In situ permittivity measurements using stand-alone end effect probe

Numerous applications using microwave frequency behavior of materials (remote sensing, non-destructive analysis) are strongly dependent on the material permittivity.  Thus, permittivity is a key parameter to develop algorithms for the retrieval of materials properties from remote sensing data. Permittivity measurements are generally carried out in laboratory because in-situ measurements are more difficult to obtain. This study deals with the development at IMS laboratory of an in situ dielectric measurement system based on a stand-alone end effect probe

Système actif hyper-fréquences porté par drone

Dans le cadre d’activités cal-val pour des missions d’observation de la Terre et pour l’étude des zones désertiques (paléo-hydrologie), nous développons un système actif hyper-fréquences en bandes C (5-6 GHz) et P(1-2 GHz) porté par drone. L’objectif est de pouvoir acquérir rapidement des profils de rétrodiffusion, type géoradar mais calibrés en amplitude, pour caractériser la réponse hyper-fréquences de surfaces naturelles. Deux prototypes ont été développés, basés sur un VNA commercial compact et des antennes cornet, et embarqués sur des porteurs DJI (M200 pour la bande C et M600 pour la bande L). Nous présenterons les premiers résultats obtenus sur des sites naturels en Aquitaine, ainsi qu’une comparaison avec des données géo-radar

Système actif hyper-fréquences porté par drone

National audienceDans le cadre d’activités cal-val pour des missions d’observation de la Terre et pour l’étude des zones désertiques (paléo-hydrologie), nous développons un système actif hyper-fréquences en bandes C (5-6 GHz) et P(1-2 GHz) porté par drone. L’objectif est de pouvoir acquérir rapidement des profils de rétrodiffusion, type géoradar mais calibrés en amplitude, pour caractériser la réponse hyper-fréquences de surfaces naturelles. Deux prototypes ont été développés, basés sur un VNA commercial compact et des antennes cornet, et embarqués sur des porteurs DJI (M200 pour la bande C et M600 pour la bande L). Nous présenterons les premiers résultats obtenus sur des sites naturels en Aquitaine, ainsi qu’une comparaison avec des données géo-radar

Wireless network of stand-alone end effect probes for soil in situ permittivity measurements over the 100MHZ-6GHz frequency range

International audienc

Effect of microwave treatment for wine microbial stabilisation: Potential use of a Weibullian mathematical model

The aim of this research was to investigate the efficiency of microwaves (MW) for wine microbiological stabilization and thereby assess the potential application of a Weibullian mathematical model in wine industry. The study focused on (i) the influence of treatment time (come-up time and temperature maintenance) and temperature on a simple wine-like matrix, as well as (ii) the specific resistance of yeast and bacteria selected according to their representativeness in red wines (A. aceti ATCC_15973, S. cerevisiae FX10, B. bruxellensis CRBO_L0619 and AWRI_1499), and finally (iii) the potential usefulness of a new mathematical model adapted to heat treatment to evaluate strain sensitivity. This research aimed to show that microwave treatment decreases the main wine-associated microorganism populations and that the reduction in viable counts mainly depends on the MW treatment temperature. Complete microbiological stabilisation was obtained under a temperature of 50 °C a very short treatment time, except in the case of A. aceti ATCC_15973. Furthermore, the Weibull parameters analyses showed that heat inactivation a wine microorganism studied did not follow first-order kinetics, indicating that we should change our way of studying thermal death curves. The findings from this study suggest that MW could be useful for the wine industry as a complement or an alternative to sulphite utilisation

Caractérisation électromagnétique de matériaux non usinables. Application a l'étude d'éclats de météorites

National audienceRadiometric measurements in microwave frequency range and submillimeter have been performed on an asteroid, S. Gulkis (JPL) and the team MIRO (Microwave Instrument on the orbiter of the spacecraft Rosetta comet), will study the physicochemical characteristics of this asteroid. However, this requires a good understanding of the complex dielectric constant of these objects. It could be specified by microwave measurements in laboratory. The team recently received meteoritic samples (Antarctica), whose composition is similar to that of an asteroid crossed by "Rosetta" in September 2008. Dielectric measurements are performed by the team CEMT (electromagnetic characterization and Remote Sensing) IMS Laboratory (UMR 5218). The samples of meteorites are very rare and can not be machined. A measurement method has been developed at IMS laboratory. The work that we describe in this paper deal with a new measurement method using a resonant cavity that we apply at L and S band. It allows measurements on samples of any shape wich can have a high permittivity

Suivi par télédétection spatiale radiométrique en bande L du permafrost en zones boréales

National audienceCe travail s’inscrit dans le projet SMOSHiLat de l’ESA (Agence Spatiale Européenne) visant à améliorer le suivi à l’échelle planétaire des sols organiques en zones boréales (pergélisol ou permafrost) à l’aide du radiomètre de la mission spatiale SMOS (capteur radiométrique en bande L – 1,4 GHz). Ces sols étaient perpétuellement gelés mais le réchauffement climatique provoque le dégel partiel de ces sols. Outre le suivi de ces phénomènes de gel/dégel comme indicateur du réchauffement climatique, ce suivi est aussi nécessaire car ces sols renferment des quantités considérables de gaz. Un dégel de ces structures pourrait provoquer une libération massive de gaz (méthane...) qui provoquerait un feed-back positif important sur le réchauffement climatique. Ce travail a consisté à concevoir des techniques de métrologie adaptées pour la caractérisation électromagnétique des sols organiques (en fonction de leur nature, de la température et de l’humidité) en laboratoire et in-situ. Pour ce dernier point nous avons conçu une sonde de mesure dédiée à la mesure in-situ des propriétés diélectriques des sols sur une large bande de fréquence(100MHz-6GHz)

In-situ multifrequency dielectric measurements to improve soil permittivity models for radiometric observations of soil in the high latitudes

International audienceIn the context of soil monitoring from microwave radiometric observations, the knowledge of the soil permittivity is an important factor in order to guarantee the accuracy of models inversions. Previous studies have showed the impact of temperature and moisture gradients in the top soil layer on remote sensing monitoring of soil. So, we aim here to investigate a way to increase our knowledge of the permittivity profile of the top soil layer, in particular at the P and L band. The solution we selected is based on a new equipment for continuous in-situ measurements of dielectric soil profiles. First measurement results over a sandy soil after rainfall are presented

Activation of the TRPV1 Thermoreceptor Induced by Modulated or Unmodulated 1800 MHz Radiofrequency Field Exposure

International audienceThe existence of effects of radiofrequency field exposure at environmental levels on living tissues and organisms remains controversial, in particular regarding potential “nonthermal” effects produced in the absence of temperature elevation. Therefore, we investigated whether TRPV1, one of the most studied thermosensitive channels, can be activated by the heat produced by radiofrequency fields and by some specific nonthermal interaction with the fields. We have recently shown that TRPV1 activation can be assessed in real-time on live cells using the bioluminescence resonance energy transfer technique. Taking advantage of this innovative assay, we monitored TRPV1 thermal and chemical modes of activation under radiofrequency exposure at 1800 MHz using different signals (CW, GSM, UMTS, LTE, Wi-Fi and WiMAX) at specific absorption rates between 8 and 32 W/kg. We showed that, as expected, TRPV1 channels were activated by the heat produced by radiofrequency field exposure of transiently-transfected HEK293T cells, but found no evidence of TRPV1 activation in the absence of temperature elevation under radiofrequency field exposure. There was no evidence either that, at fixed temperature, radiofrequency exposure altered the maximal efficacy of the agonist Capsaicin to activate TRPV1