In this article, we study numerically a Helmholtz decomposition methodology, based on a formulation of the mathematical model as a saddle-point problem. We use a preconditioned conjugate gradient algorithm, applied to...In this article, we study numerically a Helmholtz decomposition methodology, based on a formulation of the mathematical model as a saddle-point problem. We use a preconditioned conjugate gradient algorithm, applied to an associated operator equation of elliptic type, to solve the problem. To solve the elliptic partial differential equations, we use a second order mixed finite element approximation for discretization. We show, using 2-D synthetic vector fields, that this approach, yields very accurate solutions at a low computational cost compared to traditional methods with the same order of approximation.展开更多
We are interested in the coexistence of three species forming a tritrophic food chain model. Considering a linear grow for the lowest trophic species or prey, and a type III Holling functional response for the middle ...We are interested in the coexistence of three species forming a tritrophic food chain model. Considering a linear grow for the lowest trophic species or prey, and a type III Holling functional response for the middle and highest trophic species (first and second predator respectively). We prove that this model exhibits two small amplitud periodic solutions bifurcating simultaneously each one from one of the two zero-Hopf equilibrium points that the model has adequate values of its parameters. As far as we know, this is the first time that the phenomena appear in the literature related with food chain models.展开更多
Pseudoaneurisms are arterial wounds that affect all layers of an artery;although very rare they are mostly lethal and most of them are iatrogenic. Herein, we present two different cases of hepatic artery pseudoaneurys...Pseudoaneurisms are arterial wounds that affect all layers of an artery;although very rare they are mostly lethal and most of them are iatrogenic. Herein, we present two different cases of hepatic artery pseudoaneurysms derived from previous surgeries which were assessed by computed tomography angiographies and consequent conservative endovascular approaches with arteriographies, posterior cannulations and the placement of Amplatzer Vascular Plug 4 (AVP 4) systems in order to treat the pseudoaneurysm. Computed control tomographies were conducted showing no later complications. The purpose of this article is to demonstrate the importance and current clinical applications of AVP in the field of interventional radiology.展开更多
文摘In this article, we study numerically a Helmholtz decomposition methodology, based on a formulation of the mathematical model as a saddle-point problem. We use a preconditioned conjugate gradient algorithm, applied to an associated operator equation of elliptic type, to solve the problem. To solve the elliptic partial differential equations, we use a second order mixed finite element approximation for discretization. We show, using 2-D synthetic vector fields, that this approach, yields very accurate solutions at a low computational cost compared to traditional methods with the same order of approximation.
文摘We are interested in the coexistence of three species forming a tritrophic food chain model. Considering a linear grow for the lowest trophic species or prey, and a type III Holling functional response for the middle and highest trophic species (first and second predator respectively). We prove that this model exhibits two small amplitud periodic solutions bifurcating simultaneously each one from one of the two zero-Hopf equilibrium points that the model has adequate values of its parameters. As far as we know, this is the first time that the phenomena appear in the literature related with food chain models.
文摘Pseudoaneurisms are arterial wounds that affect all layers of an artery;although very rare they are mostly lethal and most of them are iatrogenic. Herein, we present two different cases of hepatic artery pseudoaneurysms derived from previous surgeries which were assessed by computed tomography angiographies and consequent conservative endovascular approaches with arteriographies, posterior cannulations and the placement of Amplatzer Vascular Plug 4 (AVP 4) systems in order to treat the pseudoaneurysm. Computed control tomographies were conducted showing no later complications. The purpose of this article is to demonstrate the importance and current clinical applications of AVP in the field of interventional radiology.
