Portail HAL de l'Université Picardie Jules Verne
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Impaired endotoxin inactivation, rather than gut translocation, is associated with organ injury in cardiac surgery with cardiopulmonary bypass
No full textInternational audienceBACKGROUNDS In patients with cardiac surgery under cardiopulmonary bypass (CPB), postoperative inflammation is a driver of adverse outcomes. Endotoxaemia is one of the factors thought to trigger this inflammatory response. The mechanism behind high endotoxin activity (increased translocation vs. reduced inactivation capacity) has never been elucidated and may imply different therapeutic candidates. OBJECTIVES We aimed to evaluate, in patients with cardiac surgery with prolonged CPB, mechanisms and consequences of endotoxaemia and the efficacy of haemo-adsorption to reduce the endotoxin burden. DESIGN Ancillary analysis of a randomised controlled trial. Patients scheduled for cardiac surgery with prolonged CPB were assigned to receive either intra-operative haemo-adsorption or standard of care. Endotoxin mass and activity were measured before surgery, at the end of CPB, 6, 24 and 48 h after the end of surgery. SETTING Operating room, Amiens University Hospital. PATIENTS Adults scheduled for cardiac surgery under CPB with an expected CPB time more than 90 min. INTERVENTION Patients were randomised to receive either haemo-adsorption or standard care during CPB. MAIN OUTCOME MEASURES Endotoxin activity. RESULTS Two hundred and ninety-five samples from 66 patients were analysed. Following CPB, we observed a reduction in endotoxin mass accompanied by a relative increase in endotoxin activity. High postoperative endotoxin activity was associated with intra-operative dobutamine requirement, increased postoperative inflammatory biomarkers and organ injury. Endotoxin plasma concentration and activity were not lower in patients treated with haemo-adsoprtion. CONCLUSION The capacity of individuals to inactivate endotoxin rather than raw endotoxin mass (i.e. Quantity) seemed to be a determinant of endotoxin noxious effect in cardiac surgery and CBP. Haemo-adsorption was not associated with a reduction of endotoxin plasma mass or activity in patients with cardiac surgery under CPB. TRIAL REGISTRATION ClinicalTrials.gov, NCT04201119NCT0420111
Failure of uniqueness for scalar conservation laws
No full textIn this article, we develop what are, to the best of our knowledge, the first negative results for scalar conservation laws. We begin with explicit examples where bounded initial data leads to L ∞ blow-up despite flux regularity. More strikingly, we demonstrate that Kružkov's entropy equalities alone fail to ensure uniqueness in this regime by constructing infinitely many entropy solutions to a single Cauchy problem with bounded initial datum, each continuous in time with respect to the L 1 norm. Thus, we demonstrate that the L ∞ assumption is essential for the doubling of variables argument, and hence for the uniqueness of entropy solutions to scalar conservation laws. On the positive side, we develop a novel theory for scalar conservation laws with spatial heterogeneity by adapting the front tracking method. We recover uniqueness by imposing a Lax-type condition in addition to the entropy inequality, motivated by the properties of our front tracking approximations. Unbounded Kružkov solutions do not necessarily satisfy the weak formulation; we show that global weak solutions may not even exist in a natural class for some Cauchy problems of this form, even when Kružkov entropy solutions exist. Finally, we construct an explicit example of global ill-posedness with bounded initial datum.</div
BPS SHEAF FOR COMMUTING VARIETIES
No full textIn this short note, we give a description of the BPS sheaf of the triple commuting variety of a reductive Lie algebra. It is shown to be isomorphic to a direct sum of constant sheaves on the cube of the center of the Lie algebra. The multiplicity of the constant sheaf is given by the number of distinguished nilpotent orbits in the Lie algebra. This answers a conjecture of the author, motivated by cohomological Donaldson-Thomas theory, in this particular case. This study relies on the virtual smallness of the approximation by schemes of the good moduli space morphism, which we establish in this paper for general (weakly) symmetric representations of reductive groups. The virtual smallness gives a lower bound on the perverse filtration, which also allows us to give a partial identification of the BPS sheaf for symmetric representations of reductive groups.</div
The BPS decomposition theorem
