Showing papers by "Fabrizio Cleri published in 2023"

Infinite ergodicity in generalized geometric Brownian motions with nonlinear drift.

Abstract: Geometric Brownian motion is an exemplary stochastic processes obeying multiplicative noise, with widespread applications in several fields, e.g., in finance, in physics, and biology. The definition of the process depends crucially on the interpretation of the stochastic integrals which involves the discretization parameter α with 0≤α≤1, giving rise to the well-known special cases α=0 (Itô), α=1/2 (Fisk-Stratonovich), and α=1 (Hänggi-Klimontovich or anti-Itô). In this paper we study the asymptotic limits of the probability distribution functions of geometric Brownian motion and some related generalizations. We establish the conditions for the existence of normalizable asymptotic distributions depending on the discretization parameter α. Using the infinite ergodicity approach, recently applied to stochastic processes with multiplicative noise by E. Barkai and collaborators, we show how meaningful asymptotic results can be formulated in a transparent way.

Effect of electronic stopping in molecular dynamics simulations of collision cascades in gallium arsenide

Abstract: Understanding the generation and evolution of defects induced in matter by ion irradiation is of fundamental importance to estimate the degradation of functional properties of materials. Computational approaches used in dierent communities, from space radiation eects to nuclear energy experiments, are based on a number of approximations that, among others, traditionally neglect the coupling between electronic and ionic degrees of freedom in the description of displacements. In this work, we study collision cascades in GaAs, including the electronic stopping power for selfprojectiles in dierent directions obtained via real time Time Dependent Density Functional Theory in Molecular Dynamics simulations of collision cascades, using the recent electron-phonon model and the previously developed two-temperature model. We show that the former can be well applied to describe the eects of electronic stopping in molecular dynamics simulations of collision cascades in a multielement semiconductor and that the number of defects is considerably aected by electronic stopping eects. The results are also discussed in the wider context of the commonly used non-ionizing energy loss model to estimate degradation of materials by cumulative displacements.

Single-cell Electrochemical Aptasensor Array

Abstract: Despite several demonstrations of electrochemical devices with limits of detection (LOD) of 1 cell/mL, the implementation of single-cell bioelectrochemical sensor arrays has remained elusive due to the challenges of scaling up. In this study, we show that the recently introduced nanopillar array technology combined with redox-labelled aptamers targeting epithelial cell adhesion molecule (EpCAM) is perfectly suited for such implementation. Combining nanopillar arrays with microwells determined for single cell trapping directly on the sensor surface, single target cells are successfully detected and analyzed. This first implementation of a single-cell electrochemical aptasensor array, based on Brownian-fluctuating redox species, opens new opportunities for large-scale implementation and statistical analysis of early cancer diagnosis and cancer therapy in clinical settings. For Table of Contents only

Silicon Compatible Process To Integrate Impedance Cytometry With Mechanical Characterization

Abstract: We introduced 3D silicon electrodes to perform impedance cytometry on single cells without compromising practical integration with sensors measuring complementary properties, e.g., mechanical properties. Microfabricated from a highly-doped SOI wafer, some design modifications were made to improve their sensing performance. According to simulations, a trajectory-free measurement can be obtained by replacing the silicon backside under the sensing area with an insulating material. In addition, enlarging the distance between the electrodes and the surrounding silicon structure and filling them with some insulating material results experimentally in better signal quality and reduced parasitics. Combining these two device modifications improves the system frequency response and the signal quality at higher frequencies. The proposed process aims at creating silicon-based electrodes for impedance spectroscopy applications while providing opportunities to integrate them with MEMS sensors and actuators.