Indexed Induction and Coinduction, Fibrationally

This paper extends the fibrational approach to induction and coinduction pioneered by Hermida and Jacobs, and developed by the current authors, in two key directions. First, we present a dual to the sound induction rule for inductive types that we developed previously. That is, we present a sound coinduction rule for any data type arising as the carrier of the final coalgebra of a functor, thus relaxing Hermida and Jacobs' restriction to polynomial functors. To achieve this we introduce the notion of a quotient category with equality (QCE) that i) abstracts the standard notion of a fibration of relations constructed from a given fibration; and ii) plays a role in the theory of coinduction dual to that played by a comprehension category with unit (CCU) in the theory of induction. Secondly, we show that inductive and coinductive indexed types also admit sound induction and coinduction rules. Indexed data types often arise as carriers of initial algebras and final coalgebras of functors on slice categories, so we give sufficient conditions under which we can construct, from a CCU (QCE) U:E \rightarrow B, a fibration with base B/I that models indexing by I and is also a CCU (resp., QCE). We finish the paper by considering the more general case of sound induction and coinduction rules for indexed data types when the indexing is itself given by a fibration

Opinion publique et Gouvernement royal au Danemark face à la Révolution française (1789-1799)

Les événements révolutionnaires français ont produit quelque écho au Danemark, monarchie absolue où règne une liberté d’expression assez large. Le débat politique s’en trouve alors singulièrement vivifié. Mais le gouvernement royal veille à limiter ce débat à des limites acceptables pour lui. Toute atteinte à l’absolutisme danois est passible des tribunaux. Au début de la Révolution française, le ton dominant à Copenhague est celui de la bienveillance parmi les esprits réformateurs proches du gouvernement. L’enthousiasme gagne les auteurs plus libéraux. La proclamation de la République et l’exécution de Louis XVI provoquent une fracture parmi les sympathisants de la Révolution. Les réformateurs rejettent en bloc l’événement tandis que les libéraux radicalisent leurs propos et le talent polémique de M.C. Bruun et P.A. Heiberg fait mouche. La capitale est aussi touchée par quelques mouvements populaires. La justice royale fait alors son œuvre. Finalement, le gouvernement royal clôt le débat public par une ordonnance du 27 septembre 1799 qui met fin à la liberté d’expression.Public Opinion and Royal Government in Denmark Confronted with the French Revolution (1789-1799) French revolutionary events had their impact on Denmark, an absolute monarchy marked by a fair degree of freedom of expression. The political debate became more lively as a result. But the royal government took pains to contain that debate within seemly limits. Any attack on Danish absolutism became a chargeable offence. At the outset of the French Revolution, the mood that dominated in Copenhagen was one of benevolence in the reforming circles close to the government. More liberal authors succombed to the enthusiasm. The proclamation of the Republic and the execution of Louis XVI led to a split among those sympathetic to the Revolution. The reformers rejected the event completely, while the liberals radicalized their discourse and the polemical talents of M. C. Bruun and P. A. Heiberg hit their mark. The capital was also affected by popular unrest. Royal justice then came into its own. Finally, the royal government closed the public debate with its ordinance of 27 September 1799 ending freedom of expression

Automating the Verification of Floating-Point Programs

International audienceIn the context of deductive program verification, handling floating-point computations is challenging. The level of proof success and proof automation highly depends on the way the floating-point operations are interpreted in the logic supported by back-end provers. We address this challenge by combining multiple techniques to separately prove different parts of the desired properties. We use abstract interpretation to compute numerical bounds of expressions, and we use multiple automated provers, relying on different strategies for representing floating-point computations. One of these strategies is based on the native support for floating-point arithmetic recently added in the SMT-LIB standard. Our approach is implemented in the Why3 environment and its front-end SPARK 2014 for the development of safety-critical Ada programs. It is validated experimentally on several examples originating from industrial use of SPARK 2014

