Science & Mathematics

Si la pratique sportive de compétition revêt une fonction de socialisation (Brustad, 1992), les effets supposés de transformation des attitudes motivationnelles qu’elle est susceptible de produire chez les jeunes sportifs demeurent peu étudiés. S’appuyant principalement sur le cadre théorique de la motivation d’accomplissement de Nicholls (1989), cette recherche a pour objet d'étudier de manière longitudinale, à l'aide de mesures répétées au cours de six trimestres, les rôles de certains agents socialisants ou autrui significatifs (entraîneurs, parents, partenaires) dans l'évolution des orientations de buts d'accomplissement, de l'estime de soi et de l'intention d'abandonner ou de poursuivre la pratique intensive du judo dans les structures fédérales réservées aux jeunes élites. Une première étude a montré que les judokas ayant abandonné le centre d’entraînement percevaient les autrui significatifs comme promouvant moins l’orientation vers la tâche et étaient eux-mêmes moins orientés vers la tâche que ceux ayant persisté sur les deux années. Une seconde étude a mis en évidence qu'au cours de leurs deux premières années de pratique intensive du judo en pôle France ou à l'INSEP, les athlètes percevaient les autrui significatifs comme promouvant de moins en moins les orientations vers la tâche et de plus en plus l'orientation vers l'ego, sans que cela n'entraîne de modifications significatives de leurs propres orientations de buts. Par ailleurs, l’estime globale de soi et certaines de ses composantes telles que les perceptions de condition physique, de compétence sportive et d'apparence physique apparaissaient augmenter au cours de cette période. L’intention d’abandonner la pratique compétitive croissait également de façon constante. Une troisième et dernière étude, testant la stabilité temporelle des modèles d'équations structurales des relations entre les différentes variables étudiées, a montré que les perceptions des rôles des autrui significatifs en termes de promotion des orientations vers la tâche demeuraient des prédicteurs positifs et constants de l’orientation vers la tâche des judokas, tandis que l'orientation vers l’ego de ces derniers était prédite essentiellement, de façon positive, par leur perception de recherche de la comparaison par leurs partenaires. Enfin, sur l'ensemble de la période, les rôles prépondérants des pairs et, de façon plus inattendue, de l’orientation vers l’ego des judokas, comme prédicteurs négatifs de l’intention d’abandonner ont été mis en évidence. Ces résultats ouvrent des perspectives pédagogiques utiles aux entraîneurs de judo soucieux de développer les conditions d'entraînement favorables à la persévérance dans la pratique et au maintien dans un système de formation des jeunes judokas les plus à même de constituer l'élite adulte de demain.

HIV-1 Gag protein orchestrates various steps of virion assembly which include genomic RNA (gRNA) selection accompanied by Gag oligomerization via capsid (CA) domain and plasma membrane (PM) binding via matrix (MA) domain for virion assembly. The selection of gRNA relies on its interaction with the nucleocapsid (NC) domain of Gag bearing two zinc fingers (ZFs). The p6 domain at the C-terminus helps the nascent virion to bud from the PM. It is known that HIV viruses have unique lipid bilayer composition, different from the originating PM. Despite substantial efforts, the roles of each ZF, aromatic amino acid (AA) residues, ZF architecture, Gag oligomerization and MA domain myristylation in Gag-gRNA interaction are still not fully understood. It is also unknown whether the Gag-PM interaction reorganizes the lipid domains of the PM. Our results showed that deletion of both ZFs or the complete NC domain completely abolished the Gag-gRNA interaction. Deletion of either ZF delayed the delivery of gRNA to the PM but did not prevent Gag-gRNA interaction. However, ZF2 played a more prominent role than ZF1 in establishing Gag-gRNA interaction. Furthermore, our data also indicate that gRNA recognition and trafficking to the PM, are governed by ZF motifs with a key role of the Tryptophan 37 in the second ZF and the ZFs architecture. Interestingly, non-myristoylated Gag was found to interact with the gRNA, whereas, non-oligomerized Gag was found to interact with the gRNA only at the PM. Furthermore, our data indicate that the Gag bound to the PM inner leaflet colocalized well with outer leaflet sphingomyelin (SM)-rich domains. Moreover, Gag-bound SM rich domains were larger than the SM domains in the absence of Gag. Further analysis revealed that the binding of Gag to the inner leaflet of the PM restricted the lateral diffusion and induced the coalescence of outer leaflet SM-rich domains. Finally, we showed that Gag oligomerization induces the coalescence of SM-rich and cholesterol-rich lipid domains.

