Portail HAL UNIV-RENNES
Not a member yet
180610 research outputs found
Sort by
Universal Electromagnetic Reference Skin Model for APD Evaluation at 6–100 GHz
No full textInternational audienceThe increasing use of the upper part of the microwave spectrum for wireless communications requires appropriate methods and instrumentation for user exposure assessment. In this context, the IEC TC106 is developing a new international standard for user exposure compliance testing of the next generation 5G/6G wireless devices operating above 6 GHz. As a part of this initiative, the development of a universal reference skin model (RSM) is fundamental for definition of reference data to be included in specifications for body phantom design. In this study, we systematically analyze the impact of the human body near-surface tissue structure on the electromagnetic field (EMF) reflection from the skin surface in the 6–100 GHz range. A conventional multi-layer model is used to calculate skin reflectance as a function of the tissue thickness for the range of thicknesses corresponding to that of typical human skin and near-surface body tissues at four body sites concerned by the 5G/6G wireless use-case scenarios, namely: head, torso, forearm, and palm. The dominant contribution from the epidermis/dermis (ED) layer to the skin reflectance is demonstrated for all body sites in the considered frequency range. A high variation in the reflectance of the palm skin at frequencies above 20 GHz is demonstrated and explained by the matching layer effect associated with a thick stratum corneum (SC). The dry skin model, represented by a semi-infinite homogeneous medium with complex permittivity equivalent to that of the ED tissue, is shown to be an appropriate RSM both for the experimental and numerical evaluation of the absorbed power density (APD) in the 6–100 GHz range. The reference data for the antenna loading and APD at the skin surface are provided for standard reference feeds at 10 GHz, 30 GHz, 60 GHz, and 90 GHz
A kinetic model for polyatomic gas with quasi-resonant collisions leading to bi-temperature relaxation processes
No full textIn this article, we extend the Boltzmann framework for polyatomic gases by introducing quasi-resonant kernels, which relax resonant interactions, for which kinetic and internal energies are separately conserved and lead to equilibrium states with two temperatures. We establish an H-theorem and analyze the quasi-resonant model's asymptotic behaviour, demonstrating a two-phase relaxation process: an initial convergence towards a two-temperature Maxwellian state followed by gradual relaxation of the two temperatures towards each other. Numerical simulations validate our theoretical predictions. The notion of quasi-resonance provides the first rigorous framework of a Boltzmann dynamics for which the distribution is at all times close to a multi-temperature Maxwellian, relaxing towards a one-temperature Maxwellian
CSI Prediction With a Single AI Model for Heterogeneous Doppler Frequencies and Multipaths
No full textInternational audienceAccurate channel prediction is increasingly impor-tant, especially in scenarios where a user equipment (UE) operatesat varying speeds, impacted by high Doppler shifts and channeldynamics. While AI-based techniques offer promising solutions,training a single model to handle different propagation pathsand a wide range of UE velocities remains challenging. Inthis work, we present a CSI prediction technique that takesadvantage of the inherent sparsity found in millimeter-waveand 5G systems. While this approach improves performance indynamic environments, models trained at specific velocities oftenstruggle to be generalized at different speeds. To overcome thislimitation, we propose a Doppler downshifting technique, whichserves as a unified AI model to enhance generalizability acrossvarious Doppler values, thereby reducing both model complexityand data requirements
The role of branching on the ultrafast dynamics and 2-photon absorption of two pyrimidine push-pull molecules
