Portail des publications scientifiques IMT Mines Alès
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In situ electric field dosimetry analysis for powerline frequency peripheral nerve magnetic stimulation
No full textInternational audienceHumans are exposed to environmental 60 Hz magnetic fields (MFs), inducing in our body electric fields (EFs) and currents, potentially stimulating the peripheral nervous system (PNS). Uncertainties exist regarding the 60 Hz MF PNS stimulation threshold. The spatially extended nonlinear node model (SENN) is used to help define international MF exposure guidelines and standards protecting workers and the general public. However, other models exist, particularly the McIntyre–Richardson–Grill (MRG) model, the new gold standard for electrostimulation. This study aims (1) to model a new extremely low frequency MF exposure system for the human leg and (2) to investigate the in situ EFs generated by the system at 60 Hz at the skin level and in the nerves of the leg using a realistic human body model with both the SENN and the MRG models. A Helmholtz like-coil system was designed to generate in situ EFs sufficient for nerve stimulation, modeled using Biot–Savart and Faraday laws. Sim4Life simulations assessed the induced EFs at skin and nerve levels using a detailed human body model and two nerve excitation frameworks: the SENN and MRG models. High EF intensities were observed in four sensory and sensory-motor nerves, with MRG-derived thresholds lower than SENN-derived thresholds. Results also highlight the significance of nerve orientation in EF induction. This study emphasizes the critical role of comprehensive modeling for the design and validation of MF exposure systems and underscores the need for experimental data to refine models, standards, and guidelines
A Comparison Between Adam and Levenberg–Marquardt Optimizers for the Prediction of Extremes: Case Study for Flood Prediction with Artificial Neural Networks
No full textInternational audienceArtificial neural networks (ANNs) adjust to the underlying behavior in the dataset using a training rule or optimizer. The most popular first-and second-order optimizers, Adam (AD) and Levenberg–Marquardt (LM), were compared with the aim of predicting extreme flash floods of a runoff-dominated hydrological system. A fully connected multilayer perceptron with a shallow structure was used to reduce complexity and limit overfitting. The inputs of the ANN were determined by rainfall–water level cross-correlation analysis. For each optimizer, the hyperparameters of the ANN were selected using a grid search and the cross-validation score on a novel criterion (PERS PEAK) mixing the persistency (PERS) and the quality of flood-peak restitution (PEAK). For an extreme and unseen event used as a test set, LM outperformed AD by 25% on all performance criteria. The peak water level of this event, 66% greater than that of the training set, was predicted by 92% after more training iterations were done by the LM optimizer. This shows that the ANN can predict beyond the ranges of the training set, given the right optimizer. Nevertheless, the LM training time was up to five times longer than that of AD during grid search
From MoCap and Unity to ergonomic scores and KPI
No full textInternational audienceIn the context of Industry 5.0, where humans are at the center of industrial evolution, human motion analysis can help enhance both productivity and ergonomics. Improving both health and performance at work by enabling the reconfiguration of a workstation is essential. This study aims, first, to review key works on motion analysis systems related to industrial requirements and, secondly, to present a solution that can help analyze motion to improve safety and key performance indicators.</div
Towards Efficient Ergonomic Optimization in Industry 5.0: The Role of REBA, Motion Capture, and Decision Support Models
No full textInternational audienceIndustry 5.0 introduces human-centered approaches to manufacturing, optimizing production systems while ensuring worker well-being. This paper explores the integration of ergonomics, particularly the REBA method, to assess musculoskeletal risks, with motion capture technology that improves the precision of these assessments. The combination of REBA and motion capture enables more accurate identification of ergonomic issues, promoting better decision-making for production optimization. By applying this integrated approach, we aim to improve worker safety and productivity while optimizing workflows. The contribution of this paper is a comprehensive literature review and the identification of gaps in integrating the REBA method with motion capture technology in the context of Industry 5.0.</div
Baculovirus Genetic Diversity and Population Structure
