1,720,995 research outputs found
Quaderno a cancelli
No full textIl testo è una nuova e completa edizione di Quaderno a cancelli, pubblicato postumo da Linuccia Saba e Aldo Marcovecchio nel 1979. Presenta il finale inedito e un nuovo riposizionamento dei materiali che nella precedente edizione erano stati arbitrariamente collocati. L'opera è introdotto da un capitolo a firma del curatore e da una lunga nota al testo che spiega lo stato in cui versa il materiale manoscritto
Deformation at Stromboli volcano (Italy) revealed by rock mechanics and structural geology
No full textWe approach the reconstruction of the recent structural evolution of Stromboli volcano (Italy) and the analysis of the interplay between tectonics, gravity and volcanic deformation. By tying together structural, lithostratigraphic and rock mechanics data, we establish that since 100 ka BP, the edifice has faulted and jointed mainly along NE-striking planes. Faults mostly dip to the NW with normal displacement. Taking also into account the presence of a NW-trending regional least principal stress and of tectonic earthquake hypocenters inside the cone, we suggest that this fracturing can be related to the transmission of tectonic forces from the basement to the cone. Dyking concentrated along a main NE-trending weakness zone (NEZ) across the volcano summit, resembling a volcanic rift, whose geometry is governed by the tectonic field. In the past 13 ka, Stromboli experienced a reorganisation of the strain field, which was linked with the development of four sector collapses affecting the NW flank, alternating with growth phases. The tectonic strain field interplayed with dyking and fracturing related to unbuttressing along the collapse shoulders. We propose that tectonics control the geometry of dykes inside the cone and that these, in turn, contribute to destabilise the cone flanks
Stability of a collapsing volcano (Stromboli, Italy) : Limit equilibrium analysis and numerical modelling
No full textStromboli is an active island volcano, belonging to the Aeolian Archipelago (Italy). In the last 13 ka it experienced four lateral collapses affecting its northwestern flank, with its most recent volcanic crisis (December 2002) associated with landslides and related tsunami events. This paper presents the first stability analysis of the Stromboli volcanic edifice. The main input is the geotechnical model of the volcano, defined on the basis of stratigraphical, lithological, material properties, and structural data, collected from in-situ surveys and laboratory tests. Two-dimensional stability analysis was performed by limit equilibrium methods (LEM) and finite difference modelling (FLAC 4.0 code), mainly focusing on the subaerial part of Stromboli's NW flank (Sciara del Fuoco). The variability of the Safety Factor was studied by deterministic, sensitivity and probabilistic analysis focusing on the effect of external forces, such as magma pressure and seismicity, as potential triggering mechanisms of lateral collapse. The LEM analyses were developed considering a maximum depth of 150-350 in for the sliding surface, to which correspond collapse volumes of 95,000-185,000 m(3)/m, respectively. The study shows that, without external forces, the investigated rock mass is stable and that the tectonic seismicity of the area alone does not destabilize the studied slope. On the contrary, magma pressure in dykes can represent a destabilizing factor. Numerical modelling results are concordant with those from LEM. In addition, the simulation reveals that deformations and superficial landslides, preannounce and contribute to retrogressive plasticization and maybe to failure surface deepening. Shallow submarine landslides represent a possible triggering mechanism, and the landslide events of 30 December 2002 consistently fit the simulated evolution. FLAC has revealed to be a useful tool for modelling such a complex system, it allowed to calibrate the response of the geotechnical model, test the validity of the assumptions, simulate the stress-strain evolution, and prepare a possible model for future scenarios. (c) 2004 Elsevier B.V. All rights reserved
Physical and mechanical properties of rock masses at Stromboli : a dataset for volcano instability evaluation
No full textStromboli island has a complex geological history with repeated changes in the volcanic activity alternating with destructive events, caldera collapses and flank landslides. The last activity resulted in the creation of the Sciara del Fuoco depression which was modified by the recent 2002-2003 landslide. The variation in lithology, degree of tectonization and disturbance has resulted in the presence of a wide spectrum of geotechnical materials. This paper summarises the physical and mechanical properties of Stromboli's intact rocks, rock masses and loose deposits, based on field surveys and laboratory tests. A new classification of the rock succession is introduced and four lithotechnical units defined: Lava, Lava-Breccia, Breccia and Pyroclastic deposit. The range of variability in bulk volume, porosity, intact rock compressive strength and geological strength index is presented. The Hoek and Brown's failure criterion was applied for each lithotechnical unit and the rock mass friction angle, apparent cohesion, tensile and compressive strength, global strength and modulus of deformation calculated in a specified stress range
Oltre i cancelli: l'ultimo Levi
No full textL'autore introduce l'opera di Quaderno a cancelli prendendo in analisi gli aspetti essenziali del percorso intellettuale di Levi, a partire dalla pubblicazione di Cristo si è fermato a Eboli e di Paura della libertà
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
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