New cut-off values for ferritin and soluble transferrin receptor for the assessment of iron deficiency in children in a high infection pressure area

Background: Due to the potential risk of iron supplementation in iron replete children, it is important to properly identify children who may require iron supplementation. However, assessment of the iron status has proven to be difficult, especially in children living in areas with high infection pressure (including malaria). Aims and Methods: Biochemical iron markers were compared to bone marrow iron findings in 381 Malawian children with severe anaemia. Results: Soluble transferrin receptor/log ferritin (TfR-F index), using a cut-off of 5.6, best predicted bone marrow iron stores deficiency (sensitivity 74%, specificity 73%, accuracy 73%). In order to improve the diagnostic accuracy of ferritin or sTfR as a stand-alone marker, the normal cut-off value needed to be increased by 810% and 83% respectively. Mean cell haemoglobin concentration (MCHC), using a cut-off of 32.1 g/dl, had a sensitivity of 67% and specificity of 64% for detecting iron stores deficiency. Conclusion: TfR-F index incorporated the high sensitivity of sTfR, a proxy for cellular iron need, and the high specificity of ferritin, a proxy for iron stores. In areas with a high infection pressure, the TfR-F index best predicted iron deficiency. However, in settings where diagnostic tests are limited, MCHC may be an acceptable alternative screening test

Carbide-free bainitic steels for rail wheel applications

In South Africa, forged wheels for rail cars are imported but cast wheels are manufactured locally, although recent developments indicate that forged wheels will in future be manufactured locally. The forged wheels are generally manufactured from AAR Class C steel, which is a high carbon, pearlitic steel used for rail application. Railway wheels are a costly component of the railway wagon as they experience wear and damage during application. Improvements in the mechanical properties are thus desired. Against this background, a project is reported on the development of durable rail steel alloys for railway wheel applications. Carbide-free bainite is a novel microstructure comprising bainitic ferrite and retained austenite/martensite but without coarse carbides in the interlath positions. The absence of carbides is achieved through the addition of a high silicon (~2wt%) content to the steel. This carbide-free bainite can achieve high tensile strength (>1000MPa) and toughness (40J, 20°C) as well as good wear resistance. These alloys have found application in areas where high strength, toughness and wear resistance are required, such as in rail steels, and have been deemed the “next generation” of rail steels. Carbide-free experimental alloys were produced in the laboratory and tested for mechanical properties such as hardness, tensile strength and impact toughness. The properties of the laboratory alloys were compared to those of standard Class C alloys used in South Africa to determine their potential use as railway wheel alloys.We would like to thank the following people and organisations, without which this study would not have been possible: the University of Pretoria for providing technical support and academic supervision, Mintek, for technical and financial support, The Department of Science and Technology (DST), Advanced Materials Initiative (AMI)-Ferrous Metals Development Network (FMDN) for their financial support, the Nelson Mandela University, Department of Physics and Centre for HRTEM for transmission kikuchi diffraction (TKD) analysis and the Nuclear Energy Council for South Africa (NECSA) for their neutron diffraction analysis.Mintek, the Department of Science and Technology (DST) and Advanced Materials Initiative (AMI)-Ferrous Metals Development Network (FMDN).http://iopscience.iop.org/journal/1757-899Xam2020Materials Science and Metallurgical Engineerin

Effect of Al addition on the solidification structure of 441 dual stabilised ferritic stainless steel

Ferritic stainless steels (FSS) develop poor surface finish during processing and this is attributed to the large columnar grains formed during solidification. Addition of alloying elements such as Al, Ti and Nb used in dual stabilized FSS improve the solidification structures. In this work, two 441 dual stabilized FSS, with 0.023 and 0.068 %Al respectively were investigated in the as-cast condition. The columnar to equiaxed zone ratio was determined by the linear interception method. The results showed that the higher the Ti/Al ratio, the higher the equiaxed ratio. The inclusions reported from SEM showed that there were more spinel inclusions of Ti-Al-O as well as more TiN precipitates in the steel with 0.023 wt% Al

Electron backscatter diffraction postprocessing techniques for studying recrystallisation phenomenon of Ferritic Stainless Steel

The following article looks at using scanning electron microscopy- electron back scatter diffraction techniques to study recrystallisation structures produced through hot rolling of 436 ferritic stainless steel. Characterisation of recrystallisation textures was undertaken through analysis of misorientation angle distribution diagrams, orientation distribution function maps, inverse pole figures and Taylor factor maps. These techniques were applied in a case study where typical industrial hot rolling conditions were simulated through uniaxial compression tests in a Bähr Dilatometer 850D, whereby the effect of strain rate and interpass time on recrystallisation structures was investigated