End-pulled polymer translocation through a many-body flexible pore

This paper studies the features of a homopolymer translocating through a flexible pore. The channel is modeled as a monolayer tube composed by monomers with two elastic parameters: spring-like two body interaction and bending three body recall interaction. In order to guarantee the stability of the system, the membrane is compounded by a lipid bilayer structure having hydrophobic body (internal), while the pore is hydrophilic in both edges. The polymer is end-pulled from the cis-side to the trans-side by a cantilever, to which is connected through a spring able to measure the force acting on the polymer during the translocation. All the structure reacts to the impacts of the monomers of the polymer with vibrations generated by the movement of its constituent bodies. In these conditions, the work done by the cantilever shows a nonmonotonic behavior with the elastic constant, revealing a resonant-like behavior in a parameter region. Moreover, the force spectroscopy registered as a function of time, is able to record the main kinetics of the polymer progression inside the pore

Volatility Effects on the Escape Time in Financial Market Models

We shortly review the statistical properties of the escape times, or hitting times, for stock price returns by using different models which describe the stock market evolution. We compare the probability function (PF) of these escape times with that obtained from real market data. Afterwards we analyze in detail the effect both of noise and different initial conditions on the escape time in a market model with stochastic volatility and a cubic nonlinearity. For this model we compare the PF of the stock price returns, the PF of the volatility and the return correlation with the same statistical characteristics obtained from real market data.Comment: 12 pages, 9 figures, to appear in Int. J. of Bifurcation and Chaos, 200

Relaxation phenomena in classical and quantum systems

et al.Relaxation phenomena in three different classical and quantum systems are investigated. First, the role of multiplicative and additive noise in a classical metastable system is analyzed. The mean lifetime of the metastable state shows a nonmonotonic behavior with a maximum as a function of both the additive and multiplicative noise intensities. In the second system, the simultaneous action of thermal and non-Gaussian noise on the dynamics of an overdamped point Josephson junction is studied. The effect of a Lévy noise generated by a Cauchy-Lorentz distribution on the mean lifetime of the superconductive metastable state, in the presence of a periodic driving, is investigated. We find resonant activation and noise enhanced stability in the presence of Lévy noise. Finally, the time evolution of a quantum particle moving in a metastable potential and interacting with a thermal reservoir is analyzed. Within the Caldeira-Legget model and the Feynman-Vernon functional approach, we obtain the time evolution of the population distributions in the position eigenstates of the particle, for different values of the thermal bath coupling strength.This work was partially supported by MIUR (Ministero dell’Istruzione dell’Universita‘ e della Ricerca), CNISM (Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia) and the Russian Foundation for Basic Research (project 11-02-01418). This work was also partially supported by the EU through Grant No. PITN-GA-2009-234970 and the Joint Italian Japanese Laboratory on “Quantum Technologies” of the Italian Ministry of Foreign Affairs.Peer Reviewe

THE BISTABLE POTENTIAL: AN ARCHETYPE FOR CLASSICAL AND QUANTUM SYSTEMS

In this work we analyze the transient dynamics of three different classical and quantum systems. First, we consider a classical Brownian particle moving in an asymmetric bistable potential, subject to a multiplicative and additive noise source. We investigate the role of these two noise sources on the life time of the metastable state. A nonmonotonic behavior of the lifetime as a function of both additive and multiplicative noise intensities is found, revealing the phenomenon of noise enhanced stability. Afterward, by using a Lotka–Volterra model, the dynamics of two competing species in the presence of Lévy noise sources is analyzed. Quasiperiodic oscillations and stochastic resonance phenomenon in the dynamics of the competing species are found. Finally the dynamics of a quantum particle subject to an asymmetric bistable potential and interacting with a thermal reservoir is investigated. We use the Caldeira–Leggett model and the approach of the Feynman–Vernon functional in discrete variable representation. We obtain the time evolution of the population distributions in energy eigenstates of the particle, for different values of the coupling strength with the thermal bath

Role of Noise in a Market Model with Stochastic Volatility

We study a generalization of the Heston model, which consists of two coupled stochastic differential equations, one for the stock price and the other one for the volatility. We consider a cubic nonlinearity in the first equation and a correlation between the two Wiener processes, which model the two white noise sources. This model can be useful to describe the market dynamics characterized by different regimes corresponding to normal and extreme days. We analyze the effect of the noise on the statistical properties of the escape time with reference to the noise enhanced stability (NES) phenomenon, that is the noise induced enhancement of the lifetime of a metastable state. We observe NES effect in our model with stochastic volatility. We investigate the role of the correlation between the two noise sources on the NES effect.Comment: 13 pages, 6 figures, Eur. Phys. J. B, in pres

