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A state-of-the-art 520–620-GHz receiver front end working at room temperature was designed, built, and measured. The receiver front-end features a GaAs-Schottky diode-based subharmonic mixer and a 260–307-GHz doubler, both fabricated with the new LERMA-LPN Schottky process on a 4-$\mu\hbox{m}$-thick GaAs membrane suspended in a waveguide with metal beamleads. Small-area mesas and optimized transmission lines with low dielectric loading are used. At 295 K ambient temperature, an average of 1284 K DSB receiver noise temperature was measured over the 520–620-GHz frequency range, including the 3.5–8.5-GHz IF chain loss. A record 1130 K minimum DSB receiver noise temperature at 557 GHz was measured. At 134 K ambient temperature, an average DSB receiver noise temperature of 685 K from 538 to 600 GHz was measured when correcting for the cryostat window loss. A minimum DSB receiver noise of 585 K was measured at an RF center frequency of 540 GHz. The 520–620-GHz receiver presented in this article allows an increase in the sensitivity of the JUpiter ICy Moons Explrorer-SWI instrument of about a factor of two compared with requirements. It will allow study of the Jovian system with particular emphasis on the chemistry, meteorology, structure, and atmospheric coupling processes of Jupiter and its icy satellites, thereby providing important data for the exploration of their habitable zones.

Many articles have shown the usefulness of electrical resistivity tomography (ERT) where characterizing spatial electrical resistivity variations over time associated with water content variations. In a case study of artificial drainage processes in comparison to isolated measurements of the temporal variation in water content, ERT could be used to obtain additional qualitative spatial information (2D or 3D). Indeed, there have been no articles relating the advantages of using ERT to study tile drainage processes. The aim of this article is to explore the effectiveness of the ERT method for delineating soil moisture spatial patterns, following their temporal variations in the context of artificial drainage. First, in the numerical description, taking into account the current knowledge on artificial drainage processes, the authors evaluate the combination of surface and cross‐borehole ERT measurements and different array types. In a field application, the surface and cross‐borehole combination helps to obtain better information on the soil structure and to optimize electrical resistivity monitoring during tile drainage processes. In the second part of the article, the comparison between the ERT data sets and ancillary data from TDR sensors provides a useful critical evaluation of ERT for studying water transfer in waterlogged soil influenced by artificial drainage. The field results showed that ERT contributes additional 2D information on resistivity as related to the water content, which complements single TDR measurements.

Réduire les transferts de contaminants agricoles en contexte drainé consiste ici à intercepter les eaux dans des infrastructures végétalisées comme les zones tampons humides artificielles (ZTHA). L’article présente tout d’abord, à partir de données scientifiques, une analyse des résultats d’efficacité de ces systèmes sur les paramètres nitrate et pesticide. Il apparaît que l’efficacité moyenne se situe autour de 50-60%, avec une large variabilité due, d’une part, à l’hydrologie et à la saisonnalité et, d’autre part, aux propriétés du polluant (nitrate et des nombreux pesticides).Les études montrent que les processus mis en jeu sont majoritairement microbiologiques, pour lesquels le facteur clé est le temps de résidence hydraulique. Parmi les autres facteurs, la végétation joue un rôle indirect, en contrôlant le chemin hydraulique et en ralentissant les écoulements, mais aussi en fournissant du carbone nécessaire à l’activité microbiologique.Un préalable à toute réflexion sur la mise en place d’infrastructure végétalisée consiste à établir un diagnostic hydrologique des écoulements et des transferts de polluant à toutes les échelles du bassin versant (de la parcelle au sous-bassin). La dynamique saisonnière des polluants diffère selon leur nature, on distingue le cas des nitrates (exportés toute l’année) et celui des pesticides (exportés sur une période posttraitement). Cette connaissance nous a conduits à proposer deux stratégies d’interception des eaux, soit « en série », soit « en parallèle » du collecteur de drainage ou du fossé d’assainissement. La stratégie « en série » intercepte toutes les eaux de drainage et est plutôt dédiée à la problématique des nitrates, tandis que la stratégie « en parallèle » cible les flux de pesticide les plus concentrés consécutivement aux applications dans le minimum de flux d’eau, en activant une vanne à l’entrée de la ZTHA, par l’agriculteur lui-même. L’article présente ensuite quelques suggestions d’aménagement (étude géotechnique, topographique…). Dans le contexte du drainage en France, l’étude d’Irstea a calculé un volume moyen de ZTHA de 76 m3/ha drainé, ce qui correspond pour une profondeur de 0,8 m à 1% du bassin versant contributeur. Cependant, les ZTHA, dont l’efficacité est certes réelle mais limitée, sont une solution complémentaire aux actions ciblant la réduction à la source.

