29 research outputs found
Hyperfine splitting of the dressed hydrogen atom ground state in non-relativistic QED
We consider a spin-1/2 electron and a spin-1/2 nucleus interacting with the
quantized electromagnetic field in the standard model of non-relativistic QED.
For a fixed total momentum sufficiently small, we study the multiplicity of the
ground state of the reduced Hamiltonian. We prove that the coupling between the
spins of the charged particles and the electromagnetic field splits the
degeneracy of the ground state.Comment: 22 page
Hyperfine splitting in non-relativistic QED: uniqueness of the dressed hydrogen atom ground state
We consider a free hydrogen atom composed of a spin-1/2 nucleus and a
spin-1/2 electron in the standard model of non-relativistic QED. We study the
Pauli-Fierz Hamiltonian associated with this system at a fixed total momentum.
For small enough values of the fine-structure constant, we prove that the
ground state is unique. This result reflects the hyperfine structure of the
hydrogen atom ground state.Comment: 22 pages, 3 figure
Ground State and Resonances in the Standard Model of Non-relativistic QED
We prove existence of a ground state and resonances in the standard model of
the non-relativistic quantum electro-dynamics (QED). To this end we introduce a
new canonical transformation of QED Hamiltonians and use the spectral
renormalization group technique with a new choice of Banach spaces.Comment: 50 pages change
Impact de la tenue de raquette sur la cinématique des membres supérieurs pour le para-badminton : étude préliminaire
National audienc
A New Postural Force Production Index to Assess Propulsion Effectiveness During Handcycling
Effet de l'inclinaison latérale des roues du fauteuil roulant sur la vitesse linéaire et sur la vitesse de pivot du basketteur
Optimisation de la performance en basket-ball handisport par la recherche du réglage optimal du fauteuil roulant
Effects of synchronous versus asynchronous mode of propulsion on wheelchair basketball sprinting
Approche comparée de l’apprentissage synchrone vs asynchrone de la propulsion en fauteuil roulant manuel
International audiencePurpose: This study aims to analyze learning differences between synchronous and asynchronous propulsion mode in manual wheelchairs.Materials and methods: Twenty novice and abled-bodied subjects (19.9 ± 1.3 years, 65.4 ± 8.8 kg, 173.6 ± 6.5 cm) participated in this study. Two sprints, in synchronous and asynchronous conditions, before and after twelve hours of sport practice including the learning of these two modes of propulsion, were realized. The rate of increase of the total force when entering the handrail, cadence, total and tangential force, speed and power were measured.Results: Significant differences before and after the twelve hours of practice are highlighted for speed (P < 0.0001), power (P = 0.006), rate of increase in total force (P = 0.02) and the tangential force (P = 0.005). The ANOVA performed also shows significant differences for the total force (P = 0.01), the velocity (P = 0.0002), the power (P = 0.002) and the tangential force (P = 0.005) between asynchronous and synchronous. Statistical analysis shows no significant interaction. The measured parameters tend to increase more significantly for the asynchronous vs. synchronous mode.Conclusion: The learning of the two modes of propulsion had significant effects on the main parameter of propulsive performance, speed. However, two of the biomechanical parameters related to the risk of injury, the rate of increase of the total force and the total force, increase significantly for the two modes of propulsion. It would be interesting to propose adapted muscle strengthening sessions during the learning phase. In addition, evolution percentages tend to be higher in asynchronous vs. synchronous propulsion. These results suggest that asynchronous instruction should be favored early on in the learning of manual wheelchair basketball.Objectifs: Cette étude vise à analyser les différences d’apprentissage existantes entre le mode de propulsion synchrone et asynchrone en fauteuil roulant manuel.Matériels et méthode: Vingt sujets valides novices (19,9 ± 1,3 ans ; 65,4 ± 8,8 kg ; 173,6 ± 6,5 cm) ont pris part à cette étude. Deux sprints, en conditions synchrone et asynchrone, avant et après douze heures de pratique sportive incluant l’apprentissage de ces deux modes de propulsion, ont été réalisés. Le taux d’augmentation de la force totale lors de la saisie de la main courante, la cadence, la force totale et tangentielle, la vitesse et la puissance ont été mesurés.Résultats: Des différences significatives avant et après les douze heures de pratique sont mises en évidence pour la vitesse (p < 0,0001), la puissance (p = 0,006), le taux d’augmentation de la force totale (p = 0,02) et la force tangentielle (p = 0,005). L’Anova réalisée montre également des différences significatives pour la force totale (p = 0,01), la vitesse (p = 0,0002), la puissance (p = 0,002) et la force tangentielle (p = 0,005) entre asynchrone et synchrone. L’analyse statistique ne montre pas d’interaction significative. Les paramètres mesurés tendent à augmenter de manière plus importante pour le mode asynchrone vs synchrone.Conclusion: L’apprentissage des deux modes de propulsion a eu des effets significatifs sur le principal paramètre de performance propulsive, la vitesse. Or, deux des paramètres biomécaniques liés aux risques de blessures, le taux d’augmentation de la force totale et la force totale, augmentent significativement pour les deux modes de propulsion. Il serait alors intéressant de proposer des séances de renforcement musculaire adaptées durant la phase d’apprentissage. De plus, les pourcentages d’évolution tendent à être plus importants en propulsion asynchrone vs synchrone. Ces résultats amènent à penser qu’il faudrait privilégier l’enseignement asynchrone de manière précoce durant l’apprentissage du basket en fauteuil roulant manuel