Link overlap influences opinion dynamics on multiplex networks of Ashkin-Teller spins.

Consider a multiplex network formed by two layers indicating social interactions: the first layer is a friendship network and the second layer is a network of business relations. In this duplex network each pair of individuals can be connected in different ways: they can be connected by a friendship but not connected by a business relation, they can be connected by a business relation without being friends, or they can be simultaneously friends and in a business relation. In the latter case we say that the links in different layers overlap. These three types of connections are called multilinks and the multidegree indicates the sum of multilinks of a given type that are incident to a given node. Previous opinion models on multilayer networks have mostly neglected the effect of link overlap. Here we show that link overlap can have important effects in the formation of a majority opinion. Indeed, the formation of a majority opinion can be significantly influenced by the statistical properties of multilinks, and in particular by the multidegree distribution. To quantitatively address this problem, we study a simple spin model, called the Ashkin-Teller model, including two-body and four-body interactions between nodes in different layers. Here we fully investigate the rich phase diagram of this model which includes a large variety of phase transitions. Indeed, the phase diagram or the model displays continuous, discontinuous, and hybrid phase transitions, and successive jumps of the order parameters within the Baxter phase.

Prescribing Patterns of Psychotropic Drugs and Risk of Violent Behavior: A Prospective, Multicenter Study in Italy.

BACKGROUND: This prospective cohort study aimed at evaluating patterns of polypharmacy and aggressive and violent behavior during a 1-year follow-up in patients with severe mental disorders. METHODS: A total of 340 patients (125 inpatients from residential facilities and 215 outpatients) were evaluated at baseline with the Structured Clinical Interview for DSM-IV Axis I and II, Brief Psychiatric Rating Scale, Specific Levels of Functioning scale, Brown-Goodwin Lifetime History of Aggression, Buss-Durkee Hostility Inventory, Barratt Impulsiveness Scale, and State-Trait Anger Expression Inventory-2. Aggressive behavior was rated every 15 days with the Modified Overt Aggression Scale and treatment compliance with the Medication Adherence Rating Scale. RESULTS: The whole sample was prescribed mainly antipsychotics with high levels of polypharmacy. Clozapine prescription and higher compliance were associated with lower levels of aggressive and violent behavior. Patients with a history of violence who took clozapine were prescribed the highest number of drugs. The patterns of cumulative Modified Overt Aggression Scale mean scores of patients taking clozapine (n = 46), other antipsychotics (n = 257), and no antipsychotics (n = 37) were significantly different (P = .001). Patients taking clozapine showed a time trend at 1-year follow-up (24 evaluations) indicating a significantly lower level of aggressive behavior. Patient higher compliance was also associated with lower Modified Overt Aggression Scale ratings during the 1-year follow-up. CONCLUSION: Both inpatients and outpatients showed high levels of polypharmacy. Clozapine prescription was associated with lower Modified Overt Aggression Scale ratings compared with any other antipsychotics or other psychotropic drugs. Higher compliance was associated with lower levels of aggressive and violent behavior.

Inhomogeneity of charge-density-wave order and quenched disorder in a high-Tc superconductor.

It has recently been established that the high-transition-temperature (high-Tc) superconducting state coexists with short-range charge-density-wave order and quenched disorder arising from dopants and strain. This complex, multiscale phase separation invites the development of theories of high-temperature superconductivity that include complexity. The nature of the spatial interplay between charge and dopant order that provides a basis for nanoscale phase separation remains a key open question, because experiments have yet to probe the unknown spatial distribution at both the nanoscale and mesoscale (between atomic and macroscopic scale). Here we report micro X-ray diffraction imaging of the spatial distribution of both short-range charge-density-wave 'puddles' (domains with only a few wavelengths) and quenched disorder in HgBa2CuO4 + y, the single-layer cuprate with the highest Tc, 95 kelvin (refs 26-28). We found that the charge-density-wave puddles, like the steam bubbles in boiling water, have a fat-tailed size distribution that is typical of self-organization near a critical point. However, the quenched disorder, which arises from oxygen interstitials, has a distribution that is contrary to the usually assumed random, uncorrelated distribution. The interstitial-oxygen-rich domains are spatially anticorrelated with the charge-density-wave domains, because higher doping does not favour the stripy charge-density-wave puddles, leading to a complex emergent geometry of the spatial landscape for superconductivity.

Nonlinear growth and condensation in multiplex networks.

Different types of interactions coexist and coevolve to shape the structure and function of a multiplex network. We propose here a general class of growth models in which the various layers of a multiplex network coevolve through a set of nonlinear preferential attachment rules. We show, both numerically and analytically, that by tuning the level of nonlinearity these models allow us to reproduce either homogeneous or heterogeneous degree distributions, together with positive or negative degree correlations across layers. In particular, we derive the condition for the appearance of a condensed state in which one node in each layer attracts an extensive fraction of all the edges.

The structure and dynamics of multilayer networks.

In the past years, network theory has successfully characterized the interaction among the constituents of a variety of complex systems, ranging from biological to technological, and social systems. However, up until recently, attention was almost exclusively given to networks in which all components were treated on equivalent footing, while neglecting all the extra information about the temporal- or context-related properties of the interactions under study. Only in the last years, taking advantage of the enhanced resolution in real data sets, network scientists have directed their interest to the multiplex character of real-world systems, and explicitly considered the time-varying and multilayer nature of networks. We offer here a comprehensive review on both structural and dynamical organization of graphs made of diverse relationships (layers) between its constituents, and cover several relevant issues, from a full redefinition of the basic structural measures, to understanding how the multilayer nature of the network affects processes and dynamics.

