École normale supérieure de Cachan

About: École normale supérieure de Cachan is a education organization based out in Cachan, Île-de-France, France. It is known for research contribution in the topics: Decidability & Nonlinear system. The organization has 2717 authors who have published 5585 publications receiving 175925 citations.

Ergodicity Results for the Stochastic Navier–Stokes Equations: An Introduction

Abstract: The theory of the stochastic Navier–Stokes equations (SNSE) has known a lot of important advances those last 20 years. Existence and uniqueness have been studied in various articles (see for instance [1, 35, 911, 13, 15, 21, 28, 30, 49, 51, 52, 66, 67]) and this part of the theory is well understood. Most of the deterministic results have been generalized to the stochastic context and it is now known that as in the deterministic case the SNSE has unique global strong solutions in dimension two. In dimension three, there exist global weak solutions and uniqueness is also a completely open problem in the stochastic case. The solutions in dimension three are weak in the sense of the theory of partial differential equations and in the sense of stochastic equations: the solutions are not smooth in space and they satisfy the SNSE only in the sense of the martingale problem. In Sect. 2 of these notes, we recall briefly these results and give the ideas of the proof.

Blind estimation of timing and carrier frequency offsets in OFDM systems

Abstract: Information fusion refers to the reconciliation of evidence presented by multiple sources of information in order to generate a decision. In the context of biometrics, evidence reconciliation plays a pivotal role in enhancing the recognition accuracy of human authentication systems and is referred to as multibiometrics. Multibiometric systems combine the information presented by multiple biometric sensors, algorithms, samples, units, or traits. Besides enhancing matching performance, these systems are expected to improve population coverage, deter spoofing and impart fault-tolerance to biometric applications. This introductory paper enumerates the various sources of biometric information that can be consolidated as well as the different levels of fusion in a biometric system. The role of using ancillary information such as biometric data quality and soft biometric traits (e.g., height) to enhance the performance of these systems is also discussed. It is becoming increasingly apparent that multibiometric systems will play a pivotal role in establishing identity in the 21st century.

Log auditing through model-checking

Abstract: Log auditing is a basic intrusion detection mechanism, whereby attacks are detected by uncovering matches of sequences of events against signatures. We argue that this is naturally expressed as a model-checking problem against linear Kripke models. A variant of the classic linear time temporal logic of Manna and Pnueli with first-order variables is first investigated in this framework. But this logic is in dire need of refinement, as far as expressiveness and efficiency are concerned. We therefore propose a second, less standard logic consisting of flat, Wolper-style linear-time formulae. We describe an efficient on-line algorithm, making the approach attractive for complex log auditing tasks. We also present a few optimizations that the use of a formal semantics affords us.

Improvement of HepG2/C3a cell functions in a microfluidic biochip.

Abstract: Current developments in tissue engineering and microtechnology fields allow the use of microfluidic biochip as microtools for in vitro investigations. In the present study, we describe the behavior of HepG2/C3a cells cultivated in a poly(dimethylsiloxane) (PDMS) microfluidic biochip coupled to a perfusion system. Cell culture in the microfluidic biochip for 96 h including 72 h of perfusion provoked a 24 h delay in cell growth compared to plate cultures. Inside the microfluidic biochip, few apoptosis, and necrosis were detected along the culture and 3D cell organization was observed. Regarding the hepatic metabolism, glucose and glutamine consumptions as well as albumin synthesis were maintained. A transcriptomic analysis performed at 96 h of culture using Affymetrix GeneChip demonstrated that 1,025 genes with a fold change above 1.8 were statistically differentially expressed in the microfluidic biochip cultures compared to plate cultures. Among those genes, phase I enzymes involved in the xenobiotic's metabolism such as the cytochromes P450 (CYP) 1A1/2, 2B6, 3A4, 3A5, and 3A7 were up-regulated. The CYP1A1/2 up-regulation was associated with the appearance of CYP1A1/2's activity evidenced by using EROD biotransformation assay. Several phase II enzymes such as sulfotransferases (SULT1A1 and SULT1A2), UDP-glucuronyltransferase (UGT1A1, UGT2B7) and phase III transporters (such as MDR1, MRP2) were also up-regulated. In conclusion, microfluidic biochip could and provide an important insight to exploring the xenobiotic's metabolism. Altogether, these results suggest that this kind of biochip could be considered as a new pertinent tool for predicting cell toxicity and clearance of xenobiotics in vitro.

On the Adequacy of Monetary Arrangements in Sub-Saharan Africa

Abstract: We examine the economic rationale for monetary union(s) in Sub-Saharan Africa through the use of cluster analysis on a sample of 17 countries. The variables used stem from the theory of optimum currency areas and from the fear-of-floating literature. It is found that the existing CFA franc zone cannot be viewed as an optimum currency area: CEMAC and UEMOA countries do not belong to the same clusters, and a 'core' of the UEMOA can be defined on economic grounds. The results support the inclusion of the Gambia, Ghana and Sierra Leone in an extended UEMOA arrangement, or the creation of a separate monetary union with the 'core' of the UEMOA and the Gambia, rather than the creation of a monetary union around Nigeria. Finally, the creation of the West African Monetary Zone (WAMZ) around Nigeria is not supported by the data.