Introduction : la stomatodynie primaire est une pathologie chronique caractérisée par une gêne intense dans la cavité buccale associée à une altération de la qualité de vie. L’absence de test diagnostique spécifique conduit à une errance diagnostique des patients. L’objectif de cette étude était de développer un score diagnostique simple et applicable en pratique clinique quotidienne. Matériels et méthodes : cette étude a été menée dans service de chirurgie orale du CHU de Bordeaux. Les patients éligibles consultaient pour une gêne dans la cavité buccale de plus de 3 mois auto-évaluée à 4/10 au moins. Un questionnaire évaluant la présence des symptômes les plus décrits dans la stomatodynie primaire a été administré à chaque participant par un praticien non formé, puis par un senior référent de la stomatodynie. Résultats : au total, 158 patients ont été inclus. Le score diagnostique retenu se composait de 6 items. Un score ≥ 5 marquait la présence d’une stomatodynie primaire (AUROC=82 %, Se=84 [69–94] %, Sp=78 [52–94] %, valeur prédictive positive=89 [74–97] %, valeur prédictive négative=70 [46–88] %). Discussion : il existe trois types de stomatodynies primaires dans lesquelles la douleur évolue différemment au cours de la journée, ce qui pourrait expliquer la perfectibilité de la sensibilité du score développé dans cette étude. Conclusion : ce score diagnostique pourrait faciliter le diagnostic de la stomatodynie. D’autres études sont nécessaires afin de tester la pertinence de ce score diagnostique dans la pratique quotidienne.

La Syrie centrale connaît à la fin de l’Antiquité, et en particulier au Ve et au VIe siècle, un fort mouvement d’expansion des sédentaires vers l’est, qui coïncide avec une importante mise en valeur de ces nouveaux territoires. Comme pour d’autres régions de l’espace méditerranéen et du Proche-Orient en particulier, à la même époque, un optimum climatique – pourtant déclinant – semble avoir permis la conquête et l’exploitation agricole de nouveaux terroirs dans une zone marginale qui n’avait jusqu’alors connu qu’une occupation sédentaire ponctuelle (hormis à l’âge du Bronze). La Syrie centrale est caractérisée par des milieux aux potentiels agronomiques très différents, souvent imbriqués. Le peuplement et la mise en valeur y sont soumis à la double contrainte de l’aridité climatique et édaphique, qui s’exerce avec une prégnance croissante vers le sud et l’est. Ces conditions, qui s’améliorent localement à la faveur de niches écologiques, ont permis à des politiques de mise en valeur et à des économies distinctes, souvent complémentaires, de voir le jour. Dans une région où les cités paraissent en grande partie absentes, l’économie antique repose d’abord sur les villages et sur quelques bourgs qui possédaient manifestement une orientation commerciale spécifique. Aux côtés des agglomérations, et souvent d’autant plus nombreux que les conditions d’implantation sont délicates, des fermes et des monastères s’affirment comme des acteurs économiques apparemment indépendants et souvent prospères. Des ensembles géographiques relativement homogènes ont donné lieu à une répartition spécifique des différentes formes de peuplement et à des économies microrégionales originales. Si l’agriculture vivrière reste la règle, il semble bien cependant qu’on observe une spécialisation locale des productions : culture du blé et accessoirement plantations à l’ouest, oléiculture et peut-être viticulture dans les plateaux basaltiques du nord-ouest et vraisemblablement un élevage spéculatif, qu’on doit vraisemblablement attribuer à des populations sédentaires, dans les secteurs sud et est de la région étudiée.