No full textWe prove the BPS decomposition theorem (a.k.a. cohomological integrality theorem) decomposing the cohomology of smooth symmetric stacks into the Weyl-invariant part of the cohomological Hall induction of the intersection cohomology of good moduli spaces. As a consequence, we establish the BPS decomposition theorem for the Borel--Moore homology of -shifted symplectic stacks and for the critical cohomology of symmetric -shifted symplectic stacks, thereby generalizing the main result of Bu--Davison--Ibáñez Nuñez--Kinjo--Pădurariu to the non-orthogonal setting. We will present three applications of our main result. First, we confirm Halpern-Leistner's conjecture on the purity of the Borel--Moore homology of -shifted symplectic stacks admitting proper good moduli spaces, extending Davison's work on the moduli stack of objects in -Calabi--Yau categories. Second, we prove versions of Kirwan surjectivity for the critical cohomology of symmetric -shifted symplectic stacks and for the Borel--Moore homology of -shifted symplectic stacks. Finally, by applying our main result to the character stacks associated with compact oriented -manifolds, we reduce the quantum geometric Langlands duality conjecture for -manifolds, as formulated by Safronov, from an isomorphism between infinite-dimensional critical cohomologies to a comparison of finite-dimensional BPS cohomologies
Nonabelian Hodge isomorphisms for stacks and cohomological Hall algebras
No full textIn this paper, we complete the nonabelian Hodge theory (NAHT) triangle of isomorphisms for stacks between the Borel-Moore homologies of the Dolbeault, Betti, and de Rham moduli stacks. We first explain how to realise the category of connections on a smooth projective curve as a subcategory of a -Calabi-Yau dg-category satisfying some appropriate geometric conditions. Then, we define a cohomological Hall algebra (CoHA) product on the Borel-Moore homology of the stack of connections on a smooth projective curve. This allows us to not only compare the Borel-Moore homologies of the stacks at the relative and absolute levels for the three sides of NAHT, but also to compare their CoHA structures: they all coincide. To compare the Dolbeault and de Rham sides, we define a relative CoHA for the Hodge-Deligne moduli space parametrising -connections. The Betti and de Rham sides are compared using the (derived) Riemann-Hilbert correspondence. The comparison of the Borel-Moore homologies of the Dolbeault and Betti moduli stacks was previously considered by the author with Davison and Schlegel Mejia (without taking the cohomological Hall algebra structures into account). This paper completes this study and provides a CoHA enhancement of the classical NAHT for curves
BPS Lie algebras for totally negative 2-Calabi-Yau categories and nonabelian Hodge theory for stacks
No full textWe define and study a sheaf-theoretic cohomological Hall algebra for suitably geometric Abelian categories of homological dimension at most two, and a sheaf-theoretic BPS algebra under the conditions that is 2-Calabi-Yau and has a good moduli space. We show that the BPS algebra for the preprojective algebra of a totally negative quiver is the free algebra generated by the intersection cohomology of the closure of the locus parameterising simple -modules in the coarse moduli space. We define and study the BPS Lie algebra of arbitrary 2-Calabi-Yau categories for which the Euler form is negative on all pairs of non-zero objects, which recovers the BPS algebra as its universal enveloping algebra for such "totally negative" 2CY categories. We show that for totally negative 2CY categories the BPS algebra is freely generated by intersection complexes of certain coarse moduli spaces as above, and the Borel-Moore homology of the stack of objects in such satisfies a Yangian-type PBW theorem for the BPS Lie algebra. In this way we prove the cohomological integrality theorem for these categories. We use our results to prove that for a smooth projective curve, and for and not necessarily coprime, there is a nonabelian Hodge isomorphism between the Borel-Moore homologies of the stack of rank and degree Higgs bundles, and the appropriate stack of twisted representations of the fundamental group of . In addition we prove the Bozec-Schiffmann positivity conjecture for totally negative quivers; we prove that their polynomials counting cuspidal functions in the constructible Hall algebra for have positive coefficients, strengthening the positivity theorem for the Kac polynomials of such quivers
CENTRALISERS OF SEMI-SIMPLE ELEMENTS ARE SEMIDIRECT PRODUCTS
