A Joint Inversion of Ground Deformation and Focal Mechanisms Data for Magmatic Source Modelling

The paucity of geodetic data acquired on active volcanoes can make the understanding of modelling magmatic systems quite difficult. In this study, we propose a novel approach, which allows improving the parameter estimation of analytical models of magmatic sources (e.g., shape, depth, dimensions, volume change, etc.) by means of a joint inversion of surface ground deformation data and P-axes of focal plane solutions. The methodology is first verified against a synthetic dataset of surface deformation and strain within the medium, and then applied to real data from an unrest episode occurred before the May 13 2008 eruption at Mt. Etna (Italy). The main results clearly indicate the joint inversion improves the accuracy of the estimated source parameters by about 70 %. The statistical tests indicate that the source depth is the parameter with the highest increment of accuracy. In addition, a sensitivity analysis confirms that displacements data are more useful to constrain the pressure and the horizontal location of the source than its depth, while the P-axes better constrain the depth estimation

Foreland segmentation along an active convergent margin: New constraints in southeastern Sicily (Italy) from seismic and geodetic observations

We performed an in-depth analysis of the ongoing tectonics of a large sector of southern Sicily, including the Hyblean Foreland and the front of the Maghrebian Chain, as well as the Ionian Sea offshore, through the integration of seismic and GPS observations collected in the nearly two decades. In particular, a dataset consisting of more than 1100 small-to moderate-magnitude earthquakes (1.0 <= M-L <= 4.6) has been used for local earthquake tomography in order to trace the characteristics of the faulting systems, and for focal mechanisms computation to resolve the current local stress field and to characterise the faulting regime of the investigated area. In addition, GPS measurements, carried out on both episodic and continuous stations, allowed us to infer the main features of the current crustal deformation pattern. Main results evidence that the Hyblean Plateau is subject to a general strike-slip faulting regime, with a maximum horizontal stress axis NW-SE to NNW-SSE oriented, in agreement with the Eurasia-Nubia direction of convergence. The Plateau is separated into two different tectonic crustal blocks by the left-lateral strike-slip Scicli-Ragusa Fault System. The western block moves in agreement with central Sicily while the eastern one accommodates part of the contraction arising from the main Eurasia-Nubia convergence. Furthermore, we provided evidences leading to consider the Hyblean-Maltese Escarpment Fault System as an active boundary characterised by a left-lateral strike-slip motion, separating the eastern block of the Plateau from the Ionian basin. All these evidences lend credit to a crustal segmentation of the southeastern Sicily. (C) 2014 Elsevier B.V. All rights reserved

La democrazia alla fine del \uabpubblico\ubb. Sfiducia, frammentazione, polarizzazione: verso una \uabbubble democracy\ubb?

This essay argues that the success of \uabpost-truth\ubb is partially connected to the characteristics of the new \uabhybrid\ubb communication scenario. The author maintains that the current context differs substantially from the democracy of parties, which has characterised a part of the 20th century, as well as from the democracy of the public, a notion formulated by Bernard Manin in the mid-1990s. As a matter of fact, the diffusion of the new media has triggered the fragmentation of the public into a plurality of self-referential segments and \uabbubbles\ubb which are (potentially) not rooted in an intersubjective sphere of communication. Considering the impact of these transformations, the essay proposes the image of a bubble democracy as an alternative to the mainstream interpretations both of the democracy of parties and of the democracy of the public and it argues that its main features are the widespread mistrust towards institutions, audience fragmentation and polarisation

Fluoration de l’émail in vitro par laser à rayons ultraviolets

28 samples of human enamel have been studied in order to measure fluoride absorption after treatment with ultraviolet radiations.Samples treated with topical application only presented limited fluoride absorption in enamel surface (up to 0,5 µm deep). The absorption rate was higher, using an U.V. lamp. In samples treated with «excimer» laser, fluoride absorption was much higher in the surface layer and occurred also deeper (3 µm).28 échantillons d’émail dentaire humain ont été analysés afin de quantifier l’absorption du fluor après traitement aux rayons ultraviolets.Les analyses ont montré que les échantillons soumis à une simple application topique présentent une absorption de fluor modeste, uniquement dans les couches superficielles de l’émail (jusqu’à 0,5 µm de profondeur). L’absorption est plus importante en utilisant une lampe à vapeur de mercure. Avec le laser «excimer», comparé aux deux autres méthodes, la fixation du fluor dans le réseau de l’émail est très supérieure en surface et se produit également en profondeur (3 µm)

Etn@ref: a geodetic reference frame for Mt. Etna GPS networks

In volcanology, one of the most important instruments for scientific community interested in modelling the physical processes related to magma movements in the shallow crust is geodetic data. Since the end of the 1980s, GPS surveys and Continuous GPS stations (CGPS) have greatly improved the possibility to measure such movements with high time and space resolution. However, physical modelling requires that any external influence on the data, not directly related to the investigated quantity, must be filtered. One major tricky factor in determining a deformation field using GPS displacement vectors and velocities is the correct choice of a stable reference frame. In this work, using more than a decade of GPS measurements, we defined a local reference frame in order to refer the Mt. Etna ground deformation pattern to a rigid block. In particular, we estimated the Euler pole for the rigid block by minimizing, with a weighted least squares inversion, the adjustments to two horizontal components of GPS velocity at 13 “fiducial” sites located within 350 km around Mt. Etna. The inversion inferred an Euler pole located at 38.450° N and -107.702° E and a rotation rate of 0.263 deg/Myr