Agonists of the β2 adrenergic receptor (ADRB2) are an important class of medications used for the treatment of respiratory diseases. They can be classified as short acting (SABA) or long acting (LABA), with each class playing a different role in patient management. In this work we explored both ligand-based and structure-based high-throughput approaches to classify β2-agonists based on their duration of action. A completely in-silico prediction pipeline using an AlphaFold generated structure was used for structure-based modelling. Our analysis identified the ligands’ 3D structure and lipophilicity as the most relevant features for the prediction of the duration of action. Interaction-based methods were also able to select ligands with the desired duration of action, incorporating the bias directly in the structure-based drug discovery pipeline without the need for further processing.

This paper presents the main results obtained while studying the fusarium-wilt suppressiveness of Chateaurenard soil. Experimental data are discussed in relation to the main theories developed to explain the phenomena ot soil suppressiveness to fusarium wilts. This suppressiveness, based fundamentally on microbiological interactions, relies on the complementary association of a general mechanism of competition for nutrients between the whole soil microflora and the entire Fusarium population and intrageneric competition between pathogenic and non-pathogenic Fusarium. This research has led to new approaches for microbiological control of fusarium wilts.

In his 1971's Dynamic Models of Segregation paper, the economist Thomas C. Schelling showed that a small preference for one's neighbors to be of the same color could lead to total segregation, even if total segregation does not correspond to individual preferences and to a residential configuration maximizing the collective utility. The present work is aimed at deepening the understanding of the properties of dynamic models of segregation based on Schelling's hypotheses. Its main contributions are (i) to offer a comprehensive and up-to-date review of this family of models ; (ii) to provide an analytical solution to the most general form of this model under rather general assumptions ; to the best of our knowledge, such a solution did not exist so far ; (iii) to analyse the effect of two devices aimed at decreasing segregation in such a model. Chapter one summarizes the ingredients of Schelling's models. We show how the choices of the agent's utility function, of the neighborhood description and of the dynamical rule can impact the outcome of a model. Based on the observation of simulations' results, we find that the neighborhood description does not have a qualitative impact. As regards the dynamical rules, we show that the Logit Behavioral rule introduced in this literature by Young (1998) ; Zhang (2004b) presents several advantages relatively to the Best Response rule. Chapter two presents a general analytical solution to the model. To that aim, Schelling's model is recasted within the framework of evolutionary game theory, as previously done by Young (1998) ; Zhang (2004b). This allows to define sufficient assumptions regarding agents' utility functions that permit predicting the final state of the system starting from any configuration. This analytical resolution is then used to consider the outcomes of Schelling's utility function and of other utility functions previously used in this context. Chapter three examines the effects of introducing coordination in the moving decisions. This coordination is achieved through two different ways. We first impose different levels of taxes proportional to the externality generated by each move of the agents. It is shown that even a low level of tax is sufficient under certain circumstances to significantly reduce segregation. We then investigate the effect of the introduction of a local coordination by vote of co-proprietors, who are defined as the closest neighbors of each agent. It is shown that even a small amount of coordination can break segregation.

The whole collection of Suidae from Kanapoi is revised in the context of the systematics and evolution of Nyanzachoerus in the Pliocene of Eastern Africa. It contains only two species, Nyanzachoerus kanamensis and Notochoerus jaegeri. The size and morphology of their premolars overlap, but not those of their m3s. No transitional form between them is known in Kenya, but some populations from Uganda and Ethiopia display intermediate characters, suggesting that No. jaegeri could be descended from a kanamensis-like ancestor. However, the cranial remains of No. jaegeri from Kanapoi are insufficient to formally establish the affinities of the species. On the basis of the dentition, Notochoerus euilus could be descended from No. jaegeri. The noticeable absence of Kolpochoerus at Kanapoi (and in the whole Turkana Basin at that time) remains unexplained. The presence of a species with affinity to Nyanzachoerus tulotos at Ekora raises the possibility that uppermost Miocene sediments occur there.

