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Gas permeability of concrete under compressive creep during drying–wetting cycles
No full textInternational audienceGas permeability is used as an indicator of concrete durability due to its strong correlation with material porosity. However, permeability is typically measured on unloaded specimens or under loading conditions that are not representative of actual structural applications. This experimental investigation aims to enhance the understanding of the impact of mechanical stress on the gas permeability and, by extension, concrete durability, under conditions approaching those of structural applications. For this purpose, a novel experimental setup was designed to measure radial gas flow through hollow concrete specimens under compressive creep loading. The setup was validated by comparing the measured gas permeabilities to those obtained using a Cembureau constant-head permeameter. The impact of two levels of compressive creep on the gas permeability of initially saturated concrete specimens was investigated over a 150-day drying period at 20 °C and 50 % relative humidity. Subsequently, the specimens were immersed in water until constant mass was reached and then dried a second time under identical hygro-mechanical conditions, in order to distinguish the effect of water saturation from that of hygro-mechanical cracking. The results show that sustained loading to 30 % of the concrete compressive strength has no significant impact on gas flow. However, loading concrete to 60 % of its compressive strength leads to a tenfold increase in measured gas permeability, compared to unloaded specimens. Monitoring the mass of the specimens revealed that the studied stress levels do not significantly impact drying kinetics. Therefore, the observed increase in gas permeability is attributed to hygro-mechanical damage
Lire "Le Métier à métisser" aujourd’hui : Entre militantisme, nomadisme enraciné et pensée écologique
No full textInternational audienceDe la poésie au roman, en passant par l’essai, René Depestre incarne l’une des figures majeures de la littérature francophone. Auteur aux multiples facettes scripturales, il est né en 1926 à Jacmel au sud d’Haïti et s’impose comme une voix engagée dans la lutte contre les politiques aliénantes, le racisme et le colonialisme. Écrivain aux identités plurielles, Depestre se définit à la fois comme Haïtien, Français, Brésilien, Tchèque, Italien ou encore Cubain . Son nomadisme enraciné traduit un désir profond de déconstruire l’identité racine : il conçoit la frontière non pas comme une barrière érigée, mais comme un espace de circulation, de rencontre et de fusion. C’est dans ce lieu de contact, cette frontière qui lie les individus que naît le métissage, principe fondamental de sa pensée, où les mondes se transforment, se créent et se recréent. René Depestre théorise cette dimension du métissage sous le terme de « métier à métisser » . C’est une façon de dépasser les enfermements (cloisonnements) identitaires, qu’ils soient raciaux, culturels ou linguistiques afin de construire une identité ouverte au carrefour de la diversité. Le métier à métisser devient ainsi la célébration de la rencontre, du brassage et de l’hybridité. Toutefois, Le métier à métisser ne se résume pas au métissage. C’est une forme d’engagement politique et poétique, relatant les combats politiques et de luttes anticoloniales de Depestre. Son écriture est également marquée par une éthique de la vie humaine et non humaine, celle du vivre-ensemble, de la symbiosis des êtres. Il s’oppose à la domination euro-occidentale qui, selon lui, s’enlise dans un impérialisme extractiviste réifiant nature, femmes et hommes. Si l’essai s’articule autour de la rencontre et de l’ouverture aux turbulences du monde pour une altérité harmonieuse, le concept de « métissage » défendu par l’auteur – aujourd’hui galvaudé par les institutions occidentales – sera également étudié à la lumière des travaux d’Édouard Glissant, qui lui a proposé d’explorer le chaos-monde à travers le concept de « créolisation ». Ce dernier ne représente-t-il pas la dimension politique et poétique du « métissage », en raison de son caractère imprévisible, imprévu, mais également de sa brutalité
Le BI 30 ou le mythe des tentations militaristes de la Ligue communiste
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Les organisations trotskistes à l’épreuve de la rupture du programme commun de gouvernement
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A Case of Constrictive Pericarditis Due to Disseminated MSSA Infection: A Rare Cause of Anasarca
No full textInternational audienceBackground: Constrictive pericarditis is an uncommon cause of systemic venous congestion and may present with generalized edema due to impaired ventricular filling. In the modern antibiotic era, bacterial pericarditis has become rare, and progression to constrictive physiology is infrequently encountered. Staphylococcus aureus–associated constrictive pericarditis is particularly uncommon and usually occurs in the setting of disseminated infection. Its insidious presentation often delays diagnosis, contributing to significant morbidity if not recognized early.Case Report: We report a 40-year-old diabetic male presenting with progressive generalized edema, dyspnea, ascites, and intermittent fever. He had a history of recurrent subcutaneous abscesses with prior cultures growing methicillin-sensitive Staphylococcus aureus (MSSA). Vitals were stable at the time of admission. Clinical examination revealed