Heterodyne holographic microscopy of gold particles

We report experimental results on heterodyne holographic microscopy of subwavelength-sized gold particles. The apparatus uses continuous green laser illumination of the metal beads in a total internal reflection configuration for dark-field operation. Detection of the scattered light at the illumination wavelength on a charge-coupled device array detector enables 3D localization of brownian particles in wate

Neural posterior estimation for exoplanetary atmospheric retrieval

Retrieving the physical parameters from spectroscopic observations of exoplanets is key to understanding their atmospheric properties. Exoplanetary atmospheric retrievals are usually based on approximate Bayesian inference and rely on sampling-based approaches to compute parameter posterior distributions. Accurate or repeated retrievals, however, can result in very long computation times due to the sequential nature of sampling-based algorithms. We aim to amortize exoplanetary atmospheric retrieval using neural posterior estimation (NPE), a simulation-based inference algorithm based on variational inference and normalizing flows. In this way, we aim (i) to strongly reduce inference time, (ii) to scale inference to complex simulation models with many nuisance parameters or intractable likelihood functions, and (iii) to enable the statistical validation of the inference results. We evaluate NPE on a radiative transfer model for exoplanet spectra petitRADTRANS, including the effects of scattering and clouds. We train a neural autoregressive flow to quickly estimate posteriors and compare against retrievals computed with MultiNest. NPE produces accurate posterior approximations while reducing inference time down to a few seconds. We demonstrate the computational faithfulness of our posterior approximations using inference diagnostics including posterior predictive checks and coverage, taking advantage of the quasi-instantaneous inference time of NPE. Our analysis confirms the reliability of the approximate posteriors produced by NPE. The accuracy and reliability of the inference results produced by NPE establishes it as a promising approach for atmospheric retrievals. Amortization of the posterior inference makes repeated inference on several observations computationally inexpensive since it does not require on-the-fly simulations, making the retrieval efficient, scalable, and testable.Comment: The paper has been submitted to AandA after a final revisio

A simulator-based autoencoder for focal plane wavefront sensing

editorial reviewedInstrumental aberrations strongly limit high-contrast imaging of exoplanets, especially when they produce quasistatic speckles in the science images. With the help of recent advances in deep learning, we have developed in previous works an approach that applies convolutional neural networks (CNN) to estimate pupil-plane phase aberrations from point spread functions (PSF). In this work we take a step further by incorporating into the deep learning architecture the physical simulation of the optical propagation occurring inside the instrument. This is achieved with an autoencoder architecture, which uses a differentiable optical simulator as the decoder. Because this unsupervised learning approach reconstructs the PSFs, knowing the true phase is not needed to train the models, making it particularly promising for on-sky applications. We show that the performance of our method is almost identical to a standard CNN approach, and that the models are sufficiently stable in terms of training and robustness. We notably illustrate how we can benefit from the simulator-based autoencoder architecture by quickly fine-tuning the models on a single test image, achieving much better performance when the PSFs contain more noise and aberrations. These early results are very promising and future steps have been identified to apply the method on real data.EPIC - NNEx

Caractéristiques cliniques et survie des patients ayant présenté des mélanomes primaires multiples (MPM): une cohorte monocentrique belge.

peer reviewe

Ulcerative Zoon's balanitis

peer reviewedZoon's balanitis is a rare genital dermatosis of unknown etiology, usually presenting as a red-orange macule or plaque with a «cayenne pepper» appearance on the glans and/or foreskin. Unfortunately, atypical presentations are not uncommon, including vegetating or ulcerative lesions. Usually, it affects middle-age to older uncircumcised men. Although it is a benign pathology, Zoon's balanitis may be superimposed on another inflammatory or neoplastic dermatosis. As topical treatments are generally non satisfactory and relapses are usual on treatment with-drawal, circumcision remains an interesting option with usually a rapid and complete remission of the symptoms.La balanite de Zoon est une dermatose génitale peu fréquente d’étiologie inconnue, se présentant habituellement par une macule ou une plaque de couleur rouge- orange avec un aspect en «poivre de cayenne», sur le gland et/ou le prépuce. Néanmoins, des formes atypiques, végétantes ou ulcérées, sont possibles. Elle touche plus souvent l’homme d’âge moyen à avancé et non circoncis. Il s’agit d’une pathologie bénigne, mais qui peut se surajouter à d’autres dermatoses inflammatoires ou néoplasiques. Les traitements topiques ne sont pas très efficaces et entraînent généralement une récidive à l’arrêt, tandis que la circoncision permet souvent une disparition rapide et complète des symptômes

The VLTI / PIONIER near-infrared interferometric survey of southern T Tauri stars. I. First results

Context : The properties of the inner disks of bright Herbig AeBe stars have been studied with near infrared (NIR) interferometry and high resolution spectroscopy. The continuum and a few molecular gas species have been studied close to the central star; however, sensitivity problems limit direct information about the inner disks of the fainter T Tauri stars. Aims : Our aim is to measure some of the properties of the inner regions of disks surrounding southern T Tauri stars. Methods : We performed a survey with the PIONIER recombiner instrument at H-band of 21 T Tauri stars. The baselines used ranged from 11 m to 129 m, corresponding to a maximum resolution of 3mas (0.45 au at 150 pc). Results : Thirteen disks are resolved well and the visibility curves are fully sampled as a function of baseline in the range 45-130 m for these 13 objects. A simple qualitative examination of visibility profiles allows us to identify a rapid drop-off in the visibilities at short baselines in 8 resolved disks. This is indicative of a significant contribution from an extended contribution of light from the disk. We demonstrate that this component is compatible with scattered light, providing strong support to a prediction made by Pinte et al. (2008). The amplitude of the drop-off and the amount of dust thermal emission changes from source to source suggesting that each disk is different. A by-product of the survey is the identification of a new milli-arcsec separation binary: WW Cha. Spectroscopic and interferometric data of AK Sco have also been fitted with a binary and disk model. Conclusions : Visibility data are reproduced well when thermal emission and scattering form dust are fully considered. The inner radii measured are consistent with the expected dust sublimation radii. Modelling of AK Sco suggests a likely coplanarity between the disk and the binary's orbital planeComment: 19 pages, 11 figure

Challenges for optical turbulence characterization and prediction at optical communication sites

editorial reviewedModelling of atmospheric optical turbulence has been of interest in astronomy for several decades, e.g. for site characterization and flexible scheduling. Nowadays, it is also considered for free-space optical communications, namely to conduct site selection and to design future optical communication systems. In this work, a general approach relying on numerical weather prediction simulations in order to perform optical turbulence prediction is presented. The approach makes use of the Weather Research and Forecasting model and raises several challenges. The latter, such as the choice of the C_n^2 models or the required temporal and spatial resolutions, are first discussed with regards to the literature. Then, optical turbulence prediction is conducted for the site of Redu, Belgium, illustrating the different challenges. These predictions are also compared with seeing measurements from a differential image motion monitor. The presented approach offers realistic seeing values that, however, do not follow rapid variations of the measured seeing. Origins of the discrepancies between measurements and predictions are to be found in the modelling of the boundary layer and motivate the use of a C_n^2 model relying on the turbulent kinetic energy. Further simulations and measurement campaigns at other optical communication sites are encouraged in order to refine some model parameters and compare statistically the prediction results.SALT