Portail des publications scientifiques IMT Mines Alès
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Investigating interbrain synchrony under teamwork disruption: an fNIRS hyperscanning study
No full textInternational audienceAbstract Background Teams are inherently adaptive entities that continuously adapt to changes or disruptions in their tasks or environments. During collaboration, interbrain synchrony (IBS) emerges, reflecting the temporal alignment of neural activity between team members. Building on this, IBS has been proposed as a potential marker of teamwork, suggesting that IBS should be sensitive to changes in teamwork. Purpose The present study investigated whether IBS is sensitive to changes in teamwork. We hypothesized that disruptions in teamwork would be accompanied by alterations in IBS dynamics. Methods Ninety-eight healthy adults (mean age = 22.5 ± 3.22 years; 69 females, 65.1%) were assigned to forty-nine dyads. Each pair completed a 20-minute computer-based navigation task while their brain activity was simultaneously recorded using fNIRS hyperscanning. Dyads in the experimental group encountered an unexpected increase in task difficulty midway through the task, whereas those in the control group completed the task without disruption. We examined three features of IBS - its overall level, temporal slope trajectory, and the temporal recurrence patterns. Results Control analyses confirmed that IBS reliably emerged during the task (χ²(1) = 50.24, p < .001) and that the experimental manipulation successfully disrupted teamwork, as reflected in altered team behavioral responses in communication (χ²(1) = 8.48, p = 0.004) and performance (χ²(1) = 24.99, p < .001). Nevertheless, no evidence was found for disruption-related changes in IBS across the three features examined (all Time x Group interactions p > .05. Conclusion These findings raise the possibility that IBS may reflect a stable collective state rather than a reactive one, thereby challenging its interpretation as a direct marker of teamwork. Methodological considerations, including the operationalization of IBS, are also discussed as potential explanations for the lack of observed change in IBS
Influence of Amorphous Silica‐Aluminas Acidic Sites Concentration on the Flame‐Retarding Properties and on the Thermal Stability of Intumescent Polypropylene Composites
No full textInternational audienceThis work evaluates the influence of the acidic sites concentration in amorphous silica‐aluminas (ASAs) on the flame‐retardant properties and the thermal stability of intumescent polypropylene (PP) composites. ASAs with different concentrations of alumina and acidic sites were synthesized by surface alumina deposition and coprecipitation methods. The polymeric composites had their flame‐retardant properties evaluated by limiting oxygen index (LOI) and UL‐94. The thermal stability was analyzed by thermogravimetric analysis (TGA). The ASAs had their textural properties evaluated by nitrogen physisorption, their chemical composition by X‐ray fluorescence (XRF) and their acidity by temperature‐programmed ammonia desorption (TPD‐NH 3 ). The results show that the presence of ASA, regardless of the synthesis method, increased the thermal stability of the composites. Besides, the presence of acidic sites favors the flame‐retardant properties of the intumescent composites, leading to LOI values of 29% and 30%, as well as a V‐0 classification in UL‐94 test. Moreover, after reaching this LOI value threshold, the increase in the acidity of these silica‐aluminas did not promote further increase in the flame‐retardant properties
Assessing Uncertainties in Mean Radiant Temperature Measurements in Controlled or Outdoor Conditions
No full textInternational audienceUrban heatwaves have a significant impact on human health and thermal comfort in cities. The Universal Thermal Climate Index (UTCI) is widely used to evaluate outdoor thermal comfort in cities. UTCI is based on meteorological inputs (air temperature, relative humidity, solar radiation…), clothing characteristics and a human physiological model. Accurate estimation of UTCI requires an accurate assessment of radiative heat exchanges between the human body and the surrounding environment. The mean radiant temperature (Tmrt) is the primary input of UTCI. Tmrt represents a simplified parameterization of the combined shortwave and longwave of radiative exchanges between the human body and its environment, expressed as a single equivalent value corresponding to a hypothetical uniform radiative enclosure. Under outdoor conditions, the estimation of radiative heat exchanges, and thus of Tmrt, remains complex due to the spatial non-uniformity of the surrounding environment and the complexity of human body geometry. In this context, the three-direction radiometer method is commonly used to measure incoming shortwaves and longwaves radiation, and based on assumptions regarding human geometry and emissivity, Tmrt can thus be reliably evaluated. However, because radiometer method is expensive, an alternative cost-effective, smaller, along with associated analytical methods have been developed. These approaches are mainly based on black and grey globes of various diameters and materials and are widely used to characterize the effect of strategies to mitigate the impacts of urban heat waves on the microclimate of cities. The accuracy, response time and representativeness of these probes with respect to human body perception of radiative effects are often questioned. This study focuses on the experimental evaluation of the uncertainties associated with the use of these cost-effective devices for estimating Tmrt. A new cylindrical probe has been designed to better represent human body geometry; its accuracy is evaluated and compared with the classical radiometer