Sznajd Complex Networks

The Sznajd cellular automata corresponds to one of the simplest and yet most interesting models of complex systems. While the traditional two-dimensional Sznajd model tends to a consensus state (pro or cons), the assignment of the contrary to the dominant opinion to some of its cells during the system evolution is known to provide stabilizing feedback implying the overall system state to oscillate around null magnetization. The current article presents a novel type of geographic complex network model whose connections follow an associated feedbacked Sznajd model, i.e. the Sznajd dynamics is run over the network edges. Only connections not exceeding a maximum Euclidean distance $D$ are considered, and any two nodes within such a distance are randomly selected and, in case they are connected, all network nodes which are no further than $D$ are connected to them. In case they are not connected, all nodes within that distance are disconnected from them. Pairs of nodes are then randomly selected and assigned to the contrary of the dominant connectivity. The topology of the complex networks obtained by such a simple growth scheme, which are typically characterized by patches of connected communities, is analyzed both at global and individual levels in terms of a set of hierarchical measurements introduced recently. A series of interesting properties are identified and discussed comparatively to random and scale-free models with the same number of nodes and similar connectivity.Comment: 10 pages, 4 figure

Relativistic model for the nonmesonic weak decay of single-lambda hypernuclei

Having in mind its future extension for theoretical investigations related to charmed nuclei, we develop a relativistic formalism for the nonmesonic weak decay of single-$\Lambda$ hypernuclei in the framework of the independent-particle shell model and with the dynamics represented by the $(\pi,K)$ one-meson-exchange model. Numerical results for the one-nucleon-induced transition rates of ${}^{12}_{\Lambda}\textrm{C}$ are presented and compared with those obtained in the analogous nonrelativistic calculation. There is satisfactory agreement between the two approaches, and the most noteworthy difference is that the ratio $\Gamma_{n}/\Gamma_{p}$ is appreciably higher and closer to the experimental value in the relativistic calculation. Large discrepancies between ours and previous relativistic calculations are found, for which we do not encounter any fully satisfactory explanation. The most recent experimental data is well reproduced by our results. In summary, we have achieved our purpose to develop a reliable model for the relativistic calculation of the nonmesonic weak decay of $\Lambda$-hypernuclei, which can now be extended to evaluate similar processes in charmed nuclei

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

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

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

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

Transient dynamics for sequence processing neural networks: effect of degree distributions

We derive a analytic evolution equation for overlap parameters including the effect of degree distribution on the transient dynamics of sequence processing neural networks. In the special case of globally coupled networks, the precisely retrieved critical loading ratio $\alpha_c = N ^{-1/2}$ is obtained, where $N$ is the network size. In the presence of random networks, our theoretical predictions agree quantitatively with the numerical experiments for delta, binomial, and power-law degree distributions.Comment: 11 pages, 6 figure

30 anos de investigação sobre externalidades do IDE para as empresas nacionais – que conclusões?

Durante as últimas três décadas, surgiu uma vasta literatura sobre a existência potencial de externalidades do IDE para as empresas nacionais, traduzidas em ganhos de produtividade. Esta ocorrência relaciona-se com o fato de as empresas multinacionais possuírem ativos intangíveis que podem ser transmitidos às empresas nacionais. A análise empírica não dá, contudo, indicações claras sobre o fenômeno. Nesta análise, abordamos o mais vasto conjunto de estudos sobre este tema até hoje reunido, levando em consideração a ocorrência de externalidades intra e inter-setoriais. Destacamos a diversidade de canais e respectivos efeitos através dos quais as externalidades para as empresas nacionais se podem materializar. Delineamos ainda rumos para um melhor esclarecimento dos fatores condicionantes da ocorrência do fenômeno, considerando que diversos estudos empíricos têm mostrado que este existirá, provavelmente, apenas para um subgrupo de empresas nacionais e/ou quando estiverem reunidas determinadas condições