47 research outputs found
Total CO2 output from Vulcano island (Aeolian Islands, Italy)
Total CO2 output from fumaroles, soil gas, bubbling gas discharges and water dissolved gases discharged
from the island, was estimated for Vulcano island, Italy. The CO2 emission from fumaroles from the La
Fossa summit crater was estimated from the SO2 crater output, while CO2 discharged through diffuse soil
emission was quantified on the basis of 730 measurements of CO2 fluxes from the soil of the island, performed
by using the accumulation chamber method. The results indicate an overall output of â
500 t day 1
of CO2 from the island. The main contribution to the total CO2 output comes from the summit area of
the La Fossa cone (453 t day 1), with 362 t day 1 from crater fumaroles and 91 t day 1 from crater soil
degassing. The release of CO2 from peripheral areas is â
20 t day 1 by soil degassing (Palizzi and Istmo areas
mainly), an amount comparable to both the contribution of water dissolved CO2 (6 t day 1), as well as to
seawater bubbling CO2 (4 t day 1 measured in the Istmo area). Presented data (September 2007) refer to a
period of moderate solphataric activity, when the fumaroles temperature were 450°C and gas/water
molar ratio of fumaroles was up to 0.16. The calculated total CO2 emission allows the estimation of the mass release and related thermal energy from the volcanic-hydrothermal system
CO2 output discharged from Stromboli Island (Italy)
Total CO2 output from soil gas and plume, discharged from the Stromboli Island, was estimated. The CO2
emission of the plume emitted from the active crater was estimated on the basis of the SO2 crater output
and C/S ratio, while CO2 discharged through diffuse soil emission was quantified on the basis of 419 measurements
of CO2 fluxes from the soil of the whole island, performed by using the accumulation chamber method.
The results indicate an overall output of â
416 t dayâ1 of CO2 from the island. The main contribution to the
total CO2 output comes from the summit area (396 t dayâ1), with 370 t/day from the active crater and
26 t dayâ1 from the Pizzo sopra La Fossa soil degassing area. The release of CO2 from peripheral areas is
â
20 t dayâ1 by soil degassing (Scari area mainly). The result of the soil degassing survey confirms the persistence
of the highest CO2 degassing areas located on the North-East crater side and Scari area
4MOST: Project overview and information for the First Call for Proposals
We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs (), and 812 fibres transferring light to the high-resolution spectrograph (). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations
Contribution à l'étude du durcissement du niobium et de certains de ses alliages liés aux interstitiels, entre 20 et 1 200 °C
Des essais de traction effectués sous vide entre 20 et 1 200 °C sur divers alliages de Niobium ont permis de distinguer trois composantes dans la contrainte de déformation plastique de ce métal. Les deux premiers termes sont la limite élastique et un terme de consolidation ; les essais ont permis de mettre en évidence l'influence des facteurs de structure (impuretés, précipités...) et des paramÚtres de la déformation (vitesse et température) sur ces deux composantes. Le troisiÚme terme caractérise des effets de durcissement, liés à des interactions interstitiels-dislocations, et les essais ont montré l'existence de pics successifs en fonction de la température ; l'étude de l'influence de la vitesse de déformation et de la concentration en oxygÚne a permis de déterminer les différents facteurs intervenant sur l'intensité de ces pics, d'interpréter leurs déplacements en température, et de les caractériser par rapport aux différents interstitiels