Portail HAL UHA (Université de Haute-Alsace)
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À la recherche de la transition de Lifshitz par intercalation d’Erbium dans une nouvelle structure de supergraphène
No full textThis thesis is part of an ongoing effort to investigate the properties of graphene at critical points in its band structure, particularly in the region of the highly electron-doped regime where the van Hove singularity and the Lifshitz transition occur. In this region, the Fermi surface can have a non-dispersive region with "flat" bands, where strong electron-electron correlation effects are expected, promoting the emergence of novel physical properties. We have studied the functionalization of epitaxial graphene on SiC(0001) by intercalation of Erbium, reaching a record doping level of 5.17 × 10¹⁴ e⁻/cm². The Fermi surface, measured by ARPES, shows a flat band around the M point of the Brillouin zone, indicating that the system has passed the Lifshitz transition. Using STM and LEED, we observed a new ordered superstructure (5.75 × 5.75R ±19°-G), forming a honeycomb arrangement with a lattice constant of 1.4 nm. XMCD measurements on the DEIMOS beamline at the SOLEIL synchrotron revealed that Er is in a trivalent state (Er³⁺), exhibiting paramagnetic behaviour and an antiferromagnetic (AF) transition at 12 K. By modifying the band structure of graphene by hydrogenation, we show that it is possible to modify the AF transition temperature. Furthermore, we highlight the RKKY interaction between the localized 4f orbitals of intercalated Er atoms, mediated by the π electrons of graphene. Finally, we show that it is possible to dope graphene from the Dirac point up to the Lifshitz transition. This new material paves the way for significant experimental and theoretical research opportunities.Ce travail de thèse s’inscrit dans la dynamique actuelle qui consiste à explorer les propriétés du graphène à des points critiques de sa structure de bande, notamment dans la zone de très fort dopage en électron où se produisent la singularité de van Hove puis la transition de Lifshitz. Dans cette zone, la surface de Fermi présente une région non dispersive où les bandes sont « plates » et où d'importants effets de corrélation électron-électron sont attendus, favorisant l'émergence de nouvelles propriétés physiques. Nous avons étudié la fonctionnalisation du graphène épitaxié sur SiC(0001) par intercalation d'Erbium, ce qui a permis d'atteindre un dopage record de 5,17 × 10¹⁴ e⁻/cm². La surface de Fermi, mesurée par ARPES, montre une bande plate autour du point M, indiquant le dépassement de la transition de Lifshitz. Nous avons observé, par STM et LEED, une nouvelle surstructure ordonnée (5,75 × 5,75R ±19°-G), formant un réseau en nid d'abeille avec un paramètre de maille de 1,4 nm. Les mesures XMCD sur la ligne DEIMOS du synchrotron SOLEIL ont révélé que l'Er est dans un état trivalent (Er³⁺), avec des propriétés paramagnétiques et une transition antiferromagnétique AF à 12 K. En modifiant la structure de bande du graphène par hydrogénation, nous démontrons qu’il est possible de changer la température de transition AF. Nous montrons ainsi une interaction RKKY entre les orbitales localisées 4f des atomes d'Er intercalés, médiée par les électrons π du graphène et qu'il est possible de doper le graphène depuis le point de Dirac jusqu’à la transition Lifshitz. Ainsi, ce nouveau matériau ouvre d'importantes perspectives de recherche, tant expérimentales que théoriques
Do endorsers contribute to the social standing of brands? Exploring social judgments about celebrities versus influencers
No full textInternational audienceAs part of their institutional work, brands mobilize their social standing to signal their value, societal appropriateness, and power to consumers. Drawing on the microfoundations of social judgment, this study describes celebrities and influencers as two distinct categories of brand endorsers in terms of legitimacy, reputation, and status and explores how these consumer judgments affect brand social standing. A mixed-methods approach is used to investigate the structure of endorsers’ social judgments, based on a qualitative study and lexicometric analysis of a 726-consumer panel. The results show that social judgments exhibit contrasting poles of meaning depending on the endorser category. Celebrity endorsers are brand-centered with abstract and symbolic legitimacy, whereas influencer