Author: cxdig

Network theory may explain the vulnerability of medieval human settlements to the Black Death pandemic

Epidemics can spread across large regions becoming pandemics by flowing along transportation and social networks. Two network attributes, transitivity (when a node is connected to two other nodes that are also directly connected between them) and centrality (the number and intensity of connections with the other nodes in the network), are widely associated with the dynamics of transmission of pathogens. Here we investigate how network centrality and transitivity influence vulnerability to diseases of human populations by examining one of the most devastating pandemic in human history, the fourteenth century plague pandemic called Black Death. We found that, after controlling for the city spatial location and the disease arrival time, cities with higher values of both centrality and transitivity were more severely affected by the plague. A simulation study indicates that this association was due to central cities with high transitivity undergo more exogenous re-infections. Our study provides an easy method to identify hotspots in epidemic networks. Focusing our effort in those vulnerable nodes may save time and resources by improving our ability of controlling deadly epidemics.


Network theory may explain the vulnerability of medieval human settlements to the Black Death pandemic
José M. Gómez & Miguel Verdú
Scientific Reports 7, Article number: 43467 (2017)


Levitation of heavy particles against gravity in asymptotically downward flows

In the fluid transport of particles, it is generally expected that heavy particles carried by a laminar fluid flow moving downward will also move downward.  We establish a theory to show, however, that particles can be dynamically levitated and lifted by such flows, thereby moving against the flow and against gravity, even when they are orders of magnitude denser than the fluid. We suggest that this counterintuitive effect has potential implications for the air-transport of water droplets and the lifting of sediments in water.


Levitation of heavy particles against gravity and against the flow
Jean-Regis Angilella, Daniel J. Case, Adilson E. Motter
Chaos 27, 031103 (2017)


Cognitive Offloading Does Not Prevent but Rather Promotes Cognitive Development

We investigate the relation between the development of reactive and cognitive capabilities. In particular we investigate whether the development of reactive capabilities prevents or promotes the development of cognitive capabilities in a population of evolving robots that have to solve a time-delay navigation task in a double T-Maze environment. Analysis of the experiments reveals that the evolving robots always select reactive strategies that rely on cognitive offloading, i.e., the possibility of acting so as to encode onto the relation between the agent and the environment the states that can be used later to regulate the agent’s behavior. The discovery of these strategies does not prevent, but rather facilitates, the development of cognitive strategies that also rely on the extraction and use of internal states. Detailed analysis of the results obtained in the different experimental conditions provides evidence that helps clarify why, contrary to expectations, reactive and cognitive strategies tend to have synergetic relationships.


Carvalho JT, Nolfi S (2016) Cognitive Offloading Does Not Prevent but Rather Promotes Cognitive Development. PLoS ONE 11(8): e0160679. doi:10.1371/journal.pone.0160679


Building a Science of Experience: Neurophenomenology and Related Disciplines

Context: More than 20 years ago Varela initiated a research program to advance in the scientific study of consciousness, neurophenomenology. Problem: Has Varela’s neurophenomenology, the solution to the “hard problem,” been successful? Which issues remain unresolved, and why? Method: This introduction sketches the progress that has been made since then and links it to the contributions to this special issue. Results: Instead of a unified research field, today we find a variety of different interpretations and implementations of neurophenomenology. We argue that neurophenomenology needs to give additional attention to its experiential dimension by addressing first-person methods’ specific challenges and by rethinking the relationship between the frameworks of the first- and third-person approaches.


Valenzuela-Moguillansky C., Vásquez-Rosati A. & Riegler A. (2017) Building a Science of Experience: Neurophenomenology and Related Disciplines. Constructivist Foundations 12(2): 131–138. Available at