No full textInternational audienceThe dynamics and two-photon absorption (2PA) properties of two pyrimidine chromophores are studied using femtosecond time-resolved fluorescence and two-photon excited fluorescence techniques. The pyrimidine is used as an electron withdrawing group and is substituted at the C2 position with a phenylacridan fragment, while diphenylaministyryl donor moieties are appended at positions C4/6 to afford the pseudo-dipolar and pseudo-quadrupolar molecules 1 and 2, respectively. Chromophore 2 shows more efficient fluorescence emission, while 1 exhibits larger Stokes shifts. Their decay pathways are discussed through an emission from a Franck-Condon charge transfer (FC-CT) and a relaxed charge transfer (R-CT) state. Ultrafast dynamics in tetrahydrofuran show population of the R-CT state for 1 that is faster than solvation, while for 2, due to its pseudo-quadrupolar nature, R-CT population is slower and occurs from the solvated FC-CT state. Finally, molecule 2 shows better 2PA properties with cross sections reaching 560 GM at 820 nm
Studying the Perception of Vibrotactile Stimulation on the Arm via a Modular Wearable Sleeve
No full textInternational audienceThis study investigates the perception of vibrotactile stimulation on the human arm using a modular wearable sleeve equipped with vibrotactile actuators. We examined three perceptual aspects: vibration localization, apparent haptic motion (AHM), and two-point discrimination (2PD). Our findings indicate that users can accurately identify the location of four distinct vibrotactile stimuli with over 95% accuracy across the wrist, forearm, upper arm, and shoulder. Additionally, participants demonstrated reliable perception of apparent motion, though minor misclassifications in directional cues were observed in the upper arm and shoulder regions. The two-point discrimination results revealed that spatial acuity decreases from the wrist to the upper arm, with the shoulder exhibiting better discrimination than expected. These findings provide preliminary insights for the design of wearable haptic feedback systems in applications such as rehabilitation, virtual reality, and assistive navigation
Early-Life Exposure to Organophosphate Esters and Child Neurodevelopment in the French National Birth Cohort
No full textInternational audienceOrganophosphorus esters (OPEs) are ubiquitous flame retardants and/or plasticizers, raising concerns regarding their possible neurodevelopmental toxicity.We aimed exploring association between pre- and post-natal exposure to OPEs and cognitive abilities among 3.5-year-old children.We included 381 mother-child pairs from the French ELFE national birth cohort. Pre- and post-natal exposures were estimated using concentrations of 9 OPEs measured in the hair of mothers collected at birth and children at age 3.5. Children’s cognitive development was evaluated using the Picture Similarities Test (PST) from the British Ability Scale. Analyses were weighted in order to transpose results to French births in 2011. For each OPE, the association with PST scores was assessed by linear regression accounting for DAG-selected adjustment covariables.The only observed association between prenatal exposure to OPEs and PST score was a decrease of 4.5 points (95%CI: -8.8, -0.3) among the 25% of mothers having the highest hair-concentrations of tri-n-butyl phosphate (TBP) versus the 25% having the lowestones. Regarding childhood exposure, we observed a decrease (-1.9 points, 95%CI: -3.0, -0.8) in PST score per twofold increase in children’s hair-concentrations of ethylhexyl diphenyl phosphate (EHDPP). Decreased scores were also observed for higher childhood exposure levels for triphenyl phosphate (TPHP). An increase in the PST score was observed for intermediate childhood exposure levels for tris(2-chloropropyl) phosphate (TCPP).Due to the ubiquitous exposure of the general population, however, further studies are urgently required to assess various subdomains of cognition before any robust conclusions on the neurodevelopmental risks of these compounds can be drawn
Le vivre ensemble en entreprise vu par les salariés de premier niveau de qualification : une construction pyramidale*
No full textInternational audienceThe notion of “living together” commonly refers to “a peaceful cohabitation between individuals or communities” (Larousse, 2022). Although schools have long been considered as the main place where this “living together” is taught and learned, it has gradually taken over other spheres of socialization, including the workplace. In a context where relationships are evolving – mostly due to the popularizationof telecommuting or the promotion of diversity – the notion of “living together” raises new managerial issues, especially in terms of team management. As a result, the notion of “living together” intrigues Management Sciences, which still