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

D. Antiseri, Foi sans métaphysique ni théologie. Collection « Avenirs », 1970

Maffre P. D. Antiseri, Foi sans métaphysique ni théologie. Collection « Avenirs », 1970. In: Revue d'histoire et de philosophie religieuses, 52e année n°1,1972. pp. 126-127

Hans-Walter Schütte, Religion und Christentum in der Theologie Rudolf Ottos, Berlin, Walter de Gruyter, 1969

Maffre P. Hans-Walter Schütte, Religion und Christentum in der Theologie Rudolf Ottos, Berlin, Walter de Gruyter, 1969. In: Revue d'histoire et de philosophie religieuses, 54e année n°4,1974. p. 569

Hans-Walter Schütte, Religion und Christentum in der Theologie Rudolf Ottos, Berlin, Walter de Gruyter, 1969

Maffre P. Hans-Walter Schütte, Religion und Christentum in der Theologie Rudolf Ottos, Berlin, Walter de Gruyter, 1969. In: Revue d'histoire et de philosophie religieuses, 54e année n°4,1974. p. 569

Limited Carbon Cycle Response to Increased Sulfide Weathering Due to Oxygen Feedback

The chemical weathering of sulfide-bearing rocks can result in the dissolution of carbonate rocks leading to degassing of (Formula presented.) to the atmosphere. While this process has been argued to be a significant geologic source of (Formula presented.), it also perturbs the geological cycles of oxygen and sulfur, triggering a cascade of geochemical feedbacks. Using a numerical model of geochemical cycles and climate, we found that due to feedbacks on atmospheric oxygen associated with the organic carbon cycle, an increase of sulfide weathering leads to a limited source of (Formula presented.) followed by a longer sink of (Formula presented.). This result is due to the stoichiometry of sulfide weathering where more (Formula presented.) is consumed than (Formula presented.) is released. If sulfide weathering increases progressively on a geological timescale, the duration of the carbon source is extended, but its magnitude is negligible before it becomes a carbon sink

Understanding the interactions between tectonic processes, erosion, weathering and climate. New insights from the DynSoil-GEOCLIM modelling approach

International audienceEarth's long-term climate stability is postulated to be maintained by the silicate weathering feedback. Long-term changes on Earth's surface can significantly affect the strength of this feedback and are proposed as drivers for climatic variations over the course of Earth History. Among these modulating processes, we focus on the role of erosion (eg, Milot et al. 2002, EPSL 196 83-98), regolith development and its shielding effect (eg, Godderis et al. 2014, Earth Sci Rev 128 122-138), and the exhumation of specific geological units, for instance mafic complexes during arc-continent collision (eg, Macdonald et al., 2019, Science 364 181-184). Understanding the interlinked effects of these processes throughout Earth History is a challenge for which numerical modeling can be helpful. The GEOCLIM model (Donnadieu et al., 2006, G3 7(11)) simulates geochemical cycles, specifically the carbon cycle, and climate dynamics on geological timescales. A newly implemented model for weathering fluxes (DynSoil) now explicitly simulates the interaction between physical erosion, climatology, and the development of chemical weathering profiles. We have integrated this model with global spatially resolved lithology to account for the varying carbon sequestration potential of different rock types. This model framework can be used to investigate the equilibrium state of carbon-climate system, as well as transient perturbations, accounting for the potential inertia of weathering profiles. Preliminary results have shown the ambiguous effect of mountain building that affects both climate circulation and continental erosion (Maffre et al. 2018, EPSL 493 174-185). Using this model, we show that the uplift of high weathering potential silicate rocks in the tropics can significantly drawdown atmospheric carbon dioxide and play a role in initiating glacial climate

(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

The distribution of sediment residence times at the foot of mountains and its implications for proxies recorded in sedimentary basins

International audienceThe geochemical and physical properties of terrigenous sediment stacked in sedimentary basins are used as proxies for the paleo-environmental conditions that prevailed during their period of deposition. Nevertheless, sediment grains have a stochastic transit from mountain sources to sedimentary basins: a fraction of grains are stored for a long time while others are recycled from old deposits. Consequently, the temporal representativity of a population of grains in a sedimentary stratum is uncertain. The potential recycling of old material is a major concern in the reconstruction of paleo-environments and this recycling is usually difficult to evaluate. In particular, the distribution of grain residence times in basins, between sources and sinks, is out of reach. Here we use a landscape evolution model that traces grains to analyse the distribution of residence times in an alluvial apron at the foot of a mountain relief. We study an end-member scenario that is the least favourable for the storage of grains: when the mountain is eroding at the same rate as rock is uplifting. In this case, the alluvial apron behaves as a by-pass zone, when averaging sediment flux over Ma, and the storage of grains of any size should be minimal. Yet, the model predicts that some grains are stored for hundreds of thousands of years before exiting the alluvial apron. Consequently, the mean residence time of sediment grains is much higher than the observed residence time of 95% of the grains exported by the alluvial apron rivers. This process may explain very long residence times found in fluvial systems by geochemical methods based on bulk measurements of sediment. Furthermore, it suggests that grains stored for a very long time, although a minority, can bias time-dependent proxies