Portail des publications scientifiques IMT Mines Alès
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Mechanization of artisanal and small-scale gold mining in Guinea: Socio-technical trajectory of a rural mining site in Upper Guinea
No full textInternational audienceSince the beginning of the 21st century, artisanal and small-scale gold mining (ASGM) in West Africa has undergone intensification and significant development due to the introduction of increasingly mechanized extraction and processing method. Mechanization generates significant transformations in the socio-technical dynamics of artisanal gold mining. In the specific context of ASGM in Upper Guinea, the article argues that small-scale innovations (ie. ‘low noise’ or ‘low technological level’ innovations) are leading to a profound socio-economic transformation of the rural environment over a long period of time. We begin by describing and analyzing the impact of the introduction of minor innovations (metal detectors, solonins and fan motors) on ASGM practices. We then examine the political, social and economic changes brought about by the adoption of these new mechanized practices, again at the rural level. Finally, we discuss the transition toward a new socio-technical regime, questioning the reshaping of local governance and its impact on new configurations of land ownership and use in rural areas
Modélisation et prévision du risque de maladie à l'aide de la télédétection et du SIG : Application aux cas de paludisme au Nigeria
No full textThroughout the thesis, the research aims, objectives and research questions presented are followed by detailed analyses, processes and methods used to achieve these tasks. This takes the form of contributions that aim to answer research questions based on their respective methods and results. In this thesis, the presented contributions are mainly categorized in to two main areas: the spatial risk factors parameters identification (Ecological, Meteorological, Socio-economic, and epidemiological) and analysis. Geostatistical and geospatial analysis, modelling, justification, and validation. The first contribution in the form of geospatial modelling of malaria risk factors using expert’s intuition to determine the relative importance of risk factors such as ecological, meteorological, socioeconomic, and epidemiological data. This model allows the assessment of the spatial distribution of malaria within the study area and a comprehensive understanding of the complex interactions between vectors, host and environment, with the aim of developing an effective tool specifically tailored to an effective management decision in the context of the introduction of Vector control measures and strategies. This contribution aims to develop a model that can be used to examine the relationship between environmental variables and their causative incidences of the disease. This will be used to understand the spatial spread of the risk, develop early warning systems, build an appropriate intervention mechanism and assess the transmission dynamics of the disease. The overall implementation of the Malaria Risk Model is aimed at better understanding the complexity of malaria transmission risk in the study area and in Nigeria as a whole. Furthermore, by identifying endemic malaria-prone regions and using various risk factor parameters covering the different domains of social composition, environment, climate and socio-economic activities, this thesis provides policymakers with the necessary tools to target malaria intervention measures to plan and implement alongside appropriate vector surveillance and optimal use of scarce resources. Lastly, given the lack of entomological data on vector distribution, the risk model can also help authorities identify the geographical regions where vector control programs and surveillance should focus.Tout au long de la thèse, les objectifs de recherche, les buts et les questions de recherche énoncés sont suivis d'analyses détaillées, de processus et de méthodes utilisés pour les atteindre. Ceci se matérialise par des contributions visant à répondre aux questions de recherche en fonction de leurs méthodes et résultats respectifs. Dans ce mémoire, les contributions présentées sont principalement classées en deux domaines principaux : l'identification des paramètres des facteurs de risque spatiaux (écologiques, météorologiques, socio-économiques et épidémiologiques) et l'analyse. L'analyse géostatistique et géospatiale, la modélisation, la justification et la validation. La première contribution, sous forme de modélisation géospatiale des facteurs de risque du paludisme, utilise l'intuition des experts pour déterminer l'importance relative des facteurs de risque tels que les données écologiques, météorologiques, socio-économiques et épidémiologiques. Ce modèle permet d'évaluer la distribution spatiale du paludisme dans la zone d'étude et de comprendre de manière exhaustive les interactions complexes entre les vecteurs, les hôtes et l'environnement, dans le but de développer un outil efficace spécifiquement adapté à une prise de décision de gestion efficace dans le contexte de l'introduction de mesures et stratégies de lutte antivectorielle. Cette contribution vise à développer un modèle pouvant être utilisé pour examiner la relation entre les variables environnementales et leurs incidences causales de la maladie. Cela sera utilisé pour comprendre la propagation spatiale du risque, développer des systèmes d'alerte précoce, construire un mécanisme d'intervention approprié et évaluer la dynamique de transmission de la maladie. L'implémentation