Generating Property-Directed Potential Invariants By Backward Analysis

This paper addresses the issue of lemma generation in a k-induction-based formal analysis of transition systems, in the linear real/integer arithmetic fragment. A backward analysis, powered by quantifier elimination, is used to output preimages of the negation of the proof objective, viewed as unauthorized states, or gray states. Two heuristics are proposed to take advantage of this source of information. First, a thorough exploration of the possible partitionings of the gray state space discovers new relations between state variables, representing potential invariants. Second, an inexact exploration regroups and over-approximates disjoint areas of the gray state space, also to discover new relations between state variables. k-induction is used to isolate the invariants and check if they strengthen the proof objective. These heuristics can be used on the first preimage of the backward exploration, and each time a new one is output, refining the information on the gray states. In our context of critical avionics embedded systems, we show that our approach is able to outperform other academic or commercial tools on examples of interest in our application field. The method is introduced and motivated through two main examples, one of which was provided by Rockwell Collins, in a collaborative formal verification framework.Comment: In Proceedings FTSCS 2012, arXiv:1212.657

Investigation of spatial and temporal metal atmospheric deposition in France through lichen and moss bioaccumulation over one century

Lichens and mosses were used as biomonitors to assess the atmospheric deposition ofmetals in forested ecosystems in various regions of France. The concentrations of 17 metals/metalloids (Al, As, Cd, Co, Cr, Cs, Cu, Fe, Mn, Ni, Pb, Sb, Sn, Sr, Ti, V, and Zn) indicated overall lowatmospheric contamination in these forested environments, but a regionalism emerged fromlocal contributions (anthropogenic activities, as well as local lithology). Taking into account the geochemical background and comparing to Italian data, the elements from both natural and anthropogenic activities, such as Cd, Pb, or Zn, did not show any obvious anomalies. However, elements mainly originating from lithogenic dust (e.g., Al, Fe, Ti) were more prevalent in sparse forests and in the Southern regions of France, whereas samples from dense forests showed an accumulation of elements from biological recycling (Mn and Zn). The combination of enrichment factors and Pb isotope ratios between current and herbarium samples indicated the historical evolution of metal atmospheric contamination: the high contribution of coal combustion beginning 150 years ago decreased at the end of the 20th century, and the influence of car traffic during the latter observed period decreased in the last few decades. In the South of France, obvious local influences were well preserved during the last century

Historiographie

François Hartog, directeur d’études Historiographie ancienne et moderne Dans l’enquête menée sur les conditions de la temporalisation du temps, trois fils ont été suivis, combinant le très ancien et le très contemporain. Comment répondre aux ruptures d’évidence, quand soudain le cours du temps vient à s’interrompre ? Nous avons commencé par interroger la notion même de crise (krisis), entendue comme crise du temps et dans le temps. Introduite par la médecine hippocratique, la krisis est, en e..

Molecular Dynamics Studies of the Nucleoprotein of Influenza A Virus: Role of the Protein Flexibility in RNA Binding

The influenza viruses contain a segmented, negative stranded RNA genome. Each RNA segment is covered by multiple copies of the nucleoprotein (NP). X-ray structures have shown that NP contains well-structured domains juxtaposed with regions of missing electron densities corresponding to loops. In this study, we tested if these flexible loops gated or promoted RNA binding and RNA-induced oligomerization of NP. We first performed molecular dynamics simulations of wt NP monomer and trimer in comparison with the R361A protein mutated in the RNA binding groove, using the H1N1 NP as the initial structure. Calculation of the root-mean-square fluctuations highlighted the presence of two flexible loops in NP trimer: loop 1 (73–90), loop 2 (200–214). In NP, loops 1 and 2 formed a 10–15 Å-wide pinch giving access to the RNA binding groove. Loop 1 was stabilized by interactions with K113 of the adjacent β-sheet 1 (91–112) that interacted with the RNA grove (linker 360–373) via multiple hydrophobic contacts. In R361A, a salt bridge formed between E80 of loop 1 and R208 of loop 2 driven by hydrophobic contacts between L79 and W207, due to a decreased flexibility of loop 2 and loop 1 unfolding. Thus, RNA could not access its binding groove in R361A; accordingly, R361A had a much lower affinity for RNA than NP. Disruption of the E80-R208 interaction in the triple mutant R361A-E80A-E81A increased its RNA binding affinity and restored its oligomerization back to wt levels in contrast with impaired levels of R361A. Our data suggest that the flexibility of loops 1 and 2 is required for RNA sampling and binding which likely involve conformational change(s) of the nucleoprotein