endorsers exhibit concrete and product-centered legitimacy. In terms of reputation and status, celebrity endorsers are perceived as having a positive reputation and high status, while influencers are judged as more nuanced, with reality TV influencers potentially damaging brand image because of reputational stigma. This study extends the literature on advertising endorsement by offering insights into the endorser legitimacy construct as a form of brand-endorser congruency, whose strength and construal level depend on the endorser category. It provides new findings on the social comparison processes involved in brand endorsement and the contamination of negative biases. At the level of brand management, the study clarifies the nature of the complementarity of the two endorser categories and the tensions that their coexistence can engender. From a managerial perspective, the study delineates multi-endorsement brand strategies and the risks associated with influencer partnership
"Vous ne passerez pas!". Les réponses du droit pénal face aux intrusions au sein des installations nucléaires
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"Entre les Etats-Unis et l’Europe, le fossé idéologique et juridique se creuse"
No full textInternational audienc
Carbon/titanium-based composite materials as negative electrodes for sodium-ion batteries
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Comparative study of biogas treatment in dry and wet conditions using modified activated carbons of CNR-115 family
No full textInternational audienceThis study investigates the effect of water vapor on the adsorption performance of modified activated carbons (ACs) from the CNR-115 family (CNR-115-ox and CNR-115-ox-am), derived from the commercial AC (CNR-115), for CO2 /CH4 separation. Breakthrough curve analysis at 0.1 MPa and 303 K showed that CO 2 consistently exhibited higher breakthrough and saturation times than CH4 , indicating stronger interactions with adsorbents of the CNR-115 family. The presence of water vapor in experiments with a 39%/59%/2% (vol.) CO2 /CH4 /H2 O mixture significantly impacted CO2 adsorption, enhancing its retention and selectivity. Under dry conditions, CNR-115-ox demonstrated higher separation efficiency due to its large BET surface area, while CNR-115-oxam showed increased CO2 adsorption capacities and selectivity under wet conditions. This improvement in performance under moist conditions is likely due to bicarbonate formation, which promotes CO2 retention. Moreover, experiments under wet conditions revealed a roll-up effect for CH4 and a slight roll-up for CO2, caused by co-adsorption of H2O. The findings emphasize the importance of considering water vapor in biogas upgrading processes to optimize adsorbent design and improve CO2 separation efficiency. Furthermore, the increased CO2 adsorption per unit area under both dry and wet conditions for CNR-115-ox-am, despite its lower BET surface, underscores the dominant influence of surface chemistry over porosity in gas adsorption. This improvement, driven by nitrogen functionalization, enhances both selectivity and adsorption efficiency, making CNR-115-ox-am a promising material for biogas upgrading applications
La délégitimation des élections et du juge électoral dans le contexte des ingérences étrangères
No full textInternational audienc
Canoniser les marges. Le monde des éditions féministes : La Tartaruga, les Edizioni delle Donne et VandA Edizioni
No full textInternational audienceFrom the very beginning, the feminist movement has sought to challenge and redefine societal norms, including in the world of publishing. From the 1970s onwards, women’s and feminist publishing houses, such as La Tartaruga, Edizioni delle Donne and VandA Edizioni, played a crucial role in disseminating works that challenged the canon, but failed to create one of their own. Is feminism, by its militant nature, condemned to remain on the margins of the literary system?Depuis ses débuts, le mouvement féministe cherche à questionner et à redéfinir les normes sociétales, y compris dans le monde éditorial. Les éditions féminines et féministes, comme La Tartaruga, les Edizioni delle Donne et VandA Edizioni, ont joué, dès les années 70, un rôle crucial en diffusant des œuvres qui défient le canon, sans pour autant arriver à en créer un d’elles-mêmes. Le féminisme, de par sa nature militante, serait-il destiné à rester aux marges du système de la littérature
