1,434 research outputs found

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

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    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

    Availability Evaluation of Service Function Chains Under Different Protection Schemes

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    Network Function Virtualization (NFV) calls for a new resource management approach where virtualized network functions (VNFs) replace traditional network hardware appliances. Thanks to NFV, operators are given a much greater flexibility, as these VNFs can be deployed as virtual nodes and chained together to form Service Function Chains (SFCs). An SFC represents a set of dedicated virtualized resources deployed to provide a certain service to the consumer. One of its most important performance requirements is availability. In this paper, the availability achieved by SFCs is evaluated analytically, by modelling several protection schemes and given different availability values for the network components. The cost of each protection scheme, based on its network resource consumption, is also taken into account. Extensive numerical results are reported, considering various SFC characteristics, such as availability requirements, number of NFV nodes and availability values of network components. The lowest-cost protection strategy, in terms of number of occupied network components, which meets availability requirement, is identified. Our analysis demonstrates that, in most cases, resource-greedy protection schemes, such as end-to-end protection, can be replaced by less aggressive schemes, even when availability requirements are in the order of five or six nines, depending on the number of elements in the service function chain

    Experimental Testing of Dynamically Optimized Photoelectron Beams

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    We discuss the design of and initial results from an experiment in space-charge dominated beam dynamics which explores a new regime of high-brightness electron beam generation at the SPARC (located at INFN-LNF, Frascati) photoinjector. The scheme under study employs the natural tendency in intense electron beams to configure themselves to produce a uniform density, giving a nearly ideal beam from the viewpoint of space charge-induced emittance. The experiments are aimed at testing the marriage of this idea with a related concept, emittance compensation, We show that the existing infrastructure at SPARC is nearly ideal for the proposed tests, and that this new regime of operating photoinjector may be the preferred method of obtaining highest brightness beams with lower energy spread. We discuss the design of the experiment, including developing of a novel time-dependent, aerogel-based imaging system. This system has been installed at SPARC, and first evidence for nearly uniformly filled ellipsoidal charge distributions recorded

    Safety of aortic aneurysm repair 8 weeks after percutaneous coronary intervention for coronary artery disease: a cohort study

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    Guidelines advice against dual antiplatelet therapy (DAPT) discontinuation less than 12 months after percutaneous coronary intervention with drug-eluting stents (DES-PCI). However, any delay of necessary surgery in patients with descending thoracic (DTA) or abdominal aortic aneurysm (AAA), treated by DES-PCI, increases the risk of aneurysm rupture/dissection. We evaluated the safety of 8-week waiting time between DES-PCI and endovascular aortic repair (EVAR). 1152 consecutive patients with coronary artery disease (CAD) needing elective DTA or AAA repair were enrolled and divided into two groups. Group A included 830 patients treated by DES-PCI for significant CAD who underwent surgery 8 weeks after implantation. Group B included 322 patients treated by DES-PCI at least 6 months before with no residual significant CAD and treated by elective EVAR. Groups were compared according to a composite of death, myocardial infarction, stent thrombosis, cerebrovascular events and bleeding. No aneurysm rupture/dissection occurred while waiting for surgery. Hospital averse events occurred in 6.2% (52/830) group A patients versus 6.5% (21/322) group B patients (p = 0.8). Mortality was 0.7% (6/830) in group A and 0.9% (3/322) in group B (p = 0.7). Multivariate predictors of events were triple vessel DES-PCI (p 3 stents implanted (p 30 mm (p = 0.02). Eight weeks of waiting after DES-PCI in addition to an adequate management of DAPT were safe in terms of cardiac morbidity and bleeding complications. No aneurysm rupture occurred in the interval before surgery
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