Inhibition of Hotspot Formation in Polymer Bonded Explosives Using an Interface Matching Low Density Polymer Coating at the Polymer–Explosive Interface

In order to elucidate how shocks in heterogeneous materials affect decomposition and reactive processes, we used the ReaxFF reactive force field in reactive molecules dynamics (RMD) simulations of the effects of strong shocks (2.5 and 3.5 km/s) on a prototype polymer bonded explosive (PBX) consisting of cyclotrimethylene trinitramine (RDX) bonded to hydroxyl-terminated polybutadiene (HTPB). We showed earlier that shock propagation from the high density RDX to the low density polymer (RDX ? Poly) across a nonplanar periodic interface (sawtooth) leads to a hotspot at the initial asperity but no additional hotspot at the second asperity. This hotspot arises from shear along the interface induced by relaxation of the stress at the asperity. We now report the case for shock propagation from the low density polymer to the high density RDX (Poly ? RDX) where we find a hotspot at the initial asperity and a second more dramatic hotspot at the second asperity. This second hotspot is enhanced due to shock wave convergence from shock wave interaction with nonplanar interfaces. We consider that this second hotspot is likely the source of the detonation in realistic PBX systems. We showed how these hotspots depend on the density mismatch between the RDX and polymer and found that decreasing the density by a factor of 2 dramatically reduces the hotspot. These results suggest that to make PBX less sensitive for propellants and explosives, the binder should be designed to provide low density at the asperity in contact with the RDX. Based on these simulations, we propose a new design for an insensitive PBX in which a low density polymer coating is deposited between the RDX and the usual polymer binder. To test this idea, we simulated shock wave propagation from two opposite directions (RDX ? Poly and Poly ? RDX) through the interface matched PBX (IM-PBX) material containing a 3 nm coating of low density (0.48 g/cm3) polymer. These simulations showed that this IM-PBX design dramatically suppresses hotspot formation

(Dé)formations du processus de néophobie. Une approche sociologique des particularités alimentaires des enfants avec un trouble du spectre autistique

International audienceMany researchers, professionals and parents underline that children with Autism Spectrum Disorders (ASD) have “eating disorders”. This research proposes to go beyond the approach in terms of “selectivity” or eating “problems”. It focuses, through the process of neophobia, on the vagaries of the construction of their eating repertoire, from birth to adolescence. The approach combines qualitative and quantitative methods. The first takes the form of interviews with parents of children with ASD aged 4 to 13 (n = 21) and the second of a questionnaire with parents of adolescents with ASD aged 12 to 16 (n = 322). While for parents difficulties in eating are not a warning sign of autism, they are identified very early on and make sense in retrospect with the diagnosis. Food refusals between the ages of 3 and 7 are considered the most problematic behaviors. The data show a strong inter-individual variation among children with ASD. A typology was constructed according to the forming/distortion of the neophobic process. The population studied is divided into six categories: supratypical (20.8%), normotypical (16.1%), infratypical (18.6%), progressive (17.7%), late (9.0%), and neophile (17.7%). The discussion opens with an analysis of the dietary particularities of the autistic population based on the work carried out on neophobia in the general population. It thus emerges that phenomena often identified as specific to the autistic population can reveal variations in the neophobic process. It therefore seems appropriate to speak of food neophobia in the plural.Nombreux sont les chercheurs, les professionnels et les parents à mettre en avant le fait que les enfants avec un Trouble du Spectre Autistique (TSA) présentent des « troubles de l’alimentation ». Cette recherche se propose de dépasser l’approche en termes de « sélectivité » ou de « problèmes » alimentaires. Elle s’intéresse, à travers le processus de néophobie, aux aléas de la construction de leur répertoire alimentaire, de la naissance à l’adolescence. La démarche combine une approche qualitative et quantitative. La première prend la forme d’entretiens avec des parents d’enfants avec TSA âgés de 4 à 13 ans (n = 21) et la seconde d’un questionnaire auprès de parents d’adolescents avec TSA âgés de 12 à 16 ans (n = 322). Si pour les parents, les difficultés dans l’alimentation ne sont pas un signe d’alerte de l’autisme, elles sont très tôt très tôt identifiées et prennent rétrospectivement, sens avec le diagnostic. Les refus alimentaires entre 3 et 7 ans sont considérés comme les comportements les plus problématiques. Les données mettent en évidence une forte variation interindividuelle au sein des enfants avec TSA. Une typologie a été construite en fonction des (dé)formations du processus néophobique. La population étudiée se répartit en six catégories : supratypique (20,8 %), normotypique (16,1 %), infratypique (18,6 %), progressive (17,7 %), tardive (9,0 %) et néophile (17,7 %). La discussion s’ouvre sur l’analyse des particularités alimentaires en population autistique à partir des travaux conduits sur la néophobie en population générale. Il ressort ainsi que des phénomènes souvent identifiés comme spécifiques à la population autistique peuvent révéler de variations du processus néophobique. Il apparaît alors judicieux de parler de néophobies alimentaires au pluriel

