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Mauro Marini

Publications and source records attributed to Mauro Marini.

3 recordsLinked to original sources

A fixed-point approach for decaying solutions of difference equations

A boundary value problem associated to the difference equation with advanced argument \begin{equation} \label{*}Δ\bigl (a_{n}Φ(Δx_{n})\bigr)+b_{n}Φ(x_{n+p} )=0,\ \ n\geq1 \tag{$*$} \end{equation} is presented, where $Φ(u)=|u|^α$sgn $u,$ $α>0,p$ is a positive integer and the sequences $a,b,$ are positive. We deal with a particular type of decaying solutions of (\ref{*}), that is the so-called intermediate solutions (see below for the definition) . In particular, we prove the existence of these type of solutions for (\ref{*}) by reducing it to a suitable boundary value problem associated to a difference equation without deviating argument. Our approach is based on a fixed point result for difference equations, which originates from existing ones stated in the continuous case. Some examples and suggestions for future researches complete the paper.

math.CA

A Dirichlet problem on the half-line for nonlinear equations with indefinite weight

We study the existence of positive solutions on the half-line $[0,\infty)$ for the nonlinear second order differential equation \[ \bigl(a(t)x^{\prime}\bigr)^{\prime}+b(t)F(x)=0,\quad t\geq0, \] satisfying Dirichlet type conditions, say $x(0)=0$, $\lim_{t\rightarrow\infty}x(t)=0$. The function $b$ is allowed to change sign and the nonlinearity $F$ is assumed to be asymptotically linear in a neighborhood of zero and infinity. Our results cover also the cases in which $b$ is a periodic function for large $t$ or it is unbounded from below.

math.CA

Estimation and Modelling of PCBs Bioaccumulation in the Adriatic Sea Ecosystem

Persistent Organic Pollutants represent a global ecological concern due to their ability to accumulate in organisms and to spread species-by-species via feeding connections. In this work we focus on the estimation and simulation of the bioaccumulation dynamics of persistent pollutants in the marine ecosystem, and we apply the approach for reconstructing a model of PCBs bioaccumulation in the Adriatic sea, estimated after an extensive review of trophic and PCBs concentration data on Adriatic species. Our estimations evidence the occurrence of PCBs biomagnification in the Adriatic food web, together with a strong dependence of bioaccumulation on trophic dynamics and external factors like fishing activity.

q-bio.PE