128 research outputs found
TRX: A Formally Verified Parser Interpreter
Parsing is an important problem in computer science and yet surprisingly
little attention has been devoted to its formal verification. In this paper, we
present TRX: a parser interpreter formally developed in the proof assistant
Coq, capable of producing formally correct parsers. We are using parsing
expression grammars (PEGs), a formalism essentially representing recursive
descent parsing, which we consider an attractive alternative to context-free
grammars (CFGs). From this formalization we can extract a parser for an
arbitrary PEG grammar with the warranty of total correctness, i.e., the
resulting parser is terminating and correct with respect to its grammar and the
semantics of PEGs; both properties formally proven in Coq.Comment: 26 pages, LMC
New magnetic-resonance-imaging-visible poly(epsilon-caprolactone)-based polyester for biomedical applications
A great deal of effort has been made since the 1990s to enlarge the field of magnetic resonance imaging. Better tissue contrast, more biocompatible contrast agents and the absence of any radiation for the patient are some of the many advantages of using magnetic resonance imaging (MRI) rather than X-ray technology. But implantable medical devices cannot be visualized by conventional MRI and a tool therefore needs to be developed to rectify this. The synthesis of a new MRI-visible degradable polymer is described by grafting an MR contrast agent (DTPA-Gd) to a non-water-soluble, biocompatible and degradable poly(epsilon-caprolactone) (PCL). The substitution degree, calculated by H-1 nuclear magnetic resonance and inductively coupled plasma-mass spectrometry, is close to 0.5% and proves to be sufficient to provide a strong and clear T1 contrast enhancement. This new MRI-visible polymer was coated onto a commercial mesh for tissue reinforcement using an airbrush system and enabled in vitro MR visualization of the mesh for at least 1 year. A stability study of the DTPA-Gd-PCL chelate in phosphate-buffered saline showed that a very low amount of gadolinium was released into the medium over 52 weeks, guaranteeing the safety of the device. This study shows that this new MRI-visible polymer has great potential for the MR visualization of implantable medical devices and therefore the post-operative management of patients. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Permanent Polymer Coating for in vivo MRI Visualization of Tissue Reinforcement Prostheses
The clinical advantage of MRI visualization of prostheses in soft tissue prolapses is very appealing as over 1?000?000 MRI-transparent synthetic meshes are implanted annually, and postoperative complications such as mesh shrinkage and migration are frequent. Here, the synthesis of a new material composed of a DTPA-Gd complex grafted onto a backbone of PMA via a covalent bond is described (DTPA-Gd-PMA). This new polymer is sprayed onto meshes and gives an MR signal for a long period without any significant release of Gd. In vitro cytocompatibility tests on fibroblasts show limited cytotoxicity. Microscopic investigations indicate that vital cells rapidly colonize the material. Finally, coated meshes implanted in rats are easily recognizable using an MR imaging system
MR Chemical engineering of polymer for medical devices visualization.
International audienc
A formally verified compiler back-end
This article describes the development and formal verification (proof of
semantic preservation) of a compiler back-end from Cminor (a simple imperative
intermediate language) to PowerPC assembly code, using the Coq proof assistant
both for programming the compiler and for proving its correctness. Such a
verified compiler is useful in the context of formal methods applied to the
certification of critical software: the verification of the compiler guarantees
that the safety properties proved on the source code hold for the executable
compiled code as well
Conception de prothÚse visible en IRM pour la prise en charge chirurgicale des prolapsus génitaux et des hernies abdominales
National audienc
Conception of an anti-infectious and MRI visible mesh used for pelvic organs prolapse and abdominal hernias surgery
International audienceLa pose chirurgicale de prothÚses afin de pallier les descentes d'organes de la zone pelvienne ou pariétale est une opération de plus en plus fréquente et requiÚre l'implantation de plus de 1 200 000 dispositifs médicaux annuellement. Or, les cas de complications et de réinterventions chirurgicales restent trÚs élevés, principalement dus aux infections associées à une réponse inflammatoire importante, ainsi qu'aux érosions, expositions et migrations des prothÚses. Ces travaux présentent différentes stratégies permettant d'apporter des propriétés de résistance à l'infection et de suivi postopératoire à l'aide d'une visibilité en IRM à des treillis. Pour cela, un enrobage de polymÚres dégradables (polyesters) piégeant des antibiotiques est créé à l'aide d'un aérographe autour des filaments des treillis tout en conservant leurs aspects morphologiques et leurs propriétés mécaniques. Cet enrobage temporaire permet une libération prolongée de principes actifs inhibant l'adhésion bactérienne, la formation de biofilm et la prolifération bactérienne périprothétique pendant plus de trois jours in vitro. ParallÚlement, des polymÚres contenant des agents de contraste greffés sur leur squelette carboné ont été utilisés comme agent d'enrobage, afin d'apporter des propriétés de visibilité en IRM aux treillis. In vitro, ces treillis enrobés induisent un signal significatif en IRM expérimentale (7 Tesla) et présentent une trÚs bonne stabilité de l'agent de contraste, quelle que soit la technique de stérilisation employée. Surgical operations for soft tissue reinforcement (i.e. pelvic organs prolapse or abdominal hernias) are common procedures and require annually at least 1,200,000 of prostheses. Unfortunately, postoperatory complications and reinterventions are still important, mainly due to infection, inflammation, erosion, exposition or meshes migration. We present here several strategies to bring to meshes anti-infective resistance and clinical follow-up capability through an MRI visible material. A coating of the mesh by degradable polymers (polyesters) trapping antibiotics was created using an airbrushing technique, without modifying dramatically the morphology and the mechanical properties of the meshes. This temporary drug reservoir-coating allows a sustained release of the drugs and hamper in vitro bacterial contamination and biofilm formation on the meshes, associated to a large periprosthetic microorganism growth inhibition for a minimum of three days. Simultaneously, magnetic resonance contras
Wave Equation Numerical Resolution: a Comprehensive Mechanized Proof of a C Program
We formally prove correct a C program that implements a numerical scheme for
the resolution of the one-dimensional acoustic wave equation. Such an
implementation introduces errors at several levels: the numerical scheme
introduces method errors, and floating-point computations lead to round-off
errors. We annotate this C program to specify both method error and round-off
error. We use Frama-C to generate theorems that guarantee the soundness of the
code. We discharge these theorems using SMT solvers, Gappa, and Coq. This
involves a large Coq development to prove the adequacy of the C program to the
numerical scheme and to bound errors. To our knowledge, this is the first time
such a numerical analysis program is fully machine-checked.Comment: No. RR-7826 (2011
- âŠ