struggle to make it concrete. As a result, and to better understand what the notion of “living together” means in the workplace, we aspire to make it concrete by offering an interpretative framework to the notion. Based on a literature review on themes related to thenotion of “living together”, this framework consists of five elements: conviviality, the acceptance of differences, recognition, autonomy, and work-life balance. This framework was then empirically tested with 48 unqualified workers. The aim was to validate, complete, or even invalidate our interpreta-tive framework. The interviews conducted showed that, for these workers, the notion of “living together” within the workplace remains close to the one within the society. Indeed, both refers to the idea of a peaceful cohabitation between individuals. However, because it is part of a specific context, workersidentified specificities to the notion of “living together” within the workplace. In fact, if the notion of “living together” within the workplace consists of the five elements presented in our interpretative framework, it eventually follows a pyramid-shaped construction, where each element is presented as a prerequisite for the next to be achievedDans sa définition usuelle, le « vivre ensemble » renvoie à une « cohabitation harmonieuse entre individus ou entre communautés » (Larousse, 2022). Si l’école est longtemps restée le haut lieu d’apprentissage du « vivre ensemble », il a néanmoins progressivement investi d’autres lieux de socialisation, notamment l’entreprise. En effet, dans un contexte de mutation des rapports au travail engendrée par l’essor du télétravail, ou de promotion de la diversité ; le « vivre ensemble » engage de nouvelles problématiques managériales, notamment en termes de gestion des équipes. Conséquence de quoi, le « vivre ensemble » interroge de plus en plus les Sciences de Gestion qui peinent pourtant à le rendre tangible. Ainsi et afin de mieux appréhender ce à quoi renvoie le « vivre ensemble » en entreprise, cet article propose de le rendre tangible, en en proposant une grille de lecture. Élaborée grâce à une revue de la littérature sur des thèmes connexes au « vivre ensemble », cette grille de lecture s’articule autour de cinq éléments : la convivialité, l’acceptation des différences, la reconnaissance, l’autonomie, et la conciliation vie personnelle et vie professionnelle. Cette grille de lecture a ensuite été testée empiriquement auprès de 48 salariés occupant des emplois de premier niveau de qualification – ce afin de la valider, de la compléter, voire de l’infirmer. Il ressort des entretiens menés que, pour les salariés, le« vivre ensemble » qu’il soit compris dans l’entreprise ou dans la société renvoie à l’idée d’une cohabitation harmonieuse. Toutefois, parce qu’il s’inscrit dans un contexte particulier – le travail – les salariés ont identifié des spécificités au « vivre ensemble » en entreprise. S’il se compose biendes cinq éléments identifiés dans notre grille de lecture, il reposerait sur une construction pyramidale où chaque élément se présenterait comme un préalable indispensable pour que le suivant puisse se réaliser
Functional Analysis of HSD17B3-Deficient Male Mice Reveals Roles for HSD17B7 and HSD17B12 in Testosterone Biosynthesis
No full textInternational audienceHistorically, 17β-hydroxysteroid dehydrogenase type 3 (HSD17B3) was thought to be the key enzyme responsible for testicular testosterone production. In humans, loss-of-function mutations in HSD17B3 impair testosterone production during prenatal life leading to impaired development of androgen-dependent tissues in 46,XY individuals. However, male mice with HSD17B3 deficiency exhibit normal testicular testosterone concentrations, normal development of reproductive organs and are fertile, suggesting that mice express other hydroxysteroid dehydrogenase enzymes capable of testicular testosterone synthesis. This study aimed to investigate whether 17β-hydroxysteroid dehydrogenase type 12 (HSD17B12), which can convert androstenedione to testosterone in mice but not in humans, compensates for the lack of HSD17B3 in Hsd17b3 knockout (KO) mice. We used CRISPR/Cas9 to substitute the amino acid in mouse HSD17B12 that is responsible for its ability to convert androstenedione to testosterone with the amino acid of the human enzyme that prevents androstenedione being used as a substrate. When this Hsd17b12 mutation was introduced into Hsd17b3 KO mice, males exhibited