Two snap-stabilizing point-to-point communication protocols in message-switched networks

A snap-stabilizing protocol, starting from any configuration, always behaves according to its specification. In this paper, we present a snap-stabilizing protocol to solve the message forwarding problem in a message-switched network. In this problem, we must manage resources of the system to deliver messages to any processor of the network. In this purpose, we use information given by a routing algorithm. By the context of stabilization (in particular, the system starts in an arbitrary configuration), this information can be corrupted. So, the existence of a snap-stabilizing protocol for the message forwarding problem implies that we can ask the system to begin forwarding messages even if routing information are initially corrupted. In this paper, we propose two snap-stabilizing algorithms (in the state model) for the following specification of the problem: - Any message can be generated in a finite time. - Any emitted message is delivered to its destination once and only once in a finite time. This implies that our protocol can deliver any emitted message regardless of the state of routing tables in the initial configuration. These two algorithms are based on the previous work of [MS78]. Each algorithm needs a particular method to be transform into a snap-stabilizing one but both of them do not introduce a significant overcost in memory or in time with respect to algorithms of [MS78]

Comparison of durability indicators obtained by Non Destructive Testing methods to monitor the durability of concrete structures

International audienceThis paper deals with the use of non destructive testing methods (NDT) to assess indicators of concrete durability and mechanical properties of reinforced concrete structures. On site, NDT methods based on electromagnetic or ultrasonic wave propagation (such as radar, impact echo, ultrasonic transmission deviceÉ) are used because they are more or less sensitive to water content and mechanical properties depending on the method. It has been shown, in a former project [1, 2], that the NDT results called Òobservablesî are linked to mechanical and durability indicators (YoungÕs modulus, compressive strength, porosity and saturation degree). Meanwhile, the relationship between observables and indicators depends on the concrete mix design. A calibration protocol is then proposed to get this relationship for the right mix of the reinforced structure studied by using a minimal number of cores. The cores are non-destructively characterised in laboratory or used to determined reference indicators by standardised destructive methods. The aims of this paper are first to present the ND calibration protocol on cores and then to validate this proposed calibration protocol. To achieve this goal, some NDT results obtained on site and on the corresponding core are compared and durability indicators deduced from NDT calibration are compared with reference durability indicators

Correlations and order parameter at a Coulomb-crystal phase transition in a three-dimensional dimer model

The three-dimensional classical dimer model with interactions shows an unexpected continuous phase transition between an ordered dimer crystal and a Coulomb liquid. A detailed analysis of the critical dimer and monomer correlation functions point to a subtle interplay between the fluctuations of the crystal order parameter and the "magnetic" degrees of freedom present in the Coulomb phase. The distribution probability of the crystal order parameter suggests an emerging continuous O(3) symmetry at the critical point.Comment: 4 pages, 4 color figures. v2: published version. New data & figure on the probability distribution of the crystal order parameter close to T

Identification of inhomogeneous concrete cover by non-contact ultrasonic method

International audienceConcrete cover degradation is induced by aggressive agents in ambiance, chemicals, moisture, or temperature variations. Due to this degradation concrete becomes inhomogeneous and usually a thin surface layer appears with porosity and elastic modulus different than the properties of deeper sound concrete. Therefore the on-site nondestructive evaluation of concrete cover is important to monitor the integrity of concrete structures and prevent their irreversible damage. In this paper the methodology applied by the classical technique used for ground structure recovery called Multichannel Analysis of Surface Waves (MASW) is used as the NDT tool to characterize the thickness and elastic modulus of concrete cover. The procedure consists in generation and reception of surface waves within the required frequency band, using the non-contact transducers which scan evaluated profiles. Then the phase velocity dispersion characteristic V(f) is extracted, and concrete cover is characterized using as the proposed velocity gradient. The dispersion characteristics are exploited by the inversion software in order to obtain the variation of shear wave velocity as a function of depth

Key questions for the evaluation of anti-amyloid immunotherapies for Alzheimer’s disease

