349 research outputs found
Comparison between two mobile absolute gravimeters: optical versus atomic interferometers
We report a comparison between two absolute gravimeters: the LNE-SYRTE cold
atoms gravimeter and FG5#220 of Leibniz Universit\"at of Hannover. They rely on
different principles of operation: atomic and optical interferometry. Both are
movable which enabled them to participated to the last International Comparison
of Absolute Gravimeters (ICAG'09) at BIPM. Immediately after, their bilateral
comparison took place in the LNE watt balance laboratory and showed an
agreement of 4.3 +/- 6.4 {\mu}Gal
Development of sustainable tools (Database and software) for Marine Litter Data management
Entregable del proyecto CleanAtlanticEste entregable describe diversas herramientas de utilidad para la gestión de datos de basura marina
CleanAtlantic sea litter geographical web
A Sea litter data viewer has been developed in the framework of the CleanAtlantic European project. This web application allows access to the litter data of different compartments of the ocean as beach litter, floating litter, and seabed litter. The users can query the statistical distributions of litter concentrations, time series, and the composition of the most frequent types of litter of each geographical item. In order to facilitate access to this type of information to all types of users independently of their data analysis skills, the viewer has developed following criteria of simplicity and usability
Attenuation of particulate organic carbon flux in the Scotia Sea, Southern Ocean, is controlled by zooplankton fecal pellets
The Southern Ocean (SO) is an important CO2 reservoir, some of which enters via the production, sinking and remineralization of organic matter. Recent work suggests the fraction of production that sinks is inversely related to production in the SO, a suggestion we confirm from 20 stations in the Scotia Sea. The efficiency with which exported material is transferred to depth (transfer efficiency) is believed to be low in high latitude systems. However, our estimates of transfer efficiency are bimodal, with stations in the seasonal ice zone showing intense losses and others displaying increases in flux with depth. Zooplankton fecal pellets dominated organic carbon flux and at stations with transfer efficiency >100 % fecal pellets were brown, indicative of fresh phytodetritus. We suggest that active flux mediated by zooplankton vertical migration and the presence of sea ice regulate the transfer of organic carbon into the oceans interior in the Southern Ocean
Volcanic ash as an oceanic iron source and sink
Volcanic ash deposition to the ocean forms a natural source of iron (Fe) to surface water microbial communities. Inputs of lithogenic material may also facilitate Fe removal through scavenging. Combining dissolved Fe (dFe) and thorium-234 observations alongside modeling, we investigate scavenging of Fe in the North Atlantic following the Eyjafjallajökull volcanic eruption. Under typical conditions biogenic particles dominate scavenging, whereas ash particles dominate during the eruption. The size of particles is important as smaller scavenging particles can become saturated with surface-associated ions. Model simulations indicate that ash deposition associated with Eyjafjallajökull likely led to net Fe removal. Our model suggests a threefold greater stimulation of biological activity if ash deposition had occurred later in the growing season when the region was Fe limited. The implications of ash particle scavenging, eruption timing, and particle saturation need to be considered when assessing the impact of ash deposition on the ocean Fe cycle and productivity
Geographical, seasonal, and depth variation in sinking particle speeds in the North Atlantic
Particle sinking velocity is considered to be a controlling factor for carbon transport to the deep sea and thus carbon sequestration in the oceans. The velocities of the material exported to depth are considered to be high in high-latitude productive systems and low in oligotrophic distributions. We use a recently developed method based on the measurement of the radioactive pair 210Po-210Pb to calculate particle sinking velocities in the temperate and oligotrophic North Atlantic during different bloom stages. Our estimates of average sinking velocities (ASVs) show that slowly sinking particles (<100?m?d?1) contribute significantly to carbon flux at all the locations except in the temperate regions during the bloom. ASVs appear to vary strongly with season, which we propose is caused by changes in the epipelagic community structure. Our results are the first field data to confirm the long-standing theory that particle sinking velocities increase with depth, with increases of up to 90% between 50 and 150?m depth
IFN-β Expression Is Directly Activated in Human Neutrophils Transfected with Plasmid DNA and Is Further Increased via TLR-4-Mediated Signaling.
Long-lived photoexcited states in polydiacetylenes with different molecular and supramolecular organization
With the aim of determining the importance of the molecular and supramolecular organization on the excited states of polydiacetylenes, we have studied the photoinduced absorption spectra of the red form of poly[1,6-bis(3,6-didodecyl-N-carbazolyl)-2,4-hexadiyne] (polyDCHD-S) and the results compared with those of the blue form of the same polymer. An interpretation of the data is given in terms of both the conjugation length and the interbackbone separation also in relation to the photoinduced absorption spectra of both blue and red forms of poly[1,6-bis(N-carbazolyl)-2,4-hexadiyne] (polyDCHD), which does not carry the alkyl substituents on the carbazolyl side groups. Information on the above properties is derived from the analysis of the absorption and Raman spectra of this class of polydiacetylenes
Geographical, seasonal, and depth variation in sinking particle speeds in the North Atlantic
- …