2,563 research outputs found
Density Distribution of a Bose-Einstein Condensate of Photons in a Dye-Filled Microcavity
The achievement of Bose-Einstein condensation of photons (phBEC) in a
dye-filled microcavity has led to a renewed interest in the density
distribution of the ideal Bose gas in a two-dimensional harmonic oscillator. We
present measurements of the radial profile of photons inside the microcavity
below and above the critical point for phBEC with a good signal-to-noise ratio.
We obtain a good agreement with theoretical profiles obtained using exact
summation of eigenstates.Comment: 5 pages, 4 figure
Density Distribution of a Bose-Einstein Condensate of Photons in a Dye-Filled Microcavity
The achievement of Bose-Einstein condensation of photons (phBEC) in a
dye-filled microcavity has led to a renewed interest in the density
distribution of the ideal Bose gas in a two-dimensional harmonic oscillator. We
present measurements of the radial profile of photons inside the microcavity
below and above the critical point for phBEC with a good signal-to-noise ratio.
We obtain a good agreement with theoretical profiles obtained using exact
summation of eigenstates.Comment: 5 pages, 4 figure
La sécurité du jeu et le jeu de la sécurité : piratage, loi et politique publique
Le présent rapport est l’objet d’une étude du lien entre les organisations criminelles et le contrôle social dans le domaine de la criminalité informatique. D’abord, nous examinerons quelques attaques montées contre des appareils de jeu électronique. Ensuite, nous analyserons de quelle façon ces cyberattaques ont été commises et quelle est la capacité de l’État et du secteur industriel à les combattre. Enfin, nous comparerons nos conclusions à celles tirées d’autres études sur le piratage dans l’industrie des jeux de hasard et nous discuterons de l’importance de nos conclusions pour les systèmes d’application de la loi, de sécurité et de protection des consommateurs.This paper studies the relationship between criminal organization and social control in the area of computer crime. We examine a “cheat at play” scheme that hacked into electronic gambling machines. We focus on how these cyber-attacks were committed and on the ability of the state and the industry to control them. We compare and contrast our findings with the research on hacking and the gambling industry and conclude by discussing the implications that our research has for law enforcement, security and public policy
No planet for HD 166435
The G0V star HD166435 has been observed by the fiber-fed spectrograph ELODIE
as one of the targets in the large extra-solar planet survey that we are
conducting at the Observatory of Haute-Provence. We detected coherent,
low-amplitude, radial-velocity variations with a period of 3.7987days,
suggesting a possible close-in planetary companion. Subsequently, we initiated
a series of high-precision photometric observations to search for possible
planetary transits and an additional series of CaII H and K observations to
measure the level of surface magnetic activity and to look for possible
rotational modulation. Surprisingly, we found the star to be photometrically
variable and magnetically active. A detailed study of the phase stability of
the radial-velocity signal revealed that the radial-velocity variability
remains coherent only for durations of about 30days. Analysis of the time
variation of the spectroscopic line profiles using line bisectors revealed a
correlation between radial velocity and line-bisector orientation. All of these
observations, along with a one-quarter cycle phase shift between the
photometric and the radial-velocity variationss, are well explained by the
presence of dark photospheric spots on HD166435. We conclude that the
radial-velocity variations are not due to gravitational interaction with an
orbiting planet but, instead, originate from line-profile changes stemming from
star spots on the surface of the star. The quasi-coherence of the
radial-velocity signal over more than two years, which allowed a fair fit with
a binary model, makes the stability of this star unusual among other active
stars. It suggests a stable magnetic field orientation where spots are always
generated at about the same location on the surface of the star.Comment: 9 pages, 8 figures, Accepted for publication in A&
Active optical decoupling circuit for radio frequency endoluminal coil
International audienceDespite the enhanced image provided by multiple-channels array coils, an accurate exploration of bowel diseases and detailed information about the gastrointestinal wall layers are still not available. The use of endoluminal RF coil located in the region of interest could potentially allow good evaluation of tumor invasion or depth of inflammatory processes [1]. However, since metallic coaxial cables are used, patient safety is threatened due to local electric field concentration that can happen and the associated local high Specific Absorption Rate (SAR) [2]. Moreover, in this case, cable isolation and traps cannot be straightforwardly employed due to limited dimension. Signal transmission based onoptical fiber is an alternative to coaxial cables to solve definitively the electromagnetic issues. On a receiver coil, both signal transmission and decoupling have to be insured. For MR signal transmission, the electro-optical conversion has been partially validated based on electro-optic effect of some crystals [3]. In this work, an active optical decoupling circuit for endoluminal coil is presented and compared to a reference coil with regular decoupling using bias signal though coaxial cable
Simultaneous two-channel MR imaging, single voxel spectroscopy and chemical shift imaging by reconfiguration of a 'standard' Biospec spectrometer
International audienceSimultaneous two channel array proton imaging, single voxel PRESS and CSI acquisitions were demonstrated after reconfiguration and minimum hardware modification of a standard 4.7T BioSpec® spectrometer. Validation of the reconfiguration was assessed in phantoms and in a mouse brain. The modified configuration used the X channel exhibiting similar SNR performances compared to the 1H channel. The SNR gain for the two channel array coil was up to 1.3 compared to the SNR obtained with a reference surface coil. Compared to regular two element coil with quadrature combination, the SNR was improved with an additional gain of 1.3. These modifications could also be applied for any X nucleu
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