The clinical benefit associated with anti-amyloid immunotherapies, a new class of drugs for the treatment of Alzheimer’s disease, is predicated on their ability to modify disease course by lowering brain amyloid levels. At the time of writing, two amyloid-lowering antibodies, aducanumab and lecanemab, have obtained United States Food and Drug Administration accelerated approval, with further agents of this class in the Alzheimer’s disease treatment pipeline. Based on limited published clinical trial data to date, regulators, payors and physicians will need to assess their efficacy, clinical effectiveness and safety, as well as cost and accessibility. We propose that attention to three important questions related to treatment efficacy, clinical effectiveness and safety should guide evidence-based consideration of this important class of drugs. These are: (1) Were trial statistical analyses appropriate and did they convincingly support claims of efficacy? (2) Do reported treatment effects outweigh safety concerns and are they generalizable to a representative clinical population of people with Alzheimer’s disease? and (3) Do the data convincingly demonstrate disease course modification, suggesting that increasing clinical benefits beyond the duration of the trials are likely? We suggest specific approaches to interpreting trial results for these drugs and highlight important areas of uncertainty where additional data and a cautious interpretation of existing results is warranted. Safe, effective and accessible treatments for Alzheimer’s disease are eagerly awaited by millions of patients and their caregivers worldwide. While amyloid-targeting immunotherapies may be promising disease-modifying Alzheimer’s disease treatments, rigorous and unbiased assessment of clinical trial data is critical to regulatory decision-making and subsequently determining their provision and utility in routine clinical practice. Our recommendations provide a framework for evidence-based appraisal of these drugs by regulators, payors, physicians and patients

Acheminement de messages instantanément stabilisant pour arbres couvrants

International audienceNous présentons un protocole instantanément stabilisant d'acheminement de messages au sein de structures couvrantes arborescentes de réseaux. Notre protocole utilise l'information fournie par un algorithme de calcul de tables de routage auto-stabilisant s'appuyant sur cette structure. Le fait que le protocole soit instantanément stabilisant signifie que tout message émis après les fautes est acheminé à son destinataire, y compris lorsque les tables de routage ne sont pas stabilisées. Notre algorithme présente l'avantage que le nombre de tampons est indépendant de tout paramètre global du réseau comme le nombre de noeuds ou le diamètre. En effet, nous montrons que le problème peut être résolu en utilisant un nombre constant de tampons par lien de communication de la structure couvrante. Cette propriété lui confère l'avantage de tolérer le passage à l'échelle

Snap-Stabilizing Message Forwarding Algorithm on Tree Topologies

In this paper, we consider the message forwarding problem that consists in managing the network resources that are used to forward messages. Previous works on this problem provide solutions that either use a significant number of buffers (that is n buffers per processor, where n is the number of processors in the network) making the solution not scalable or, they reserve all the buffers from the sender to the receiver to forward only one message %while using D buffers (where D refers to the diameter of the network) . The only solution that uses a constant number of buffers per link was introduced in [1]. However the solution works only on a chain networks. In this paper, we propose a snap-stabilizing algorithm for the message forwarding problem that uses the same complexity on the number of buffers as [1] and works on tree topologies.Nous considérons dans ce papier le problème d'acheminement de messages qui consiste à gérer les ressources du réseau. Des Solutions ont été proposées, soit qui utilisent un nombre significatif de buffers (n buffers par processeur où n correspond au nombre de processeurs dans le réseau), ce qui rend cette solution non adaptée au réseaux à grande échelle. Soit elles doivent réserver tout les buffers de la source à la destination. La seule solution qui utilise un nombre constant de buffers par lien a été introduite dans [1], cela dit cette solution fonctionne seulement sur des topologies linéaires. Dans ce papier, nous proposons un algorithme instantanément stabilisant pour le problème d'acheminement de messages ayant la même complexité en terme de nombre de buffers que [1] et qui fonctionne sur des topologies en arbre