1,007 research outputs found
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 dâune thromboangĂ©ite oblitĂ©rante de LĂ©o Buerger
Notre objectif est de rapporter une observation particuliÚre 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 aprÚs 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 hétérogÚne de 5 cm de grand axe avec lyse costale du deuxiÚme 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 soulÚve le rÎle pathogÚne du tabac dans la genÚse de ces deux maladies. Une surveillance thoracique (clinique et radiologique) rigoureuse se trouve justifiée chez le porteur d'une thromboangéite oblitérante surtout que cette derniÚre se déclare classiquement à un ùge 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 dâun cas
Introduction : Les adĂ©nomes parathyroĂŻdiens posent le problĂšme de leur diagnostic topographique. A partir dâun cas clinique dâadĂ©nome parathyroĂŻdien intrathymique, les auteurs rappellent lâintĂ©rĂȘt dâun bilan localisateur prĂ©opĂ©ratoire. Observation : Il s'agit dâun homme ĂągĂ© de 19 ans prĂ©sentant une hyperparathyroĂŻdie primitive. La scintigraphie Ă laSestamibi a montrĂ© une hyperfixation inhabituelle du radiotraceur au niveau du creux sus sternal, permettant dâĂ©voquer le diagnostic dâun adĂ©nome parathyroĂŻdien intrathymique. Il a Ă©tĂ© rĂ©alisĂ© une adĂ©nectomie en utilisant une voie dâabord cervicale et l'Ă©volution post-opĂ©ratoire Ă©tait favorable. Conclusion : La scintigraphie Sestamibi constitue l'examen de choix pour Ă©tablir le diagnostic topographique des adĂ©nomes parathyroĂŻdiens. Cet examen permet de limiter la voie dâabord chirurgicale et dâĂ©viter les cervicotomies blanches.Mots-clĂ©s : AdĂ©nome parathyroĂŻdien, 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 âânanophysiologyâ â of insects
Mucormycose rhinosinusienne a extension palatine
Les mucormycoses sont des infections fongiques, aigues, rares et souvent fatales. Elles touchent avec prĂ©dilection les sujets immunodĂ©primĂ©s. La forme rhinocĂ©rĂ©brale est la plus frĂ©quente. Le diagnostic repose sur lâexamen clinique, anatomopathologique et mycologique. Lâapproche thĂ©rapeutique doit ĂȘtre multidisciplinaire. Les auteurs rapportent lâhistoire clinique dâun patient, ayant prĂ©sentĂ© une mucormycose rhinosinusienne avec atteinte du palais au dĂ©cours dâune infection dentaire. A travers cette observation, ils discutent les diffĂ©rents aspects cliniques, les moyens du diagnostic et les modalitĂ©s thĂ©rapeutiques de la mucormycose rhinocĂ©rĂ©brale.Mots clĂ©s : Infection fongique, mucormycose rhinocĂ©rĂ©brale, zygomycĂštes, pronostic, traitement
Kyste hydatique du massĂ©ter: a propos dâun cas
La localisation cervico faciale et particuliĂšrement musculaire massĂ©tĂ©rine est exceptionnelle mĂȘme en zone dâendĂ©mie. Le kyste hydatique au niveau de cette localisation pose un problĂšme de diagnostic et des difficultĂ©s thĂ©rapeutiques du fait de la prĂ©sence de filets nerveux du VII. Les auteurs rapportent un cas rare de localisation primaire dâun kyste hydatique au niveau du muscle massĂ©ter.Mots clĂšs : Kyste hydatique, face, massĂ©ter, imagerie, chirurgie
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