305,275 research outputs found
Constraining the dynamics of volcanic eruptions by characterization of pumice textures
No full textWe have characterized the textures of pumice clasts from Phlegraean Fields to gain insights into the conduit flow-dynamics of alkaline explosive eruptions. Vesicularities, vesicle number densities, and vesicle sizes and shapes were measured to obtain the bulk and groundmass properties of the juvenile fraction of Campanian Ignimbrite (CI) and Agnano Monte Spina (AMS) eruptions. The results report the coexistence of three end-member pumice types in the deposits of both eruptions, 1) microvesicular, 2) tube and 3) expanded, which differ according to clast morphology and the macro- to microscopic vesicle texture. Vesicularities (0.85-0.94 for CI, 0.51-0.91 for AMS) and vesicle number densities (2-4×105 cm-2 in CI, 3×105-106 cm-2 in AMS) span quite a wide range in all the three pumice types. Overall, tube pumices exhibit the highest bulk (0.89) and groundmass (CI 0.85, AMS 0.82) average vesicle volume fractions but the lowest average vesicle number densities (CI 2×105, AMS 4×105 cm-2). Comparison with textures of calc-alkaline pumices has revealed many similarities and points to a common origin and distribution of the products from both magma compositions within the volcanic conduit. In addition, the results of the textural analysis were interpreted in the light of the conduit flow modeling of Phlegraean Fields eruptions. The comparison of textural observations with results from simulations of conduit magma ascent has exhibited a good agreement between measured and numerically calculated vesicularities for both compositions, helping to constrain the overall dynamics of alkaline versus calc-alkaline eruptions
Figure e configurazioni. Il ruolo del semi-simbolismo
No full textRiflessioni sul ruolo delle dinamiche figurativo-configurazionali per l'analisi semisimbolica dei valori di senso associati a forma estese di testualità. A partire da un caso di studio specifico (i layout dei punti-vendita di due grandi catene di distribuzione dell'elettronica di consumo) il contributo sviluppa una prospettiva analitica legata alla messa a fuoco di "immagini descrittive", rese possibili dalle associazioni semisimboliche tra tratti e valori
Quando si deve comunicare. La comunicazione dei censimenti tra identità locali e nuove tecnologie
No full textGoing 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Constraining the dynamics of volcanic eruptions by characterization of pumice textures
No full textWe have characterized the textures of pumice clasts from Phlegraean Fields to gain insights into the conduit
flow-dynamics of alkaline explosive eruptions. Vesicularities, vesicle number densities, and vesicle sizes and
shapes were measured to obtain the bulk and groundmass properties of the juvenile fraction of Campanian Ignimbrite
(CI) and Agnano Monte Spina (AMS) eruptions. The results report the coexistence of three end-member
pumice types in the deposits of both eruptions, 1) microvesicular, 2) tube and 3) expanded, which differ according
to clast morphology and the macro- to microscopic vesicle texture. Vesicularities (0.85-0.94 for CI,
0.51-0.91 for AMS) and vesicle number densities (2-4×105 cm-2 in CI, 3×105-106 cm-2 in AMS) span quite a
wide range in all the three pumice types. Overall, tube pumices exhibit the highest bulk (0.89) and groundmass
(CI 0.85, AMS 0.82) average vesicle volume fractions but the lowest average vesicle number densities (CI
2×105, AMS 4×105 cm-2). Comparison with textures of calc-alkaline pumices has revealed many similarities and
points to a common origin and distribution of the products from both magma compositions within the volcanic
conduit. In addition, the results of the textural analysis were interpreted in the light of the conduit flow modeling
of Phlegraean Fields eruptions. The comparison of textural observations with results from simulations of
conduit magma ascent has exhibited a good agreement between measured and numerically calculated vesicularities
for both compositions, helping to constrain the overall dynamics of alkaline versus calc-alkaline eruptions.PublishedJCR Journalope
Breve nota sull’enunciazione e su alcune sue estensioni all’ambito visivo
No full textIl testo critica l'idea, spesso diffusa nell'ambito degli studi di semiotica visiva, secondo cui si possa avere "enunciazione" in senso stretto e non metaforico nei sistemi semiotica diversi da quello linguistico, come pure critica l'idea che si possa avere l'equivalente dei deittici nei sistemi non linguistici. Pone inoltre una distinzione tra la nozione di "produzione" e quella di "enunciazione", interpretando l'uso che spesso si fa nelle semiotiche visive del termine "enunciazione" come un uso distorto che si avvicina piuttosto a quello di "produzione
Testure
No full textLa Festschrift in onore di Omar Calabrese raccoglie contributi di autori internazionali negli ambiti disciplinari cui calabrese stesso ha contribuito con lavori decisivi: semiotica e semiotica dell'immagine, teoria delle arti di tradizione strutturalista, studi sui mass media, comunicazione politica
Eruption dynamics of the 22–23 April 2015 calbuco volcano (Southern Chile): Analyses of tephra fall deposits
No full textAfter 54 years since its last major eruption in 1961, Calbuco Volcano (Ensenada, Southern Chile) reawakened with few hours of warning on 22 April 2015 at 18:05 local time. The main explosive eruption consisted of two eruption pulses (lasting ~1.5 and 6 h each one) on 22 and 23 April, producing stratospheric (>15 km height) eruption columns. The erupted materials correspond to porphyritic basaltic andesite (~55 wt.% of SiO2). The tephra fall affected mainly the area northeast of the volcano and the finest ash was deposited over Southern Chile and Patagonia Argentina. We studied the tephra fall deposits of both pulses in terms of stratigraphy, distribution, volume, emplacement dynamics and eruption source parameters. Here, we show field observations that have been made 5-470 km downwind and distinguish five layers (Layers A, B, B1, C and D) representing different stages of the eruption evolution: eruption onset (Layer A; pulse 1), followed by the first paroxysmal event (Layer B; pulse 1), in some places interbedded by layer B1, tentatively representing the sedimentation of a secondary plume during the end of pulse 1. We recognized a second paroxysm (Layer C; pulse 2) followed by the waning of the eruption (Layer D; pulse 2). The total calculated bulk tephra fall deposit volume is 0.27 ± 0.007 km3 (0.11-0.13 km3 dense rock equivalent), 38% of which was erupted during the first phase and 62% during the second pulse. This eruption was a magnitude 4.45 event (VEI 4 eruption) of subPlinian type.Fil: Romero, J. E.. Universidad de Atacama; ChileFil: Morgavi, D.. Università di Perugia; ItaliaFil: Arzilli, F.. University of Manchester; Reino UnidoFil: Daga, Romina Betiana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Caselli, Alberto Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Negro; ArgentinaFil: Reckziegel, Florencia Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Viramonte, Jose German. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Díaz Alvarado, J.. Universidad de Atacama; ChileFil: Polacci, M.. University of Manchester; Reino UnidoFil: Burton, M.. University of Manchester; Reino UnidoFil: Perugini, D.. Università di Perugia; Itali
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