Rôle de la stabilométrie dans l’évaluation des corrélations entre les troubles crânio-mandibulaires (TCM) et les troubles de l’équilibre (TE)

We examined three groups:- 29 patients suffering from balance disorders and craniomandibular disorders but not from vestibular disease;- 21 patients suffering from balance disorders, craniomandibular disorders and vestibular disease;- 26 patients suffering from craniomandibular disorders but not from vestibular disease or balance sorders.All cases were examined by the odontologist and otoneurologist and tested by computerized stabilometry; they were reexamined after six months of therapy by an occlusal stabilization splint. The static analysis of the results shows a significative reduction of the postural oscillations in all patients.Trois groupes de patients ont été examinés :- 29 sujets présentant des TE et des TCM sans vestibulopathie;- 21 sujets présentant des TE et des TCM associés à une vestibulopathie;- 26 sujets avec TCM sans TE ni vestibulopathie.Après une visite odontologique et otoneurologique complétée par une stabilométrie assistée par ordinaeur, les 3 groupes ont tous été recontrôlés après 6 mois de thérapie avec plaque de stabilisation. L’analyse les données a permis de constater une réduction significative des oscillations posturales chez tous les patients

L’emploi de la stabilométrie assistée par ordinateur dans le diagnostic des troubles crânio-mandibulaires (TCM)

The aim of this study was to evaluate the influence of the cervical region and the stomatognatic system on the balance control. We examined 35 healthy subjects and 201 balance disorder patients; of the 201 patients 60 suffered also from craniomandibular disorders (CMD) and 40 from cervical rachis disease. All cases were tested by computerized stabilometry executed in Romberg position: with closed eyes, retroflexed head and two cotton roles between the dental archs. The results show that cervical rachis disease and stomatognatic dysfunction have a significative influence on the balance control; however, this influence is smaller than that of vestibular disease; moreover, the computer stabilometry allows to measure the degree of ascending or descending correlation between the posture and stomatognatic system.Le but de cette étude a été d’évaluer l’influence de la région cervicale et de l’appareil stomatognatique sur le contrôle postural. On a examiné 35 sujets normaux et 201 patients avec troubles de l’équilibre, dont 60 présentaient aussi des troubles cranio-mandibulaires (TCM) et 40 une pathologie du rachis cervical. Tous les patients ont été soumis à un examen stabilométrique assisté par ordinateur, effectué en position de Romberg: les yeux fermés, la tête en rétroflexion, en occlusion modifiée par rouleaux interdentaires. Les résultats indiquent que les pathologies du rachis cervical et celles de l’appareil stomatognatique ont une influence significative sur le contrôle postural; toutefois, cette influence est nettement inférieure à celle des pathologies vestibulaires. Ils montrent également que la stabilométrie permet de mesurer le degré de corrélation ascendant ou descendant entre la posture et l’appareil stomatognatique

Study of the reaction pbar p -> phi phi from 1.1 to 2.0 GeV/c

A study has been performed of the reaction pbar p -> 4K using in-flight antiprotons from 1.1 to 2.0 GeV/c incident momentum interacting with a hydrogen jet target. The reaction is dominated by the production of a pair of phi mesons. The pbar p -> phi phi cross section rises sharply above threshold and then falls continuously as a function of increasing antiproton momentum. The overall magnitude of the cross section exceeds expectations from a simple application of the OZI rule by two orders of magnitude. In a fine scan around the xi/f_J(2230) resonance, no structure is observed. A limit is set for the double branching ratio B(xi -> pbar p) * B(xi -> phi phi) < 6e-5 for a spin 2 resonance of M = 2.235 GeV and Width = 15 MeV.Comment: 13 pages, 13 figures, 2 tables, Latex. To be published in Phys. Rev.

Scalar Mesons in a Chiral Quark Model with Glueball

Ground-state scalar isoscalar mesons and a scalar glueball are described in a U(3)xU(3) chiral quark model of the Nambu--Jona-Lasinio (NJL) type with 't Hooft interaction. The latter interaction produces singlet-octet mixing in the scalar and pseudoscalar sectors. The glueball is introduced into the effective meson Lagrangian as a dilaton on the base of scale invariance. The mixing of the glueball with scalar isoscalar quarkonia and amplitudes of their decays into two pseudoscalar mesons are shown to be proportional to current quark masses, vanishing in the chiral limit. Mass spectra of the scalar mesons and the glueball and their main modes of strong decay are described.Comment: 10 pages, LaTeX text, requires svjour.cls and svepj.cl