normal reproductive tracts but reduced testicular testosterone production with a consequential reduction in seminal vesicle weight. This suggests HSD17B12 contributes toward testosterone production in the absence of HSD17B3, but other enzymes must also contribute. We therefore quantified other testicular hydroxysteroid dehydrogenases, finding that HSD17B7 mRNA and protein was markedly upregulated in Hsd17b3 KO testes. We confirmed that mouse, but not human, HSD17B7 can produce testosterone in vitro. We conclude that compared to humans, mice exhibit increased plasticity in testosterone production via hydroxysteroid dehydrogenase enzymes to support androgen action and male fertility
L'apport de la micromorphologie à l'étude des structures de crémation. Cas du bûcher funéraire du Bronze moyen de la ZAC « Val-Vert – Croix Blanche » (Le Plessis-Pâté, Essonne) et de l'aire de crémation de la nécropole antique de « l'avenue Édouard Herriot » (Vannes, Morbihan)
No full textInternational audienceL'approche présentée, inscrite dans des problématiques relevant de l'archéologie funéraire couplées à celles de la géoarchéologie, a pour objectif la restitution des modes de fonctionnement de structures de crémation par le biais de l'analyse micromorphologique.À travers deux cas concrets, nous présentons le type de données que nous pouvons obtenir par de telles analyses et lesinterprétations envisageables qui en découlent.Le premier exemple porte sur le bûcher funéraire de la nécropole de l'âge du Bronze moyen de la ZAC « Val-Vert » au Plessis-Pâté (91), dont l'étude micromorphologique révèle un potentiel usage multiple et des parois non construites. Le second exemple concerne la nécropole antique de « l'avenue Édouard Herriot » à Vannes (56), dont l'analyse du comblement du lieu de crémation permet de définir plus précisément une succession sédimentaire litée, traduisant une alternance de plusieurs phases successives de crémation et de périodes d'abandon durant lesquelles la structure, après curage, semble rester ouverte et exposée aux intempéries
Deep Dust – An ICDP Drilling Project to Probe Continental Climate from the Late-Paleozoic Icehouse to the end-Permian Hothouse
No full textInternational audienceThe Permian witnessed some of the most profound climatic, biotic, and tectonic events in Earth’s history. Global orogeny leading to the assembly of Pangea culminated by middle Permian time, and included multiple orogenic belts in the equatorial Central Pangean Mountains, from the Variscan-Hercynian system in the East to the Ancestral Rocky Mountains in the West. Earth’s penultimate global icehouse peaked in early Permian time, transitioning to full greenhouse conditions by late Permian time, constituting the only example of icehouse collapse on a fully vegetated Earth. The Late Paleozoic Ice Age was the longest and most intense glaciation of the Phanerozoic. Reconstructions of atmospheric composition in the Permian record the lowest CO2 and highest O2 levels of the Phanerozoic, with average CO2 levels comparable to the Quaternary, rapidly warming climate. Fundamental shifts occurred in atmospheric circulation: a global megamonsoon developed, and the tropics became anomalously arid with time. Extreme environments are well documented in the form of voluminous dust deposits, acid-saline lakes and groundwaters, extreme continental temperatures and aridity, and major shifts in biodiversity, ultimately culminating in the largest extinction of Earth history at the Permian-Triassic boundary.The Deep Dust project seeks to elucidate paleoclimatic conditions and forcings through the Permian at temporal scales ranging from millennia to Milankovitch cycles and beyond by acquiring continuous core in continental lowlands known to harbor stratigraphically complete records dominated by loess and lacustrine strata. Our initial site is in the midcontinental U.S.— the Anadarko Basin (Oklahoma), which harbors a complete continental Permian section from western equatorial Pangaea. We will also address the nature and character of the modern and fossil microbial biosphere, the chemistry of saline lake waters and groundwaters, Mars-analog conditions, and exhumation histories of source regions. Importantly, data from Deep Dust will be integrated with Earth-system modelling. This is crucial for putting the (necessarily local) drill core data into the broader global context and for understanding relevant mechanisms and feedbacks of the Permian Earth system