No full textInternational audienceBaculoviruses can naturally regulate lepidopteran populations and are used as biological insecticides. The genetic diversity of these viruses affects their survival and efficacy in pest control. For nucleopolyhedroviruses, occlusion-derived virions and the occlusion body facilitate the transmission of groups of genomes, whereas this is not the case for granuloviruses. We review the evidence for baculovirus genetic diversity in the environment, in the host insect, and in occlusion bodies and virions. Coinfection allows defective genotypes to persist through complementation and results in the pseudotyping of virus progeny that can influence their transmissibility and insecticidal properties. Genetic diversity has marked implications for the development of pest resistance to virus insecticides. We conclude that future research is warranted on the physical segregation of genomes during virus replication and on the independent action of virions during infection. We also identify opportunities for studies on the transmission of genetic diversity and host resistance to viruses
GIRAFE: Glottal Imaging Dataset for Advanced Segmentation, Analysis, and Facilitative Playbacks Evaluation
No full textInternational audienceThe advances in the development of Facilitative Playbacks extracted from High-Speed videoendo- scopic sequences of the vocal folds are hindered by a notable lack of publicly available datasets annotated with the semantic segmentations corresponding to the area of the glottal gap. This fact also limits the reproducibility and further exploration of existing research in this field.To address this gap, GIRAFE (Glottal Imaging Repository for Advanced Segmentation, Analysis, and Facilitative Playbacks Evaluation) is a data repository designed to facilitate the devel- opment of advanced techniques for the semantic segmentation, analysis, and fast evaluation of High-Speed videoendoscopic sequences of the vocal folds. The repository includes 65 high-speed videoendoscopic recordings from a cohort of 50 patients (30 female, 20 male). The dataset com- prises 15 recordings from healthy controls, 26 from patients with diagnosed voice disorders, and 24 with an unknown health condition. All of them were manually annotated by an expert, including the masks corresponding to the semantic segmentation of the glottal gap. The repository is also complemented with the automatic segmentation of the glottal area using different state-of-the-art approaches.This data set has already supported several studies, which demonstrates its usefulness for the development of new glottal gap segmentation algorithms from High-Speed-Videoendoscopic sequences to improve or create new Facilitative Playbacks. Despite these advances and others in the field, the broader challenge of performing an accurate and completely automatic semantic segmentation method of the glottal area remains open
Multiscale physiological responses to organic and inorganic pollution in the invasive mosquitofish Gambusia holbrooki
No full textInternational audienceAnthropic activities often lead to the contamination of freshwater ecosystems by organic and inorganic pollutants with potential deleterious effects on wildlife health. However, some species such as the invasive mosquitofish (Gambusia holbrooki) can thrive in such polluted habitats, but the underpinning mechanisms are still unknown. The aim of this study was to characterize the physiological responses of mosquitofish living along different pollution gradients in the south of France. Eleven sites were selected according to various levels of pollutants in the water (pesticides, pharmaceuticals) and in mosquitofish tissue (PAHs, PBDEs, PCBs, organochlorines, metals). The level of the different pollutants varied among sites resulting in contrasted pollution gradients. The biological response of mosquitofish was measured using biomarkers of biotransformation, oxidative status, neurotoxicity and histopathological alteration in gills and liver. Muscle lipids, hepatosomatic condition, body condition and reproductive status were also measured. We used a Structural Equation Modelling (SEM) approach to characterize the direct and indirect effects of pollutants across biological levels. Results showed that high levels of POPs and metals affected biotransformation processes in both sexes, as well as non-enzymatic antioxidants level and resulted in gill histopathological alterations in females. In addition, pesticides increased the energetic demand reflected by reduced lipid storage in females and hepatosomatic condition in males. Interestingly, responses to pollution varied among sexes since females responded to a broader range of pollutant types than males. This study highlights some of the key traits underlying the tolerance to pollution of the mosquitofish, which could partly explain their invasive success in polluted ecosystems
The neural basis of hunger, thirst, and satiety in the insular cortex
