Multi-species grandcanonical models for networks with reciprocity

Reciprocity is a second-order correlation that has been recently detected in all real directed networks and shown to have a crucial effect on the dynamical processes taking place on them. However, no current theoretical model generates networks with this nontrivial property. Here we propose a grandcanonical class of models reproducing the observed patterns of reciprocity by regarding single and double links as Fermi particles of different `chemical species' governed by the corresponding chemical potentials. Within this framework we find interesting special cases such as the extensions of random graphs, the configuration model and hidden-variable models. Our theoretical predictions are also in excellent agreement with the empirical results for networks with well studied reciprocity.Comment: 4 pages, 1 figur

Generalized Bose-Fermi statistics and structural correlations in weighted networks

We derive a class of generalized statistics, unifying the Bose and Fermi ones, that describe any system where the first-occupation energies or probabilities are different from subsequent ones, as in presence of thresholds, saturation, or aging. The statistics completely describe the structural correlations of weighted networks, which turn out to be stronger than expected and to determine significant topological biases. Our results show that the null behavior of weighted networks is different from what previously believed, and that a systematic redefinition of weighted properties is necessary.Comment: Final version accepted for publication on Physical Review Letter

Detecting spatial homogeneity in the world trade web with Detrended Fluctuation Analysis

In a spatially embedded network, that is a network where nodes can be uniquely determined in a system of coordinates, links' weights might be affected by metric distances coupling every pair of nodes (dyads). In order to assess to what extent metric distances affect relationships (link's weights) in a spatially embedded network, we propose a methodology based on DFA (Detrended Fluctuation Analysis). DFA is a well developed methodology to evaluate autocorrelations and estimate long-range behaviour in time series. We argue it can be further extended to spatially ordered series in order to assess autocorrelations in values. A scaling exponent of 0.5 (uncorrelated data) would thereby signal a perfect homogeneous space embedding the network. We apply the proposed methodology to the World Trade Web (WTW) during the years 1949-2000 and we find, in some contrast with predictions of gravity models, a declining influence of distances on trading relationships.Comment: 15 pages, 7 figure

Eine schrecklich nette Familie?! Sozialen Wandel bildkompetent untersuchen und gestalten

Zugänge zu Bildern erfordern bilddidaktische Überlegungen, die im Kunstunterricht ein zentrales Anliegen einnehmen, um subjektorientierte und kompetenz­orientierte Lernprozesse zugleich für Schüler/innen zu ermöglichen. Die kunst­pädagogischen Handlungsfelder beziehen sich jedoch nicht nur auf die rezeptiv- reflexive, sondern auch auf die gestaltende Herstellung von Bildern. Die Fotografie stellt dabei ein Medium und eine Bildart dar, die mittlerweile technisch schnell verfügbar, vermeintlich zügig erfassbar und selbst leicht umsetzbar erscheint. Bildnerisch-ästhetische Strukturen entstehen jedoch vor dem Hintergrund eines kulturellen Bildreservoirs, das historisch gewachsen ist und wofür sich Jugendliche die nötigen Kenntnisse und Fähigkeiten rezeptiver, produktiver und reflexiver Art erst aneignen müssen. Am Beispiel von fotografischen Gruppenporträts zum Thema «Familie» werden in Referenz zur Bildgattung in der Malerei in diesem Beitrag ein didaktisierter Zugang zur Verlangsamung der Bildwahrnehmung, eine bildspezifische Untersuchungsmethode in Form von vergleichenden Kompositionsskizzen und Gestaltungslösungen aus einem Leistungskurs der Jahrgangsstufe 12 (G9) vorgestellt

Mortality Rate In Children Caused By Traffic Accidents According To Geographical Regions - Brazil, 1997 - 2005.

Fatal injuries in children caused by motor vehicle accidents represent a common situation in many countries worldwide. The present study addresses the mortality rate in children as vehicle passengers in Brazil, from 1997 to 2005. To evaluate mortality rates, the number of deaths was collected from the National Mortality Information System (SIM) and the population size was obtained using the Brazilian Bureau Census (IBGE) data available at DATASUS. Mortality rates were estimated in three-year periods and analyzed according to age groups (younger than 1 year old, 1-4 years old, 5-9 years old) and geographical regions using a 95% confidence interval. Overall results showed mortality rates of 5.68, 7.32 and 6.78 (per 1,000,000) for the 1997-1999, 2000-2002 and 2003-2005 periods, respectively for the whole country. Children younger than 1 year old had a mortality rate of 10.18 (per 1,000,000), which was higher than for the other age groups. For the period analyzed, the highest rates were observed for the Mid-West and South regions of Brazil, with rates of 13.88 and 11.47 (per 1,000,000), respectively. These results show the risk of fatal injury in children caused by motor vehicle accidents and may contribute to the establishment of educational campaigns aiming injury prevention in children as vehicle passengers.15308-1

