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

Attività economica e atti antieconomici nell'esercizio dell'impresa

The paper analyzes the impact of uneconomical acts in the functioning of the firm, in order to determine whether they always contrast with the legal principle of cost-effectiveness (in terms of balanced-budget), provoking liabilities or phenomena of unfair competition, or they are, under certain conditions, consistent with it. The presence in legislation, in doctrinal analysis, and in judicial case law of some criteria, which link the uneconomical act to commercial enterprise and neutralize their negative effects on the budget balance, allows not to exlude, in general terms, their compatibility with a correct and market-oriented functioning of the firm

Structure and Evolution of the World Trade Network

The \emph{World Trade Web} (WTW), the network defined by the international import/export trade relationships, has been recently shown to display some important topological properties which are tightly related to the Gross Domestic Product of world countries. While our previous analysis focused on the static, undirected version of the WTW, here we address its full evolving, directed description. This is accomplished by exploiting the peculiar reciprocity structure of the WTW to recover the directed nature of international trade channels, and by studying the temporal dependence of the parameters describing the WTW topology.Comment: Proceedings of the "First Bonzenfreies Colloquium on Market Dynamics and Quantitative Economics", Alessandria (ITALY) September 9-10, 2004. One of the three awarded talk

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

Atherothrombosis and Oxidative Stress: Mechanisms and Management in Elderly

Significance: The incidence of cardiovascular events (CVEs) increases with age, representing the main cause of death in an elderly population. Aging is associated with overproduction of reactive oxygen species (ROS), which may affect clotting and platelet activation, and impair endothelial function, thus predisposing elderly patients to thrombotic complications. Recent Advances: There is increasing evidence to suggest that aging is associated with an imbalance between oxidative stress and antioxidant status. Thus, upregulation of ROS-producing enzymes such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and myeloperoxidase, along with downregulation of antioxidant enzymes, such as superoxide dismutase and glutathione peroxidase, occurs during aging. This imbalance may predispose to thrombosis by enhancing platelet and clotting activation and eliciting endothelial dysfunction. Recently, gut-derived products, such as trimethylamine N-oxide (TMAO) and lipopolysaccharide, are emerging as novel atherosclerotic risk factors, and gut microbiota composition has been shown to change by aging, and may concur with the increased cardiovascular risk in the elderly. Critical Issues: Antioxidant treatment is ineffective in patients at risk or with cardiovascular disease. Further, anti-thrombotic treatment seems to work less in the elderly population. Future Directions: Interventional trials with antioxidants targeting enzymes implicated in aging-related atherothrombosis are warranted to explore whether modulation of redox status is effective in lowering CVEs in the elderly

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

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

A quantitative-informational approach to logical consequence

In this work, we propose a definition of logical consequence based on the relation between the quantity of information present in a particular set of formulae and a particular formula. As a starting point, we use Shannon‟s quantitative notion of information, founded on the concepts of logarithmic function and probability value. We first consider some of the basic elements of an axiomatic probability theory, and then construct a probabilistic semantics for languages of classical propositional logic. We define the quantity of information for the formulae of these languages and introduce the concept of informational logical consequence, identifying some important results, among them: certain arguments that have traditionally been considered valid, such as modus ponens, are not valid from the informational perspective; the logic underlying informational logical consequence is not classical, and is at the least paraconsistent sensu lato; informational logical consequence is not a Tarskian logical consequence

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

Laue Lens Development for Hard X-rays (>60 keV)

Results of reflectivity measurements of mosaic crystal samples of Cu (111) are reported. These tests were performed in the context of a feasibility study of a hard X-ray focusing telescope for space astronomy with energy passband from 60 to 600 keV. The technique envisaged is that of using mosaic crystals in transmission configuration that diffract X-rays for Bragg diffraction (Laue lens). The Laue lens assumed has a spherical shape with focal length $f$. It is made of flat mosaic crystal tiles suitably positioned in the lens. The samples were grown and worked for this project at the Institute Laue-Langevin (ILL) in Grenoble (France), while the reflectivity tests were performed at the X-ray facility of the Physics Department of the University of Ferrara.Comment: 6 pages, 12 figures, accepted for publication in IEEE Transactions on Nuclear Scienc