The various polymorphs of tris(8-hydroxyquinoline) gallium(III) (GaQ3) have been prepared and identified in powders and thin films. Three nonsolvated polymorphs have been identified, and their structures have been obtained from powder X-ray diffraction (PXRD). GaQ3 polymorphs were found to be isomorphous to the α, β, and δ structures reported for the aluminum analogue tris(8-hydroxyquinoline) aluminum(III) (AlQ3). The α, β, and the solvated structures are racemates of the meridional isomer, whereas the δ polymorph, formed by annealing the α form to 380 °C under vacuum, contains the facial isomer as demonstrated by FT-IR spectroscopy. The α→δ phase transformation can be described as a thermal isomerization reaction in the solid state that largely preserves the unit cell parameters of the initial α structure. Transmission electron microscopy (TEM) and electron diffraction demonstrate that the α structure is formed in oriented films on poly(tetrafluoroethylene) substrates for a substrate temperature Ts = 100 °C. Evidence is found for a high level of structural defects within needles of α GaQ3. The fluorescence at 293 K of the crystal structures containing mer GaQ3 exhibits the same structural dependence as observed in the case of AlQ3:  the maximum of fluorescence is red-shifted with increasing density of the crystal structure.

Highly oriented films of titanyl phthalocyanine (TiOPc) were obtained by high-vacuum sublimation onto an oriented poly(tetrafluoroethylene) (PTFE) substrate. The dependence of the structure and morphology on deposition parameters (substrate temperature Ts, deposition time t, and deposition rate τ) was followed by X-ray diffraction, transmission electron microscopy (TEM), and atomic force microscopy (AFM) to uncover the origin of the oriented growth process. At Ts = 100 °C, an original growth mechanism was observed whereby α-TiOPc microcrystallites were formed by the static coalescence and reorganization of small amorphous aggregates in close contact. Nucleation of α-TiOPc is initiated at the PTFE macrosteps from which oriented crystallization propagates, leading to uniform α-TiOPc films with a twinned texture and a dense (0 1 0) contact plane. The molecules are in an edge-on orientation, with their molecular plane oriented parallel to the PTFE chains. At the mesoscale, the nucleation of crystalline α-TiOPc involves the alignment and oriented coalescence of amorphous prenucleation aggregates along the PTFE macrosteps, i.e., a graphoepitaxial process. At the molecular scale, it is proposed that the TiOPc orientation and the preferential nucleation of the α polymorph are enforced by the topography and structure of the PTFE macrosteps in conjunction with the requirement for a minimal nucleation free energy. The optical absorption of the films in the near infrared is found to be strongly correlated with the structural and morphological modifications in the films. The oriented character of the α-TiOPc films results in a strong polarization of the 850-nm band perpendicular to the PTFE chain axis direction.

Barium hexaferrite, BaFe12O19, was prepared by a new method which consists in reacting boron oxide, B2O3, on barium monoferrite, BaFe2O4BaFe2O4was synthesized according to three procedures; ceramic, nitrate, and copreciptation. Barium ferrite is recovered by dissolving the formed barium borate, BaB2O4. This method is available for Co- and Ti-doped hexaferrite suitable for magnetic recording.

Hexagonal ferrites in the BaO-Fe2O3- CoO system have the M, Y, Z, W and S structures. BaFe12-xCOxO19-x prepared by the glass synthesis method crystallizes with the M structure but forx > O a few CoFe2O4 (S) crystallizes at first and then is located at the core of the recovered platelets of hexaferrite M. BaFe16-xCO2 +xO27-xFx prepared in the saure way has not the W structure but is a mixture of cobalt doped M and S.

The effect of acetone vapours on the phase transformation x → α was studied by means of electron microscopy, X-ray diffractometry, electron spin resonance (ESR) and optical spectroscopy on thin films and powders of lithium phthalocyanine (PcLi). The exposure of amorphous films of PcLi, deposited at a substrate temperature of 15 °C onto glass slides, to solvent vapours of acetone at room temperature, induces important changes in the morphology and crystalline structure of the films. Exposure to acetone vapours under low pressure (200 mbar)leads to an x-like structure with low crystallinity, uniform coverage and no preferential ordering. Longer exposure in a saturated acetone vapour atmosphere results in an important phase transformation to the α form which leads to crystallites up to several micrometres large lying in the plane of the substrate and forming a discontinuous coverage. In the case of x powders treated in liquid acetone, a phase transformation to the α form of PcLi is observed. This x → α phasechange induced by the acetone vapour treatment is interpreted in terms of crystal size effects and compared with the phase transformation observed in thin films deposited at various substrate temperatures in the range 25–225 °C.

Context. Coronagraphic techniques are required to observe substellar mass companions close to nearby bright stars by direct imagery. Phase mask coronagraphs are particularly interesting because they give access to the innermost regions. While the principle of the first such concept was validated experimentally a decade ago, the achieved brightness attenuation was too low to be conclusive, probably due to the imperfect thickness profile of the mask.Aims. We have manufactured and tested a second-generation Roddier & Roddier coronagraph in preparation for the development of more elaborate phase mask designs, planned to be used in the future European Extremely Large Telescope.Methods. A monolithic phase mask was made by ion beam machining. Experimentally obtained coronagraphic images were compared with simulated images.Results. Good agreement with theory was obtained. A peak attenuation of 216 was achieved, and a contrast of ~10-5was measured at 5.7?$\lambda/D$. The results exploring contrasts obtained at different distances from the star for different mask dimensions are particularly interesting, confirming predictions made in the literature.

Context. Coronagraphic techniques are required to observe substellar mass companions close to nearby bright stars by direct imagery. Phase mask coronagraphs are particularly interesting because they give access to the innermost regions. While the principle of the first such concept was validated experimentally a decade ago, the achieved brightness attenuation was too low to be conclusive, probably due to the imperfect thickness profile of the mask.