Search results for "LCA"
showing 10 items of 1995 documents
On norm attaining operators and multilinear maps
2014
El principal punto de interés de esta tesis es el estudio de extensiones de los teoremas de Bishop-Phelps y Bishop-Phelps-Bollobás a diferentes contextos. Esta tesis se divide en tres capítulos. En el primero hacemos un repaso de la teoría de funcionales que alcanzan la norma. En este resumen introducimos el Teorema de Bishop-Phelps y el Teorema de Bishop-Phelps-Bollobás. El segundo capítulo está dedicado al estudio de extensiones de los resultados de Bishop-Phelps y Bishop-Phelps-Bollobás al caso de operadores. En la sección 2.2 estudiaremos la extensión de estos resultados al caso de operadores desde el punto de vista de alcanzar el radio numérico, para concluir en la sección 2.3.1 que el…
UV camera measurement at a dormant volcano
2010
The UV camera is now becoming a new important tool in the armory of volcano geochemists for high rate SO2 flux measurements. The high spatial resolution of the camera is particularly useful for exploring multiple-source SO2 gas emissions, as the large composite fumarolic systems topping most quiescent volcanoes. We report here on the first SO2 flux measurements from individual fumaroles of the fumarolic field of La Fossa crater (Vulcano island, Aeolian island), which we performed using a UV camera in two field campaigns on November 12, 2009 and February 4, 2010. Making advantage of the high temporal and spatial resolution of the UV camera, we derived ~0.5 Hz SO2 flux time-series for the mai…
Vulcamera: a program for measuring volcanic SO2 with UV cameras
2011
UV Cameras for volcanic monitoring
2011
This work, following the field setup of Kantzas et al (2010), with the addition of a single point DOAS telescope, investigated the range of data available utilizing a two camera, dual filter setup and demonstrated its value for future use in the study of degassing volcanic systems.
Reworking of the Tarim Craton by underplating of mantle plume-derived magmas: Evidence from Neoproterozoic granitoids in the Kuluketage area, NW China
2011
Abstract Most Neoproterozoic granitoids in the Kuluketage area, northern Tarim Craton are characterized by strongly depleted HREE abundances and high Sr/Y and (La/Yb) N ratios, showing typical geochemical features of adakitic rocks. Zircon U–Pb dating of three adakitic plutons yielded Neoproterozoic ages (754 ± 4, 790 ± 3 and 798 ± 3 Ma). The adakitic granitoids exhibit low MgO and TiO 2 contents. Their low Cr, Co and Ni abundances, low ɛ Hf ( t ) values (−21 to −11) and high FeO T /MgO ratios (mostly 2.2–2.9) preclude the possibility of being derived from partial melts of delaminated lower crust. The relatively low ɛ Hf ( t ) values and old Hf two-stage model ages ( T DM 2 = 2 . 42 – 3 .0 …
Dynamics of outgassing and plume transport revealed by proximal Unmanned Aerial System (UAS) measurements at Volcán Villarrica, Chile
2019
Volcanic gas emissions are intimately linked to the dynamics of magma ascent and outgassing, and, on geological timescales, constitute an important source of volatiles to the Earth's atmosphere. Measurements of gas composition and flux are therefore critical to both volcano monitoring and to determining the contribution of volcanoes to global geochemical cycles. However, significant gaps remain in our global inventories of volcanic emissions, (particularly for CO2, which requires proximal sampling of a concentrated plume) for those volcanoes where the near‐vent region is hazardous or inaccessible. Unmanned Aerial Systems (UAS) provide a robust and effective solution to proximal sampling of …
Redox estimates through trace elements partitioning: application on two Italian volcanoes, model comparison and overview on different geodynamic envi…
2021
Oxygen fugacity of Earth’s mantle is one of the most debated issues of petrology. While is evident that the arc-related magmas are more oxidized than MORB and intraplate magmas, however, is not yet possible to produce a model that can uniquely determine this thermodynamic parameter for the depth of the Earth. Furthermore, there is not a clear cause that create this difference of redox conditions between volcanic products. Recently, several experimental models based on the V partitioning between olivine and mafic melt were published and proposed as tools for investigating the redox state of mantle melts for different geodynamic environments. During this PhD we have applied different oxybarom…
REAL-TIME MEASUREMENT OF VOLCANIC GASES BASED ON INFRARED SPECTROSCOPY
The interpretation of volcanic gas datasets offers key information to build/validate geological models relevant to a variety of volcanic processes and behaviours, including eruptions. Major efforts have therefore been spent in recent years to improve our ability to measure volcanic gas compositions and fluxes. In the last decades, near-infrared room-temperature diode lasers, though in an experimental phase, are finding applications in volcanic gas studies. In this PhD dissertation, I use the GasFinder 2.0, a commercial tunable diode infrared laser transmitter-receiver unit, operating in the 1.3-1.7 m wavelength range, in the attempt to measure CO2 mixing ratios and fluxes in volcanic gas e…
Short-period volcanic gas precursors to phreatic eruptions: Insights from Poás Volcano, Costa Rica
2016
Texto completo del documento Volcanic eruptions involving interaction with water are amongst the most violent and unpredictable geologic phenomena on Earth. Phreatic eruptions are exceptionally difficult to forecast by traditional geophysical techniques. Here we report on short-term precursory variations in gas emissions related to phreatic blasts at Poás volcano, Costa Rica, as measured with an in situ multiple gas analyzer that was deployed at the edge of the erupting lake. Gas emitted from this hyper-acid crater lake approaches magmatic values of SO2/CO21–6 days prior to eruption. The SO2flux derived from magmatic degassing through the lake is measureable by differential optical absorpti…
Contribution à la compréhension des relations entre calcarénites et calcaires à rudistes du Barrémien inférieur dans le Vercors méridional (sud-est d…
2006
12 pages; Ce travail porte sur les calcaires à rudistes (Monopleuridae et Requienidae du Barrémien inférieur et base du Barrémien supérieur, essentiellement) du Vercors méridional. Il s'intéresse tout particulièrement aux relations qui existent entre ce faciès et les calcarénites barrémiennes de ce secteur. Les coupes levées et les panoramas réalisés montrent que le motif de dépôt des formations concernées est répétitif et indique, pour ce qui concerne les calcarénites, une diminution de l'hydrodynamisme que l'on interprète comme due à une augmentation de l'accommodation. Les calcaires à rudistes sus-jacents, et qui se mettent en place avant des calcaires argileux ou des dépôts marneux, sem…