1,721,141 research outputs found
On the molecular mechanisms driving pain perception and emergent collective behaviors
No full textA stochastic model to investigate the microscopic processes which trigger the sensation of pain is considered. The model, presented in Di Patti and Fanelli [Di Patti F, Fanelli D. Can a microscopic stochastic model explain the emergence of pain cycles in patients? J Stat Mech 2009. doi:10.1088/1742-5468/2009/01/P01004], accounts for the action of analgesic drug and introduces an effect of competition with the inactive species populating the bloodstream. Regular oscillations in the amount of bound receptors are detected, following a resonant amplification of the stochastic component intrinsic to the system. The condition for such oscillations to occur are here studied, resorting to combined numerical and analytical techniques. Extended and connected patches of the admissible parameters space are detected which do correspond to the oscillatory behaviors. These findings are discussed with reference to the existing literature on patients' response to the analgesic treatment. © 2009 Elsevier B.V. All rights reserved
A stochastic reaction scheme for drug/metabolite interaction
No full textWe present a simplified stochastic model to investigate the mechanisms of action of tramadol, a centrally acting analgesic, used for treating pain. The model accounts for the process of metabolization through the cytochrome CYP2D6 and the interactions between molecules and target receptors. The proposed formulation is stochastic in nature and allows to speculate on the role of finite-size fluctuations. Analytically, the master equation, governing the process under scrutiny, is derived and studied in the mean-field limit. The analysis of the associated asymptotic behavior proves interesting for its potential medical implications. The analysis of fluctuations is carried on via the van Kampen expansion. Numerical simulations are also performed to confirm the adequacy of our theoretical prediction. © 2009 Elsevier Ltd. All rights reserved
Can a microscopic stochastic model explain the emergence of pain cycles in patients?
No full textA stochastic model is introduced here to investigate the molecular mechanisms which trigger the perception of pain. The action of analgesic drug compounds is discussed in a dynamical context, where the competition with inactive species is explicitly accounted for. Finite size effects inevitably perturb the mean-field dynamics: oscillations in the amount of bound receptors are spontaneously manifested, driven by the noise which is intrinsic to the system under scrutiny. These effects are investigated both numerically, via stochastic simulations, and analytically, through a large size expansion. The claim that our findings could provide a consistent interpretative framework for explaining the emergence of cyclic behaviors in response to analgesic treatments is substantiated. © 2009 IOP Publishing Ltd
The Role of Income Distribution in the Diffusion of Corporate Social Responsibility
Full text linkThe purpose of this paper is to investigate the link between CSR growth and income distribution. We present a general equilibrium model where social responsibility enters both firms' and consumers' decisions. The model admits the existence of multiple equilibria, each of them characterized by a different diffusion of CSR. We study the conditions under which there exists a virtuous circle which ties increases in the diffusion of CSR to reductions in income inequality and viceversa. Under certain circumstances, any policy which promotes the diffusion of CSR induces a reduction of income inequality. By contrast, when such conditions are not satisfied, only redistributive policies may generate the virtuous circle
Stochastic turing patterns on a network
No full textThe process of stochastic Turing instability on a scale-free network is discussed for a specific case study: the stochastic Brusselator model. The system is shown to spontaneously differentiate into activator-rich and activator-poor nodes outside the region of parameters classically deputed to the deterministic Turing instability. This phenomenon, as revealed by direct stochastic simulations, is explained analytically and eventually traced back to the finite-size corrections stemming from the inherent graininess of the scrutinized medium. © 2012 American Physical Society
Stochastic turing patterns in the Brusselator model
No full textA stochastic version of the Brusselator model is proposed and studied via the system size expansion. The mean-field equations are derived and shown to yield to organized Turing patterns within a specific parameters region. When determining the Turing condition for instability, we pay particular attention to the role of cross-diffusive terms, often neglected in the heuristic derivation of reaction-diffusion schemes. Stochastic fluctuations are shown to give rise to spatially ordered solutions, sharing the same quantitative characteristic of the mean-field based Turing scenario, in term of excited wavelengths. Interestingly, the region of parameter yielding to the stochastic self-organization is wider than that determined via the conventional Turing approach, suggesting that the condition for spatial order to appear can be less stringent than customarily believed. © 2010 The American Physical Society
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Physics of long-range interacting systems
No full textThis title deals with an important class of many-body systems: those where the interaction potential decays slowly for large inter-particle distance. In particular, systems where the decay is slower than the inverse inter-particle distance raised to the dimension of the embedding space. Gravitational and Coulomb interactions are the most prominent examples. However, it has become clear that long-range interactions are more common than previously thought. This has stimulated a growing interest in the study of long-range interacting systems, with a better understanding of the many peculiarities in their behaviour
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