Search results for " Planetary"
showing 10 items of 5408 documents
A quantitative analysis of stratospheric HCl, HNO3, and O3 in the tropopause region near the subtropical jet
2014
The effects of chemical two-way mixing on the Extratropical Transition Layer (ExTL) near the subtropical jet are investigated by stratospheric tracer-tracer correlations. To this end, in situ measurements were performed west of Africa (25-32 ◦ N) during the Transport and Composition of the Upper Troposphere Lower Stratosphere (UTLS)/Earth System Model Validation (TACTS/ESMVal) mission in August/September 2012. The Atmospheric chemical Ionization Mass Spectrometer sampling HCl and HNO3 was for the first time deployed on the new German High Altitude and Long range research aircraft (HALO). Measurements of O3, CO, European Centre for Medium-Range Weather Forecasts (ECMWF) analysis, and the tig…
Measurements of HONO, NO, NOyand SO2in aircraft exhaust plumes at cruise
2011
Measurements of gaseous nitrogen and sulfur oxide emissions in young aircraft exhaust plumes give insight into chemical oxidation processes inside aircraft engines. Particularly, the OHA¢Â�Â�induced formation of nitrous acid (HONO) from nitrogen oxide (NO) and sulfuric acid (H2SO4) from sulfur dioxide (SO2) inside the turbine which is highly uncertain, need detailed analysis to address the climate impact of aviation. We report on airborne in situ measurements at cruise altitudes of HONO, NO, NOy, and SO2 in 9 wakes of 8 different types of modern jet airliners, including for the first time also an A380. Measurements of HONO and SO2 were made with an ITCIMS (Ion Trap Chemical Ionization Mass …
Red and far-red sun-induced chlorophyll fluorescence as a measure of plant photosynthesis
2015
Remote estimation of Sun-induced chlorophyll fluorescence emitted by terrestrial vegetation can provide an unparalleled opportunity to track spatiotemporal variations of photosynthetic efficiency. Here we provide the first direct experimental evidence that the two peaks of the chlorophyll fluorescence spectrum can be accurately mapped from high-resolution radiance spectra and that the signal is linked to variations in actual photosynthetic efficiency. Red and far red fluorescence measured using a novel airborne imaging spectrometer over a grass carpet treated with an herbicide known to inhibit photosynthesis was significantly higher than the corresponding signal from an equivalent untreated…
Interlamellar Reactions of Tetracalcium Aluminate Hydrates with Water and Organic Compounds
1967
Tetracalcium aluminate hydrates are the first example of layer-structured crystals containing neutral sheets, which are highly capable of interlamellar adsorption of water and neutral organic compounds. In this respect tetracalcium aluminate hydrates present new aspects of the phenomenon of swelling, and bring about the challenge of comparison with the frequently examined clay-organic compounds. This report is concerned with the probable monolayer structure of tetracalcium aluminate hydrate which forms five hydration stages. A summary concerning configuration and properties of adsorption complexes with approximately 500 selected organic substances follows. As far as these substances are hom…
A laboratory study on the scavenging of SO2 by snow crystals
1990
Abstract A laboratory experiment is described where the uptake of SO2 by dendritic snow crystals was studied. In a first experimental series the uptake of SO2 was investigated during the growth of the snow crystals from water vapor with and without the presence of H2O2 in the air. In a second series of experiments we studied the uptake of SO2 by snow crystals which had completed their growth. The results of our experiments showed that under both conditions SO2 became scavenged by snow crystals. The uptake of SO2 was particularly pronounced during the growth of the snow crystals, and at temperatures close to 0°C where a quasi-liquid layer exists at the surface of ice. As expected, the SO2 up…
Multiphase chemistry in a microphysical radiation fog model—A numerical study
1993
A microphysical radiation fog model is coupled with a detailed chemistry module to simulate chemical reactions in the gas phase and in fog water during a radiation fog event. In the chemical part of the model the microphysical particle spectrum is subdivided into three size classes corresponding to non-activated aerosol particles, small and large fog droplets. Chemical reactions in the liquid phase are separately calculated in the small and in the large droplet size class. The impact of the chemical constitution of activated aerosols on fogwater chemistry is considered in the model simulations. The mass transfer of chemical species between the gas phase and the two liquid phases is treated …
Synthesis of β-tubulin mRNA in neural induction and specification
1990
Ľibridazionein situ condotta su embrioni diXenopus laevis con cDNA di β-tubulina ha dimostrato un forte incremento nelle cellule della piastra neurale e delľectoderma laterale dopo la gastrulazione, quando il cordomesoderma viene a contatto con ľectoderma. Esperimenti condotti su espianti di ectoderma neurale presuntivo eseguiti prima e dopo ľinduzione neurale suggeriscono che le cellule abbiano gia un orientamento specifico in senso neurale allo stadio di blastula. prima che ľinduzione avvenga.
Réactivité vis-à-vis de l'oxygène de spinelles de fer-vanadium de taille nanométrique et distribution cationique
1997
Resume L'etat de division des spinelles de fer-vanadium nanometriques V x Fe 3− x O 4 (0 ⩽ x ⩽ 2 ) permet d'oxyder au sein-meme de la structure spinelle les ions du fer et du vanadium. Les analyses calorimetriques et thermogravimetriques, ainsi que la spectroscopie infrarouge, montrent que les ions Fe B 2+ ,V B 3+ et Fe A 2+ sont oxydes successivement en ions Fe 3+ et V 5+ a des temperatures inferieures a 450 °C. Les spinelles lacunaires a valence mixte qui en resultent, ont un taux en lacunes croissant avec x, qui peut etre superieur a ceux determines jusqu'alors pour ce type d'oxydes.
Chemical characterization of iron in atmospheric aerosols
1992
Abstract The total Fe content, the soluble fractions of Fe(II) and Fe(III), and several species of Fe were determined in various atmospheric aerosol samples by means of atomic absorption spectrometry, ion chromatography and Mossbauer spectrometry.
Analyzing Regional Geographic Challenges: The Resilience of Chinese Vineyards to Land Degradation Using a Societal and Biophysical Approach
2021
Land degradation, especially soil erosion, is a societal issue that affects vineyards worldwide, but there are no current investigations that inform specifically about soil erosion rates in Chinese vineyards. In this review, we analyze this problem and the need to avoid irreversible damage to soil and their use from a regional point of view. Information about soil erosion in vineyards has often failed to reach farmers, and we can affirm that to this time, soil erosion in Chinese vineyards has been more of a scientific hypothesis than an agronomic or environmental concern. Two hypotheses can be presented to justify this review: (i) there are no official and scientific investigations on viney…