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Is Africa Different? Historical Conflict and State Development
No full textWe show that the consequences of historical warfare for state development differ for
Sub-Saharan Africa. We identify the locations of more than 1,500 conflicts in Africa, Asia,
and Europe from 1400 to 1799. We find that historical warfare predicts common-interest
states defined by high fiscal capacity and low civil conflict across much of the OldWorld.
For Sub-Saharan Africa, historical warfare predicts special-interest states defined by high
fiscal capacity and high civil conflict. Our results offer new evidence about where and
when “war makes states.
Information Recovery in Behavioral Networks
No full textIn the context of agent based modeling and network theory, we focus on the problem of recovering behavior-related choice information from origin-destination type data, a topic also known under the name of network tomography. As a basis for predicting agents' choices we emphasize the connection between adaptive intelligent behavior, causal entropy maximization, and self-organized behavior in an open dynamic system. We cast this problem in the form of binary and weighted networks and suggest information theoretic entropy-driven methods to recover estimates of the unknown behavioral flow parameters. Our objective is to recover the unknown behavioral values across the ensemble analytically, without explicitly sampling the configuration space. In order to do so, we consider the Cressie-Read family of entropic functionals, enlarging the set of estimators commonly employed to make optimal use of the available information. More specifically, we explicitly work out two cases of particular interest: Shannon functional and the likelihood functional. We then employ them for the analysis of both univariate and bivariate data sets, comparing their accuracy in reproducing the observed trends
Systemic Risk Analysis on Reconstructed Economic and Financial Networks
No full textWe address a fundamental problem that is systematically encountered when modeling real-world complex systems of societal relevance: the limitedness of the information available. In the case of economic and financial networks, privacy issues severely limit the information that can be accessed and, as a consequence, the possibility of correctly estimating the resilience of these systems to events such as financial shocks, crises and cascade failures. Here we present an innovative method to reconstruct the structure of such partially-accessible systems, based on the knowledge of intrinsic node-specific properties and of the number of connections of only a limited subset of nodes. This information is used to calibrate an inference procedure based on fundamental concepts derived from statistical physics, which allows to generate ensembles of directed weighted networks intended to represent the real system—so that the real network properties can be estimated as their average values within the ensemble. We test the method both on synthetic and empirical networks, focusing on the properties that are commonly used to measure systemic risk. Indeed, the method shows a remarkable robustness with respect to the limitedness of the information available, thus representing a valuable tool for gaining insights on privacy-protected economic and financial systems
Dynamics to Equilibrium in Network Games: Individual Behavior and Global Response
No full textVarious social contexts can be depicted as games of strategic interactions on networks, where an individual’s welfare depends on both her and her partners’ actions. Whereas much attention has been devoted to Bayes-Nash equilibria in such games, here we look at strategic interactions from an evolutionary perspective. To this end, we present the results of a numerical simulations program for these games, which allows us to find out whether Nash equilibria are accessible by adaptation of player strategies, and in general to identify the attractors of the evolution. Simulations allow us to go beyond a global characterization of the cooperativeness at equilibrium and probe into individual behavior. We find that when players imitate each other, evolution does not reach Nash equilibria and, worse, leads to very unfavorable states in terms of welfare. On the contrary, when players update their behavior rationally, they self-organize into a rich variety of Nash equilibria, where individual behavior and payoffs are shaped by the nature of the game, the social network’s structure and the players’ position within the network. Our results allow to assess the validity of mean-field approaches we use to describe the dynamics of these games. Interestingly, our dynamically-found equilibria generally do not coincide with (but show qualitatively the same features of) those resulting from theoretical predictions in the context of one-shot games under incomplete information
Spatial imagery relies on a sensory independent, though sensory sensitive, functional organization within the parietal cortex: A fMRI study of angle discrimination in sighted and congenitally blind individuals