Value-based decision-making involves trading off the cost associated with an action against its expected reward. Research has shown that both physical and mental effort constitute such subjective costs, biasing choices away from effortful actions, and discounting the value of obtained rewards. Facing conflicts between competing action alternatives is considered aversive, as recruiting cognitive control to overcome conflict is effortful. Moreover, engaging control to proactively suppress irrelevant information that could conflict with task-relevant information would presumably also be cognitively costly. Yet, it remains unclear whether the cognitive control demands involved in preventing and resolving conflict also constitute costs in value-based decisions. The present study investigated this question by embedding irrelevant distractors (flanker arrows) within a reversal-learning task, with intermixed free and instructed trials. Results showed that participants learned to adapt their free choices to maximize rewards, but were nevertheless biased to follow the suggestions of irrelevant distractors. Thus, the perceived cost of investing cognitive control to suppress an external suggestion could sometimes trump internal value representations. By adapting computational models of reinforcement learning, we assessed the influence of conflict at both the decision and learning stages. Modelling the decision showed that free choices were more biased when participants were less sure about which action was more rewarding. This supports the hypothesis that the costs linked to conflict management were traded off against expected rewards. During the learning phase, we found that learning rates were reduced in instructed, relative to free, choices. Learning rates were further reduced by conflict between an instruction and subjective action values, whereas learning was not robustly influenced by conflict between one's actions and external distractors. Our results show that the subjective cognitive control costs linked to conflict factor into value-based decision-making, and highlight that different types of conflict may have different effects on learning about action outcomes.

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The purpose of this review is to focus from an experimental point-of-view on the new physical properties of some of the thinnest superconducting films that can be fabricated and studied in situ nowadays with state-of-the-art methods. An important characteristic of the films we address is that the underlying electronic system forms a two-dimensional electron gas (2DEG). Up to now there are only few of these systems. Such true 2D superconductors can be divided into two classes: surface-confined or interface-confined films. Because the second types of films are burried below the surface, they are not accessible to purely surface-sensitive techniques like angular-resolved photoemission spectroscopy (ARPES) or scanning tunneling spectroscopy (STS). As a consequence the bandstructure characteristics of the 2DEG cannot be probed nor the local superconducting properties. On the other hand, in situ prepared surface-confined films are nowadays accessible not only to ARPES and STS but also to electrical transport measurements. As a consequence surface-confined systems represent at present the best archetypes on which can be summarized the new properties emerging in ultimately thin superconducting films hosting a 2DEG, probed by both macroscopic and microscopic measurement techniques. The model system we will widely refer to consists of a single atomic plane of a conventional superconductor, like for example lead (Pb), grown on top of a semiconducting substrate, like Si(111). In the introductory part 1 we first introduce the topic and give historical insights into this field. Then in the section 2, we introduce useful concepts worked out in studies of so-called 'granular' and 'homogeneous' superconducting thin films that will be necessary to understand the role of non-magnetic disorder on 2DEG superconductors. In this section, we also briefly review the superconducting properties of crystalline Pb/Si(111) ultrathin films grown under ultrahigh vacuum (UHV) conditions in order to illustrate their specific properties related to quantum-size effects. In the next section 3 we review the growth methods and structural properties of the presented 2DEG surface-confined superconductors. In section 4, we review the electronic structure and Fermi surface properties as measured by macroscopic ARPES and confront them to ab initio DFT calculations based on the characterized atomic structures of the monolayers. The following section 5 reviews the macroscopic properties inferred from in situ electrical transport measurements methods, including attempts to study the Berezinsky–Kosterlitz–Thouless 2D regime. In the last section 6, we summarize the emerging local spectroscopic properties measured by STS. These latter demonstrate variations of the local superconducting properties at a scale much shorter than the superconducting coherence length due to a combined effect of non-magnetic disorder and two-dimensionality. Further peculiar local spectroscopic effects are presented giving evidence for the presence of a mixed singlet-triplet superconducting order parameter induced by the presence of a strong Rashba spin–orbit coupling term at the surface. These local signatures will be discussed along with ARPES and transport measurements in parallel high magnetic field on closely related systems. Finally, we present in anisotropic Pb and In monolayers the peculiar role played by atomic steps on vortex properties, leading to the observation by STS of mixed Abrikosov–Josephson vortices in agreement with in situ macroscopic transport measurements. From the overview of all recent experimental and theoretical results it appears that these surface 2D superconductors, such as one monolayer of Pb on Si(111), are ideal templates to engineer and realize topological superconductivity.

L'autel commémoratif du mémorial du massacre de Nankin est un autel honorant les âmes des victimes du massacre qui a eu lieu entre le 13 décembre 1937 et février 1938 pendant la guerre sino-japonaise.