Generic Fibrational Induction

This paper provides an induction rule that can be used to prove properties of data structures whose types are inductive, i.e., are carriers of initial algebras of functors. Our results are semantic in nature and are inspired by Hermida and Jacobs' elegant algebraic formulation of induction for polynomial data types. Our contribution is to derive, under slightly different assumptions, a sound induction rule that is generic over all inductive types, polynomial or not. Our induction rule is generic over the kinds of properties to be proved as well: like Hermida and Jacobs, we work in a general fibrational setting and so can accommodate very general notions of properties on inductive types rather than just those of a particular syntactic form. We establish the soundness of our generic induction rule by reducing induction to iteration. We then show how our generic induction rule can be instantiated to give induction rules for the data types of rose trees, finite hereditary sets, and hyperfunctions. The first of these lies outside the scope of Hermida and Jacobs' work because it is not polynomial, and as far as we are aware, no induction rules have been known to exist for the second and third in a general fibrational framework. Our instantiation for hyperfunctions underscores the value of working in the general fibrational setting since this data type cannot be interpreted as a set.Comment: For Special Issue from CSL 201

Endoscopic and Percutaneous Preoperative Biliary Drainage in Patients with Suspected Hilar Cholangiocarcinoma

INTRODUCTION: Controversy exists over the preferred technique of preoperative biliary drainage (PBD) in patients with hilar cholangiocarcinoma (HCCA) requiring major liver resection. The current study compared outcomes of endoscopic biliary drainage (EBD) and percutaneous transhepatic biliary drainage (PTBD) in patients with resectable HCCA. METHODS: One hundred fifteen consecutive patients were explored for HCCA between 2001 and July 2008 and assigned by initial PBD procedure to either EBD or PTBD. RESULTS: Of these patients, 101 (88%) underwent PBD; 90 patients underwent EBD as primary procedure, and 11 PTBD. The technical success rate of initial drainage was 81% in the EBD versus 100% in the PTBD group (P = 0.20). Stent dislocation was similar in the EBD and PTBD groups (23% vs. 20%, P = 0.70). Infectious complications were significantly more common in the endoscopic group (48% vs. 9%, P < 0.05). Patients in the EBD group underwent more drainage procedures (2.8 vs. 1.4, P < 0.01) and had a significantly longer drainage period until laparotomy (mean 15 weeks vs. 11 weeks in the PTBD group; P < 0.05). In 30 patients, EBD was converted to PTBD due to failure of the endoscopic approach. CONCLUSIONS: Preoperative percutaneous drainage could outperform endoscopic stent placement in patients with resectable HCCA, showing fewer infectious complications, using less procedure

Stenting and interventional radiology for obstructive jaundice in patients with unresectable biliary tract carcinomas

Together with biliary drainage, which is an appropriate procedure for unresectable biliary cancer, biliary stent placement is used to improve symptoms associated with jaundice. Owing to investigations comparing percutaneous transhepatic biliary drainage (PTBD), surgical drainage, and endoscopic drainage, many types of stents are now available that can be placed endoscopically. The stents used are classified roughly as plastic stents and metal stents. Compared with plastic stents, metal stents are of large diameter, and have long-term patency (although they are expensive). For this reason, the use of metal stents is preferred for patients who are expected to survive for more than 6 months, whereas for patients who are likely to survive for less than 6 months, the use of plastic stents is not considered to be improper. Obstruction in a metal stent is caused by a tumor that grows within the stent through the mesh interstices. To overcome such problems, a covered metal stent was developed, and these stents are now used in patients with malignant distal biliary obstruction. However, this type of stent has been reported to have several shortcomings, such as being associated with the development of acute cholecystitis and stent migration. In spite of these shortcomings, evidence is expected to demonstrate its superiority over other types of stent

Opinion publique et gouvernement royal au Danemark face à la Révolution française (1789-1799)

