Ultra-cold atoms in an optical cavity: two-mode laser locking to the cavity avoiding radiation pressure

The combination of ultra-cold atomic clouds with the light fields of optical cavities provides a powerful model system for the development of new types of laser cooling and for studying cooperative phenomena. These experiments critically depend on the precise tuning of an incident pump laser with respect to a cavity resonance. Here, we present a simple and reliable experimental tuning scheme based on a two-mode laser spectrometer. The scheme uses a first laser for probing higher-order transversal modes of the cavity having an intensity minimum near the cavity's optical axis, where the atoms are confined by a magnetic trap. In this way the cavity resonance is observed without exposing the atoms to unwanted radiation pressure. A second laser, which is phase-locked to the first one and tuned close to a fundamental cavity mode drives the coherent atom-field dynamics.Comment: 7 pages, 7 figure

Dimensional Crossover in Bragg Scattering from an Optical Lattice

We study Bragg scattering at 1D optical lattices. Cold atoms are confined by the optical dipole force at the antinodes of a standing wave generated inside a laser-driven high-finesse cavity. The atoms arrange themselves into a chain of pancake-shaped layers located at the antinodes of the standing wave. Laser light incident on this chain is partially Bragg-reflected. We observe an angular dependence of this Bragg reflection which is different to what is known from crystalline solids. In solids the scattering layers can be taken to be infinitely spread (3D limit). This is not generally true for an optical lattice consistent of a 1D linear chain of point-like scattering sites. By an explicit structure factor calculation we derive a generalized Bragg condition, which is valid in the intermediate regime. This enables us to determine the aspect ratio of the atomic lattice from the angular dependance of the Bragg scattered light.Comment: 4 pages, 5 figure

Multiple Reflections and Diffuse Scattering in Bragg Scattering at Optical Lattices

We study Bragg scattering at 1D atomic lattices. Cold atoms are confined by optical dipole forces at the antinodes of a standing wave generated inside a laser-driven cavity. The atoms arrange themselves into an array of lens-shaped layers located at the antinodes of the standing wave. Light incident on this array at a well-defined angle is partially Bragg-reflected. We measure reflectivities as high as 30%. In contrast to a previous experiment devoted to the thin grating limit [S. Slama, et al., Phys. Rev. Lett. 94, 193901 (2005)] we now investigate the thick grating limit characterized by multiple reflections of the light beam between the atomic layers. In principle multiple reflections give rise to a photonic stop band, which manifests itself in the Bragg diffraction spectra as asymmetries and minima due to destructive interference between different reflection paths. We show that close to resonance however disorder favors diffuse scattering, hinders coherent multiple scattering and impedes the characteristic suppression of spontaneous emission inside a photonic band gap

Cancer pulmonaire au cours d’une thromboangéite oblitérante de Léo Buerger

Notre objectif est de rapporter une observation particulière de néoplasie pulmonaire survenant au cours d'une angéite oblitérante de Léo Buerger. Il s'agit d'un patient de 42 ans, grand tabagique (30 PA) diagnostiqué ayant la maladie de Buerger devant l'association de phlébites et d'artérite distale avec des oblitérations et des sténoses artérielles confirmées par l'échographie, le doppler veineux et artériel, la phlébographie et l'artériographie. Quatorze ans après le diagnostic initial de la vascularite, il se présentait avec une douleur et faiblesse du membre supérieur droit. L'examen clinique concluait à une névralgie cervico brachiale type C7-C8. La radiographie de thorax montrait une opacité apicale droite hétérogène de 5 cm de grand axe avec lyse costale du deuxième arc antérieur droit. Le scanner X thoracique montrait une masse tumorale du segment apical droit associée à des adénopathies médiastinales. La biopsie bronchique concluait à un carcinome épidermoïde bien différencié. Cette association soulève le rôle pathogène du tabac dans la genèse de ces deux maladies. Une surveillance thoracique (clinique et radiologique) rigoureuse se trouve justifiée chez le porteur d'une thromboangéite oblitérante surtout que cette dernière se déclare classiquement à un âge plus jeune que celui du cancer broncho-pulmonaire

Ad- and desorption of Rb atoms on a gold nanofilm measured by surface plasmon polaritons