Utilisation d'un robot pour faciliter l'émergence de la communication sociale chez l'enfant avec autisme

International audienc

Dynamic epistemic logics: promises, problems, shortcomings, and perspectives

International audienceDynamic epistemic logics provide an account of the evolution of agents’ belief and knowledge when they learn the occurrence of an event. These logics started to become popular about 20 years ago and by now there exists a huge number of publications about them. The present paper briefly summarises the existing body of literature, discusses some problems and shortcomings, and proposes some avenues for future research

Sensory processing related to attention in children with ASD, ADHD, or typical development: results from the ELENA cohort

Autism-spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) are early neurodevelopmental conditions that share clinical characteristics, raising important issues in clinical diagnosis. We aimed to compare (1) sensory processing in four groups of children: ASD alone, ASD + ADHD, ADHD alone, and typical development (TD) and (2) the association between sensory processing and attention in the three groups with neurodevelopmental disorders. Our sample included 120 children aged from 6 to 12 years divided into four groups: ASD alone (N = 43), ASD + ADHD (N = 18), ADHD alone (N = 28), and TD (N = 31). Atypical sensory processing was more frequent in ASD and/or ADHD than in TD, without a significant difference between ASD and ADHD. However, the variance analysis of attention problems revealed differences between the ADHD and ASD groups. Thus, the rate of atypical sensory processing was comparable between the ASD and ADHD groups, suggesting that further studies are needed to explore atypical SP in all neurodevelopmental disorders

Dietary patterns and their socio-demographic determinants in 10 European countries: Data from the DAFNE databank

Objective: To describe the dietary patterns of 10 European countries and their socio-demographic determinants, using the comparable between-countries DAFNE data. Design: Analysis of standardized and postharmonized data collected through the national household budget surveys. Setting: Nationally representative surveys undertaken in 10 European countries, generally in the second half of the 1990s. Results: The differences in the fruit and vegetable consumption previously identified between Mediterranean and Northern European countries seem to be leveling out, particularly in relation to fruit consumption. Pulses, however, still characterize the diet of the Mediterraneans. Straying from their traditional food choices, Mediterraneans recorded high availability of unprocessed red meat, while Central and Northern Europeans preferably consumed meat products. The household availability of beverages (alcoholic and non-alcoholic) is generally higher among Central and Northern European populations. Principal component (PC) analysis led to the identification of two dietary patterns in each of the 10 countries. The first was similar in all countries and indicated 'wide-range' food buyers. The second was slightly more varied and described 'beverage and convenience' food buyers. PC1 was common among households of retired and elderly members, while PC2 was common among households located in urban or semi-urban areas and among adult Scandinavians living alone. Conclusions: The dietary patterns identified point towards a progressive narrowing of dietary differences between North and South European countries. The comparable between-countries DAFNE data could prove useful in ecological studies, in the formulation of dietary guidelines and public health initiatives addressing specific population groups. © 2006 Nature Publishing Group All rights reserved