Microstructure and mechanical properties of selective laser melted Ti-3Al-8V-6Cr-4Zr-4Mo compared to Ti-6Al-4V

Beta Ti-alloys are known for their high fracture toughness and ductility, and are used in applications where these properties are needed, such as the aerospace and biomedical industries. The selective laser melting of the alpha + beta Ti-6Al-4V alloy has been extensively studied for applications in the aerospace industry. Although there has been success in building small parts, the acicular α′ microstructure becomes a problem when large parts (800 × 400 × 500 mm3) are built. The acicular α′ microstructure of Ti-6Al-4V causes low fracture toughness and low ductility (<10% elongation), which causes the parts to warp and delaminate from the base plate, even before completion, due to the stress build-up. This work investigated the microstructure and mechanical properties of the beta titanium alloy Ti-38644 and two-phase Ti-6Al-4V in the as-built condition, using scanning electron microscopy with electron backscattered diffraction imaging, optical microscopy, micro-Vickers hardness and tensile tests. Ti-6Al-4V had a fine martensitic α′ structure inside columnar β grains, whereas Ti-38644 had a fully β microstructure, resulting in lower strength. The percentage elongation of Ti-38644 was thrice that of Ti-6Al-4V, showing potential for building large parts.the CSIR (Council for Scientific and Industrial Research, South Africa) and the Department of Science and Technology, South Africa.http://www.elsevier.com/locate/mseahj2020Materials Science and Metallurgical Engineerin

Dealing with a traumatic past: the victim hearings of the South African truth and reconciliation commission and their reconciliation discourse

In the final years of the twentieth and the beginning of the twenty-first century, there has been a worldwide tendency to approach conflict resolution from a restorative rather than from a retributive perspective. The South African Truth and Reconciliation Commission (TRC), with its principle of 'amnesty for truth' was a turning point. Based on my discursive research of the TRC victim hearings, I would argue that it was on a discursive level in particular that the Truth Commission has exerted/is still exerting a long-lasting impact on South African society. In this article, three of these features will be highlighted and illustrated: firstly, the TRC provided a discursive forum for thousands of ordinary citizens. Secondly, by means of testimonies from apartheid victims and perpetrators, the TRC composed an officially recognised archive of the apartheid past. Thirdly, the reconciliation discourse created at the TRC victim hearings formed a template for talking about a traumatic past, and it opened up the debate on reconciliation. By discussing these three features and their social impact, it will become clear that the way in which the apartheid past was remembered at the victim hearings seemed to have been determined, not so much by political concerns, but mainly by social needs

Household typology for relating social diversity and technical change: The example of rural households in the Khambashe area of the Eastern Cape Provine of South Africa

1 tables 5 graph. Communication*INRA, Centre de Versailles-Grignon (FRA) Diffusion du document : INRA, Centre de Versailles-Grignon (FRA)International audienc

Retrieving Biko: a black consciousness critique of whiteness

There is an important history often neglected by genealogies of ‘critical whiteness studies’: Steve Biko's Black Consciousness critique of white liberalism. What would it mean to retrieve this criticism in the context of white anti-racism in the post-apartheid era? Said's (2003) contrapuntal method proves useful here as a juxtaposing device whereby the writings of a past figure can be critically harnessed, travelling across temporal and ideological boundaries to interrogate the present. Four interlinked modes of disingenuous white anti-racism can thus be identified: (1) a fetishistic preoccupation with disproving one's racism; (2) ostentatious forms of anti-racism that function as means of self-promotion, as paradoxical means of white self-love; (3) the consolidation and extension of agency through redemptive gestures of ‘heroic white anti-racism’; (4) ‘charitable anti-racism’ which fixes tolerance within a model of charity, as an act of generosity and that reiterates the status and role of an anti-racist benefactor

Synthesis, structural characterization and antimycobacterial evaluation of several halogenated non-nitro benzothiazinones

8-Nitro-1,3-benzothiazin-4-ones (BTZs), with BTZ043 and PBTZ169 as the most advanced compounds, represent a new class of potent antitubercular agents, which irreversibly inhibit decaprenylphosphoryl-β-D-ribose-2′-epimerase (DprE1), an enzyme crucial for cell wall synthesis in the pathogen Mycobacterium tuberculosis. Synthesis, structural characterization and in vitro testing against Mycobacterium aurum DSM 43999 and M. tuberculosis H37Rv of halogenated 2-(4-ethoxycarbonylpiperazin-1-yl)-1,3-benzothiazin-4-ones lacking a nitro group are reported. X-ray crystallography reveals that the structure of the BTZ scaffold can significantly deviate from planarity. In contrast to recent reports, the results of the present study indicate that further investigation of halogenated non-nitro BTZs for antitubercular activity is less than a promising approach

Microstructure and mechanical properties of selective laser melted Ti-3Al-8V-6Cr-4Zr-4Mo compared to Ti-6Al-4V

