Stochastic modelling of imatinib-treated leukemic cells dynamics

2007

External noise effects on the electron velocity fluctuations in semiconductors

2007

Subphotospheric convection and magnetic activity dependence on metallicity and age: Models and tests

2001

We present an extensive study on the dependence of the convective turnover time (conv) on the stellar metallicity and age for main-sequence stars of masses 0.6{1.6 M. To this aim we have used and compared predictions by stellar models based on the classical Mixing Length Theory and models incorporating a Full Spectrum of Turbulence treatment of subphotospheric convection. We show that the metallicity eect is relevant for dG stars but negligible for dK stars, while stellar age is important when computing the turnover times for red dwarfs younger than logt 8:5 yr. A scatter by up to a factor 3 could be spuriously introduced in the activity vs. Rossby number relationships if such eects are neg…

Enhancement of stability in systems with metastable states

2007

The investigation of noise‐induced phenomena in far from equilibrium systems is one of the approach used to understand the behaviour of physical and biological complex systems. Metastability is a generic feature of many nonlinear systems, and the problem of the lifetime of metastable states involves fundamental aspects of nonequilibrium statistical mechanics. The enhancement of the life‐time of metastable states through the noise enhanced stability effect and the role played by the resonant activation phenomenon will be discussed in models of interdisciplinary physics: (i) Ising model (ii) Josephson junction; (iii) stochastic FitzHugh‐Nagumo model; (iv) a population dynamics model, and (v) …

Activity, Rotation And Convection in Orion: Are the Data Inconsistent with the MS Activity-Rossby Number Relation?

2004

A relation between activity and rotation in young ~ 1Myr PMS in often not observed, suggesting that the mechanism responsible for the X-ray emission may differ from the α - ω dynamo. We re-investigate the matter utilizing recent X-ray and rotational data on the Orion Nebula Cluster (ONC).

Dependence of coronal X-ray emission on spot-induced brightness variations in cool main sequence stars

2003

The maximum amplitude (A m a x ) of spot-induced brightness variations from long-term V-band photometry and the ratio L x /L ? o l between X-ray and bolometric luminosities are suitable indicators of the level of magnetic activity in the photosphere and in the corona of late-type stars, respectively. By using these activity indicators we investigate the dependence of coronal X-ray emission on the level of photospheric starspot activity in a homogeneous sample of low mass main sequence field and cluster stars of different ages (IC 2602, IC 4665, IC 2391, a Persei, Pleiades and Hyades). First, the activity-rotation connection at the photospheric level is re-analysed, as well as its dependence…

Stochastic Dynamics in Polymer Translocation

2007

Environmental Noise and Nonlinear Relaxation in Biological Systems

2012

We analyse the effects of environmental noise in three different biological systems: (i) mating behaviour of individuals of 'Nezara viridula' (L.) (Heteroptera Pentatomidae); (ii) polymer translocation in crowded solution; (iii) an ecosystem described by a Verhulst model with a multiplicative Lèvy noise. Specifically, we report on experiments on the behavioural response of 'N. viridula' individuals to sub-threshold deterministic signals in the presence of noise. We analyse the insect response by directionality tests performed on a group of male individuals at different noise intensities. The percentage of insects which react to the sub-threshold signal shows a non-monotonic behavior, charac…

Noise influence on electron dynamics in semiconductors driven by a periodic electric field

2008

Studies about the constructive aspects of noise and fluctuations in different non-linear systems have shown that the addition of external noise to systems with an intrinsic noise may result in a less noisy response. Recently, the possibility to reduce the diffusion noise in semiconductor bulk materials by adding a random fluctuating contribution to the driving static electric field has been tested. The present work extends the previous theories by considering the noise-induced effects on the electron transport dynamics in low-doped n-type GaAs samples driven by a high-frequency periodic electric field (cyclostationary conditions). By means of Monte Carlo simulations, we calculate the change…

Monte Carlo Study of Diffusion Noise Reduction in GaAs Operating under Periodic Conditions

2009

The effects of an external correlated source of noise on the intrinsic carrier noise in a low‐doped GaAs bulk, operating under periodic conditions, are investigated. Numerical results confirm that the dynamical response of electrons driven by a high‐frequency periodic electric field receives a benefit by the constructive interplay between the fluctuating field and the intrinsic noise of the system. In particular, in this contribute we show a nonmonotonic behavior of the integrated spectral density, which value critically depends on the correlation time of the external noise source.

Heating and Cooling: Designing a Low Energy Home

2014

This unit is aimed at engaging students in designing and building an energy-efficient scale model house through the understanding of relevant concepts of energy flow in thermal systems. It is developed into 4 subunits that analyse the different processes of thermal energy transfer (conduction, convection and radiation). The project intends also to introduce pupils to infrared thermography, thermal imaging and thermograms, i.e. infrared imaging science. The content area of the unit is energy and power in thermal systems. The subunits are suitable for 14-16 year old students while the data analysis and more theoretical parts of the unit are suitable for 16-18 year old students. The estimated …

Cancer growth dynamics: stochastic models and noise induced effects

2009

In the framework of the Michaelis‐Menten (MM) reaction kinetics, we analyze the cancer growth dynamics in the presence of the immune response. We found the coexistence of noise enhanced stability (NES) and resonant activation (RA) phenomena which act in an opposite way with respect to the extinction of the tumor. The role of the stochastic resonance (SR) in the case of weak cancer therapy has been analyzed. The evolutionary dynamics of a system of cancerous cells in a model of chronic myeloid leukemia (CML) is investigated by a Monte Carlo approach. We analyzed the effects of a targeted therapy on the evolutionary dynamics of normal, first‐mutant and cancerous cell populations. We show how …

DOSE DEPENDENT SURVIVAL RESPONSE IN CHRONIC MYELOID LEUKEMIA UNDER CONTINUOUS AND PULSED TARGETED THERAPY

2010

A simulative study of cancer growth dynamics in patients affected by Chronic Myeloid Leukemia (CML), under the effect of a targeted dosedependent continuous or pulsed therapy, is presented. We have developed a model for the dynamics of CML in which thestochastic evolution of white blood cell populations are simulated by adopting a Monte Carlo approach. Several scenarios in the evolutionary dynamics of white blood cells, as a consequence of the efficacy of the different modelled therapies, pulsed or continuous, are described. The best results, in terms of a permanent disappearance of the leukemic phenotype, are achieved with a continuous therapy and higher dosage. However, our findings demon…

An experience of elicited inquiry elucidating the electron transport in semiconductor crystals

2016

In this study we report the results of an inquiry-driven learning path experienced by a sample of 10 electronic engineering students, engaged to investigate the electron transport in semiconductors. The undergraduates were first instructed by following a lecture-based class on condensed matter physics and then involved into an inquiry based path of simulative explorations. The students were invited by two instructors to explore the electron dynamics in a semiconductor bulk by means of Monte Carlo simulations. The students, working in group, had to design their own procedure of exploration, as expected in a traditional guided inquiry. But they experienced several difficulties on planning and…

X-ray emission in cool main sequence stars

2003

The maximum amplitude A_max_ of spot-induced brightness variations from long-term V-band photometry and the ratio L_X_/L_bol_ between X-ray and bolometric luminosities are suitable indicators of the level of magnetic activity in the photosphere and in the corona of late-type stars, respectively. By using these activity indicators we investigate the dependence of coronal X-ray emission on the level of photospheric starspot activity in a homogeneous sample of low mass main-sequence field and cluster stars of different ages (IC 2602, IC 4665, IC 2391, {alpha} Per, Pleiades and Hyades). Cone search capability for table J/A+A/410/671/table1 (Photometry)