Self-similar expansion of the density profile in a turbulent Bose-Einstein condensate

In a recent study we demonstrated the emergence of turbulence in a trapped Bose-Einstein condensate of Rb-87 atoms. An intriguing observation in such a system is the behavior of the turbulent cloud during free expansion.The aspect ratio of the cloud size does not change in the way one would expect for an ordinary non-rotating (vortex-free) condensate. Here we show that the anomalous expansion can be understood, at least qualitatively, in terms of the presence of vorticity distributed throughout the cloud, effectively counteracting the usual reversal of the aspect ratio seen in free time-of-flight expansion of non-rotating condensates.Comment: 8 pages, 4 figure

Generation of vortices and observation of Quantum Turbulence in an oscillating Bose-Einstein Condensate

We report on the experimental observation of vortex formation and production of tangled vortex distribution in an atomic BEC of Rb-87 atoms submitted to an external oscillatory perturbation. The oscillatory perturbations start by exciting quadrupolar and scissors modes of the condensate. Then regular vortices are observed finally evolving to a vortex tangle configuration. The vortex tangle is a signature of the presence of a turbulent regime in the cloud. We also show that this turbulent cloud has suppression of the aspect ratio inversion typically observed in quantum degenerate bosonic gases during free expansion.Comment: to appear in JLTP - QFS 200

Echinoderms from Todos os Santos Bay and Aratu Bay (Bahia, Brazil)

Neste trabalho são registrados os equinodermos (exceto Holothuroidea) obtidos durante a execução do projeto "Marine Environmental Evaluation of the Todos os Santos Bay-MAREMBA" em julho/agosto de 1996 e durante o projeto "Geoecologia das comunidades bentônicas infralitorais da Baía de Todos os Santos (BTS), BA, Brasil: diversidade biótica e sedimentológica", (1997). Um total de 33 espécies pertencentes a 15 famílias foram registradas e re-descritas. A distribuição de Ophiactis brasiliensis Manso, 1988 e Amphiodia trychna H.L. Clark, 1918 é estendida para a região nordeste do Brasil. A classe Ophiuroidea foi dominante nas amostragens em termos de abundância e freqüência de ocorrência, em particular as espécies Amphiodia atra Stimpson, 1852, Amphipholis subtilis (Ljungman, 1867), Ophiactislymani Ljungman, 1871 e Ophiostigma isocanthum (Say, 1825). O asteróide Oreaster reticulatus (Linnaeus, 1758) é considerado vulnerável à exploração humana e foi escasso durante as coletas. Outras espécies encontradas na BTS, tais como os asteroides Luidia clathrata (Say, 1825) e L. senegalensis (Lamarck, 1816) e o equinóide Eucidaristribuloides (Lamarck, 1816) figuram na lista nacional de espécies de invertebrados aquáticos ameaçados de extinção._______________________________________________________________________________ ABSTRACT: We present the results of the studies on biodiversity of Echinodermata (except Holothuroidea) from the Projects "Marine Environmental Evaluation of the Todos os Santos Bay - MAREMBA" (July/August 1996) and "Geoecology of the Benthic Infralitoral Communities of Todos os Santos Bay (BTS), Bahia, Brazil" (1997). A total of 33 species from 15 families were registered and re-described. The distribution of Ophiactis brasiliensis Manso, 1988 and Amphiodia trychna H.L. Clark, 1918 is extended to northwestern Brazil. The class Ophiuroidea was dominant in samples in terms of abundance and frequency of occurrence, in particular Amphiodia atra Stimpson, 1852, Amphipholis subtilis (Ljungman, 1867), Ophiactislymani Ljungman, 1871and Ophiostigma isocanthum (Say, 1825). The asteroid Oreaster reticulatus (Linnaeus, 1758) is considered vulnerable to human exploration and was scarce during the surveys. Other species found at BTS, such the asteroids Luidia clathrata (Say, 1825) and L. senegalensis (Lamarck, 1816) and the echinoid Eucidaristribuloides (Lamarck, 1816)are included in the national list of threatened invertebrate species