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Evolution of tribolayer in GH2132/GH4169 fretting wear at elevated temperatures
No full textInternational audienceTo investigate the development of the tribolayer in the GH2132/GH4169 superalloy pair, a systematic tangential fretting wear interruption test was conducted to analyze the microstructure, chemical composition, formation mechanism, and evolutionary characteristics of the tribolayer at 600℃. The results reveal that in the early stages of fretting, severe plastic deformation of material in the contact area and dislocation accumulation within the grains promote dynamic recrystallization and crack initiation, ultimately resulting in significant adhesive wear. As the test progresses, tribo-sintering of oxidized debris and continuous grain refinement give rise to a dense nanocrystalline tribolayer with enhanced hardness. This tribolayer, which is composed of nanocrystalline metal oxides, unoxidized nanograins, and amorphous phases, forms at the contact interface and serves as a mechanically and chemically robust barrier. It suppresses metal-to-metal contact, slows oxidation, and significantly reduces the wear rate, thereby stabilizing the worn surface
The first applications of mescaline in psychiatry: The case of Madame Louise Françoise R. and its contemporary relevance
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Off-target: Herbicides in cereal fields favour competitive weeds over non-target species
No full textInternational audienceWeed diversity plays an important role in maintaining resilient agroecosystems, yet agricultural practices, such as pesticide applications, significantly shape weed communities. Previous studies have primarily focused on comparing organic and conventional farming, with a particular emphasis on land-use intensification. However, less attention has been given to the specific effects of herbicides, insecticides, and fungicides on weed communities, including the species affected and the mechanisms driving these changes, based on farmer-recorded application data. Our study examined the impact of herbicide, fungicide, and insecticide useboth in terms of Treatment Frequency Index (TFI), i.e., intensity of application, and quantity (QA) -on weed communities in 96 non-organic cereal fields over 4 years. We did not detect any effect of insecticide metrics on weed communities. Interestingly, our results indicate that TFI of fungicide decreased weed abundance, whereas QA did not. In contrast, for herbicides, QA had a stronger negative impact on weed communities than TFI. This suggests that TFI of fungicide, which may reflect low-dose but frequent applications, could exert indirect and long-term effects on weed suppression. In comparison, QA of herbicide more directly reflects the toxic load delivered to weeds and is therefore a better predictor of their suppression. Our results reveal that herbicides are the main factor shaping weed communities by decreasing the abundance of non-target/non-competitive species while replacing them with competitive species. These findings point out the potential ineffectiveness of herbicide application on problematic weeds and emphasise the need to reconsider the use of herbicides to maintain weed diversity in agricultural landscapes
An experimental method for determining the in-plane shear modulus of carbon fibres
No full textInternational audienceThe performance of bituminous materials is often evaluated using rheological properties measured within the linear viscoelastic region. If there is a univocal temperature dependence of all the relaxation times, data obtained in different operating conditions can be translated onto a logarithmic scale where they partially overlap and merge into a single master curve. This is the well-known time–temperature superposition principle that has been successfully applied for decades. However, the empirical nature of the method has led to many different procedures being used for the graphical construction of the master curve. In addition, the continuously increasing calculating power has led to new approaches, such as the simultaneous modelling of the represented viscoelastic function. Losing track of the basic statements of the method is the hidden drawback of this wide range of available protocols with the risk of artefacts and incongruences being introduced in the construction of the master curves. This review summarizes these basic statements together with the empirical and phenomenological approaches developed over the years. The aim of this study is to help the reader in choosing the most appropriate method to build the master curves. Although the subject of the review is of general application, the field of bitumen is focused on
Des rituels pour animer des statuettes divinatoires. Le cas des Flores Mercurii de Babilonia super opera artis magice
No full textInternational audienceLes "Flores Mercurii de Babilonia super opera artis magice" constituent l’une des annexes qui circulent en marge de la tradition magique d’origine hébraïque du "Liber Razielis", et plus particulièrement de sa version en sept livres placée sous le patronage d’Alphonse X de Castille (1252-1284). Fait assez rare en contexte occidental, elles prescrivent l’élaboration d’"images", autrement dit de statuettes, que divers rituels permettent d’animer ou de "vivifier" pour en obtenir des révélations, notamment sur l’avenir
Making the Invisible Tangible: Joint Art-science Methods for Materializing Urban Air Pollution
No full textInternational audienceIn the current ecological emergency context, air toxicity—a felt but invisible milieu—is a growing issue. Particulate matter andgases generated by transport, construction, or industrial activities have significant impacts on human and more-than-human health (Manisalidis et al., 2020; Montréal, 2022; Canada, 2022), raising socio-environmental questions related to accessibility to a healthy environment (Chen, 2011; Graham, 2015; Liboiron, 2021). How to make air pollution tangible? To address this question, the chapter draws on the case of [re]capture (2020-2024), a research-creation project that comprises a gallery installation and a series of outdoor experiments driven by instruments that capture atmospheric data along the Montreal Metropolitan Expressway (Québec, Canada). Through the lens of ‘air filtration,’ [re]capture explores how data materialization strategies can give shape at once to air’s microscopic invisibility and the macroscopic dimension of its issues. Based on bio-materials investigation and data capture in urban settings, the project involves community workshops, a public exhibition, and a comparative study of air monitoring infrastructures across two sites in Montreal and Paris. With filtration approached as an exchange between materials, technologies, researchers, and publics, the chapter explores how this art-science framework involving the study of scientific instruments can decompartmentalize knowledge to generate sensory and sensitive experiences of air pollution, and how artistic objects can be mobilized to co-create new forms of public experimentation and ecological imaginaries. Examining the links between artistic and scientific practices, the built environment, ecosystems, and communities, it seeks to encourage social uses of research-creation
Detection efficiency and spatial resolution of Monolithic Active Pixel Sensors bent to different radii
No full textInternational audienceBent monolithic active pixel sensors are the basis for the planned fully cylindrical ultra low material budget tracking detector ITS3 of the ALICE experiment. This paper presents results from testbeam campaigns using high-energy particles to verify the performance of 50 um thick bent ALPIDE chips in terms of efficiency and spatial resolution. The sensors were bent to radii of 18, 24 and 30 mm, slightly smaller than the foreseen bending radii of the future ALICE ITS3 layers. An efficiency larger than and a spatial resolution of approximately 5 um, in line with the nominal operation of flat ALPIDE sensors, is obtained at nominal operating conditions. These values are found to be independent of the bending radius and thus constitute an additional milestone in the demonstration of the feasibility of the planned ITS3 detector. In addition, a special geometry in which the beam particles graze the chip and traverse it laterally over distances of up to 3 mm is investigated