Effects of network topology on wealth distributions

We focus on the problem of how wealth is distributed among the units of a networked economic system. We first review the empirical results documenting that in many economies the wealth distribution is described by a combination of log--normal and power--law behaviours. We then focus on the Bouchaud--M\'ezard model of wealth exchange, describing an economy of interacting agents connected through an exchange network. We report analytical and numerical results showing that the system self--organises towards a stationary state whose associated wealth distribution depends crucially on the underlying interaction network. In particular we show that if the network displays a homogeneous density of links, the wealth distribution displays either the log--normal or the power--law form. This means that the first--order topological properties alone (such as the scale--free property) are not enough to explain the emergence of the empirically observed \emph{mixed} form of the wealth distribution. In order to reproduce this nontrivial pattern, the network has to be heterogeneously divided into regions with variable density of links. We show new results detailing how this effect is related to the higher--order correlation properties of the underlying network. In particular, we analyse assortativity by degree and the pairwise wealth correlations, and discuss the effects that these properties have on each other.Comment: References adde

Antimicrobial peptides for novel antiviral strategies in the current post-COVID-19 pandemic

The recent pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has highlighted how urgent and necessary the discovery of new antiviral compounds is for novel therapeutic approaches. Among the various classes of molecules with antiviral activity, antimicrobial peptides (AMPs) of innate immunity are among the most promising ones, mainly due to their different mechanisms of action against viruses and additional biological properties. In this review, the main physicochemical characteristics of AMPs are described, with particular interest toward peptides derived from amphibian skin. Living in aquatic and terrestrial environments, amphibians are one of the richest sources of AMPs with different primary and secondary structures. Besides describing the various antiviral activities of these peptides and the underlying mechanism, this review aims at emphasizing the high potential of these small molecules for the development of new antiviral agents that likely reduce the selection of resistant strains

Fitness-dependent topological properties of the World Trade Web

Among the proposed network models, the hidden variable (or good get richer) one is particularly interesting, even if an explicit empirical test of its hypotheses has not yet been performed on a real network. Here we provide the first empirical test of this mechanism on the world trade web, the network defined by the trade relationships between world countries. We find that the power-law distributed gross domestic product can be successfully identified with the hidden variable (or fitness) determining the topology of the world trade web: all previously studied properties up to third-order correlation structure (degree distribution, degree correlations and hierarchy) are found to be in excellent agreement with the predictions of the model. The choice of the connection probability is such that all realizations of the network with the same degree sequence are equiprobable.Comment: 4 Pages, 4 Figures. Final version accepted for publication on Physical Review Letter

Ferramentas Lógicas e Matemáticas Contemporâneas

Neste artigo apresentamos um panorama objetivo do surgimento e das características da Análise Não- Standard (ANS) de Abraham Robinson, da Lógica Paraconsistente e do Cálculo Diferencial Paraconsistente (CDP) de Newton Carneiro Affonso da Costa, entre outras considerações acerca das ferramentas lógicas e matemáticas contemporâneas. Destacamos o CDP como um Cálculo ainda em construção, intimamente relacionado com teorias que preservam as mais importantes propriedades do Cálculo clássico e que, da mesma forma, apresenta inegáveis potencialidades para aplicações concretas. De facto, o Cálculo Paraconsistente estende o Cálculo tradicional e aproxima ideias presentes na Análise Infinitesimal de Newton e Leibniz e na Análise Não-Standard de Robinson, sob o uso da lógica paraconsistente e de teorias paraconsistentes de conjuntos (ver Batens et al., 2000; Robinson, 1996; da Costa, 1963, 1993; e D’Ottaviano, 1990)

Indoor radon exposure and lung cancer risk: a meta-analysis of case-control studies

The aim of this study was to assess a potential relationship between indoor radon exposure and the incidence of lung cancer worldwide. A systematic literature search was carried out in PubMed, Web of Science, and Google Scholar to identify relevant studies published in English conducted in the last 15 years until January 2016. Summary relative risks (RR) and the corresponding 95% confidence intervals (CIs) were calculated using a random-effects model and the influence of moderators using a mixed-effects model. Heterogeneity was assessed using the Q, I2 and H2 tests, and the source of heterogeneity was detected by meta-regression analysis. Publication bias was evaluated with Egger’s regression symmetry test and the contour-enhanced funnel plot. Leave-one-out sensitivity analysis was performed. Twenty-five lung cancer studies (case-control studies) with 13,569 cases and 22,701 controls were included. Indoor Radon exposure was significantly associated with increased risk for lung cancer (RR, 1.19; 95% CI, 1.02–1.39). Study location analysis showed that radon exposure was associated with increased risk for lung cancer from forty degrees absolute latitude (RR, 1.09; 95% CI, 0.92–1.31), to fifty degrees (RR 1.26; 95% CI, 1.08–1.48), to sixty degrees (RR, 1.46; 95% CI, 1.12–1.91). Indoor radon exposure may be associated with increased risk for lung cancer