Oxidation of cellulose in pressurized carbon dioxide

This work presents first results upon oxidation of type II cellulose by nitrogen dioxide dissolved in carbon dioxide at high pressure. This reaction leads to oxidized cellulose, a natural-based bioresorbable fabric used for biomedical applications. The oxidation reaction takes place in a heterogeneous fluid–solid system. Kinetics of oxidation is presented here and effects of operating conditions such as pressure, temperature and initial moisture content of cellulose are investigated. Results are presented in terms of degree of oxidation of cellulose and quality of the final oxidized cellulose, which has been characterized using liquid-state and solid-state 13C NMR. The experimental results show the existence of possible secondary reactions which may lead to oxidized cellulose with insufficient mechanical strength. An attempt is made to evidence and understand the role of CO2 as a solvent in this system. Indeed, although supercritical CO2 appears to be a suitable candidate as a solvent for oxidation reactions, some inhibiting effect on nitrogen dioxide activity are observed in this case

Interest towards human, animal and object in children with autism spectrum disorders: an ethological approach at home

International audienceAutistic spectrum disorders (ASD) are characterised by attention deficits in communication and social interactions and a lack of interest in people. Data are mostly based on clinical situations. However, recent studies have shown a more mixed situation where children with ASD (ASD children) displayed interest towards humans, in both experimental and natural settings. The aim of this study was to assess the interest of ASD children in a natural standardised home setting. Here, we hypothesised that ASD children would display more interest towards animate stimuli-human and pet-when in the child's home than in the lab experimental setting. We used an ethological approach involving observations, a methodological alternative to lab static techniques, to investigate the behaviour of ninety 6- to 12-year-old ASD and typical development (TD) children. Our results were consistent with those of the literature revealing that the ASD children displayed interest towards animate stimuli as did children with TD children. Interestingly, while the ASD children showed higher interest towards humans, e.g. their parent, than the TD children did, they showed less interest towards pet compared to the TD children. Our results suggested that animals are not inherently easy to decode for ASD children, in contrast with previous experiences where a pet was regarded as a more attractive partner, easier to be understood. At last, the ASD children changed more frequently their focus point than the TD children did. These differences may be explained by the reduced attention skills in ASD or the study's context. To conclude, larger exploratory studies in natural settings conducted beyond ordinary human to human interactions are crucial for better understanding of the underlying mechanisms involved in social interactions in ASD