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Fatigue properties of additively manufactured tool steel

(2024-09) Johnston, Charmaine M; Tshabalala, Lerato C; Davids, M

Tool steel is routinely used by the Experimental Aerodynamics group at the Council for Scientific and Industrial Research (CSIR), South Africa, to manufacture critical components for wind tunnel testing. This steel is known for its high strength properties in both tension and compression, and has a good combination of machinability, ductility, and fracture toughness. The emergence of the Additive Manufacturing (AM) technology provides an alternative to traditional manufacturing procedures in the production of wind tunnel model parts and instrumentation; however, use of the AM technology requires knowledge, inter alia, of the fatigue characteristics of the AM materials. Test specimens were manufactured from tool steel powder using the Selective Laser Melting (SLM) technology and subjected to fatigue and tensile tests. The thermal treatments were used for stress relieving and aging the additively manufactured part; the processes used in this project were found to have an adverse effect on the properties of the material.

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Fatigue properties of additively manufactured tool steel

(2024-09) Johnston, Charmaine M; Tshabalala, Lerato C; Davids, M

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Carboxy-PEG-thiol functionalized gold nanoparticle conjugates for the detection of SARS-CoV-2: Detection tools and analytical method development

(2024-12) Hlekelele, Lerato; Setshedi, Katlego Z; Mandiwana, Vusani; Kalombo, Lonji; Lemmer, Yolandy; Chauke, Chauke P; Maity, Arjun

Addressing the need for accessible SARS-CoV-2 testing, carboxy-PEG 12-thiol functionalized gold nanoparticles conjugates were developed for rapid point-of-care (POC) detection against SARS-CoV-2 spike protein, pseudo-SARS-CoV-2, and authentic Beta SARS-CoV-2 virus particles. These conjugates leverage gold nanoparticles (AuNPs) as signal transducers, cross-linked to either angiotensin-converting enzyme 2 (ACE2) or SARS-CoV-2 spike protein receptor-binding domain (RBD) antibodies as bioreceptors and showed a distinct color shift from pink to blue. To assess their POC feasibility, the conjugates were integrated into facemasks and breathalyzers, wherein aerosolized SARS-CoV-2 antigens were successfully detected, producing a color change within 10 and 30 minutes for the breathalyzer and facemask prototypes, respectively. Furthermore, we explored quantitative analysis using varying concentrations of SARS-CoV-2 spike protein. Both conjugates demonstrated a linear relationship between blue color intensity and virus concentration, with linear ranges of 0.08–0.6 ng/mL and 0.04–0.5 ng/mL, respectively. Low limits of detection and quantification were also achieved. They exhibited specificity, responding solely to SARS-CoV-2 even in complex matrices containing diverse proteins, including the SARS-CoV-1 spike protein. Precision tests yielded coefficient of variations below 2 %, showcasing their remarkable reproducibility. This work presents a promising approach for rapid, sensitive, and specific POC detection of SARS-CoV-2 paving the way for improved pandemic response and management.

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Artificial sweeteners in surface waters from Asian, African and Middle Eastern countries: Utility as molecular markers and water pollution status in 2010–2019

(2024-01) Visser

To explore the utility of artificial sweeteners (Acesulfame: ACE; sucralose: SUC; saccharin: SAC; cyclamate: CYC) as molecular markers and to establish a historical benchmark of the water pollution status in the 2010 decade, 272 surface water samples, including river water, sewage, and livestock wastewater, were collected from African (Ghana, Kenya, Mozambique, South Africa), Asian (Vietnam, Indonesia, Thailand, Philippines, Cambodia, Malaysia, India, and Japan) and Middle Eastern (Iran and Lebanon) countries during 2010–2019 and were analyzed for the artificial sweeteners by high performance liquid chromatograph with tandem mass spectrometer coupled with online solid-phase extractor. ACE was most frequently detected (87% of the samples) due to its widespread use and lower detection limit (2 ng/L). SUC was less frequently detected (51%) because of its lower sensitivity and detection limit of 100 ng/L, and less widespread use in some low-income countries, probably due to its higher price. SAC and/or CYC were abundant in surface waters of most countries, despite their biodegradable nature. This was ascribed to intensive usage of SAC and CYC and extensive inputs of untreated sewage to rivers due to limited installation of sewage treatment systems. Concentrations of the sweeteners were higher in urbanized rivers (~1 μg/L to ~100 μg/L) than those in corresponding suburban and rural sites, reflecting spatial patterns of sewage inputs. Furthermore, concentrations of the sweeteners were positively correlated with those of linear alkylbenzenes (LABs) for all countries except Malaysia. These results confirm the utility of artificial sweeteners as indicators of sewage inputs. SAC and CYC could be indicators of untreated sewage inputs. ACE has proved to be the most sensitive and reliable marker to assess inputs of sewage, i.e., both treated and untreated, to surface waters. However, ACE concentrations in secondary effluents and receiving waters in Tokyo decreased two orders of magnitude from 2011 to 2019, while sucralose did not show such a marked decrease. This is probably due to the upgrading of activated sludge treatment, i.e., introducing anaerobic-anoxic-oxic (A2O) treatment and resultant higher removal of ACE. Therefore, the measurement of multiple markers, including SUC, is recommended for long-term monitoring.

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Recent advances in biochar: Synthesis techniques, properties, applications, and hydrogen production

(2024-05) Visser, ED; Seroka, Ntalane S; Khotseng, L

The field of material sciences has evolved vastly in the last two decades, largely due to the discovery of carbon nanomaterials such as graphene and its derivatives. Although they offer positive characteristics, the cost of production and material processing of these carbon nanomaterials has limited their application. However, scientists have started searching for cheaper and more environmentally friendly alternatives. Biochar, a carbonaceous material derived from biowaste, is the most viable alternative, as it offers characteristics on par with traditional carbon nanomaterials. This review will discuss the production of biochar from biomass, methods of production, the effects various conditions have on the production of biochar, biomass selection, current biochar applications, and the potential biochar has to produce hydrogen as an energy carrier.