Overview of the current use of levosimendan in France: a prospective observational cohort study

Abstract Background Following the results of randomized controlled trials on levosimendan, French health authorities requested an update of the current use and side-effects of this medication on a national scale. Method The France-LEVO registry was a prospective observational cohort study reflecting the indications, dosing regimens, and side-effects of levosimendan, as well as patient outcomes over a year. Results The patients included ( n = 602) represented 29.6% of the national yearly use of levosimendan in France. They were treated for cardiogenic shock ( n = 250, 41.5%), decompensated heart failure ( n = 127, 21.1%), cardiac surgery-related low cardiac output prophylaxis and/or treatment ( n = 86, 14.3%), and weaning from veno-arterial extracorporeal membrane oxygenation ( n = 82, 13.6%). They received 0.18 ± 0.07 µg/kg/min levosimendan over 26 ± 8 h. An initial bolus was administered in 45 patients (7.5%), 103 (17.1%) received repeated infusions, and 461 (76.6%) received inotropes and or vasoactive agents concomitantly. Hypotension was reported in 218 patients (36.2%), atrial fibrillation in 85 (14.1%), and serious adverse events in 17 (2.8%). 136 patients (22.6%) died in hospital, and 26 (4.3%) during the 90-day follow-up. Conclusions We observed that levosimendan was used in accordance with recent recommendations by French physicians. Hypotension and atrial fibrillation remained the most frequent side-effects, while serious adverse event potentially attributable to levosimendan were infrequent. The results suggest that this medication was safe and potentially associated with some benefit in the population studied

O’Gorman, lecteur d’Acosta

Ne serait-ce que du point de vue de sa réception, La invención de América est la partie la plus marquante de l’œuvre d’O’Gorman. Cet ouvrage synthétique, bref, marque l’aboutissement d’un long et patient travail d’analyse et d’édition des chroniques des Indes du XVIe siècle. Colomb, Oviedo, Gómara, Las Casas, etc. : tous sont présents dans La invención à l’exception de José de Acosta, auteur qu’O’Gorman avait pourtant introduit, annoté et publié pour le Fondo de Cultura Económicaen 1941 puis de nouveau en 1962. L’éclipse de ce livre dans la synthèse o’gormanienne est difficilement explicable notamment si l’on fait le constat des nombreux parallèles qui existent entre le chroniqueur du XVIe et l’historien du XXe. L’objectif de cet essai est de parcourir la lecture faite par O’Gorman d’Acosta pour donner, dans un premier temps, une explication à cette éclipse, pour montrer ensuite, qu’elle est plus le signe d’une communion que d’un éloignement entre les deux œuvres, pour illustrer enfin, combien la question américaine a été centrale pour l’élaboration de l’historiographie moderne.The Invention of America is probably the most prominent, at least the most visible part of O’Gorman’s work. This short book is the culmination of a long and patient work of erudition and publication of the sixteenth century Indies chronicles. Colombus, Oviedo, Gómara, Las Casas, etc: all are present in the Invention with the exception of José de Acosta, author that O'Gorman had yet introduced, annotated and published in 1941 and 1962. The eclipse of this book in the o'gormanian masterpiece is particularly difficult to explain if we realize the many parallels between the sixteenth and the twentieth century historians. The objective of this essay is first to browse through the O'Gorman reading of Acosta, then to show it is more a sign of connection than of distance, and finally, to illustrate the extent to which the “American question” has been central for the making of historiography since the beginning of modernity

Les voyages du récit. Culture écrite et expansion européenne à l’Époque moderne : le cas de la Compagnie Hollandaise des Indes Orientales

composition du jury Monsieur François Hartog, École des Hautes Études en Sciences Sociales, Directeur,Monsieur Romain Bertrand, Fondation Nationale des Sciences Politiques,Monsieur François-Joseph Ruggiu, Université de Paris IV-Sorbonne,Monsieur Jean-Frédéric Schaub, École des Hautes Études en Sciences Sociales,Monsieur Nigel Worden, University of Cape Town. Thèse soutenue le 1er juillet 2010 Résumé Pour saisir les relations multiples qui se sont nouées entre la culture écrite et l’expansion ..