No full textInternational audienceBody energy and fluid homeostasis are fundamental for our survival. However, our inability to quantify theinternal states that drive this homeostasis - hunger, thirst, and satiety - has limited our understanding of homeostatic mechanisms. To overcome this, we apply a free feeding and drinking behavioral paradigm combined with a novel hunger-thirst transition model to reveal relative degrees of hunger and thirst. By using this method coupled with in vivo calcium imaging of cells in the insula, a region linked to interoception, we identified specific neural dynamics representing hunger or thirst state through the mapping of population neural activity and hunger/thirst degrees calculated by feeding/drinking behavioral patterns in the Hidden Markov Model. Additionally, we discovered a small, but morphologically diverse, population of glutamatergic leptin receptor (LepR) positive cells in the insula and claustrum (INSLepR cells) that form local connections within the insula and external connections to the basolateral amygdala (BLA). These cells are well suited to directly detect circulating leptin levels as the signal of body fat composition or satiety and to regulate homeostatic ingestive behavior. Leptin administration in the insula selectivelyincreased the intrinsic excitability of INSLepR cells, suppressed feeding, and reduced body weight. Finally,optogenetic stimulation of INSLepR cells or their axonal terminals in the BLA suppressed feeding.Taken together, our data supports a model that insula neural population dynamics represent hunger and thirst internal states, and INSLepR cells integrate satiety signals through direct interoceptive input via leptin to regulate body energy homeostasis
Study of mechanical properties of elementary flax basalt fibres from recycled composites
No full textInternational audienceThis document deals with the study of the mechanical properties of elementary flax and basalt fibres extracted from composites based on thermoplastic polymer matrices, which is a part of RECYCOMP project.The composites from which these fibres will be extracted are pultruded materials produced by the Materials, Metallurgy and Processes Technological Research Institute (IRT M2P). The work presented in this article was carried out as part of the RECYCOMP project, which is the project focusing on composite materials of the French PEPR research programme 'Recyclability, Recycling and Reincorporation of Materials. One of the aims of this project is to find an optimal way of extracting natural and synthetic fibres and to characterise them with a view to their reuse. The targeted extraction method is solvolysis using supercritical water. To validate the extraction method, we are going to carry out tensile tests and morphological analysis on single virgin fibres and extracted fibres from the extraction process. These tests on the fibres, carried out before processing and after extraction, are designed to optimise the solvolysis process to guarantee the performance of the recycled fibre.for different settings of the process parameters
Can motion capture improve task-based fMRI studies of motor function post-stroke? A systematic review
No full textInternational audienceBackgroundVariability in motor recovery after stroke represents a major challenge in its understanding and management. While functional MRI has been used to unravel interactions between stroke motor function and clinical outcome, fMRI alone cannot clarify any relation between brain activation and movement characteristics.ObjectivesWe aimed to identify fMRI and kinematic coupling approaches and to evaluate their potential contribution to the understanding of motor function post-stroke.MethodA systematic literature review was performed according to PRISMA guidelines on studies using fMRI and kinematics in post-stroke individuals. We assessed the internal, external, statistical, and technological validity of each study. Data extraction included study design and analysis procedures used to couple brain activity with movement characteristics.ResultsOf the 404 studies found, 23 were included in the final review. The overall study quality was moderate (0.6/1). Thirteen studies used kinematic information either parallel to the fMRI results, or as a real-time input to external devices, for instance to provide feedback to the patient. Ten studies performed a statistical analysis between movement and brain activity by either using kinematics as variables during group or individual level regression or correlation. This permitted establishing links between movement characteristics and brain activity, unraveling cortico-kinematic relationships. For instance, increased activity in the ipsilesional Premotor Cortex was related to less smooth movements, whereas trunk compensation was expressed by increased activity in the contralesional Primary Motor Cortex.ConclusionOur review suggests that the coupling of fMRI and kinematics may provide valuable insight into cortico-kinematic relationships. The optimization and standardization of both data measurement and treatment procedures may help the field to move forward and to fully use the potential of multimodal cortico-kinematic integration to unravel the complexity of post-stroke motor function and recovery