method and with black and grey globes commonly used. The experimental campaigns include tests conducted in a controlled environment (wind tunnel) as well as outdoor measurements. The influences of surface emissivity, globe diameter, and globe material on Tmrt estimation are investigated. The wind tunnel setup, combined with a xenon lamp to simulate solar radiation, allows precise control over airflow, radiation, and thermal conditions affecting globe temperature measurements. This setup is used to evaluate the sensitivity of the different probes to the controlled variables. Outdoor experiments investigate real thermal radiation conditions and a wider range of meteorological variables, including cloud cover, wind regimes, and solar angles. Using experimental results obtained from the outdoor campaign, Tmrt values derived from globe measurements are compared with reference values
Assessment of the impact of the irradiation process on the final properties of radiation-resistant polypropylene materials used for medical devices
No full textInternational audienceThe global demand for sterile medical devices is increasing due to technological advancements and growing health care needs. Although Electron beam (EB) and X-ray have existed for a long time, they have been less utilized compared to other sterilization methods such as ethylene oxide and Gamma irradiation. Currently, their application is developing, offering new possibilities in response to a rapidly expanding sterilization market. This study assesses the impact of these irradiation techniques on polypropylene (PP) materials used in medical devices, focusing on their mechanical properties, structural changes, and color stability. PP is known for its sensitivity to irradiation, which makes the evaluation of its properties under different irradiation conditions particularly relevant. Three different PP grades, with varying radiotolerance claims, were exposed to controlled irradiation doses (30, 45, and 85 kGy). Analyses including electron spin resonance (ESR), rheology, tensile testing and colorimetry were carried out. They were also employed in conjunction with principal component analysis (PCA). The results allowed to evaluate irradiation-induced modification. Results indicate that Gamma irradiation induces the most significant degradation due to its low dose rate, leading to increased chain scission and oxidation effects. E-beam irradiation has the least impact, while X-ray effects are generally lower to Gamma irradiation at equivalent doses. The study highlights the importance of selecting appropriate PP formulations to ensure optimal post-irradiation performance, particularly in the context of transitioning from traditional sterilization methods to E-beam or emerging X-ray technology
Impact of sulfamethoxazole, trimethoprim, diclofenac, carbamazepine, and their mixture on the metabolism of Lemna minor: a targeted metabonomic study
No full textInternational audienceMetabolomics is an analytical profiling technique that measures and compares large numbers of metabolites in biological samples, providing insight into metabolic mechanisms. There are few studies concerning the effects of xenobiotics and their transformation products on aquatic plant metabolites, which can uptake and detoxify them using untargeted metabolomics. Objectives This study investigates how pharmaceuticals, including diclofenac (DCF) and carbamazepine (CBZ), as well as sulfamethoxazole (SMX) and trimethoprim (TRIM), present in aquatic environments, can influence the biosynthetic pathways of Lemna minor .Based on previous research on the effects of DCF, SMX, and TRIM on Lemna pathways, specifically phenylalanine, tyrosine, and tryptophan biosynthesis, folate biosynthesis, and the phenylpropanoid pathway, including flavonoid and anthocyanin metabolism. Methods Lemna was incubated with DCF, CBZ, SMX, and TRIM alone and in a mixture (MIX) at 5 ppb (5 µg/L) for 5 days, at concentrations near environmental levels. The methanolic extract was analysed using a Q Exactive Focus Orbitrap to investigate changes in the aforementioned biosynthetic pathways, as reported in previous studies. Results Lemna can modulate its pathways to produce more phenolic compounds as a defence mechanism against various drugs. This modulation can be considered an indicator for each drug. Conclusions The presence of pharmaceuticals in the aquatic environment can affect the biosynthetic pathways of Lemna . Therefore, Lemna minor can be used as a model to study the stress-response of different pharmaceuticals on plant metabolites and their pathways
Obesity is linked to impaired sensorimotor synchronization during walking but not tapping
No full textInternational audienceThis study compares dynamic stability between individuals with obesity and those of normal weight. Participants performed audiomotor synchronization tasks involving a metronome with sudden phase shifts, both while walking and during finger tapping. The aim was to assess how these perturbations affected participants’ ability to synchronize their movements with auditory beats. Resynchronization was evaluated using the beat–movement relative phase, which quantifies the temporal discrepancy between the auditory cue and the corresponding motor event. The return to a stable relative phase following a perturbation—a process often described in terms of “relaxation time”—was quantified using a decay coefficient, which served as an index of dynamic stability. The results indicated that participants with obesity had greater difficulty resynchronizing their movements during the walking task, but not during the finger tapping task. This suggests that body mass significantly impacts motor control and synchronization in tasks involving whole-body movement. These findings are important for informing rehabilitation and intervention strategies tailored to individuals with obesity
