Generalised Sandpile Dynamics on Artificial and Real-World Directed Networks

Clinical, immunological, and genetic investigations in a rare association of type 1 diabetes with xeroderma pigmentosum

Xeroderma pigmentosum (XP) is a rare genodermatosis predisposing to skin cancers. Autoimmune diseases related to XP are rarely discussed in the literature. Type 1 diabetes (T1D) has been associated with other genodermatoses like Cockayne syndrome, but it has never been described in XP. In the present study, we report the rare occurrence of T1D in XP patients. Five XP patients belonging to 4 consanguineous families originating from different regions of Tunisia were investigated. Their ages ranged between 8 and 18 years. All the patients had a severe hypovitaminosis D. All the patients had positive GAD antibody levels, and 4 of them had familial history of other autoimmune diseases. The spectrum of XP was variable in all the patients, with dermatological and neurological symptoms, and the occurrence of some cancers. Various hypotheses have been proposed to explain this association, among of which we cite the role of immunomodulation and down-regulation of ATP-dependent DNA excision repair protein genes, implying that impaired DNA repair may contribute to the development of some autoimmune diseases. Vitamin D3 deficiency secondary to sun protective measures was found in all patients and thus may play a role in increasing T1D risk in these patients.

1/x power-law in a close proximity of the Bak-Tang-Wiesenfeld sandpile

A cellular automaton constructed by Bak, Tang, and Wiesenfeld (BTW) in 1987 to explain the 1/f noise was recognized by the community for the theoretical foundations of self-organized criticality (SOC). Their conceptual work gave rise to various scientific areas in statistical physics, mathematics, and applied fields. The BTW core principles are based on steady slow loading and an instant huge stress-release. Advanced models, extensively developed far beyond the foundations for 34 years to successfully explain SOC in real-life processes, still failed to generate truncated 1/x probability distributions. This is done here through returning to the original BTW model and establishing its larger potential than the state-of-the-art expects. We establish that clustering of the events in space and time together with the core principles revealed by BTW lead to approximately 1/x power-law in the size-frequency distribution of model events.

Cognitive science as complexity science

It is uncontroversial to claim that cognitive science studies many complex phenomena. What is less acknowledged are the contradictions among many traditional commitments of its investigative approaches and the nature of cognitive systems. Consider, for example, methodological tensions that arise due to the fact that like most natural systems, cognitive systems are nonlinear; and yet, traditionally cognitive science has relied on linear statistical data analyses. Cognitive science as complexity science is offered as an interdisciplinary framework for the investigation of cognition that can dissolve such contradictions and tensions. Here, cognition is treated as exhibiting the following four key features: emergence, nonlinearity, self-organization, and universality. This framework integrates concepts, methods, and theories from such disciplines as systems theory, nonlinear dynamical systems theory, and synergetics. By adopting this approach, the cognitive sciences benefit from a common set of practices to investigate, explain, and understand cognition in its varied and complex forms. This article is categorized under: Computer Science > Neural Networks Psychology > Theory and Methods Philosophy > Foundations of Cognitive Science Neuroscience > Cognition.

Directed Abelian sandpile with multiple downward neighbors

We study the directed Abelian sandpile model on a square lattice, with K downward neighbors per site, K>2. The K=3 case is solved exactly, which extends the earlier known solution for the K=2 case. For K>2, the avalanche clusters can have holes and side branches and are thus qualitatively different from the K=2 case where avalanche clusters are compact. However, we find that the critical exponents for K>2 are identical with those for the K=2 case, and the large-scale structure of the avalanches for K>2 tends to the K=2 case.