Search

La longue histoire de la sélection des animaux domestiques est marquée par l’association toujours plus étroite entre les technologies et le développement économique. Aujourd’hui, la connaissance récente de l’ADN devient une référence incontournable pour la sélection des troupeaux, en particulier des vaches laitières. À partir d’une large enquête qualitative menée sur la race Montbéliarde dans l’arc jurassien, nous interrogeons cette innovation ainsi que le concept de temps qui sans statut ontologique, nous permet de dilater la complexité de l’élevage aujourd’hui. D’un côté, ces changements illustrent fidèlement les nombreux travaux qui démontent les ressorts modernes de l’accélération, mais de l’autre, les pratiques et les mots qui les accompagnent pointent aussi le fait que la durée peut rester à la base des compétences des éleveurs et du sens qu’ils accordent à leur métier.

The future of South Africa's economic growth rests on addressing critical scarce-skills labour shortages. Matriculants are called on to break the cycle of poverty by entering the scarce-skills workforce. The demonstration of a high level of mathematics, science, and technology competency is viewed as a gateway towards achieving this goal. The South African Department of Basic Education has invested much effort towards improving mathematics, science and technology competencies among learners by implementing various mathematics improvement strategies in public schools. The existing research, however, shows that these initiatives have yielded little success among learners from impoverished schooling contexts. Reasons for this limitation were explored by means of the systematic review reported on in this paper. The review focused on literature relating to mathematics improvement strategies in public schools implemented by the South African Department of Basic Education. The limitations of these initiatives were critically evaluated and gaps in various documented strategies were identified. The findings highlight an evident need for a shift in focus of future interventions if the national goal to address scarce-skills labour demands through educating the impoverished South African youth is to be successfully realised. Suggestions are offered on how this change might happen.

β‐tricalcium phosphate (β‐TCP, β‐Ca3(PO4)2) is an attractive biomaterial for bone repair applications. However, its sintering and mechanical properties are limited by a problematic phase transition to α‐TCP. Cationic doping of β‐TCP is able to postpone the formation of α‐TCP allowing higher sintering temperatures and better mechanical properties. The co‐doping of β‐TCP with Mg2+ and Sr2+ has already been studied in detail, but the addition of antibacterial cations (Ag+ and Cu2+) on the Mg–Sr β‐TCP co‐doped composition remains unexplored. Thus, two co‐doped β‐TCP compositions were realized by aqueous precipitation technique without any secondary phase and compared with undoped β‐TCP: Mg–Sr (2.0–2.0 mol%) and Mg–Sr–Ag–Cu (2.0–2.0–0.1–0.1 mol%). Differential thermal analysis and dilatometry analyses showed a slight decrease of the β‐TCP → α‐TCP phase transition temperature for the Mg–Sr–Ag–Cu (2.0–2.0–0.1–0.1% mol) composition as compared to the Mg–Sr (2.0–2.0 mol%). However, both exhibited much higher transition temperatures than undoped β‐TCP. The addition of Ag+ and Cu2+ slightly reduces the grain size after sintering compared to the Mg–Sr (2.0–2.0 mol%) and the undoped compositions. The co‐doped compositions also exhibited improved mechanical properties, specifically a higher Vickers hardness and elastic modulus. Finally, cell proliferation assays showed that the presence of dopants, even Ag+ and Cu2+, does not affect the survival and proliferation of cells. Thus, the use of Mg2+, Sr2+, Ag+, and Cu2+ co‐doped β‐TCP could be very promising for biomedical applications due to the improvements of these dopants on the thermal stability and mechanical and biological properties. [ABSTRACT FROM AUTHOR]