A quasi-pure Bose-Einstein condensate immersed in a Fermi sea

We report the observation of co-existing Bose-Einstein condensate and Fermi gas in a magnetic trap. With a very small fraction of thermal atoms, the 7Li condensate is quasi-pure and in thermal contact with a 6Li Fermi gas. The lowest common temperature is 0.28 muK = 0.2(1) T_C = 0.2(1) T_F where T_C is the BEC critical temperature and T_F the Fermi temperature. Behaving as an ideal gas in the radial trap dimension, the condensate is one-dimensional.Comment: 4 pages, 5 figure

Collective Oscillations of an Imbalanced Fermi Gas: Axial Compression Modes and Polaron Effective Mass

We investigate the low-lying compression modes of a unitary Fermi gas with imbalanced spin populations. For low polarization, the strong coupling between the two spin components leads to a hydrodynamic behavior of the cloud. For large population imbalance we observe a decoupling of the oscillations of the two spin components, giving access to the effective mass of the Fermi polaron, a quasi-particle composed of an impurity dressed by particle-hole pair excitations in a surrounding Fermi sea. We find $m^*/m=1.17(10)$, in agreement with the most recent theoretical predictions.Comment: 4 pages, 4 figures, submitted to PR

Formation of a Matter-Wave Bright Soliton

We report the production of matter-wave solitons in an ultracold lithium 7 gas. The effective interaction between atoms in a Bose-Einstein condensate is tuned with a Feshbach resonance from repulsive to attractive before release in a one-dimensional optical waveguide. Propagation of the soliton without dispersion over a macroscopic distance of 1.1 mm is observed. A simple theoretical model explains the stability region of the soliton. These matter-wave solitons open fascinating possibilities for future applications in coherent atom optics, atom interferometry and atom transport.Comment: 11 pages, 5 figure

Experimental Study of the BEC-BCS Crossover Region in Lithium 6

We report Bose-Einstein condensation of weakly bound $^6$Li$_2$molecules in a crossed optical trap near a Feshbach resonance. We measure a molecule-molecule scattering length of$170^{+100}_{-60}$ nm at 770 G, in good agreement with theory.We study the expansion of the cloud in the BEC-BCS crossoverregion.Comment: 4 pages, 3 figures, submitted to PR

Expansion of a lithium gas in the BEC-BCS crossover

We report on experiments in $^6$Li Fermi gases near Feshbach resonances. A broad s-wave resonance is used to form a Bose-Einstein condensate of weakly bound $^6$Li$_2$ molecules in a crossed optical trap. The measured molecule-molecule scattering length of $170^{+100}_{-60}$ nm at 770 G is found in good agreement with theory. The expansion energy of the cloud in the BEC-BCS crossover region is measured. Finally we discuss the properties of p-wave Feshbach resonances observed near 200 Gauss and new s-wave resonances in the heteronuclear $^6$Li- $^7$Li mixture.Comment: 10 pages, 3 figures, Proceedings of ICAP 200

Durée courte d’antibiothérapie

RésuméLes durées de traitement antibiotique ne reposent pas sur un rationnel scientifique fort. Pourtant à l’heure de l’émergence dramatique de résistance bactérienne, réduire la pression de sélection par la réduction de la durée d’exposition devrait être un enjeu majeur. En outre, la diminution des coûts et des effets indésirables associés renforce l’intérêt des traitements courts. Malheureusement, peu d’études de méthodologie satisfaisante sont disponibles dans la littérature. Nous présentons le rationnel et l’intérêt à un raccourcissement des durées de traitement antibiotique ainsi que les principales données disponibles concernant les infections fréquentes comme les infections urinaires, pulmonaires, ostéoarticulaires et intra-abdominales. Enfin, nous mettons en perspective les difficultés à évaluer les durées de traitement ainsi que les possibles solutions et méthodologies innovantes.AbstractAntibiotic treatment durations are not well documented. Yet, dramatic emergence of multi-drug resistant organisms should lead to tend to decrease antibiotic selection pressure. Furthermore, it could lower health costs and reduce associated adverse events. Unfortunately, only few studies with rigorous methodology have been performed. We present the available data on frequent infections such as urinary tract infections, community acquired pneumonia, bone and joint infections and intra-abdominal infections. We underline the difficulties to perform such trials and discuss original options to a better evaluation of treatment duration

Comparability of Self Rated Health: Cross Sectional Multi-Country Survey Using Anchoring Vignettes

Objective: To examine differences in expectations for health using anchoring vignettes, which describe fixed levels of health on dimensions such as mobility. Design: Cross sectional survey of adults living in the community. Setting: China, Myanmar, Sri Lanka, Pakistan, Turkey, and United Arab Emirates. Participants: 3012 men and women aged 18 years and older (self ratings); subsample of 406 (vignette ratings). Main outcome measures: Self rated mobility levels and ratings of hypothetical vignettes using the same questions and response categories. Results: Consistent rankings of vignettes are evidence that vignettes are understood in similar ways in different settings, and internal consistency of orderings on two mobility questions indicates good comprehension. Variation in vignette ratings across age groups suggests that expectations for mobility decline with age. Comparison of responses to two different mobility questions supports the assumption that individual ratings of hypothetical vignettes relate to expectations for health in similar ways as self assessments. Conclusions: Anchoring vignettes could provide a powerful tool for understanding and adjusting for the influence of different health expectations on self ratings of health. Incorporating anchoring vignettes in surveys can improve the comparability of self reported measures