Results: The numerical results confirm that the specialized-enhancement RedCap (se-RedCap) and enhanced RedCap (eRedCap) outperform legacy cellular LPWANs and conventional RedCap when considering coverage, energy efficiency, and throughput. Conclusion: This paper successfully covers two types of usage scenarios: the very low data rate typically seen in LPWAN and the high data rate of up to 300 Mbps, which is not yet compatible with the existing RedCap system. As a result, the GA-NN model creates se-RedCap and eRedCap, providing support for these two scenarios, respectively.
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, I
As 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.
A 6-bit, 500-MS/s current-steering DAC in SiGe BiCMOS technology and considerations for SFDR performance
(Elsevier, 2015-04) Reddy, Reeshen; Sinha, S
This 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.
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, JR
The 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.
A comparative analysis between isotropic and optimization binary diagram influenced by nickel-doping on the LiMn2O4 spinel type
(2024-12) Malatji, K; Maphanga, Rapela R; Ngoepe, P
The study explores the Ni-rich transition metal as a dopant on the Mn (16d) site of the LiMn1-xNixO4 cathode material. However, lithium manganese oxide is hindered by a limited cycle life, caused by the dissolution of manganese into the electrolyte during electrochemical cycling. Doping lithium-ion battery materials with TM generally enhances their ability to maintain electrochemical capacity over many cycles without compromising the initial reversible capacity at room temperature. This study utilised the genetic algorithm approach and first-principles calculations to investigate the LiMn2O4 spinel structure. This method identified the most stable phases by simplifying atomic interactions in the LiMn2O4-LiNi2O4 system using a series of clusters, which facilitated the corresponding thermodynamic analysis. The comparison and exploration between the full optimized and volume optimized binary calculation was to observe the % difference of the two binary diagrams yielding 13 meV and 1.1 meV, respectively. The two binary ground state diagrams depict the miscibility constituent’s behaviour, producing new phases (62 and 77) with different coordinates. The study revealed the five most stable phases at the ground state line, one of which is the opposite (LiMn0.5Ni1.5O4) at X = 0.75 of the high-potential cathode material LiMn0.5Ni1.5O4.
A comparison of weldability and mechanical properties of additive manufactured and bulk Ti6Al4V alloy
(2024-11) Akinlabi, ET; Omoniyi, PO; Mahamood, RM; Arthur, Nana KK; Pityana, Sisa L; Skhosane, Besabakhe S; Okamoto, Y; Shinonaga, T; Maina, MR; Akinlabi, SA; Jen, TC
Titanium and its alloys, especially the Ti6Al4V, have tremendous use in the aerospace and biomedical industries. Since conceptualizing additive manufacturing techniques, it has been one of the most popular manufacturing techniques used on Titanium and its alloys. However, building large parts of the Ti6Al4V through additive manufacturing can be cumbersome due to the multiphysics involved in the heating and cooling of the material and the limited building space. This article examines the weldability of additive manufactured Ti6Al4V, manufactured through laser metal deposition (LMD) technique, and bulk sheet metal of Ti6Al4V manufactured through the rolling process. The welds were characterized using hardness, tensile, X-ray diffraction (XRD), and the evolving microstructure. Results show martensitic microstructure within the fusion zone, resulting in high hardness within the zone, which is confirmed in the XRD results. Failure occurred at the LMD heat-affected zone side of the sample due to the martensitic microstructure within the zone. The research further affirms the feasibility of joining Ti6Al4V manufactured through different routes through laser welding.
