Anisotropic Atom-Surface Interactions in the Casimir-Polder Regime

The distance-dependence of the anisotropic atom-wall interaction is studied. The central result is the 1/z^6 quadrupolar anisotropy decay in the retarded Casimir-Polder regime. Analysis of the transition region between non-retarded van der Waals regime (in 1/z^3) and Casimir-Polder regime shows that the anisotropy cross-over occurs at very short distances from the surface, on the order of 0.03 Lambda, where Lambda is the atom characteristic wavelength. Possible experimental verifications of this distance dependence are discussed.Comment: 5 pages, 2 figure

Negative-index media for matter-wave optics

We consider the extension of optical meta-materials to matter waves. We show that the generic property of pulsed comoving magnetic fields allows us to fashion the wave-number dependence of the atomic phase shift. It can be used to produce a transient negative group velocity of an atomic wave packet, which results into a negative refraction of the matter wave. Application to slow metastable argon atoms Ar*(3P2) shows that the device is able to operate either as an efficient beam splitter or an atomic meta-lens. Implications of "meta-media" in atom optics are considered.Comment: 4 pages, 4 figures, submitted at PRL 4 November 200

Jail fever (epidemic typhus) outbreak in Burundi.

We recently investigated a suspected outbreak of epidemic typhus in a jail in Burundi. We tested sera of nine patients by microimmunofluorescence for antibodies to Rickettsia prowazekii and Rickettsia typhi. We also amplified and sequenced from lice gene portions specific for two R. prowazekii proteins: the gene encoding for citrate synthase and the gene encoding for the rickettsial outer membrane protein. All patients exhibited antibodies specific for R. prowazekii. Specific gene sequences were amplified in two lice from one patient. The patients had typical clinical manifestations, and two died. Molecular techniques provided a convenient and reliable means of examining lice and confirming this outbreak. The jail-associated outbreak predates an extensive ongoing outbreak of louse-borne typhus in central eastern Africa after civil war and in refugee camps in Rwanda, Burundi (1), and Zaire

Dynamics of evanescent matter waves in negative-index media

International audiencenumbers: 03.75.-b Matter Waves 03.75.Be Atom and Neutron Optics 37.10.Gh Atom Traps and Guides 42.25.-p Wave Optics ABSTRACT Semi-evanescent and evanescent matter-waves produced by an atom wave packet impinging a repulsive barrier can be back-refracted and reconstructed by the application of negative-index " comoving " potential pulses. One shows that those collapses and revivals generate a matter wave confined on both sides of the barrier border (" surface matter wave ") and should be observable via the retardation of atom reflection from the barrier interface. This property, joined to the possibility recently demonstrated of inducing negative refraction of atom waves, makes such potentials a matter-wave counterpart of negative-index materials or " meta materials " well-known in light optics

Action principle formulation for motion of extended bodies in General Relativity

We present an action principle formulation for the study of motion of an extended body in General Relativity in the limit of weak gravitational field. This gives the classical equations of motion for multipole moments of arbitrary order coupling to the gravitational field. In particular, a new force due to the octupole moment is obtained. The action also yields the gravitationally induced phase shifts in quantum interference experiments due to the coupling of all multipole moments.Comment: Revised version derives Octupole moment force. Some clarifications and a reference added. To appear in Phys. Rev.

Population genetics of abnormal haemoglobins in Burkina Faso, West Africa

Les fréquences géniques des hémoglobines A (HbA), HbS et HbC, ont été étudiées au Burkina-Faso (BF) ainsi que dans une région avoisinante du Niger : Ayorou. La fréquence d'HbS est plus élevée dans le Sahel (Nord du BF et Ayorou) que dans la zone de savane. L'inverse est trouvé pour HbC. Les résultats essentiels de ce travail sont : (a) la confirmation d'un pic de la fréquence génique de HbC dans le centre du BF (plateau Mossi); (b) une corrélation négative entre les fréquences de HbS et HbC. Cavalli-Sforza et Bodmer ont observé que cette corrélation atteint une intensité significativement différente de celle qui est attendue, par suite de la relation allélique entre HbS et HbC; (c) la comparaison de ces résultats avec les données rassemblées par Livingstone montre une modification de la valeur sélective des différents génotypes au cours des dernières années. Les individus AS ont une valeur sélective plus basse et les AA et SS en ont une plus haute. Nos données sont favorables à l'hypothèse du relâchement partiel de la sélection dans cette région. (Résumé d'auteur