Growing multiplex networks.

We propose a modeling framework for growing multiplexes where a node can belong to different networks. We define new measures for multiplexes and we identify a number of relevant ingredients for modeling their evolution such as the coupling between the different layers and the distribution of node arrival times. The topology of the multiplex changes significantly in the different cases under consideration, with effects of the arrival time of nodes on the degree distribution, average shortest path length, and interdependence.

Mean-field methods in evolutionary duplication-innovation-loss models for the genome-level repertoire of protein domains.

We present a combined mean-field and simulation approach to different models describing the dynamics of classes formed by elements that can appear, disappear, or copy themselves. These models, related to a paradigm duplication-innovation model known as Chinese restaurant process, are devised to reproduce the scaling behavior observed in the genome-wide repertoire of protein domains of all known species. In view of these data, we discuss the qualitative and quantitative differences of the alternative model formulations, focusing in particular on the roles of element loss and of the specificity of empirical domain classes.

GABAergic hub neurons orchestrate synchrony in developing hippocampal networks.

Brain function operates through the coordinated activation of neuronal assemblies. Graph theory predicts that scale-free topologies, which include "hubs" (superconnected nodes), are an effective design to orchestrate synchronization. Whether hubs are present in neuronal assemblies and coordinate network activity remains unknown. Using network dynamics imaging, online reconstruction of functional connectivity, and targeted whole-cell recordings in rats and mice, we found that developing hippocampal networks follow a scale-free topology, and we demonstrated the existence of functional hubs. Perturbation of a single hub influenced the entire network dynamics. Morphophysiological analysis revealed that hub cells are a subpopulation of gamma-aminobutyric acid-releasing (GABAergic) interneurons possessing widespread axonal arborizations. These findings establish a central role for GABAergic interneurons in shaping developing networks and help provide a conceptual framework for studying neuronal synchrony.

A novel keratinase from Clostridium sporogenes bv. pennavorans bv. nov., a thermotolerant organism isolated from solfataric muds.

A bacterium which can grow on chicken feathers and which exhibits keratinolytic activity was isolated from solfataric muds. It was classified as belonging to the genus Clostridium and closely related to C. sporogenes. Based on its unique capability to degrade chicken feathers, it was designated as Clostridium sporogenes bv. pennavorans bv. nov. The keratinase purified from the culture supernatant is a monomer of 28.7kDa molecular mass. The enzyme is relatively thermostable and is active over a broad range of temperature and pH. Specific enzymatic assays demonstrate that keratinase can act on a large variety of soluble and insoluble protein substrates.

[Psychological issues related to multiple sclerosis]. / Aspetti psicologici dello sclerosi multipla.

This study sought to investigate some psychological issues related to multiple sclerosis (MS), in particular, the relations existing between illness representations, personality factors and coping strategies and, consequently, the specific coping strategies employed in adjusting emotionally to MS. Sixty-nine MS patients attending the University Polyclinic of Modena were administered the following battery: a questionnaire regarding demographic and illness features, the Illness Perception Questionnaire-Revised (IPQ-R), the Coping Orientations to Problems Experienced Questionnaire (COPE) and Cognitive Behavioural Assessment Hospital Form (CBA-H). Patients' physical disability level was also evaluated using the Expanded Disability Status Scale (EDSS). Results suggest that personality factors and patients' perception of their illness play an important role in activating one or other type of coping strategy. Regarding problem-focused coping strategies, the most significant predictors that emerged from stepwise linear multiple regression analysis were perception of the disease as cyclical (timeline cyclical dimension) and a low score in neuroticism, indicating good emotional stability of the subject. For emotion-centered coping strategies, the regression model identified as best predictors: the belief that chance or bad luck are the most important causes of the illness, perception of the disease as cyclical, extroversion and a cooperative mode of interacting with others, and the presence of interpersonal difficulties. Finally, with regard to disadaptive coping strategies, the best predictors resulting from the analysis were, once again, perception of the disease as cyclical, and interpersonal difficulties.

Bose-Einstein condensation in complex networks.

The evolution of many complex systems, including the World Wide Web, business, and citation networks, is encoded in the dynamic web describing the interactions between the system's constituents. Despite their irreversible and nonequilibrium nature these networks follow Bose statistics and can undergo Bose-Einstein condensation. Addressing the dynamical properties of these nonequilibrium systems within the framework of equilibrium quantum gases predicts that the "first-mover-advantage," "fit-get-rich," and "winner-takes-all" phenomena observed in competitive systems are thermodynamically distinct phases of the underlying evolving networks.

Renormalization-group study of one-dimensional systems with roughening transitions.

A recently introduced real-space renormalization-group technique, developed for the analysis of processes in the Kardar-Parisi-Zhang universality class, is generalized and tested by applying it to a different family of surface-growth processes. In particular, we consider a growth model exhibiting a rich phenomenology even in one dimension. It has four different phases and a directed percolation-related roughening transition. The renormalization method reproduces extremely well all of the phase diagram, the roughness exponents in all the phases, and the separatrix among them. This proves the versatility of the method and elucidates interesting physical mechanisms.