The Influence of Inert Packaging on the shelf Ageing of Gamma-Irradiation Sterilised ultra-high molecular weight polyethylene

Ultra-high molecular weight polyethylene (UHMWPE) is used for wear applications in total hip prostheses and total knee prostheses. Sterilisation of these prostheses is commonly by gamma-irradiation. This process creates reactive free radicals in the UHMWPE, greatly increasing its susceptibility to oxidative degradation. This study has investigated the influence of air and vacuum packaging on the properties of gamma-irradiated UHMWPE (GUR1050) following 3 years of shelf ageing. The findings indicate that vacuum packaging minimises oxidative degradation reactions that occur for UHMWPE during shelf ageing. However, gamma-irradiation of vacuum-packaged UHMWPE promotes a degree of cross-linking. It is proposed that this may enhance the wear performance of UHMWPE. Accelerated ageing studies indicate that 3 years of shelf ageing would also seem to reduce the susceptibility of gamma-irradiated UHMWPE to oxidative degradation upon removal from its vacuum packaging.

The Masculine Habitus as 'Distributed Cognition': A Case Study of 5- to 6-Year-Old Boys in an English Inner-City, Multi-Ethnic Primary School

This article provides a case study demonstrating the active role that 5- to 6-year-old boys in an English inner-city, multi-ethnic primary school play in the appropriation and reproduction of their masculine identities. It is argued that the emphasis on physicality, violence and racism found among the boys cannot be understood without reference to the immediate contexts of the local community and the school within which they are located. In making this argument the article draws upon and applies the concept of the habitus and develops this with the notion of 'distributed cognition' as proposed in sociocultural theory. Some of the implications of this analysis for working with boys in early years settings are discussed in the conclusion.