No full textLet G be a reductive algebraic group over an algebraically closed field, and let s ∈ G be a semisimple element. We show that the centraliser of s is the semi-direct product of its identity component by its group of components.We then look at the case where G is defined over an algebraic closure of a finite field Fq, and F is a Frobenius endomorphism attached to an Fqstructure on G. Under the additional assumption that s lies in an F -stable maximal torus such that F acts trivially on the Weyl group, we show that if the centraliser of s is F -stable we can make the above semi-direct product decomposition F -stable.</div
AI for IoMT Security: A Comprehensive Survey of Intrusion Detection and System Architectures
No full textInternational audienceRecent advances in the Internet of Medical Things (IoMT) have significantly improved data processing and patient care within Smart Healthcare systems. However, these developments have also expanded the surface of potential cyber threats targeting sensitive medical infrastructures. To address these challenges, a variety of security approaches both traditional and Artificial Intelligence (AI)-based have been proposed to strengthen the resilience of IoMT environments. In particular, Machine Learning (ML) and Deep Learning (DL) techniques have demonstrated strong capabilities in detecting and mitigating abnormal behaviors and malicious activities. This paper provides a comprehensive survey of recent AI-driven methods applied to IoMT security, with a particular focus on intrusion detection systems (IDS), the availability and characteristics of public datasets, and architectural considerations for deploying security solutions across Cloud, Fog, and Edge computing layers. The paper also discusses legal and ethical concerns related to data protection in healthcare contexts. Finally, the study outlines open challenges and future research directions for developing robust, adaptive, and trustworthy security frameworks in the IoMT ecosystem
Trade, Growth, and Policy Recommendations: Analyzing Economic Development in Africa and China
No full textUne version courte de ce papier a été présentée à la conférence du Monetary Research Center (MRC) de l’Université de Sofia en décembre 2025.This analysis has a twofold aim: to examine the role of trade in economic growth from both theoretical and empirical perspectives, and to offer policy recommendations within the framework of Africa-China commercial cooperation. Fueled by China's demand for natural resources and rapid economic expansion, trade between Africa and China has surged in recent decades, significantly influencing African development. Africa's GDP has grown through increased exports-particularly timber, minerals, and oil-driven by Chinese demand.Empirical evidence suggests that while trade with China has generally supported African growth, the benefits have been unevenly distributed. The influx of low-cost Chinese goods has sometimes undermined local industries, and the trade balance remains skewed in favor of China. This pattern, characterized by raw material exports and finished goods imports, poses risks to industrialization and value addition in Africa. In response, the study presents targeted recommendations to address these challenges.</div
Design and experimental validation of a robust and real-time power management strategy and control system for a hybrid electric vehicle
No full textInternational audienceHybrid energy storage systems combining fuel cells, batteries, and supercapacitors are gaining significant attention for electric vehicle applications due to their ability to enhance efficiency and durability. This paper presents a new energy management strategy for a multi-source electric vehicle system integrating a fuel cell, a lithium-ion battery, and a supercapacitor. Each source plays a distinct role based on its power and energy characteristics, enabling optimal power distribution. The proposed strategy employs frequency decomposition, fuzzy logic and deterministic rules to optimize power sharing, ensuring system stability, enhanced efficiency, and extended component lifespan. The fuel cell supplies steady power, while the battery regulates the DC bus voltage and provides intermediate power support. The supercapacitor manages highfrequency transient power demands, mitigating stress on the fuel cell and battery. Real-time simulations and experimental validation on a hybrid storage system test bench demonstrate the effectiveness of the proposed strategy under Worldwide Harmonized Light Vehicles Test Procedure and Artemis driving cycles. The results confirm stable DC bus voltage regulation, accurate current tracking, and improved energy efficiency, with the supercapacitor effectively absorbing transient power fluctuations. The findings highlight the potential of hybrid energy management in fuel cell-based electric vehicles, contributing to improved system longevity and overall performance