IA-CCF: Individual accountability for permissioned ledgers

Permissioned ledger systems allow a consortium of members that do not trust one another to execute transactions safely on a set of replicas. Such systems typically use Byzantine fault tolerance (BFT) protocols to distribute trust, which only ensures safety when fewer than 1/3 of the replicas misbehave. Providing guarantees beyond this threshold is a challenge: current systems assume that the ledger is corrupt and fail to identify misbehaving replicas or hold the members that operate them accountable—instead all members share the blame. We describe IA-CCF, a new permissioned ledger system that provides individual accountability. It can assign blame to the individual members that operate misbehaving replicas regardless of the number of misbehaving replicas or members. IA-CCF achieves this by signing and logging BFT protocol messages in the ledger, and by using Merkle trees to provide clients with succinct, universally-verifiable receipts as evidence of successful transaction execution. Anyone can audit the ledger against a set of receipts to discover inconsistencies and identify replicas that signed contradictory statements. IACCF also supports changes to consortium membership and replicas by tracking signing keys using a sub-ledger of governance transactions. IA-CCF provides strong disincentives to misbehavior with low overhead: it executes 47,000 tx/s while providing clients with receipts in two network round trips

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

Canadian quadrilles /

In bound volumes: Copyright Deposits 1820-186

(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

Characterization of protein adsorption onto FePt nanoparticles using dual-focus fluorescence correlation spectroscopy

Using dual-focus fluorescence correlation spectroscopy, we have analyzed the adsorption of three human blood serum proteins, namely serum albumin, apolipoprotein A-I and apolipoprotein E4, onto polymer-coated, fluorescently labeled FePt nanoparticles (~12 nm diameter) carrying negatively charged carboxyl groups on their surface. For all three proteins, a step-wise increase in hydrodynamic radius with protein concentration was observed, strongly suggesting the formation of protein monolayers that enclose the nanoparticles. Consistent with this interpretation, the absolute increase in hydrodynamic radius can be correlated with the molecular shapes of the proteins known from X-ray crystallography and solution experiments, indicating that the proteins bind on the nanoparticles in specific orientations. The equilibrium dissociation coefficients, measuring the affinity of the proteins to the nanoparticles, were observed to differ by almost four orders of magnitude. These variations can be understood in terms of the electrostatic properties of the proteins. From structure-based calculations of the surface potentials, positively charged patches of different extents can be revealed, through which the proteins interact electrostatically with the negatively charged nanoparticle surfaces

Highly dispersed Au, Ag and Au-Ag alloy nanoparticles encapsulated in single crystal multi-hollow silicalite-1

MICROSCOPIE+ING+RAT:ATU:LBU:JRO:FRMInternational audienceNanoalloy

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

International audienc