Robustness of the European power grids under intentional attack

The power grid defines one of the most important technological networks of our times and sustains our complex society. It has evolved for more than a century into an extremely huge and seemingly robust and well understood system. But it becomes extremely fragile as well, when unexpected, usually minimal, failures turn into unknown dynamical behaviours leading, for example, to sudden and massive blackouts. Here we explore the fragility of the European power grid under the effect of selective node removal. A mean field analysis of fragility against attacks is presented together with the observed patterns. Deviations from the theoretical conditions for network percolation (and fragmentation) under attacks are analysed and correlated with non topological reliability measures.Comment: 7 pages, 4 figure

Factors associated with severe dry eye in primary Sjögren´s syndrome diagnosed patients

Introduction Primary Sjögren?s syndrome (pSS) is an autoimmune disease, characterized by lymphocytic infiltration of exocrine glands and other organs, resulting in dry eye, dry mouth and extraglandular systemic findings. Objective To explore the association of severe or very severe dry eye with extraocular involvement in patients diagnosed with primary Sjögren?s syndrome. Methods SJOGRENSER registry is a multicenter cross-sectional study of pSS patients. For the construction of our main variable, severe/very severe dry eye, we used those variables that represented a degree 3?4 of severity according to the 2007 Dry Eye Workshop classification. First, bivariate logistic regression models were used to identify the effect of each independent variable on severe/very severe dry eye. Secondly, multivariate analysis using regression model was used to establish the independent effect of patient characteristics. Results Four hundred and thirty-seven patients were included in SJOGRENSER registry; 94% of the patients complained of dry eye and 16% developed corneal ulcer. Schirmer?s test was pathological in 92% of the patients; 378 patients presented severe/very severe dry eye. Inflammatory articular involvement was significantly more frequent in patients with severe/very severe dry eye than in those without severe/very severe dry eye (82.5 vs 69.5%, p = 0,028). Inflammatory joint involvement was associated with severe/very severe dry eye in the multivariate analysis, OR 2.079 (95% CI 1.096?3.941). Conclusion Severe or very severe dry eye is associated with the presence of inflammatory joint involvement in patients with pSS. These results suggest that a directed anamnesis including systemic comorbidities, such as the presence of inflammatory joint involvement or dry mouth in patients with dry eye, would be useful to suspect a pSS

Markov dynamics as a zooming lens for multiscale community detection: non clique-like communities and the field-of-view limit

In recent years, there has been a surge of interest in community detection algorithms for complex networks. A variety of computational heuristics, some with a long history, have been proposed for the identification of communities or, alternatively, of good graph partitions. In most cases, the algorithms maximize a particular objective function, thereby finding the `right' split into communities. Although a thorough comparison of algorithms is still lacking, there has been an effort to design benchmarks, i.e., random graph models with known community structure against which algorithms can be evaluated. However, popular community detection methods and benchmarks normally assume an implicit notion of community based on clique-like subgraphs, a form of community structure that is not always characteristic of real networks. Specifically, networks that emerge from geometric constraints can have natural non clique-like substructures with large effective diameters, which can be interpreted as long-range communities. In this work, we show that long-range communities escape detection by popular methods, which are blinded by a restricted `field-of-view' limit, an intrinsic upper scale on the communities they can detect. The field-of-view limit means that long-range communities tend to be overpartitioned. We show how by adopting a dynamical perspective towards community detection (Delvenne et al. (2010) PNAS:107: 12755-12760; Lambiotte et al. (2008) arXiv:0812.1770), in which the evolution of a Markov process on the graph is used as a zooming lens over the structure of the network at all scales, one can detect both clique- or non clique-like communities without imposing an upper scale to the detection. Consequently, the performance of algorithms on inherently low-diameter, clique-like benchmarks may not always be indicative of equally good results in real networks with local, sparser connectivity.Comment: 20 pages, 6 figure

Spatial optimality in power distribution networks

Critical infrastructures can be characterized as networks where nodes and edges are embedded in space. Transportation networks, the internet, and power grids, are examples of networks where spatial constrains are relevant. An important consequence of space is that there is a cost associated with the length of edges which in turn has important effects on the topological structure of and on the dynamical processes which take place on these spatial networks. In this paper we investigate the effect of the wiring cost in the spatial organization of a sample of power distribution networks by means of shuffling the networks in systematic ways. We show that although they share similar topologies, suboptimal networks (i.e., those with topologies not organized to reduce the wiring cost) seem to accumulate more failures. Consequences of these results and further work are finally discussed and outlined.Peer Reviewe

Experience with Isabelle A generic theorem prover

Preliminary versionAvailable from British Library Document Supply Centre- DSC:8723.247(CU-CL-TR--143) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Enfermedades autoinmunes sistémicas coexistentes con la infección crónica por el virus de la hepatitis C (Registro HISPAMEC): patrones de expresión clínica e inmunológica en 180 casos

Objectives. To describe the clinical and immunologic characteristics of a large series of patients with systemic autoimmune diseases (SAD) associated with chronic hepatitis C virus (HCV) infection. Methods. We analysed 180 patients diagnosed with SAD and chronic HCV infection seen consecutively at our centres during the last 10?years. The clinical and immunological patterns of disease expression were compared with 180 SAD?matched patients without chronic HCV infection. Results. A total of 180 HCV patients fulfilled the classification criteria for the following SAD: Sjögren's syndrome (n ?=?77), systemic lupus erythematosus (n ?=?43), rheumatoid arthritis (n ?=?14), antiphospholipid syndrome (n ?=?14), polyarteritis nodosa (n ?=?8) and other SAD (n ?=?24). One hundred and thirty (72%) patients were female and 50 (28%) male, with a mean age at SAD diagnosis of 50?years. The main immunologic features were antinuclear antibodies in 69% of patients, cryoglobulinaemia in 62%, hypocomplementaemia in 56% and rheumatoid factor (RF) in 56%. Compared with the SAD?matched HCV?negative group, SAD?HCV patients presented a lower prevalence of females (P ?=?0.016), an older age at SAD diagnosis (P ?=?0.039) and a higher prevalence of vasculitis (P ?<?0.001) and neoplasia (P ?<?0.001). Immunologically, SAD?HCV patients presented a lower prevalence of antinuclear (P ?=?0.036), anti?extractable nuclear antigen (P ?=?0.038) and anti?DNA (P ?=?0.005) antibodies, and a higher frequency of RF (P ?=?0.003), hypocomplementaemia (P ?<?0.001) and cryoglobulins (P ?<?0.001). Conclusions. In comparison with an SAD?matched HCV?negative population, SAD?HCV patients were older and more likely to be male, with a higher frequency of vasculitis, cryoglobulinaemia and neoplasia. This complex pattern of disease expression is generated by a chronic viral infection that induces both liver and autoimmune disease