Two distinct desynchronization processes caused by lesions in globally coupled neurons

To accomplish a task, the brain works like a synchronized neuronal network where all the involved neurons work together. When a lesion spreads in the brain, depending on its evolution, it can reach a significant portion of relevant area. As a consequence, a phase transition might occur: the neurons desynchronize and cannot perform a certain task anymore. Lesions are responsible for either disrupting the neuronal connections or, in some cases, for killing the neuron. In this work, we will use a simplified model of neuronal network to show that these two types of lesions cause different types of desynchronization.Comment: 5 pages, 3 figure

Asymmetric information and imperfect competition in the loan market

We measure the consequences of asymmetric information in the Italian market for small business lines of credit. Exploiting detailed, proprietary data on a random sample of Italian firms, the population of medium and large Italian banks, individual lines of credit between them, and subsequent individual defaults, we estimate models of demand for credit, loan pricing, loan use, and firm default based on the seminal work of Stiglitz and Weiss (1981) to measure the extent and consequences of asymmetric information in this market. While our data include a measure of observable credit risk comparable to that available to a bank during the application process, we allow firms to have private information about the underlying riskiness of their project. This riskiness influences banks’ pricing of loans as higher interest rates attract a riskier pool of borrowers, increasing aggregate default probabilities. Data on default, loan size, demand, and pricing separately identify the distribution of private riskiness from heterogeneous firm disutility from paying interest. Preliminary results suggest evidence of asymmetric information, separately identifying adverse selection and moral hazard. We use our results to quantify the impact of asymmetric information on pricing and welfare, and the role imperfect competition plays in mediating these effects

Energy and volume of vector fields on spherical domains

We present in this paper a \boundary version" for theorems about minimality of volume and energy functionals on a spherical domain of threedimensional Euclidean sphere

Subsystem density functional theory with meta generalized gradient approximation exchange-correlation functionals

We analyze the methodology and the performance of subsystem density functional theory (DFT) with meta-generalized gradient approximation (meta-GGA) exchange-correlation functionals for non-bonded systems. Meta-GGA functionals depend on the Kohn-Sham kinetic energy density (KED), which is not known as an explicit functional of the density. Therefore, they cannot be directly applied in subsystem DFT calculations. We propose a Laplacian-level approximation to the KED which overcomes the problem and provides a simple and accurate way to apply meta-GGA exchange-correlation functionals in subsystem DFT calculations. The so obtained density and energy errors, with respect to the corresponding supermolecular calculations, are comparable with conventional approaches, depending almost exclusively on the approximations in the non-additive kinetic embedding term. An embedding energy error decomposition explains the accuracy of our method.Comment: 14 pages, 3 figure

Phase synchronization of coupled bursting neurons and the generalized Kuramoto model

Bursting neurons fire rapid sequences of action potential spikes followed by a quiescent period. The basic dynamical mechanism of bursting is the slow currents that modulate a fast spiking activity caused by rapid ionic currents. Minimal models of bursting neurons must include both effects. We considered one of these models and its relation with a generalized Kuramoto model, thanks to the definition of a geometrical phase for bursting and a corresponding frequency. We considered neuronal networks with different connection topologies and investigated the transition from a non-synchronized to a partially phase-synchronized state as the coupling strength is varied. The numerically determined critical coupling strength value for this transition to occur is compared with theoretical results valid for the generalized Kuramoto model.Comment: 31 pages, 5 figure