Co-occurrence of resonant activation and noise-enhanced stability in a model of cancer growth in the presence of immune response

We investigate a stochastic version of a simple enzymatic reaction which follows the generic Michaelis-Menten kinetics. At sufficiently high concentrations of reacting species, the molecular fluctuations can be approximated as a realization of a Brownian dynamics for which the model reaction kinetics takes on the form of a stochastic differential equation. After eliminating a fast kinetics, the model can be rephrased into a form of a one-dimensional overdamped Langevin equation. We discuss physical aspects of environmental noises acting in such a reduced system, pointing out the possibility of coexistence of dynamical regimes where noise-enhanced stability and resonant activation phenomena can be observed together.Comment: 18 pages, 11 figures, published in Physical Review E 74, 041904 (2006

Exploring the protective function of positivity and regulatory emotional self-efficacy in time of pandemic covid-19

Despite several empirical studies on the 2019 coronavirus disease (COVID-19) pandemic that have highlighted its detrimental effect on individuals’ mental health, the identification of psychological factors that may moderate its impact on individuals’ behavior and well-being remains partly unexplored. The present study was conceived to examine the mediation role of regulatory emotional self-efficacy in the relationship between positivity and anxiety, depression, and perceived self-efficacy in complying with the containment measures to contrast the COVID-19 spread. Furthermore, the moderation role of age was tested. A sample of 1258 participants (64.2% women; Mage = 42.09, SD = 13.62) enrolled from the Italian general population answered an online survey aimed at investigating the role of individual differences in facing the COVID-19 pandemic. We opted for a snowball recruiting procedure to find participants. The online survey was disseminated through email invitation and using social media platforms (i.e., Facebook, Instagram). A multi-group path analysis model was performed using Mplus 8.4 to explore the hypothesized relations among variables. The following criteria were employed to evaluate the goodness of fit: χ2 likelihood ratio statistic, CFI and TLI > 0.95, RMSEA < 0.06 and SRMR < 0.08. The findings corroborated the protective role of both positivity and regulatory emotional self-efficacy in reducing individuals’ anxiety and depressive symptoms, as well as in fostering individuals’ capabilities in complying with the containment measures imposed by the government to reduce the risk of illness and to contain the spread of the virus COVID-19. Specifically, regulatory emotional self-efficacy beliefs partially mediated the relations between positivity and anxiety and depressive symptoms and fully mediated the effect of positivity on perceived self-efficacy beliefs in complying with the containment measures. These paths were equal across ages. The results of the present study appear relevant to implementing psychological interventions aimed to reduce the deleterious effects of the COVID-19 pandemic on mental health through the promotion of individuals’ optimistic orientation and emotion regulation

Gestione sostenibile delle foreste Mediterranee e uso energetico delle biomasse forestali residuali

he book describes the reasons that led the Regional Department of Rural and Territorial Development to take part in the PROFORBIOMED Project. They can be summarized by the need to dispose of a tool for the sustainable management of all the state-owned forests of the Region. As a matter of fact, the Project aims at developing a model of sustainable forest management, through the recovery and reuse of wood scraps from ordinary silvicultural operations, to be used for the production of power and heat inside of a process adopting natural renewable energy sources. The main actions taken and the methodologies adopted are described, as well as the principles and instruments required for the setting up and execution of the work. Some of the most relevant are: the drafting of “Forest Management Plans”, the “Short Supply Chain” and the “Biomass Traceability Protocol”, together with the application of “Best Practices” of Management and the “Monitoring of impacts” caused by the woody biomass extraction procedures. The “forest – wood – energy” chain developed and proposed is exclusively related to the territory pertaining to one municipality, and with CHP plants fed with biomass exclusively produced within the territory of each municipality, in strict compliance with the “sustainable forest management” principles, as well as with the fundamental principle of “short supply chain”. For these reasons the CHP plans proposed shall be sized according to the biomass available in each municipality, with the possibility of integrating residual forest biomass with other waste wood resources potentially available in the territory and coming from prunings in agricultural activities. Therefore, the replicable model prepared and proposed by PROFORBIOMED aims at appraising from the economic point of view a waste product, such is currently considered the residual forest biomass from the forests of Sicily, and at the same time significantly improving the natural environment, thanks to the reduction in oil consumption

Noise delayed decay of unstable states: theory versus numerical simulations

We study the noise delayed decay of unstable nonequilibrium states in nonlinear dynamical systems within the framework of the overdamped Brownian motion model. We give the exact expressions for the decay times of unstable states for polynomial potential profiles and obtain nonmonotonic behavior of the decay times as a function of the noise intensity for the unstable nonequilibrium states. The analytical results are compared with numerical simulations.Comment: 9 pages, 6 figures, in press in J. Phys.