arXiv subjects

Florencia Carusela

Publications and source records attributed to Florencia Carusela.

3 recordsLinked to original sources

arXiv2026

Soft thermal diodes: grafted polymers provide a highly tunable thermal rectification

We explore the heat-rectification properties of a two-phase fluid confined in a nano-chamber with one wall coated with end-grafted polymers using molecular-dynamics simulations. We find a significant thermal diode effect for a wide range of chamber fillings for both very stiff and fully flexible polymers. A stationary heat flux is imposed on the system by fixing the walls at two different temperatures, computing the heat flow as a function of the filling density. The fluid presents a liquid phase, located close to the cold wall, and, for many fillings, a vapor phase in contact with the hot wall. A vapor-liquid interface is also present and located at different distances from the walls, depending on the fluid filling. We study the system by comparing two operational modes: a direct mode, in which the polymers are grafted on the hot wall and exposed to the vapor phase. In the inverse mode, the wall temperatures are swapped and the fluid rearranges to adapt to the interchanged temperature gradient. We calculate the mean heat flow, number density and temperature profiles for the stationary state in both modes. From them, we computed the density and temperature profiles, heat rectification coefficient, and resistivity profiles, for the two studied extreme cases of polymer bending rigidity. We found that, the nano-chamber presents a significant degree of heat rectification with different characteristics and filling density ranges. We describe the conditions to be met to obtain high thermal rectification as regards fluid filling, polymer properties and fluid-polymer affinity. They can be fine-tuned according to the application or material availability. In the direction parallel to the walls the system is easily scalable towards macroscopic sizes, without affecting the thermal rectification. This makes the soft-diode mechanism very versatile in geometry, size and materials choice.

cond-mat.soft↗

arXiv2025

A non-homogeneous, non-stationary and path-dependent Markov anomalous diffusion model

A novel probabilistic framework for modelling anomalous diffusion is presented. The resulting process is Markovian, non-homogeneous, non-stationary, non-ergodic, and state-dependent. The fundamental law governing this process is driven by two opposing forces: one proportional to the current state, representing the intensity of autocorrelation or contagion, and another inversely proportional to the elapsed time, acting as a damping function. The interplay between these forces determines the diffusion regime, characterized by the ratio of their proportionality coefficients. This framework encompasses various regimes, including subdiffusion, Brownian non-Gaussian, superdiffusion, ballistic, and hyperballistic behaviours. The hyperballistic regime emerges when the correlation force dominates over damping, whereas a balance between these mechanisms results in a ballistic regime, which is also stationary. Crucially, non-stationarity is shown to be necessary for regimes other than ballistic. The model's ability to describe hyperballistic phenomena has been demonstrated in applications such as epidemics, software reliability, and network traffic. Furthermore, deviations from Gaussianity are explored and violations of the Central Limit Theorem are highlighted, supported by theoretical analysis and simulations. It will also be shown that the model exhibits a strong autocorrelation structure due to a position dependent jump probability.

math-ph↗

arXiv2011

A null model for testing thermodynamic optimization in ecological systems

Several authors have hypothesized that ecological systems are subject to thermodynamic optimization, which, if proven correct, could represent a long sought general principle of organization in ecology. Although there have been recent advances, this still remains as an unresolved topic, and ecologists lack a general method to test thermodynamic optimization hypotheses in specific systems. Here we present a general, novel approach that allows generating a null model for testing thermodynamic optimization on ecological systems. We first describe the general methodology, which is based in the analysis of a parametrized mathematical model of the system and the explicit consideration of constraints. Next we present an application example to an animal population using a general age-structured population model and physiological parameters from the literature. We finalize discussing the relevance of this work in the context of the current state of ecology, and implications for the further development of a thermodynamic ecological theory.

q-bio.QM↗