RESUMO
We have created a long-lived (≈40 s) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier across one side of the torus creates a tunable weak link in the condensate circuit, which can affect the current around the loop. Superflow stops abruptly at a barrier strength such that the local flow velocity at the barrier exceeds a critical velocity. The measured critical velocity is consistent with dissipation due to the creation of vortex-antivortex pairs. This system is the first realization of an elementary closed-loop atom circuit.
RESUMO
We have realized a conical matter wave lens. The repulsive potential of a focused laser beam was used to launch a Bose-Einstein condensate into a radially expanding wavepacket whose perfect ring shape was ensured by energy conservation. In spite of significant interactions between atoms, the spatial and velocity widths of the ring along its radial dimension remained extremely narrow, as also confirmed by numerical simulations. Our results open the possibility for cylindrical atom optics without the perturbing effect of mean-field interactions.
RESUMO
E relatado o caso de um paciente de 27 anos, sem fatores de risco e antecedentes de coronariopatia na familia, acometido de infarto do miocardio transmural apos eletrocussao acidental. A cinecoronariografia realizada 30 dias apos, mostrou arterias coronarias normais e acinesia antero-apical. Os autores discutem a etiopatogenia, dando enfase a possibilidade de vasoespasmo coronario ou trombose coronaria com recanalizacao