Impact of thermal treatment on the crystallization behavior and mechanical properties of semicrystalline PLGA
No full textInternational audiencePoly (lactic-co-glycolic acid) (PLGA) copolymers with high glycolic acid (GA) content (PLGA80 with 81 mol% and PLGA90 with 90 mol%) are promising candidates for sustainable food packaging due to their degradability and favorable barrier properties. However, their processability is challenging and the relationship between thermal behavior, microstructure, and mechanical performance is poorly understood. This study investigates the influence of thermal processing parameters, specifically drying and thermopressing temperature, on the crystallization behavior and mechanical properties. The thermal processing behavior is first simulated by preheating the pellets at selected preheating temperatures (210–250 °C for PLGA90 and 190–200 °C for PLGA80) and analyzed using DSC, TGA, POM, and WAXS. Increasing preheating temperature reduces the degree of crystallinity from 23% to 2% for PLGA90 pellets and from 17% to 2% for PLGA80 pellets, and can increases crystal size. At critical preheating temperatures (250 °C for PLGA90 and 200 °C for PLGA80), no clear crystallization peak was detected. Films produced under these different conditions exhibit predominantly amorphous structures, due to fast cooling rate and/or thermal degradation during thermopressing. For PLGA90, Young's modulus decreases from 440 ± 40 MPa when processed at 210 °C to 230 ± 35 MPa when processed at 230 °C, while elongation at break increases from 190 ± 90 % to 740 ± 175%, respectively. Processing temperatures close to the melting point are therefore advantageous for maintaining a high Young's modulus, whereas higher processing temperatures yield exceptional ductility, an important property for flexible film packaging. Depending on the targeted application, the processing temperature of PLGA films can thus be tailored to balance their stiffness and ductility
MODÈFONE - Modèle fantôme pour pression intracrânienne
No full textThis report presents the MODÈFONE project, whose objective is to develop a simplified experimental model of the cerebrospinal system in order to investigate fluid-structure interactions and physiological adaptations under altered gravity conditions, with a particular focus on microgravity. The experimental setup is based on a pulsatile hydraulic circuit reproducing systolic and diastolic dynamics, coupled with deformable elements simulating vascular compliance and a cranial compartment immersed in a fluid representing cerebrospinal fluid. This model enables the analysis of cranial and spinal pressures as well as their pulsatility. The purpose of this report is to describe the design and the results of the experimental setup.Ce rapport présente le projet MODÈFONE, dont l’objectif est de développer un modèle expérimental simplifié du système cérébrospinal afin d’étudier les interactions fluide–structure et les adaptations physiologiques en conditions de gravité modifiée, en particulier en micropesanteur.Le dispositif expérimental repose sur un circuit hydraulique pulsatile reproduisant la dynamique systolique et diastolique, couplé à des éléments déformables simulant la compliance vasculaire et à un compartiment crânial immergé dans un fluide représentant le liquide cérébrospinal. Ce modèle permet d’analyser les pressions crânienne et spinale ainsi que leur pulsatilité.L’objectif de ce rapport est de décrire la conception et les résultats du dispositif expérimental
Energy: Mining and Extraction
No full textInternational audienceReducing greenhouse gas emissions is crucial to mitigating climate change. It mainly involves decreasing the use of fossil fuels and moving toward so-called “cleaner and low-carbon technologies and systems.” The International Energy Agency (IEA) proposes several scenarios to mitigate CO2 emissions. The Net Zero Emissions (NZE) by 2050 scenario bets on the accelerated implementation of the “energy transition,” with a threefold increase in renewable electricity installations and a significant expansion of solar and wind power. By 2035, the increase in global electricity consumption is estimated between 50% and 84% (Boubault and Maïzi 2019). So, the term “energy transition” is criticized by historians (Fressoz 2024) for implying that a new energy source replaces the previous one, but this is not the case. They prompt a reconsideration of this term, which, until now, has merely consisted of..
Interpersonal Violence in French Sports Clubs: Who Are the Victims?
No full textInternational audienceThe purpose of this study was to provide an accurate depiction of interpersonal violence (IV) in French sports. Thus, the aim of this study was to (a) measure the prevalence of IV experienced by French athletes since joining their current club, (b) accurately describe the victim's profile based on several risk factors, (c) and investigate IV according to a specific timeframe. A total of 2,250 athletes completed the French adaptation of the IV in Sport. Our results indicate a high prevalence of IV in the sporting environment, with 59.7% of participants reporting exposure to at least one form of IV and 3.8% reporting exposition to all forms of IV, highlighting the scale of this phenomenon in French sports clubs. Type of sport was the most influential risk factor for experiencing physical violence while the level of competition appeared to increase the experience of psychological violence, neglect and sexual violence. The results point to the relevance of measuring IV in a specific context and during a specific timeframe, even when accounting for the fact that participants who reported IV were significantly more likely to abandon the questionnaire before completing it