David Fumex, Public Opinion and Royal Government in Denmark Confronted with the French Revolution (1789-1799). French revolutionary events had their impact on Denmark, an absolute monarchy marked by a fair degree of freedom of expression. The political debate became more lively as a result. But the royal government took pains to contain that debate within seemly limits. Any attack on Danish absolutism became a chargeable offence. At the outset of the French Revolution, the mood that dominated in Copenhagen was one of benevolence in the reforming circles close to the government. More liberal authors succombed to the enthusiasm. The proclamation of the Republic and the execution of Louis XVI led to a split among those sympathetic to the Revolution. The reformers rejected the event completely, while the liberals radicalized their discourse and the polemical talents of M.-C. Bruun and P-A. Heiberg hit their mark. The capital was also affected by popular unrest. Royal justice then came into its own. Finally, the royal government closed the public debate with its ordinance of 27 September 1799 ending freedom of expression.Les événements révolutionnaires français ont produit quelque écho au Danemark, monarchie absolue où règne une liberté d'expression assez large. Le débat politique s'en trouve alors singulièrement vivifié. Mais le gouvernement royal veille à limiter ce débat à des limites acceptables pour lui. Toute atteinte à l'absolutisme danois est passible des tribunaux. Au début de la Révolution française, le ton dominant à Copenhague est celui de la bienveillance parmi les esprits réformateurs proches du gouvernement. L'enthousiasme gagne les auteurs plus libéraux. La proclamation de la République et l'exécution de Louis XVI provoquent une fracture parmi les sympathisants de la Révolution. Les réformateurs rejettent en bloc l'événement tandis que les libéraux radicalisent leurs propos et le talent polémique de M.-C. Bruun et R-A. Heiberg fait mouche. La capitale est aussi touchée par quelques mouvements populaires. La justice royale fait alors son œuvre. Finalement, le gouvernement royal clôt le débat public par une ordonnance du 27 septembre 1 799 qui met fin à la liberté d'expression.Fumex David. Opinion publique et gouvernement royal au Danemark face à la Révolution française (1789-1799). In: Annales historiques de la Révolution française, n°333, 2003. pp. 103-119

Role of protein sulfation in biomolecular interactions : focus on the chemokine receptor CXCR4

La sulfatation protéique est une modification post-traductionnelle qui intervient principalement sur les récepteurs cellulaires. Parmi eux, le récepteur CXCR4 est particulièrement étudié en raison de son implication dans de nombreux processus physiopathologiques (réponse immunitaire, infection au VIH). Le domaine extracellulaire de 38 acides aminés de CXCR4 (le peptide P38), contenant trois tyrosines connues pour être sulfatées, est important pour l’interaction avec son ligand spécifique, la chimiokine SDF-1α/CXCL12 (Stromal Cell-Derived Factor-1α). Le rôle de la sulfatation de CXCR4 dans cette interaction est encore méconnu.Le peptide P38 a été synthétisé et sulfaté de façon régiosélective sur toutes les tyrosines (peptides mono-, di- ou tri-sulfatés, soit 7 combinaisons). L’impact du nombre et de la position des groupements sulfate le long du peptide P38 sur son interaction avec SDF-1α a été étudié par électrophorèse capillaire d’affinité (ACE) couplée ou non à la spectrométrie de masse électrospray (ESI-MS). Une interaction entre P38 et SDF-1α a été mise en évidence par ACE. Une augmentation de l’affinité peut être associée à l’augmentation du degré de sulfatation de P38. La stœchiométrie des complexes a ensuite été déterminée en utilisant l’ACE-MS, qui a mis en évidence une majorité de complexes 1:1, quel que soit le peptide étudiéCes travaux ouvrent la voie à l'étude d'une interaction à trois partenaires avec des glycosaminoglycanes.Sulfation is one of the most important post-translational modifications of proteins. The known sulfated proteins are mostly cell receptors and among them, CXCR4 attracts growing attention because of its involvement in numerous physio-pathological processes (immune response, HIV infection). The 38 amino-acid extracellular domain of CXCR4 (P38 peptide), containing three tyrosine residues known to be sulfated, is important for the interaction with its specific ligand, the SDF-1α/CXCL12 chemokine (Stromal cell-derived factor-1α). The role of sulfation in this interaction remains to be established.The P38 peptide was chemically synthesized and regioselectively sulfated on all the tyrosines (mono-, di- or tri-sulfated peptides, 7 combinations). The impact of both distribution and position of sulfate groups on the interaction between P38 and SDF-1α was studied by affinity capillary electrophoresis (ACE) hyphenated to electrospray mass spectrometry (ESI-MS).An interaction between P38 and SDF-1α was highlighted by ACE. It was strongly enhanced by the increase of P38 sulfation degree. The complex stoichiometry was then determined by ACE-MS, and 1:1 complexes were predominantly obtained, with all the peptides. This work opens the orad to the three-partner interaction studies involving glycosaminoglycans