A comprehensive review of metal-organic frameworks sorbents and their mixed-matrix membranes composites for biogas cleaning and CO2/ CH4 separation
(2024-09) Duma, Zama G; Makgwane Peter R, MN; Masukume, Mike; Swaartbooi, Ashton M; Rambau, Khavharendwe; Mehlo, Thembelihle; Mavhungu, Tshidzani
Metal-organic framework (MOF) sorbent materials have recently gained considerable attention in gas separation technology. This is because of their unique structural properties, such as high gas permeability and selectivity promoted by large porosity and high surface areas. Integrating MOF fillers with polymer membranes to construct mixed-matrix membranes (MMMs) has enhanced gas separation and capture performance and stability. This review provides a comprehensive current status development in MOFs and their integrated MMMs composites with focused applications in biogas cleaning for the removal of common trace impurities such as hydrogen sulfide (H2S), ammonia (NH3), siloxanes, and moisture and upgrading of the subsequent carbon dioxide/methane (CO2/CH4) mixture to bio-methane and biogenic CO2. We highlight the structural properties and descriptors critical for designing MOF sorbents and MOF-based MMMs to improve their adsorption capacities and separation efficiency in biogas cleaning and upgrading. The tuneable surface modifications of MOFs boasted by the surface-endowed basic-acidic sites and coordinated open metal sites effectively provide high adsorption capacities and separation selectivities in biogas processing. The combination of MOFs and membranes offers high separation efficiencies of biogas-derived CO2 and CH4 for their diverse potential downstream utilisation. Future perspectives on advancing further developments in MOF sorbents and MOFs-based MMMs for biogas cleaning and upgrading to access sustainable and green derivatives with fewer carbon footprints while beneficiating wastes for adopting a circular economy are highlighted to provide solutions to the shortcomings.
A DFT study of the ternary metal chalcogenides (XAlS2) materials for photovoltaic and high-temperature applications
(2024) Maphanga, Rapela R; Santosh, MS; Rugute, E; Dima, Ratshilumela S; Mondal, P; Maleka, Prettier M; Tshwane, David M; Maluta, E; Rtimif, S
This work employs density functional theory (DFT) to investigate the structural, electronic, and optical properties of XAlS2 (X =Li, Na, K, Rb, and Cs) nanomaterials for potential use in photovoltaic applications. A comprehensive first-principles analysis has been conducted using GGA-PBE, GGA-PBEsol, and LDA functionals to examine LiAlS2, NaAlS2, KAlS2, RbAlS2, and CsAlS2. The findings reveal distinctive band gaps within this set of materials, with LiAlS2 and NaAlS2 exhibiting indirect band gaps and KAlS2, RbAlS2, and CsAlS2 possessing direct band gaps. Analyzing the partial density of states indicates that the valence band predominantly arises from S-3p and Al-3p orbitals, showcasing covalent bonding through hybridization. Furthermore, the examination of the optical properties of XAlS2 materials suggests their notable light absorption in the ultraviolet range, positioning them as promising candidates for photovoltaic applications. Additionally, the lattice thermal conductivity of two dynamically stable systems has been investigated and their thermoelectric properties have been calculated. Notably, a dimensionless figure of merit of 2.78 for LiAlS2 has been identified, marking it as a strong contender for high-temperature thermoelectric applications.
A greener, rapid and accurate microwave-assisted hydrogen peroxide digestion method for ICP-OES determination of heavy metals in pet food samples
(2024-07) Ncube, N; Tancu, Yolanda; Mketo, N
Microwave-assisted hydrogen peroxide digestion (MW-AHPD) method for determination of Cd, As, Pb, Sn, and Cr in South African pet food samples by inductively coupled plasma-optical emission spectroscopic (ICP-OES) is reported. Multivariate tools and wheat flour certified reference material (FAP80467) assessed limiting factors and reproducibility of the methods respectively. The resulted optimum conditions were: 200 ◦ and 5 mol/L for temperature, time, sample mass and H 2 O 2 C, 40 mins, 0.5 g, concentration, respectively. The method demonstrated excellent accuracy (96–98%), reproducibility (≤ 2.1%) and high detection limits (0.0675–0.3765 µg/g). Then, real pet food samples made from maize, rice, vegetables, fish, and wheat were digested and concentration levels of Cd, Pb, As, Cr and Sn ranged between 11.2 and 22.6, 6.4–11.9, 3.44–13.4, 0.44–2.98 and 0.18–0.98 µg/ g, respectively. The three metal ions were above the minimum tolerable limits (Cd: 10 µg/g, Pb:10 µg/g, As: 12.5 µg/g) for some of the fish and wheat.

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