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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Cognitive mechanisms underlying the determining of relevance : the causal role of body states / Pertinence des signaux sociaux pour l'observateur : Rôle de la posture et mécanismes sous-jacents

Chadwick, Michèle 17 September 2015 (has links)
La quantité d’informations à laquelle nous sommes chaque jour confrontésconditionne notre survie à la capacité de détecter rapidement ce qui est le pluspertinent dans notre environnement. Nos cerveaux ont ainsi évolué afin dedéclencher, en réponse aux stimuli pertinents, des changements d’état affectif quinous informent alors de l’existence et de la nature de ces stimuli. Or, tandis que lesétats émotionnels, induits par des états corporels, impactent notre perception desstimuli émotionnels, l’influence de ces états corporels sur l’évaluation de lapertinence de stimuli externes est méconnue. Nous avons ici examiné le rôle queces états du corps, transitoires et socialement signifiants, jouent dans l'évaluation dela pertinence des expressions faciales de menace. Lors de nos testscomportementaux, où variaient le degré de pertinence des stimuli et le focusattentionnel, nous avons modulé l'état corporel des participants à l’aide de posturesdominantes ou non dominantes réalisées avant les tâches. Nous avons alorsdémontré que ces postures influencent l'évaluation de la pertinence des expressionsde menace, en accord avec le statut social qu’elles incarnent. De plus, ceci n’a étérévélé que lorsque le traitement de ces stimuli était implicite, soulignant alors lasaillance de ces derniers. Ainsi, nos résultats démontrent que les états corporelsinfluencent non seulement l'évaluation de la pertinence, mais la déterminent, car desstimuli par ailleurs pertinents ne sont plus évalués comme tels selon la postureadoptée. Ces résultats suggèrent que l’état du corps interagit avec nos états affectifspour signaler à l’observateur quels indices sociaux sont pertinents. / Given the quantity of information with which we are constantly confronted, our survival depends on the ability to rapidly detect and attend to what is most relevant. To this end, our brains have evolved to trigger changes in our affective state in response to relevant objects and events, which inform us of their existence and of their nature. While body-induced affective states impact the perception of congruent emotional stimuli, it is still unknown whether body-induced affective states influence the manner in which the relevance of external stimuli is determined and therefore perceived. Here, we examined the role that socially meaningful transient body states play in the evaluation of relevance of facial displays of threat. In a series of behavioral experiments, we modulated participants’ body state, instructing them to hold dominant or non-dominant postures prior to behavioral tests, in which we varied the degree of relevance of the stimuli and the focus of attention. We first demonstrated that these body postures, in accordance with the social status they embody, influenced the evaluation of the relevance of threatening facial displays. Moreover, this impact occurred where facial displays were processed implicitly, highlighting the saliency of these social cues. Overall, our studies demonstrate, that body states, not only influence the evaluation of relevance, but determine it, as otherwise relevant social cues, were no longer evaluated as such. These findings suggest that body states interact with affective states to signal which social cues are relevant to the observer.
2

Non-Orthogonality and Electron Correlations in Nanotransport : Spin- and Time-Dependent Currents

Fransson, Jonas January 2002 (has links)
<p>The concept of the transfer Hamiltonian formalism has been reconsidered and generalized to include the non-orthogonality between the electron states in an interacting region, e.g. quantum dot (QD), and the states in the conduction bands in the attached contacts. The electron correlations in the QD are described by means of a diagram technique for Hubbard operator Green functions for non-equilibrium states. </p><p>It is shown that the non-orthogonality between the electrons states in the contacts and the QD is reflected in the anti-commutation relations for the field operators of the subsystems. The derived forumla for the current contains corrections from the overlap of the same order as the widely used conventional tunneling coefficients. </p><p>It is also shown that kinematic interactions between the QD states and the electrons in the contacts, renormalizes the QD energies in a spin-dependent fashion. The structure of the renormalization provides an opportunity to include a spin splitting of the QD levels by polarizing the conduction bands in the contacts and/or imposing different hybridizations between the states in the contacts and the QD for the two spin channels. This leads to a substantial amplification of the spin polarization in the current, suggesting applications in magnetic sensors and spin-filters.</p>
3

Non-Orthogonality and Electron Correlations in Nanotransport : Spin- and Time-Dependent Currents

Fransson, Jonas January 2002 (has links)
The concept of the transfer Hamiltonian formalism has been reconsidered and generalized to include the non-orthogonality between the electron states in an interacting region, e.g. quantum dot (QD), and the states in the conduction bands in the attached contacts. The electron correlations in the QD are described by means of a diagram technique for Hubbard operator Green functions for non-equilibrium states. It is shown that the non-orthogonality between the electrons states in the contacts and the QD is reflected in the anti-commutation relations for the field operators of the subsystems. The derived forumla for the current contains corrections from the overlap of the same order as the widely used conventional tunneling coefficients. It is also shown that kinematic interactions between the QD states and the electrons in the contacts, renormalizes the QD energies in a spin-dependent fashion. The structure of the renormalization provides an opportunity to include a spin splitting of the QD levels by polarizing the conduction bands in the contacts and/or imposing different hybridizations between the states in the contacts and the QD for the two spin channels. This leads to a substantial amplification of the spin polarization in the current, suggesting applications in magnetic sensors and spin-filters.

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