Identifying the starting point of a spreading process in complex networks

When dealing with the dissemination of epidemics, one important question that can be asked is the location where the contamination began. In this paper, we analyze three spreading schemes and propose and validate an effective methodology for the identification of the source nodes. The method is based on the calculation of the centrality of the nodes on the sampled network, expressed here by degree, betweenness, closeness and eigenvector centrality. We show that the source node tends to have the highest measurement values. The potential of the methodology is illustrated with respect to three theoretical complex network models as well as a real-world network, the email network of the University Rovira i Virgili

On the Efficiency of Data Representation on the Modeling and Characterization of Complex Networks

Specific choices about how to represent complex networks can have a substantial effect on the execution time required for the respective construction and analysis of those structures. In this work we report a comparison of the effects of representing complex networks statically as matrices or dynamically as spase structures. Three theoretical models of complex networks are considered: two types of Erdos-Renyi as well as the Barabasi-Albert model. We investigated the effect of the different representations with respect to the construction and measurement of several topological properties (i.e. degree, clustering coefficient, shortest path length, and betweenness centrality). We found that different forms of representation generally have a substantial effect on the execution time, with the sparse representation frequently resulting in remarkably superior performance

Determinant factors of FDI spillovers - What do we really know?

The evaluation of aggregate FDI spillovers to domestic firms has yielded mixed results. However, analysis has recently taken a step forward with the evaluation of the factors determining the existence, dimension, and sign of FDI spillovers. We survey the arguments that support these factors and the empirical evidence already produced. FDI spillovers depend on many factors, frequently with an undetermined effect. The absorptive capacities of domestic firms and regions are preconditions for incorporating the benefits of these FDI externalities. Regarding the remaining factors, the results show contrary effects or, in some cases, are still insufficient to draw reliable conclusions.info:eu-repo/semantics/acceptedVersio

Determinant factors of structural similarity at the regional level: evidence from Portugal

There is scant evidence on the determinant factors of structural similarity between geographical spaces; moreover, it has been produced considering only the national level. The present study provides evidence on this topic at the regional level, based on the analysis of 275 Portuguese counties. The results obtained confirm the importance of several explanatory factors, suggesting that the structural similarity between Portuguese counties increases with geographical proximity, the existence of a shared boundary, the similarity of factor endowments in terms of physical and human capital and the similarity in terms of economic centrality and market dimension. Key words: productive structure, Portugal, structural similarity, factor endowments, economic geograph

Trade performance of the less developed African countries

Adopting a long term perspective, covering four decades, we evaluate the trade performance of a vast group of less developed African countries (LDAC). Besides some general trade indicators, we apply a constant market share analysis in order to decompose export performance (measured through the market share growth rate) into several components with specific economic interpretation. Our main conclusions are: (i) the sectoral specialization structure of LDAC exports has remained heavy in commodities but the composition of the basket of goods exported has changed considerably with a very strong concentration in crude oil (mainly in the last two decades), (ii) the geographical structure of exports has also changed, with an important increase of the relative importance of China and USA, (iii) LDAC not only show a negative competitiveness effect, but are also penalized by their sectoral and geographical specialization, and (iv) the most favorable evolution is observed in the most recent sub-period (2000-2007), but it is insufficient to reverse the negative trend of the previous decades.info:eu-repo/semantics/acceptedVersio

Does the location of manufacturing determine service sectors’ location choices? Evidence from Portugal

Considering the case of Portugal over the period 1995-2000, this paper analyses whether the location of market services is explained by the geographical proximity of the industrial sectors that use these services as intermediate inputs. A rather detailed level of regional disaggregation is used, namely the county level (275 counties). This influence is confirmed by the results of some location indices and by the regressions made for each sector. An alternative spatial unit is also used, consisting of the county itself combined with those with which it shares boundaries, showing the relevance of the level of regional disaggregation for the results obtained

Individual and family variables on adherence to treatment, metabolic control and quality of life in adolescents with type 1 diabetes

