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Interazioni crosta-mantello e connessioni con il sistema geodinamico nell’origine e circolazione dei fluidi dell’Arcipelago delle Comore - Oceano Indiano
No full textL'area di studio si concentra su due isole dell'arcipelago delle Comore: Grande Comore e Mayotte, situate all'interno del Canale di Mozambico e in un complicato sistema geodinamico di grande interesse a causa dell'attività vulcanica e sismica attualmente esistente e di cui attualmente manca un quadro descrittivo completo. In particolare, per quanto riguarda la geochimica dei fluidi, esiste ancora una conoscenza molto limitata delle emissioni di gas e fluidi.
Sull'isola Grande Comore ci si è concentrati sul vulcano Karthala, il più attivo dell'Oceano Indiano occidentale dopo il Piton de la Fournaise a La Reunion. Karthala è un vulcano a scudo basaltico che ha eruttato regolarmente nell'ultimo secolo, quattordici eruzioni sono elencate dal 1904 ad oggi, e l'ultima eruzione è del 2007. Lo studio del degassamento diffuso del vulcano Karthala, con particolare attenzione all'emissione di CO2 dai fianchi del vulcano, e del degassamento fumarolico sommitale è fondamentale per la valutazione dello stato di attività del vulcano.
Mayotte è l'isola più vecchia dell'arcipelago e nessuna eruzione recente è stata registrata a dall'ultima intorno al 2050 a.C. ± 500; tuttavia, l'attività vulcanica a Mayotte è ancora presente sotto forma di una vasta area di degassamento subaereo e subacqueo nella piccola isola a nord-est di Mayotte: Petite Terre. Qui due zone ad alto degassamento sono presenti: la spiaggia sud-orientale (BAS); e il lago Dziani situato nella parte nord dell'isola di Petite Terre. L’isola è stata recentemente interessata da una crisi sismica che è durata diversi mesi, ed è stata accompagnata dalla formazione del più grande vulcano sottomarino degli ultimi secoli, a circa 50 km dalla sua costa.
La tesi è divisa in due sezioni: la prima si concentra sulle emissioni di gas di Karthala e dell’area BAS a Petite Terre, con lo scopo di identificare le principali caratteristiche, similitudini e differenze; la seconda sezione della tesi si concentra sulla differenza tra le due aree di gorgogliamento di Petite Terre, dove sarà incluso lo studio delle emissioni di gas del lago Dziani che sono state indagate solo nelle indagini più recenti.
I risultati di questa tesi convergono verso il riconoscimento di alcune notevoli peculiarità:
1. Le emissioni di CO2 nel suolo sono spazialmente distribuite lungo le principali caratteristiche strutturali sia della Grande Comore che di Petite Terre; tuttavia, la firma isotopica del carbonio delle emissioni di CO2 nel suolo evidenzia un basso contributo magmatico nelle aree distali del vulcano Karthala, e un contributo magmatico più alto nelle emissioni di CO2 a Petite Terre, relativamente al periodo di osservazione.
2. La firma isotopica dell'elio è tipicamente bassa e compresa nell'intervallo di valori ~6 ≤ Rc/Ra ≤ ~7.5 a Petite Terre e ~4.6 ≤ Rc/Ra ≤ ~5.8 a Karthala.
3. L'area di gorgogliamento sul mare (BAS) e al lago Dziani (Mayotte) hanno probabilmente una alimentazione comune; tuttavia, il lago Dziani è significativamente influenzato da processi secondari legati alle attività biotiche nel lago che ne determinano una maggiore variabilità della chimica del gas, nel 13C (CH4 e CO2) rispetto a BAS.
4. L'aumento del valore di Rc/Ra tra il 2008 e il 2018-19, e un non raggiunto equilibrio isotopico di 13CCH4 dal fluido idrotermale, può essere attribuito all'attività vulcanica che ha generato il nuovo vulcano sottomarino a 50 km al largo di Petite Terre.
Quest’ultima considerazione è anche coerente con l'interpretazione finale di questo lavoro, dove l'ingresso di fluido riscaldato ricco di CO2 nel sistema idrotermale di Petite Terre è una conseguenza della perturbazione del sistema idraulico superficiale legata alla eruzione sottomarina, con conseguente aumento delle temperature di equilibrio nel 2018 e successivo raffreddamento durante e dopo l'attività sismo-vulcanica.The study area focuses on two islands of the Comoros archipelago, Grande Comore and Mayotte, located within the Mozambique Channel and in a complicated geodynamic system of great interest due to the volcanic and seismic activity that currently exists and of which a complete descriptive picture is currently lacking. In particular, there is still very limited knowledge of gas and fluid geochemistry.
On Grande Comore, the focus was on the Karthala volcano, the most active volcano in the western Indian Ocean after Piton de la Fournaise in La Reunion. Karthala is a basaltic shield volcano that has erupted regularly over the last century, fourteen eruptions are listed from 1904 to the present, with the last eruption in 2007. The knowledge of the diffuse degassing of the Karthala volcano, with particular attention to the emission of CO2 from the flanks and of the summit fumarolic area is fundamental for the assessment of the state of activity of the volcano.
Mayotte is the oldest island in the archipelago and no recent eruptions have been recorded since the last one around 2050 BC ± 500; however, volcanic activity in Mayotte is still present in the form of a large area of subaerial and underwater outgassing on the small island to the north-east of Mayotte: Petite Terre. Two areas of high outgassing are present here: the south-eastern beach (BAS); and Lake Dziani located in the northern part of the island of Petite Terre. The island was recently affected by a seismic crisis that lasted several months, and was accompanied by the formation of the largest submarine volcano in recent centuries, about 50 km from its coast.