No full textAbstract Although vision offers distinctive information to space representation, individuals who lack vision since birth often show perceptual and representational skills comparable to those found in sighted individuals. However, congenitally blind individuals may result in impaired spatial analysis, when engaging in ‘visual’ spatial features (e.g., perspective or angle representation) or complex spatial mental abilities. In the present study, we measured behavioral and brain responses using functional magnetic resonance imaging in sighted and congenitally blind individuals during spatial imagery based on a modified version of the mental clock task (e.g., angle discrimination) and a simple recognition control condition, as conveyed across distinct sensory modalities: visual (sighted individuals only), tactile and auditory. Blind individuals were significantly less accurate during the auditory task, but comparable-to-sighted during the tactile task. As expected, both groups showed common neural activations in intraparietal and superior parietal regions across visual and non-visual spatial perception and imagery conditions, indicating the more abstract, sensory independent functional organization of these cortical areas, a property that we named supramodality. At the same time, however, comparisons in brain responses and functional connectivity patterns across experimental conditions demonstrated also a functional lateralization, in a way that correlated with the distinct behavioral performance in blind and sighted individuals. Specifically, blind individuals relied more on right parietal regions, mainly in the tactile and less in the auditory spatial processing. In sighted, spatial representation across modalities relied more on left parietal regions. In conclusions, intraparietal and superior parietal regions subserve supramodal spatial representations in sighted and congenitally blind individuals. Differences in their recruitment across non-visual spatial processing in sighted and blind individuals may be related to distinctive behavioral performance and/or mental strategies adopted when they deal with the same spatial representation as conveyed through different sensory modalities
A Two-Player Differential Game Model for the Management of Transboundary Pollution and Environmental Absorption
No full textIt is likely that the decentralized structure at the level of nations of decision-making
processes related to polluting emissions will aggravate the decline in the efficiency of carbon sinks.
A two-player differential game model of pollution is proposed. It accounts for a time-dependent
environmental absorption efficiency and allows for the possibility of a switching of the biosphere
from a carbon sink to a source. The impact of negative externalities from the transboundary
pollution non-cooperative game wherein countries are dynamically involved is investigated. The
differences in steady state between cooperative, open-loop, and Markov perfect Nash equilibria
are studied. For the latter, two numerical methods for its approximation are compared
Molecularly imprinted polymeric micro- and nano-particles for the targeted delivery of active molecules
No full textMolecular imprinting (MI) represents a strategy to introduce a ‘molecular memory’ in a polymeric system obtaining materials with specific recognition properties. MI particles can be used as drug delivery systems providing a targeted release and thus reducing the side effects. The introduction of molecular recognition properties on a polymeric drug carrier represents a challenge in the development of targeted delivery systems to increase their efficiency. This review will summarize the limited number of drug delivery MI particles described in the literature along with an overview of potential solutions for a larger exploitation of MI particles as targeted drug delivery carriers. Molecularly imprinted drug carriers can be considered interesting candidates to significantly improve the efficiency of a controlled drug treatment
Chemical synthesis of a biodegradable PEGylated copolymer from ε-caprolactone and γ-valerolactone: evaluation of reaction and functional properties
No full textThis paper reports the chemical synthesis of methoxy poly(ethyleneglycol)-block-poly(ε-caprolactone-co-4-hydroxyvalerate) from ε-caprolactone and γ-valerolactone, a five-membered ring rarely used in chemical synthesis due to its low reactivity. This procedure enabled production of copolymers with controlled ratios of repeating units and molecular weights, as demonstrated by GPC, FT-IR and NMR characterization. Copolymer degradation rate was found to depend on macromolecular composition, and finely tuneable in a wide range of values. Similarly, hydrophilicity was dependent on γ-valerolactone content, and could be accurately controlled by varying the composition of the reaction feed. Importantly, this copolymer showed lower levels of acidic degradation products than other biodegradable polymers, thus resulting in improved biocompatibility. These encouraging results demonstrate the feasibility of the chemical synthesis of a novel and versatile material with interesting properties that fill a gap in the range of commercially available biodegradable polymers