A Diabetes é uma doença crónica com um grande impacto na vida dos adolescentes. A literatura publicada nos últimos anos tem demonstrado a importância dos factores psicológicos e psicossociais na adesão ao tratamento e controlo metabólico. No entanto, são escassos no nosso país estudos que articulem as variáveis familiares (ambiente familiar, suporte social) com variáveis psicológicas (ansiedade face à doença, crenças de auto-eficácia face ao tratamento) com a adesão, o controlo metabólico e a qualidade de vida. O presente estudo, realizado com 157 adolescentes, utentes da consulta de Diabetologia Pediátrica da UAG da Mulher e da Criança do Hospital de S. João, mostra que os aspectos sócio-familiares (nomeadamente o suporte social familiar e o nível de conflito no ambiente familiar) exercem uma poderosa influência no comportamento de adesão ao tratamento e na qualidade de vida do adolescente, nas variáveis psicológicas, nomeadamente na percepção de barreiras ao tratamento, no stress face à doença e na percepção de autoeficácia.Diabetes is a chronic disease that has a great impact on adolescent’s life. The influence of psychological factors on diabetes is well known. Literature shows the importance of psychological and psychosocial on adherence and metabolic control. However, very few studies articulate family variables (family environment, family social support) with psychological variables (anxiety, self efficacy) with adherence, metabolic control and quality of life. This study attempted to research the influence of family environment, family social support, self-efficacy and stress towards diabetes on adolescent’s adherence, quality of life and metabolic control. Results showed that all these family variables have a great impact on stress toward diabetes and self-efficacy. In particular social support and family conflict seem to be very important on determination of adherence behavior and quality of life. Those psychosocial factors are of great importance if one wants to design interventions to increase adherence to treatment and quality of life among adolescents

Leucoencefalitis aguda hemorrágica de Weston Hurst. Estudio neuropatológico de un caso

Summary. Introduction. Acute hemorrhagic leukoencephalitis (AHL), or Hurst disease is a rare, usually fatal, disease, probably due to an autoimmune cross reaction against myelin antigens present in the central nervous system, and which forms a spectrum of postinfeccious demyelinating diseases with acute disseminated encephalomyelitis. Case report. The patient was a 21 year old female who presented with an acute encephalopathy and generalized seizures following a 15 day febrile syndrome attributed to amygdalitis; a laboratory work-up, including CSF, was non-diagnostic, and a brain CT scan revealed diffuse cerebral edema. After 12 days the patient died from nosocomial pneumonia and multi-organ failure; neuropathological examination of the brain confirmed the diagnosis of Hurst acute hemorrhagic leukoencephalitis, with a weak perilesional inflammatory reaction, unlike the usual picture in AHL. Discussion. AHL should be a part of the differential diagnosis of acute encephalopathic diseases, particularly if preceded by systemic infections. The atypical laboratory findings, and the impossibilty of performing a brain MRI were obstacles to the diagnosis in this case. The relative paucity of the perivascular infiltrate is an atypical finding, and could be due to apoptotic clearance of the inflammatory cells, as has been described in other autoimmune demyelinating diseases

Analyzing Trails in Complex Networks

Even more interesting than the intricate organization of complex networks are the dynamical behavior of systems which such structures underly. Among the many types of dynamics, one particularly interesting category involves the evolution of trails left by moving agents progressing through random walks and dilating processes in a complex network. The emergence of trails is present in many dynamical process, such as pedestrian traffic, information flow and metabolic pathways. Important problems related with trails include the reconstruction of the trail and the identification of its source, when complete knowledge of the trail is missing. In addition, the following of trails in multi-agent systems represent a particularly interesting situation related to pedestrian dynamics and swarming intelligence. The present work addresses these three issues while taking into account permanent and transient marks left in the visited nodes. Different topologies are considered for trail reconstruction and trail source identification, including four complex networks models and four real networks, namely the Internet, the US airlines network, an email network and the scientific collaboration network of complex network researchers. Our results show that the topology of the network influence in trail reconstruction, source identification and agent dynamics.Comment: 10 pages, 16 figures. A working manuscript, comments and criticisms welcome

A Complex Network Approach to Topographical Connections

The neuronal networks in the mammals cortex are characterized by the coexistence of hierarchy, modularity, short and long range interactions, spatial correlations, and topographical connections. Particularly interesting, the latter type of organization implies special demands on the evolutionary and ontogenetic systems in order to achieve precise maps preserving spatial adjacencies, even at the expense of isometry. Although object of intensive biological research, the elucidation of the main anatomic-functional purposes of the ubiquitous topographical connections in the mammals brain remains an elusive issue. The present work reports on how recent results from complex network formalism can be used to quantify and model the effect of topographical connections between neuronal cells over a number of relevant network properties such as connectivity, adjacency, and information broadcasting. While the topographical mapping between two cortical modules are achieved by connecting nearest cells from each module, three kinds of network models are adopted for implementing intracortical connections (ICC), including random, preferential-attachment, and short-range networks. It is shown that, though spatially uniform and simple, topographical connections between modules can lead to major changes in the network properties, fostering more effective intercommunication between the involved neuronal cells and modules. The possible implications of such effects on cortical operation are discussed.Comment: 5 pages, 5 figure