The thesis is divided into two sections: the first focuses on gas emissions from Karthala and the BAS area at Petite Terre, with the aim of identifying the main characteristics, similarities and differences; the second section of the thesis focuses on the difference between the two bubbling areas at Petite Terre, where the study of gas emissions from Lake Dziani, which have only been investigated in more recent surveys, will be included.
The results of this thesis converge towards the recognition of some remarkable peculiarities:
1. Soil CO2 emissions are spatially distributed along the main structural features of both Grande Comore and Petite Terre; however, the carbon isotopic signature of soil CO2 emissions shows a low magmatic contribution in the distal areas of Karthala volcano, and vice-versa a higher magmatic contribution in CO2 emissions at Petite Terre, relative to the period of observation.
2. The helium isotopic signature is typically low and in the range of ~6 ≤ Rc/Ra ≤ ~7.5 at Petite Terre and ~4.6 ≤ Rc/Ra ≤ ~5.8 at Karthala.
3. The bubbling area on the sea (BAS) and at Dziani lake (Mayotte) are likely fed by a common source; however, Dziani lake is significantly affected by secondary processes that are mainly related to biotic activities in the lake, which result in the higher variability of gas chemistry, 13C in methane and CO2 than BAS.
4. The increased value of Rc/Ra between 2008 and 2018-19, and a not-reached isotopic equilibrium of 13CCH4 from the hydrothermal fluid, may be ascribed to the volcanic activity that generated the new submarine volcano 50 km offshore from Petite Terre.
The latter consideration is also consistent with the final interpretation of this work, where the input of heated CO2-rich fluid into the Petite Terre hydrothermal system is a consequence of the perturbation of the shallow plumbing system by the offshore submarine eruption, resulting in higher equilibrium temperatures in 2018 and subsequent cooling down during and after the seismo-volcanic activity
Etna CO2 Soil Flux during 2002-2010 (ECSF2002_2010)
No full textThe ETNAGAS network comprises 19 monitoring stations distributed across the flanks of Mount Etna, specifically designed for the continuous observation of soil-emitted carbon dioxide (CO₂). Each station is equipped with infrared (IR) sensors for the precise measurement of CO₂ concentrations, along with meteorological sensors that record key environmental parameters including air temperature, atmospheric pressure, wind speed and direction, and precipitation. These data enable the estimation of CO₂ soil fluxes through the application of the method proposed by Gurrieri and Valenza (1988) (see Methods for details). The ETNAGAS network represents a high-resolution geochemical surveillance system and constitutes an integral component of the national framework for monitoring volcanic gas emissions. Its primary objective is to contribute to the assessment of the volcanic activity state of Mount Etna through systematic and spatially distributed measurements of gaseous emissions.The monitoring stations of the ETNAGAS network were entirely developed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), Palermo section. These stations are capable of continuously measuring several environmental and geochemical parameters, including soil CO₂ concentration, atmospheric temperature, pressure, relative humidity, rainfall, wind speed, and wind direction. Data are acquired at hourly intervals and automatically transmitted to the monitoring center at INGV-Palermo. It should be noted that not all stations are equipped with the full suite of meteorological sensors.
CO₂ fluxes from the soil can be derived from the recorded data using the dynamic (or dilution) method described by Gurrieri and Valenza (1988). This method is based on measuring the CO₂ content in a mixture of soil gas and atmospheric air (Cd), obtained using a probe inserted approximately 50 cm into the ground. Soil gases enter the probe through its base and are mixed with ambient air; this mixture is then pumped into an infrared (IR) spectrophotometer, which measures the CO₂ concentration.
According to Gurrieri and Valenza, the measured diluted concentration (Cd) is empirically related to the actual soil CO₂ flux (ϕCO₂) through a relationship established under laboratory conditions, across a range of gas permeabilities (0.36–123 mm²) and pumping flow rates (0.4–4.0 L/min) [Camarda et al., 2006a, 2006b].
REFERENCE
• Camarda, M., S. Gurrieri, and M. Valenza (2006a), CO2 flux measurements in volcanic areas using the dynamic concentration method: Influence of soil permeability, J. Geophys. Res., 111, B05202, doi:10.1029/2005JB003898. Camarda, M., S. Gurrieri, and M. Valenza (2006b), In situ permeability measurements based on a radial gas advection model: Relationships between soil permeability and diffuse CO2 degassing in volcanic areas, Pure Appl. Geophys., 163(4), 897–914, doi:10.1007/s00024-006-0045-y.
• Gurrieri, S., and M. Valenza (1988), Gas transport in natural porous mediums: A method for measuring CO2 flows from the ground in volcanic and geothermal areas, Rend. Soc. Ital. Mineral. Petrol., 43, 1151–1158.
• Gurrieri, S., M. Liuzzo, and G. Giudice, (2008), Continuous monitoring of soil CO2 flux on Mt. Etna: The 2004–2005 eruption and the role of regional tectonics and volcano tectonics, J. Geophys. Res., 113, B09206, doi:10.1029/2007JB005003, 2008.
• Liuzzo M., Gurrieri S., Giudice G. & Giuffrida G. (2013) - Ten years of soil CO2 continuous monitoring on Mt. Etna: Exploring the relationship between processes of soil degassing and volcanic activity. Geochem. Geophys. Geosyst., 14, 2886-2899. https://doi. org/10.1002/ggge.2019
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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