Hybrid quantum systems made of cold atoms near nanostructured surfaces are expected to open up new opportunities for the construction of quantum sensors and for quantum information. For the design of such tailored quantum systems the interaction of alkali atoms with dielectric and metallic surfaces is crucial and required to be understood in detail. Here, we present real-time measurements of the adsorption and desorption of Rubidium atoms on gold nanofilms. Surface plasmon polaritons (SPP) are excited at the gold surface and detected in a phase sensitive way. From the temporal change of the SPP phase the Rubidium coverage of the gold film is deduced with a sensitivity of better than 0.3 % of a monolayer. By comparing the experimental data with a Langmuir type adsorption model we obtain the thermal desorption rate and the sticking probability. In addition, also laser-induced desorption is observed and quantified.Comment: 9 pages, 6 figure

Self-synchronization and dissipation-induced threshold in collective atomic recoil lasing

Networks of globally coupled oscillators exhibit phase transitions from incoherent to coherent states. Atoms interacting with the counterpropagating modes of a unidirectionally pumped high-finesse ring cavity form such a globally coupled network. The coupling mechanism is provided by collective atomic recoil lasing, i.e., cooperative Bragg scattering of laser light at an atomic density grating, which is self-induced by the laser light. Under the rule of an additional friction force, the atomic ensemble is expected to undergo a phase transition to a state of synchronized atomic motion. We present the experimental investigation of this phase transition by studying the threshold behavior of this lasing process

Adenome parathyroidien intrathymique: a propos d’un cas

Introduction : Les adénomes parathyroïdiens posent le problème de leur diagnostic topographique. A partir d’un cas clinique d’adénome parathyroïdien intrathymique, les auteurs rappellent l’intérêt d’un bilan localisateur préopératoire. Observation : Il s'agit d’un homme âgé de 19 ans présentant une hyperparathyroïdie primitive. La scintigraphie à laSestamibi a montré une hyperfixation inhabituelle du radiotraceur au niveau du creux sus sternal, permettant d’évoquer le diagnostic d’un adénome parathyroïdien intrathymique. Il a été réalisé une adénectomie en utilisant une voie d’abord cervicale et l'évolution post-opératoire était favorable. Conclusion : La scintigraphie Sestamibi constitue l'examen de choix pour établir le diagnostic topographique des adénomes parathyroïdiens. Cet examen permet de limiter la voie d’abord chirurgicale et d’éviter les cervicotomies blanches.Mots-clés : Adénome parathyroïdien, thymus, scintigraphie

Atomic Force Microscopy Study of Nano-Physiological Response of Ladybird Beetles to Photostimuli

Background: Insects are of interest not only as the most numerous and diverse group of animals but also as highly efficient bio-machines varying greatly in size. They are the main human competitors for crop, can transmit various diseases, etc. However, little study of insects with modern nanotechnology tools has been done. Methodology/Principal Findings: Here we applied an atomic force microscopy (AFM) method to study stimulation of ladybird beetles with light. This method allows for measuring of the internal physiological responses of insects by recording surface oscillations in different parts of the insect at sub-nanometer amplitude level and sub-millisecond time. Specifically, we studied the sensitivity of ladybird beetles to light of different wavelengths. We demonstrated previously unknown blindness of ladybird beetles to emerald color (,500nm) light, while being able to see UV-blue and green light. Furthermore, we showed how one could study the speed of the beetle adaptation to repetitive flashing light and its relaxation back to the initial stage. Conclusions: The results show the potential of the method in studying insects. We see this research as a part of what might be a new emerging area of ‘‘nanophysiology’ ’ of insects

Mucormycose rhinosinusienne a extension palatine

Les mucormycoses sont des infections fongiques, aigues, rares et souvent fatales. Elles touchent avec prédilection les sujets  immunodéprimés. La forme rhinocérébrale est la plus fréquente. Le diagnostic repose sur l’examen clinique, anatomopathologique et mycologique. L’approche thérapeutique doit être multidisciplinaire. Les auteurs rapportent l’histoire clinique d’un patient, ayant présenté une mucormycose rhinosinusienne avec atteinte du palais au décours d’une infection dentaire. A travers cette observation, ils discutent les différents aspects cliniques, les moyens du diagnostic et les modalités thérapeutiques de la mucormycose rhinocérébrale.Mots clés : Infection fongique, mucormycose rhinocérébrale, zygomycètes, pronostic, traitement

Kyste hydatique du masséter: a propos d’un cas

La localisation cervico faciale et particulièrement musculaire massétérine est exceptionnelle même en zone d’endémie. Le kyste hydatique au niveau de cette localisation pose un problème de diagnostic et des difficultés thérapeutiques du fait de la présence de filets nerveux du VII. Les auteurs rapportent un cas rare de localisation primaire d’un kyste hydatique au niveau du muscle masséter.Mots clès : Kyste hydatique, face, masséter, imagerie, chirurgie