globale du modèle de risque du paludisme vise à mieux comprendre la complexité du risque de transmission du paludisme dans la zone d'étude et au Nigeria dans son ensemble. De plus, en identifiant les régions endémiques à risque de paludisme et en utilisant divers paramètres de facteurs de risque couvrant les différents domaines de la composition sociale, de l'environnement, du climat et des activités socio-économiques, cette thèse fournit aux décideurs les outils nécessaires pour cibler les mesures d'intervention contre le paludisme afin de planifier et de mettre en œuvre, aux côtés d'une surveillance vectorielle appropriée et d'une utilisation optimale des ressources rares. Enfin, compte tenu du manque de données entomologiques sur la distribution des vecteurs, le modèle de risque peut également aider les autorités à identifier les régions géographiques sur lesquelles les programmes de lutte antivectorielle et de surveillance doivent se concentrer
Flammability of Novolac epoxy cured with aromatic diamines
No full textInternational audienceThe modification of Novolac epoxy with the organophosphorus compound 9,10-dihydro-9-oxa-10-phosphaphenanthren-10-oxide (DOPO) to reduce flammability and its influence on curing reactions has been investigated. Three aromatic diamine curing agents were used, namely 4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenylsulphone (DDS), and diethyltoluenediamine (DETDA). The thermal stability and dynamic-mechanical behaviour of the cured resin depend on interactions of the curing agent with DOPO. The onset degradation temperature decreased with increasing phosphorus content, indicating the influence of DOPO on thermal stability. The DDM 3 %P sample exhibited the highest glass transition (Tg) of 136 °C, while DDS-crosslinked simples displayed the highest Tg of 147 °C among all samples. An improvement in the reaction of Novolac epoxy to fire was achieved by incorporating DOPO compound, as indicated by cone calorimetry results, showing up to a 67 % reduction in the peak heat release rate (pHRR) and 53 % reduction in total heat release (THR) for DDM 3 %P. The modified samples containing DOPO presented a self-extinguishing performance, displaying a UL-94 V-0 rating and a limiting oxygen index (LOI) values reached a maximum of 37.1 % for DDM 3 %P, with less flame propagation than for neat Novolac epoxy
Environmentally-friendly, binder-free, non-flammable particleboard with enhanced properties
No full textInternational audienceNonflammable binderless particleboards were manufactured from spruce and hempshives by steam explosion and hot pressing. An unpurified aqueous extract of phytic acid was employed for flame retardancy. Phytic acid is a renewable phosphorus molecule of plant origin, present in significant quantities in oilseed cakes. The effect of the steam explosion and/or the flame-retardant treatment on the mechanical properties and thermal stability of binderless particleboards was investigated. The results showed that the mechanical properties of the binderless particleboards were significantly impacted by the flame-retardant treatment in particular the swelling. For the untreated specimens, the results for swelling at the end of the test ranged from 5 % to 60 %. In contrast, the results for the treated samples ranged from 3 % to 10 %. Moreover, fire retardant treatment of the binderless particleboards reduced Heat Release Rate (HRR) and the mass loss rate, increased the residual mass fraction, resulted in lower average effective heat of combustion values, and usually resulted in longer ignition times
The dynamics of approach and avoidance motivations in sport: An attempt at agent-based system modeling
No full textInternational audienceBased on the complex dynamical system perspective, approach and avoidance motivations in achievement context have been conceptual-ized by Gernigon et al. (2015) as two competing attractors. The strength of approach and avoidance attractors is assumed to evolve over timedepending on the complex interactions among three key social cognitive variables (competence expectancies, expected benefit for the self, and threat for the self) that take place within and across personal, contextual, and situational levels. The complexity of these interactions is notaccessible via conventional statistical tools, but can be modeled by computer programs (Gernigon et al., 2023) such as Agent-Based Models (ABMs). The first aim of this work was to develop a first version of an ABM capable of simulating the dynamics of approach and avoidance motivational patterns consistently with the literature on achievement motivation and with Gernigon et al.’s (2015) dynamical model of approach and avoidance motivation. The second aim was to compare the data resulting from the simulations with longitudinal datarelating to the motivational states reported weekly by 10 athletes who were pursuing an important mid-term (from 1 to 2 years) goal. De-trended Fluctuation Analysis (DFA; Peng et al., 1993) was used to detect typical signatures of complex dynamical phenomena in the formof 1/f power-law distributions (i.e., pink noise) in the time series of both virtual and ecological data sets. The time series of the ecological datashowed 1/f distributions, whereas those of data resulting from the ABM’s simulations did not (brown noise). In other words, the ecological data did reflect a non-linear dynamics typical of complex systems, whereas virtual data mainly evolved under the influence of random information. Therefore, future improvements to the ABM of approach and avoidance motivation are needed to make the model more able to resist to external perturbations, consistent with the nonlinear dynamics observed in real life
