146 research outputs found
Low temperature reflectivity study of ZnO/(Zn,Mg)O quantum wells grown on M-plane ZnO substrates
We report growth of high quality ZnO/Zn0.8Mg0.2O quantum well on M-plane
oriented ZnO substrates. The optical properties of these quantum wells are
studied by using reflectance spectroscopy. The optical spectra reveal strong
in-plane optical anisotropies, as predicted by group theory, and marked
reflectance structures, as an evidence of good interface morphologies.
Signatures ofc onfined excitons built from the spin-orbit split-off valence
band, the analog of exciton C in bulk ZnO are detected in normal incidence
reflectivity experiments using a photon polarized along the c axis of the
wurtzite lattice. Experiments performed in the context of an orthogonal photon
polarization, at 90^{\circ}; of this axis, reveal confined states analogs of A
and B bulk excitons. Envelope function calculations which include excitonic
interaction nicely account for the experimental report
Drop impact dynamics on slippery liquid-infused porous surfaces: influence of oil thickness
Slippery liquid-infused porous surfaces (SLIPS) are porous nanostructures
impregnated with a low surface tension lubricant. They have recently shown
great promise in various applications that require non-wettable
superhydrophobic surfaces. In this paper, we investigate experimentally the
influence of the oil thickness on the wetting properties and drop impact
dynamics of new SLIPS. By tuning the thickness of the oil layer deposited
through spin-coating, we show that a sufficiently thick layer of oil is
necessary to avoid dewetting spots on the porous nanostructure and thus
increasing the homogeneity of the liquid distribution. Drop impact on these
surfaces is investigated with a particular emphasis on the spreading and
rebound dynamics when varying the oil thickness and the Weber number
Exploring high repetitivity remote sensing time series for mapping and monitoring natural habitats ; A new approach combining OBIA and k-partite graphs
International audienc
GaN-AlGaN Heterostructure Field-Effect Transistors over Bulk GaN Substrates
We report on AlGaN/GaN heterostructures and heterostructurefield-effect transistors(HFETs) fabricated on high-pressure-grown bulk GaN substrates. The 2delectron gas channel exhibits excellent electronic properties with room-temperature electron Hall mobility as high as μ=1650 cm2/V s combined with a very large electron sheet density ns≈1.4×1013 cm−2.The HFET devices demonstrated better linearity of transconductance and low gate leakage, especially at elevated temperatures. We also present the comparative study of high-current AlGaN/GaN HFETs(nsμ\u3e2×1016 V−1 s−1) grown on bulk GaN, sapphire, and SiC substrates under the same conditions. We demonstrate that in the high-power regime, the self-heating effects, and not a dislocation density, is the dominant factor determining the device behavior
The DACAPO-PESO campaign: Dynamics, Aerosol, Cloud and Precipitation Observations in the Pristine Environment of the Southern Ocean: An overview
This article gives an overview of the DACAPO-PESO field experiment,
which has taken place in Punta Arenas, Chile, from November 2018 to November 2021,
and showcases first exciting research results that have already emerged from it.In diesem Artikel wird ein Überblick über das DACAPO-PESO
Experiment gegeben, welches von November 2018 bis November 2021 in Punta Arenas,
Chile, stattgefunden hat. Außerdem werden erste spannende Forschungsergebnisse
vorgestellt, die bereits daraus gewonnen wurden
Physiological, phenometric and productive changes in soybean crop due to the use of kinetin
Differential responses between mature and young leaves of sunflower plants to oxidative stress caused by water deficit
Can physiological endpoints improve the sensitivity of assays with plants in the risk assessment of contaminated soils?
Site-specific risk assessment of contaminated areas indicates prior areas for intervention, and provides helpful information for risk managers. This study was conducted in the Ervedosa mine area (Bragança, Portugal), where both underground and open pit exploration of tin and arsenic minerals were performed for about one century (1857-1969). We aimed at obtaining ecotoxicological information with terrestrial and aquatic plant species to integrate in the risk assessment of this mine area. Further we also intended to evaluate if the assessment of other parameters, in standard assays with terrestrial plants, can improve the identification of phytotoxic soils. For this purpose, soil samples were collected on 16 sampling sites distributed along four transects, defined within the mine area, and in one reference site. General soil physical and chemical parameters, total and extractable metal contents were analyzed. Assays were performed for soil elutriates and for the whole soil matrix following standard guidelines for growth inhibition assay with Lemna minor and emergence and seedling growth assay with Zea mays. At the end of the Z. mays assay, relative water content, membrane permeability, leaf area, content of photosynthetic pigments (chlorophylls and carotenoids), malondialdehyde levels, proline content, and chlorophyll fluorescence (Fv/Fm and ΦPSII) parameters were evaluated. In general, the soils near the exploration area revealed high levels of Al, Mn, Fe and Cu. Almost all the soils from transepts C, D and F presented total concentrations of arsenic well above soils screening benchmark values available. Elutriates of several soils from sampling sites near the exploration and ore treatment areas were toxic to L. minor, suggesting that the retention function of these soils was seriously compromised. In Z. mays assay, plant performance parameters (other than those recommended by standard protocols), allowed the identification of more phytotoxic soils. The results suggest that these parameters could improve the sensitivity of the standard assays
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