Publications by authors named "Bernardo Martins Rocha"

Premature birth poses a challenge to public health, with one in ten babies being born prematurely worldwide. The pathological distension of the uterus can create tension in the uterine wall, triggering contractions that may lead to birth, including premature birth. While there has been an increase in the use of computational models to study pregnancy in recent years, ethical challenges have limited research on the mechanical properties of the uterus during gestation.

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Cardiac Purkinje networks are a fundamental part of the conduction system and are known to initiate a variety of cardiac arrhythmias. However, patient-specific modeling of Purkinje networks remains a challenge due to their high morphological complexity. This work presents a novel method based on optimization principles for the generation of Purkinje networks that combines geometric and activation accuracy in branch size, bifurcation angles, and Purkinje-ventricular-junction activation times.

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Myocarditis is a general set of mechanisms that manifest themselves into the inflammation of the heart muscle. In 2017, more than 3 million people were affected by this disease worldwide, causing about 47,000 deaths. Many aspects of the origin of this disease are well known, but several important questions regarding the disease remain open.

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Late in 2019, China identified a new type of coronavirus, SARS-CoV-2, and due to its fast spread, the World Health Organisation (WHO) declared a pandemic named COVID-19. Some variants of this virus were detected, including the Delta, which caused new waves of infections. This work uses an extended version of a SIRD model that includes vaccination effects to measure the impact of the Delta variant in three countries: Germany, Israel and Brazil.

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Over the last months, mathematical models have been extensively used to help control the COVID-19 pandemic worldwide. Although extremely useful in many tasks, most models have performed poorly in forecasting the pandemic peaks. We investigate this common pitfall by forecasting four countries' pandemic peak: Austria, Germany, Italy, and South Korea.

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Article Synopsis
  • By April 2020, COVID-19 had infected 1.5 million people globally, leading to over 80,000 deaths across 209 countries, causing significant strain on health systems.
  • Different countries have varied responses to the pandemic, with successful measures in South Korea, contrasting with the struggles seen in Italy and the early phases in Brazil, highlighting the effectiveness of policies like social distancing.
  • Mathematical models indicate South Korea's strong isolation efforts and case reporting, while Brazil and Italy face high underreporting and less effective isolation, emphasizing the need for robust mitigation strategies, especially in economically vulnerable nations.
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Article Synopsis
  • Proposed numerical methods address the cardiac electrophysiology model, which involves the electrical activity of the heart described by a nonlinear reaction-diffusion PDE coupled with ODEs for electrochemical reactions in cells.
  • The methods integrate an operator splitting technique for the PDE with primal hybrid methods for spatial discretization, allowing for flexible approximations of the Lagrange multiplier.
  • Results from convergence studies demonstrate optimal rates of convergence, and numerical experiments indicate that these new methods are often more efficient than traditional numerical techniques when using preconditioned iterative approaches for solving linear systems.
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Ectopic beats are known to be involved in the initiation of a variety of cardiac arrhythmias. Although their location may vary, ectopic excitations have been found to originate from infarct areas, regions of micro-fibrosis and other heterogeneous tissues. However, the underlying mechanisms that link ectopic foci to heterogeneous tissues have yet to be fully understood.

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Computational modeling of the heart is a subject of substantial medical and scientific interest, which may contribute to increase the understanding of several phenomena associated with cardiac physiological and pathological states. Modeling the mechanics of the heart have led to considerable insights, but it still represents a complex and a demanding computational problem, especially in a strongly coupled electromechanical setting. Passive cardiac tissue is commonly modeled as hyperelastic and is characterized by quasi-incompressible, orthotropic, and nonlinear material behavior.

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The use of computer models as a tool for the study and understanding of the complex phenomena of cardiac electrophysiology has attained increased importance nowadays. At the same time, the increased complexity of the biophysical processes translates into complex computational and mathematical models. To speed up cardiac simulations and to allow more precise and realistic uses, 2 different techniques have been traditionally exploited: parallel computing and sophisticated numerical methods.

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This paper compares different numerical methods for the solution of myocyte models of cardiac electrophysiology. In particular, it presents how the technique called uniformization method substantially increases the stability of simple first-order methods such as Euler explicit method and Rush-Larsen (RL) method, for the solution of modern electrophysiology models that are based on continuous-time Markov chains (MCs) for the description of subcellular structures, such as ion channels. The MCs are often associated with stiff ordinary differential equations that severely limit the time step used by these traditional methods.

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Article Synopsis
  • Recent advances in medical imaging and numerical techniques are enhancing computer models of ventricular electrophysiology by incorporating more anatomical and biophysical details.
  • A significant challenge in these models is parameterization due to the large number of variables that need to align with experimental or patient data.
  • This study presents techniques to optimize bidomain parameters for better matching of activation sequences, including an iterative algorithm for fine-tuning bulk conductivities and a method for separating these conductivities based on prescribed anisotropy ratios.
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