L’Itinerario de J.H. van Linschoten ou l’histoire d’un divorce entre le livre et la Compagnie Hollandaise des Indes Orientales (VOC), 1595-1619

Les compagnies commerciales et coloniales de l’époque moderne n’ont qu’à de rares exceptions retenu l’attention de l’histoire du livre. Intermédiaires de la circulation d’écrits entre les continents, elles constituent pourtant des objets d’études incontournables pour que l’histoire du livre sorte du seul cadre national et pose la question du rôle de la culture écrite dans le désenclavement du monde à partir du XVIe siècle. Pour comprendre l’attitude de la Compagnie Hollandaise des Indes Orientales (VOC) face à l’imprimé, cet article revient sur le cas bien connu de l’Itinerario de Jan Huygen van Linschoten (1595-1596), un livre qui, s’il a incarné quelques années la complémentarité entre le monde du livre et le projet ultramarin, a très vite scellé leur antagonisme. Suite aux plaintes des directeurs de la Compagnie inquiets de sa large diffusion, il motiva en effet l’émission d’un privilège de librairie en 1619 qui entérinait le divorce entre le livre et la mer pour toute la durée du Siècle d’Or

Estimation of the remaining useful life of systems in the presence of uncertainties

La mise en place d’une politique de maintenance prévisionnelle est un défi majeur dans l’industrie qui tente de réduire le plus possible les frais relatifs à la maintenance. En effet, les systèmes sont de plus en plus complexes et demandent un suivi de plus en plus poussé afin de rester opérationnels et sécurisés. Une maintenance prévisionnelle nécessite d’une part d’évaluer l’état de dégradation des composants du système, et d’autre part de pronostiquer l’apparition future d’une panne. Plus précisément, il s’agit d’estimer le temps restant avant l’arrivée d’une défaillance, aussi appelé Remaining Useful Life ou RUL en anglais. L’estimation d’une RUL constitue un réel enjeu car la pertinence et l’efficacité des actions de maintenance dépendent de la justesse et de la précision des résultats obtenus. Il existe de nombreuses méthodes permettant de réaliser un pronostic de durée de vie résiduelle, chacune avec ses spécificités, ses avantages et ses inconvénients. Les travaux présentés dans ce manuscrit s’intéressent à une méthodologie générale pour estimer la RUL d’un composant. L’objectif est de proposer une méthode applicable à un grand nombre de cas et de situations différentes sans nécessiter de modification majeure. De plus, nous cherchons aussi à traiter plusieurs types d’incertitudes afin d’améliorer la justesse des résultats de pronostic. Au final, la méthodologie développée constitue une aide à la décision pour la planification des opérations de maintenance. La RUL estimée permet de décider de l’instant optimal des interventions nécessaires, et le traitement des incertitudes apporte un niveau de confiance supplémentaire dans les valeurs obtenues.Predictive maintenance strategies can help reduce the ever-growing maintenance costs, but their implementation represents a major challenge. Indeed, it requires to evaluate the health state of the component of the system and to prognosticate the occurrence of a future failure. This second step consists in estimating the remaining useful life (RUL) of the components, in Other words, the time they will continue functioning properly. This RUL estimation holds a high stake because the precision and accuracy of the results will influence the relevance and effectiveness of the maintenance operations. Many methods have been developed to prognosticate the remaining useful life of a component. Each one has its own particularities, advantages and drawbacks. The present work proposes a general methodology for component RUL estimation. The objective i to develop a method that can be applied to many different cases and situations and does not require big modifications. Moreover, several types of uncertainties are being dealt With in order to improve the accuracy of the prognostic. The proposed methodology can help in the maintenance decision making process. Indeed, it is possible to select the optimal moment for a required intervention thanks to the estimated RUL. Furthermore, dealing With the uncertainties provides additional confidence into the prognostic results