Beta Ti-alloys are known for their high fracture toughness and ductility, and are used in applications where these properties are needed, such as the aerospace and biomedical industries. The selective laser melting of the alpha + beta Ti-6Al-4V alloy has been extensively studied for applications in the aerospace industry. Although there has been success in building small parts, the acicular α′ microstructure becomes a problem when large parts (800 × 400 × 500 mm3) are built. The acicular α′ microstructure of Ti-6Al-4V causes low fracture toughness and low ductility (<10% elongation), which causes the parts to warp and delaminate from the base plate, even before completion, due to the stress build-up. This work investigated the microstructure and mechanical properties of the beta titanium alloy Ti-38644 and two-phase Ti-6Al-4V in the as-built condition, using scanning electron microscopy with electron backscattered diffraction imaging, optical microscopy, micro-Vickers hardness and tensile tests. Ti-6Al-4V had a fine martensitic α′ structure inside columnar β grains, whereas Ti-38644 had a fully β microstructure, resulting in lower strength. The percentage elongation of Ti-38644 was thrice that of Ti-6Al-4V, showing potential for building large parts.the CSIR (Council for Scientific and Industrial Research, South Africa) and the Department of Science and Technology, South Africa.http://www.elsevier.com/locate/mseahj2020Materials Science and Metallurgical Engineerin

Ethanolic extracts of South African plants, Buddleja saligna Willd. and Helichrysum odoratissimum (L.) Sweet, as multifunctional ingredients in sunscreen formulations

Exposure to solar ultraviolet (UV) radiation is a major contributing factor to the increasing number of skin cancer cases. Interest has grown to use plant extracts as natural ingredients in cosmetic formulations due to their photoprotective effect, antioxidant and anti-inflammatory activity, as well as other biological activities. The aim of this study was to evaluate the biological activity of two South African plant extracts, Helichrysum odoratissimum (L.) Sweet. and Buddleja saligna Willd., and to successfully incorporate these extracts into sunscreen formulations (o/w emulsions) due to their reported biological activity. Ethanolic extracts were prepared from the leaves and stems of H. odoratissimum and B. saligna and evaluated for their antioxidant activity, mutagenic potential and antiproliferative activity against human dermal fibroblasts (MRHF). The extracts were further characterized using gas chromatography-mass spectrometry (GC-MS). Thereafter, the extracts were incorporated into separate sunscreen formulations to evaluate the in vivo dermal irritancy potential, in vivo sun protection factor, in vitro UVA protection, photostability and long term stability of the formulation, to confirm that by incorporating the extracts, the stability or photoprotective effect of the sunscreen formulation was not reduced and that these formulation were considered safe for topical application. Three separate sunscreen formulations were prepared; the base sunscreen formulation (formulation A), the base sunscreen formulation containing B. saligna (formulation B) and H. odoratissimum (formulation C) respectively. Both extracts showed significant radical scavenging activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay with a fifty percent inhibitory concentration (IC50) of 5.13 ± 0.07 and 8.16 ± 0.34 µg/mL for H. odoratissimum and B. saligna respectively. No mutagenic activity was observed when the extracts were tested in the Ames assay using Salmonella typhimurium (TA98 and TA100). The PrestoBlue® cell viability assay was used to determine the antiproliferative activity of the extracts against MRHF cells, both extracts showed an IC50 value >90 µg/mL. Photoprotective activity was measured using in vivo sun protection factor (SPF) test method according to South African (SANS 1557) and International (ISO 24444) standards as well as the in vitro UVA SPF testing procedure (ISO 24443). The SPF results showed that the formulations had broad-spectrum UV protection with SPF values of 15.8±0.41, 16.1±0.66 and 16.0±0.49 and UVAPF values of 6.47±0.06, 6.45±0.06 and 6.47±0.07 for formulation A, B and C respectively. Furthermore, the formulations remained stable under normal and extreme conditions and the plant extracts did not affect the photoprotective effect of the sunscreen formulations and contributed towards the formulations stability. Additionally, each of the formulations were photostable, whereas the formulations with the addition of the extracts showed an incremental increase in photostability when compared to the base formulation. Both these extracts have been previously reported to display antiproliferative activity against skin cancer cell lines (previously published data), with an IC50 value of 31.80 ± 0.35 µg/mL (human malignant melanoma, UCT-MEL-1) for B. saligna and IC50 values of 15.50 ± 0.20 (human epidermoid carcinoma, A431) and 55.50 ± 6.60 µg/mL (human malignant melanoma, A375) for H. odoratissimum, contributing towards the medicinal benefit of using these extracts as ingredients into sunscreen formulations. Therefore, Helichrysum odoratissimum and Buddleja saligna could be considered as useful and viable additives to sunscreen formulations due to their reported biological activity.The National Research Foundation of South Africahttp://www.elsevier.com/locate/sajb2021-11-01hj2021Chemical EngineeringParaclinical SciencesPlant Production and Soil Scienc