We developed a method to calculate the magnetoresistance of magnetic nanostructures. We discretize a magnetic disk in small cells and numerically solve the Landau-Lifshitz-Gilbert (LLG) equation in order to obtain its magnetization profile. We consid
er a anisotropic magnetoresistance (AMR) that depends on the local magnetization as the main source of the magnetoresistance. We then use it as an input to calculate the resistance and current distribution numerically, using a relaxation method. We show how magnetoresistance measurements can be useful to obtain information on the magnetic structure. Additionally, we obtain non-homogeneous current distributions for different magnetic configurations in static and dynamical regimes.
We use detrended fluctuation analysis (DFA) to study the dynamics of blood pressure oscillations and its feedback control in rats by analyzing systolic pressure time series before and after a surgical procedure that interrupts its control loop. We fo
und, for each situation, a crossover between two scaling regions characterized by exponents that reflect the nature of the feedback control and its range of operation. In addition, we found evidences of adaptation in the dynamics of blood pressure regulation a few days after surgical disruption of its main feedback circuit. Based on the paradigm of antagonistic, bipartite (vagal and sympathetic) action of the central nerve system, we propose a simple model for pressure homeostasis as the balance between two nonlinear opposing forces, successfully reproducing the crossover observed in the DFA of actual pressure signals.
