Search results for "cycle"

Lagrangian matches between observations from aircraft, lidar and radar in an orographic warm conveyor belt

2020

Warm conveyor belts (WCBs) are important airstreams in extratropical cyclones, often leading to the formation of intense precipitation and the amplification of upper-level ridges. This study presents a case study that involves aircraft, lidar and radar observations in a WCB ascending from western Europe towards the Baltic Sea during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) and T-NAWDEX-Falcon in October 2012, a preparatory campaign for the THORPEX North Atlantic Waveguide and Downstream Impact Experiment (T-NAWDEX). Trajectories were used to link different observations along the WCB, that is, to establish so-called Lagrangian matches between observations. To this aim, …

Ortho -Functionalized Aryltetrazines by Direct Palladium-Catalyzed C−H Halogenation: Application to Fast Electrophilic Fluorination Reactions

2016

International audience; A general catalyzed direct C-H functionalization of s-tetrazines is reported. Under mild reaction conditions, N-directed ortho-C-H activation of tetrazines allows the introduction of various functional groups, thus forming carbon-heteroatom bonds: C-X (X=I, Br, Cl) and C-O. Based on this methodology, we developed electrophilic mono- and poly-ortho-fluorination of tetrazines. Microwave irradiation was optimized to afford fluorinated s-aryltetrazines, with satisfactory selectivity, within only ten minutes. This work provides an efficient and practical entry for further accessing highly substituted tetrazine derivatives (iodo, bromo, chloro, fluoro, and acetate precurso…

Synergistic effect of W incorporation and pulsed current mode on wear and tribocorrosion resistance of coatings grown by plasma electrolytic oxidatio…

2019

Ceramic coatings were grown by plasma electrolytic oxidation on 7075 Al alloy using unipolar and bipolar pulsed current waveforms with 20 and 40% cathodic duty cycles, from a silicate-based bath without and with the addition of Na2WO4. Pancake-like morphology was dominant on the coatings grown by unipolar waveform, while the bipolar waveforms promoted volcano-like morphology, increased the roughness of the coating surface and the formation of more compact layers. The coatings produced using the bipolar waveforms provided higher resistances toward both tribocorrosion and dry sliding conditions, while further improvement was achieved by the presence of tungsten. The coatings produced in tungs…

Lagrangian matches between observations from aircraft, lidar and radar in a warm conveyor belt crossing orography

2021

Warm conveyor belts (WCBs) are important airstreams in extratropical cyclones, often leading to the formation of intense precipitation and the amplification of upper-level ridges. This study presents a case study that involves aircraft, lidar and radar observations in a WCB ascending from western Europe towards the Baltic Sea during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) and T-NAWDEX-Falcon in October 2012, a preparatory campaign for the THORPEX North Atlantic Waveguide and Downstream Impact Experiment (TNAWDEX). Trajectories were used to link different observations along the WCB, that is, to establish so-called Lagrangian matches between observations. To this aim, a…

Bacterial communities in stratified humic lakes

2012

Russian immigrant entrepreneurship in Finland : narratives of eight Russian immigrant entrepreneurs

2014

Introduire un dispositif de renforcement disciplinaire en 1ère année universitaire permet-il aux étudiants d'obtenir de meilleures notes ?

2014

Avec le Plan Réussite en Licence (PRL), de nouveaux dispositifs d'aides à la réussite ont été expérimentés au sein des universités françaises. Or, l'étude de l'efficacité de ces dispositifs demeure peu développée, mis à part la méthodologie du travail universitaire (Coulon, 2005) ou le tutorat (Danner, 2000). Il est ainsi difficile d'identifier quel type de mesure semble le plus approprié pour agir le plus efficacement sur la réussite des étudiants, ne serait-ce que parce que peu de recherches se concentrent sur les questions d'apprentissage dans l'enseignement supérieur français (Fave-Bonnet et Clerc, 2001). L'ambition de cette communication est de mesurer les effets d'un nouveau type de d…

Stable carbon and oxygen isotope fractionation in bivalve (Placopecten magellanicus) larval aragonite

2008

Abstract The relationship between stable isotope composition (δ13C and δ18O) in seawater and in larval shell aragonite of the sea scallop, Placopecten magellanicus, was investigated in a controlled experiment to determine whether isotopes in larval shell aragonite can be used as a reliable proxy for environmental conditions. The linear relationship between δ13CDIC and δ13Caragonite (r2 = 0.97, p  δ 13 C DIC = 1.15 ( ± 0.05 ) ∗ δ 13 C aragonite - 0.85 ( ± 0.04 ) The relationship between δ13CDIC and δ13Caragonite described for P. magellanicus resulted in larval shell aragonite that was depleted on average by 1.82‰ (SD = 0.22‰, range = 1.1–2.1‰) from predicted equilibrium values based on the r…

Carbon cycle and sea-water palaeotemperature evolution at the Middle-Late Jurassic transition, eastern Paris Basin (France).

2014

14 pages; International audience; A very high-resolution carbon and oxygen stable isotope analysis (bulk-carbonate) of a biostratigraphically well-constrained Callovian-Oxfordian series is provided here for the first time. The homogeneity of the clayey series and the weak diagenetic alteration allow the isotopic signal variations to be considered as primary in origin. A prominent and brief negative excursion in the δ13C curve (−2‰), occurring at the start of the Middle Callovian (Jason Zone - Obductum Subzone) and correlated regionally, suggests a possible methane release. The increasing δ13C values thereafter up to the Early Oxfordian, concomitant with a warming episode, highlight the buri…