130,503 research outputs found
Magmatic Processes at Euganean Hills (Veneto Volcanic Province, Italy): Clinopyroxene Investigation to Unravel Magmatic Interactions
No full textThe Euganean Hills (NE Italy) magmatic district represents the final volcanic activity of the Veneto Volcanic Province. Alkaline to subalkaline magmatic suite dominated by intermediate to felsic volcanic rocks characterises the latest volcanic activity of the Euganean Hills. Magmatic (intrusive and volcanic) enclaves are common in Euganean Hills trachytes. We used the ability of clinopyroxene to record variations of P, T, and fO2 to reconstruct the geological history of the volcanic enclaves and trachytic host. Despite similar major and trace elements composition, clinopyroxene from host is higher in Ca and Na (and Fe3+) and lower in Mg than enclaves and is slightly enriched in trace elements but with the same pattern distribution. Minor differences in geochemistry and crystal structure of clinopyroxene from enclaves and trachytic host suggest similar parental magmas that differs by small degrees of fractional crystallisation. Clinopyroxene geobarometry performed combining X-ray diffraction with mineral geochemistry for volcanic enclaves–trachytic host combined with amphibole geobarometry for intrusive enclaves and crystal mushes points to a crystallisation pressure range between 4.8–2.0 kbars. Our data support the model of a complex system of magma chambers at intermediate to shallow crustal level where mafic magma accumulated, evolved by fractionation processes and mixed
Degassing behaviour at basaltic volcanoes: New insights from experimental investigations of different conduit geometry and magma viscosity
No full textUnderstanding gas-magma dynamics in volcanic conduits and linking them with the associated geophysical signals at the surface is of fundamental importance in monitoring active volcanoes. In the past, a significant number of studies have been devoted to this topic, addressing the onset, the key factors governing each degassing regime and the related markers at the surface, particularly at basaltic volcanoes. Here, we first review such a broad and increasing literature, focusing on the main approaches used in the attempt of deciphering conduit dynamics by indirect observations: 1) analogue laboratory experiments; and 2) seismo-acoustic measurements. Then, we combine the two techniques into a novel set of experiments, addressing a crucial, yet unexplored, issue: the irregularity (i.e. the departure from an ideal smooth cylindrical shape) of the conduit surface. We built a set of epoxy conduits with various fractal dimensions (D c ; i.e. irregularity) of the internal surface, using silicone oil as a proxy for magma. Different degassing patterns (bubbly, slug and churn-annular flow) were reproduced by changing systematically: 1) injected gas flux (5 to 180 × 10 −3 l/s); 2) analogue magma viscosity (10 to 1000 Pas); 3) fractal dimension (D c ) of the conduit surface (i.e. D c = 2, D c = 2.18 and D c = 2.99). The experiments were monitored by means of a video-camera and a set of sensor aimed to detect the seismic and acoustic signals. Results show that viscosity strongly influences the transition among degassing patterns and the recurrence rate of slug bursts at the surface. Moreover, we observed an increase of the exponent of the power law equation linking squared seismic amplitude to gas flow rate with conduit roughness; the opposite trend was noticed with increasing liquid viscosity. These results have important implications for linking seismic tremor to eruption source parameters such as the volume discharge rate at different volcanoes or for investigating its temporal evolution at a single vent
ILCatalogo: a digital archive for theatre cultural heritage
No full textIn this article the final results of the research project "Digital archive of the artistic heritage of Emanuele Luzzati: the
theatre" will be presented. The project, lasting two years, was funded under the Convention between the Region of
Liguria and ILC-CNR for “Higher education projects Operational Programme (OP) Regional Competitiveness and
Employment (CRO) European Social Fund (ESF) 2007-2013 Liguria Region axis IV Human Capital Specific Objective I /
6” and it ended on April 30th, 2015. The main theme of the research was on the structuring, integration, accessibility and
maintenance of archives and the scope of intervention is related to cultural heritage
Experimental magma mixing between rhyolitic and basaltic melts: implications for the Bruneau-Jarbidge magmatism, Snake River Plain (USA)
No full textInterdiffusion of major elements at 1 atmosphere between natural shoshonitic and rhyolitic melts
No full textRheological evolution of eruptible Basaltic-Andesite Magmas under dynamic conditions: The importance of plagioclase growth rates
No full textThe effects of crystal nucleation and growth on the viscosity of andesitic magmas are investigated at 1 atm. Pressure. The data are used to describe the rheological evolution of andesitic magmas and to derive empirical equations to model the crystallization dynamics. Viscosity experiments were performed at temperatures of 1473, 1483, and 1493 K with shear rates of 0.5 s−1 by using wide-gap concentric cylinder viscometry. We focused on eruptible magmas (i.e., crystal contents well-below ~50%) by following the time evolution of crystal nucleation and growth of a natural andesitic magma, while continuously monitoring the changes in viscosity. At near-equilibrium conditions, the basaltic-andesite contains 6, 13, and 25 area % crystals at 1493, 1483, and 1473 K, respectively, resulting in a viscosity increase of ca. 1 log unit. We show that the timescale of viscosity increase is mainly dictated by the delay time preceding crystallization and markedly decreases with increasing undercooling (from 22 to 42 K) and shear rates (from 0.1 to 1 s−1). The plagioclase growth rates estimated from our data are in the order of ~3–5 × 10−6 cm/s, which is much faster than the rates estimated for crystallization in static conditions. We conclude that the effect of the shear rate must be taken into account in modelling magmatic and volcanic processes, especially when transient changes in viscosity need to be estimated. Our results are important for understanding the dynamics of lava flows where deformation plays a significant role in promoting crystallization
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Assimilation of rhyolitic magma by basaltic recharge in the Bruneau-Jarbidge eruptive center, Snake River Plain (USA)
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