Cellulose Nanocrystals as Reinforcements in Thermoplastic Composites: Effect of Processing Route on Dispersion
No full textInternational audienc
Presynaptic Dopaminergic Imaging Characterizes Patients with REM Sleep Behavior Disorder Due to Synucleinopathy
No full textInternational audienceObjective To apply a machine learning analysis to clinical and presynaptic dopaminergic imaging data of patients with rapid eye movement (REM) sleep behavior disorder (RBD) to predict the development of Parkinson disease (PD) and dementia with Lewy bodies (DLB). Method s In this multicenter study of the International RBD study group, 173 patients (mean age 70.5 ± 6.3 years, 70.5% males) with polysomnography‐confirmed RBD who eventually phenoconverted to overt alpha‐synucleinopathy (RBD due to synucleinopathy) were enrolled, and underwent baseline presynaptic dopaminergic imaging and clinical assessment, including motor, cognitive, olfaction, and constipation evaluation. For comparison, 232 RBD non‐phenoconvertor patients (67.6 ± 7.1 years, 78.4% males) and 160 controls (68.2 ± 7.2 years, 53.1% males) were enrolled. Imaging and clinical features were analyzed by machine learning to determine predictors of phenoconversion. Results Machine learning analysis showed that clinical data alone poorly predicted phenoconversion. Presynaptic dopaminergic imaging significantly improved the prediction, especially in combination with clinical data, with 77% sensitivity and 85% specificity in differentiating RBD due to synucleinopathy from non phenoconverted RBD patients, and 85% sensitivity and 86% specificity in discriminating PD‐converters from DLB‐converters. Quantification of presynaptic dopaminergic imaging showed that an empirical z ‐score cutoff of −1.0 at the most affected hemisphere putamen characterized RBD due to synucleinopathy patients, while a cutoff of −1.0 at the most affected hemisphere putamen/caudate ratio characterized PD‐converters. Interpretation Clinical data alone poorly predicted phenoconversion in RBD due to synucleinopathy patients. Conversely, presynaptic dopaminergic imaging allows a good prediction of forthcoming phenoconversion diagnosis. This finding may be used in designing future disease‐modifying trials. ANN NEUROL 2024;95:1178–119
Explicit and implicit sense of agency in depersonalisation experiences
No full textInternational audienceThe sense of agency, the feeling of controlling one’s bodily actions and the world is altered in Depersonalisation (DP), a condition that makes people feel detached from one’s self and body. To investigate the link between depersonalisation and both implicit and explicit sense of agency, an online study was conducted using the influential Intentional Binding paradigm in a sample of non-clinical DP participants. The results did not reveal significant differences between individuals with low and high occurrences of DP experiences on the implicit and explicit sense of agency. However, participants with high occurrences of DP experiences showed a more time-sensitive explicit sense of agency and greater temporal distortions for short intervals in the absence of self-initiated motion. These results suggest that there is a discrepancy between implicit and explicit sense of agency in people with high levels of depersonalisation. Altogether, these findings call for further investigations of the key role of time perception on altered sense of self and agency in both non-clinical and clinical populations, to disentangle the mechanisms associated with the explicit and implicit sense of agency
Tackling the evaporation rates of volatile HNS: A lab-scale experiment to serve marine pollution response
No full textInternational audienceRelease of volatile Hazard Noxious Substances (HNS) at sea can lead to the formation of toxic,flammable or explosive gas plumes that can travel large distances and pose risks over a wide areain relatively short timescales. Yet, when an emergency is declared, key information regarding theshort-term behavior of HNS is not available for responders. For volatile organic compounds(VOCs), one critical parameter that should be systematically predicted and/or assessed is theevaporation kinetics: this would warn first-responders against risks of gas clouds that mightoriginate from the HNS slick. This paper presents new experimental data on the evaporationkinetics of several VOCs that were collected using the new Cedre’s wind tunnel in the frameworkof the MANIFESTS1 project. The air and liquid temperatures as well as the wind velocity profilewere continuously monitored above the pool. The evaporation of each liquid was monitoredfollowing the weight loss fraction over time. The final objective was to assess mass fluxes at thesea-air interface and to compare it to analytical models. The evaporation process was generallyhighlighted by a sharp decrease in temperature of the liquid. At constant wind conditions, the massflow rates were the highest for vinyl acetate, cyclohexane and acrylonitrile, and the lowest forpetroleum benzine. Increasing wind velocities led to higher evaporation rates of chemicals, i.e. afaster evaporation of the slick. These new data were finally compared to the OSERIT (Oil SpillEvaluation and Response Integrated Tool) – Evaporation module developed in MANIFESTS andwill contribute to the improvement of the prediction accuracy of existing evaporation models. Thiswill offer crisis management stakeholders more precise information regarding the formation oftoxic gas clouds (Go/No Go decision)