anasarca, elevated jugular venous pressure, ascites, and a tender anterior chest wall swelling. Investigations demonstrated high serum–ascites albumin gradient, high-protein ascites, and transudative pleural effusion, suggesting a cardiac etiology. Echocardiography and cardiac magnetic resonance imaging (MRI) revealed diffuse pericardial thickening with classical features of constrictive physiology. Blood and pus cultures confirmed disseminated MSSA infection. The patient improved with culture-directed antimicrobial therapy and subsequently underwent pericardiectomy, with significant clinical recoveryConclusion: This case illustrates a rare presentation of constrictive pericarditis secondary to disseminated MSSA infection in a patient with diabetes mellitus. It highlights the importance of recognizing infectious causes of constrictive pericarditis in patients presenting with unexplained anasarca and recurrent staphylococcal infections, as early diagnosis and timely intervention can significantly improve outcomes
Crossbreeding of German Brown X N’dama Cattle at Ibadan – II – Pattern of Reproductive Performance of the Purebreds and Crossbreds
No full textInternational audienceA crossbreeding programme between purebred German brown and N’dama was carried out at the University of Ibadan Teaching and Research farm between 1970 – 1988. Reproductive data of 537 purebred and crossbreds’ records from the programme were used for this analysis involving purebred German brown (GBP), purebred N’dama (NDL), 75% N’dama-bred, 50% N’dama-bred, 37.5% N’dama-bred and 25% N’dama-bred based on the level of N’dama gene inheritance. The least square means and analysis of variance procedure for unequal subclass number as outlined by SAS (1990) was used in the analysis. Calving rate (%) of the 50% and 75% N’dama inheritance were 53.04% and 51.06% respectively and significantly (P<0.05) better than calving rate for all other genotypes, which were significantly (P>0.05) not different from each other. However, age at first calving for 37.5%-, 25%- and 50% N’dama-bred were 26.72 months, 31.23 months and 33.96 months respectively, and were significantly (P<0.05) younger than those of the exotic German brown (40.12 months), 75% N’dama crossbred (42.05 months) and local N’dama (43.65 months). Calving interval (months) for crossbreds 37.5%-, 75%- and 50% N’dama-bred were 11.41 months, 12.01 months and 12.81 months respectively, were significantly (P<0.05) shorter than German brown, 25% N’dama-bred and N’dama cows with intervals of 15.85 months, 15.91 months and 15.97 months respectively. This study concluded that 75% N’dama-bred and 50% N’dama-bred including 37.5% N’dama-bred performed better than the purebreds and 25% N’dama-bred cows. The finding suggested improved performance with moderate-high N’dama inheritance
Synergistic Effects of Biochar and Arbuscular Mycorrhizal Fungi on Soil Fertility and Crop Productivity in the Lowland Area of South-West Nigeria: A Review
No full textInternational audienceLowland (Fadama) agro-ecosystems in southern Nigeria are constrained by phosphorus (P) deficiency, low organic matter, and seasonal waterlogging, which limit the productivity of crops such as rice, cassava, and fluted pumpkin (Telfairia occidentalis). Combining biochar application with inoculation of Arbuscular mycorrhizal fungi (AMF) offers a promising solution to these constraints through enhancements in soil structural stability, nutrient-holding capacity, and biologically mediated phosphorus availability. This review synthesizes key literature (2010-2025), including Nigerian field studies and global meta-analyses, to evaluate the mechanisms and evidence supporting Biochar-AMF synergy in lowland systems. Findings indicate that combined applications often outperform single amendments, enhancing P uptake, water-use efficiency, and crop yields-particularly when Biochar is well-characterized and AMF strains are suited to local soils. However, research gaps persist regarding long-term trials, native AMF screening, and standardization of locally derived Biochars. In practice, optimizing Biochar-AMF integration can enhance soil fertility management and promote sustainable crop production in Nigeria’s lowland agro-ecosystems
Sampled Data-Based Observer and Resilient Event-Triggered Controller Design for Cyber-Physical Systems to Mitigate Bounded Mixed Cyber Attacks
No full textInternational audienceThis article addresses the secure control problem for cyber-physical systems (CPSs) subject to energy-bounded mixed network attacks, which comprise both false-data-injection (FDI) attacks and denial-of-service (DoS) attacks occurring simultaneously. To cope with transmission constraints and the unavailability of full state measurements, we design a novel sampled-data observer that concurrently estimates system states and reconstructs FDI attacks, thereby enabling effective attack compensation within the control loop. Moreover, we introduce a resilient event-triggered mechanism (ETM) capable of tolerating energy-bounded DoS attacks. By integrating this mechanism with the proposed observer, we construct an observer-based event-triggered controller that ensures system stability without requiring detailed attack information. The controller guarantees asymptotically bounded convergence under mixed attacks while avoiding restrictive assumptions in the existence analysis. Numerical simulations conducted on a three-tank system and an inverted pendulum system validate the effectiveness and superior performance of the proposed approach compared to existing methods