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

Thermal counting statistics in an atomic two-mode squeezed vacuum state

We measure the population distribution in one of the atomic twin beams generated by four-wave mixing in an optical lattice. Although the produced two-mode squeezed vacuum state is pure, each individual mode is described as a statistical mixture. We confirm the prediction that the particle number follows an exponential distribution when only one spatio-temporal mode is selected. We also show that this distribution accounts well for the contrast of an atomic Hong--Ou--Mandel experiment. These experiments constitute an important validation of our twin beam source in view of a future test of a Bell inequalities.Comment: SciPost submissio

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&

Tuning of observer-based estimators: theory and application to the on-line estimation of kinetic parameters

This paper deals with the tuning of observer-based estimators. Initially, these algorithms were designed for estimating on-line kinetic parameters, like specific growth rates, in bioprocesses, and have proved to be very successful in practical applications. Here a systematic tuning approach that allows a decoupled estimation of each parameter and the assignment of the estimator dynamics independently of the process dynamics is proposed. The presented approach is illustrated on an animal cell culture example in numerical simulation and with real-life data

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

Sulfonated copolymers as heparin-mimicking stabilizer of fibroblast growth factor : size, architecture, and monomer distribution effects

Fibroblast growth factors (FGF) are involved in a wide range of biological processes such as cell proliferation and differentiation. In living organisms, the binding of FGF to its receptors are mediated through electrostatic interactions between FGF and naturally occurring heparin. Despite its prevalent use in medicine, heparin carries notable limitations, namely; its extraction from natural sources (expensive, low yield and extensive purification), viral contamination, and batch-to-batch heterogeneity. In this work a range of synthetic homopolymers and copolymers of sodium 2-acrylamido-2-methylpropane sulfonate (AMPS®) were evaluated as potential FGF stabilisers. This was studied by measuring the proliferation of BaF3-FR1c cells, as a model assay, and the results will be compared with the natural stabilisation and activation of FGF by heparin. This study explores the structure-activity relationship of these polysulfonated polymers with a focus on the effect of molecular weight, co-monomer type, charge dispersion and polymer architecture on protein stabilisation