Article
Mathematics, Applied
Nicolas Alejandro Barnafi Wittwer, Simone DI Gregorio, Luca Dede, Paolo Zunino, Christian Vergara, Alfio Quarteroni
Summary: The importance of myocardial perfusion in the early stage of cardiac disease is not well researched. This study proposes a mathematical model that considers the interactions among the systemic circulation, coronary vessels, and myocardium. By decoupling the computational cost, the model accurately simulates a heartbeat under healthy conditions and effectively captures phenomena arising from the interaction of multiple components.
SIAM JOURNAL ON APPLIED MATHEMATICS
(2022)
Article
Mechanics
Carlos A. Galeano-Rios, Radu Cimpeanu, Isabelle A. Bauman, Annika MacEwen, Paul A. Milewski, Daniel M. Harris
Summary: This study investigates the phenomenon of a millimetre-size superhydrophobic sphere impacting on a quiescent bath, where it can be propelled back into the air while transferring energy to the fluid. Different physical parameters are explored to understand the dependence of rebound behavior, and various models are developed to explain the observed trends. The experiments, simulations, and models provide insights into the complex multi-scale system and reveal new phenomena at different ends of the Weber number spectrum.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Geochemistry & Geophysics
Yder Masson
Summary: This study presents a distributional finite-difference method (DFDM) for simulating the propagation of elastic waves in heterogeneous media in the time domain. DFDM decomposes the modeling domain into multiple elements of arbitrary sizes. When large elements are used, the method is computationally efficient and resembles the finite-difference method. When smaller elements are used, DFDM is more similar to the finite-element or spectral element methods and allows for meshing complicated structures. The proposed algorithm accurately models elastic wave propagation in heterogeneous media and accommodates non-conformal meshes.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Biology
Lei Fan, Jenny S. S. Choy, Farshad Raissi, Ghassan S. Kassab, Lik Chuan Lee
Summary: Cardiac resynchronization therapy (CRT) response is affected by pacing site and coronary perfusion, which may have clinical implications in improving treatment outcomes.
COMPUTERS IN BIOLOGY AND MEDICINE
(2022)
Article
Engineering, Geological
Matthew R. Kuhn
Summary: The paper presents a multi-phase, multi-scale rational method for modeling and predicting free-field wave propagation and the weakening and liquefaction of near-surface soils using the discrete element method (DEM). The method involves analyzing various conditions and phenomena related to seismic shaking and post-shaking consolidation period, as well as refining the DEM for realistically simulating soil behavior and solving propagation and liquefaction factors.
Article
Geochemistry & Geophysics
Luqian Jiang, Wei Zhang
Summary: A new equivalent medium parametrization method has been developed to reduce the interface error of finite-difference methods in heterogeneous media on coarse grids. The method shows satisfactory results in simulating seismic waveforms and can be used in conjunction with higher-order and optimized schemes.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Multidisciplinary Sciences
Dominic G. Whittaker, Rebecca A. Capel, Maurice Hendrix, Xin Hui S. Chan, Neil Herring, Nicholas J. White, Gary R. Mirams, Rebecca-Ann B. Burton
Summary: The study used mathematical modeling to investigate the safety profile of HCQ, CQ, and other QT-prolonging anti-infective agents. It found that the risk of Torsade de Pointes arrhythmia increases with concentration and when combined with other QT-prolonging drugs.
ROYAL SOCIETY OPEN SCIENCE
(2021)
Article
Geochemistry & Geophysics
Maria Koroni, Anselme Borgeaud, Andreas Fichtner, Frederic Deschamps
Summary: The core-mantle boundary (CMB) is a significant internal boundary in the Earth that strongly influences its dynamics. However, there is currently a lack of agreement between models of CMB topographic variations. This study analyzes seismic waves interacting with the CMB to understand the difficulties in inferring CMB topography and provides sensitivity kernels to explain the behavior of measured traveltimes.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Engineering, Geological
Robert Bird, Adriana Paluszny, Robin N. Thomas, Robert W. Zimmerman
Summary: This work presents a detailed three-dimensional finite element model for wave propagation in rock blasting, combined with a postprocessing procedure to determine fracture intensity. The model incorporates a constitutive model for brittle materials under high strain rates and high pressures, as well as an instantaneous tensile failure model. The model is validated through numerical experiments and shown to accurately predict fracture intensity. The observed damage patterns closely match the fractures in the experiments.
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES
(2023)
Article
Geochemistry & Geophysics
Erik F. M. Koene, Jens Wittsten, Johan O. A. Robertsson
Summary: Finite-difference modelling of seismic waves near dipping interfaces often results in artifacts. These errors can be reduced through anti-aliasing techniques or replacing the interface with an equivalent medium. In acoustic media, anti-aliasing methods yield the smallest errors, while in elastic media, the SM calculus provides the best accuracy, albeit at a higher computational cost.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Engineering, Marine
Ruixue Liu, Cosan Daskiran, Abhishek Mukherjee, Qin Xin, Fangda Cui, Simone Marras, Hena Farooqi, Heather Dettman, Michel Boufadel
Summary: A mesoscale oil spill test tank was used to study the mixing energy and particle behavior near the shorelines. Different types of waves were generated and their velocities and energy dissipation rates were measured. Large-Eddy Simulation (LES) was conducted to further analyze the particle movement under typical wave conditions. The results showed that droplet inertia had a significant impact on particle accumulation.
Article
Mathematics, Applied
Nicolas Barnafi, Paolo Zunino, Luca Dede, Alfio Quarteroni
Summary: This paper discusses a previously proposed model for a deformable porous material, focusing on a linearized version of the model, mathematical analysis, and numerical approximation. The analysis particularly emphasizes the well-posedness of the model and the stability of the numerical discretization scheme, with attention to how the choice of polynomial degree for approximation depends on the porosity of the mixture.
COMPUTERS & MATHEMATICS WITH APPLICATIONS
(2021)
Article
Mathematics, Applied
Shang Wang, Jun Meng, Jingfang Fan
Summary: This study investigates teleconnections using a climate network approach and reveals their distribution patterns and intensity. The results show that the impacts of teleconnections have increased prominently in the Southern Hemisphere over the past few decades. The study also identifies climate-sensitive regions, such as southeastern Australia, which are likely to face exacerbating impacts of global warming.
Article
Mechanics
Nicolas Moreno, Marco Ellero
Summary: We propose a fully Lagrangian heterogeneous multiscale method (LHMM) for modeling complex fluids with microscopic features. The method discretizes the fluctuating Navier-Stokes equations using smoothed dissipative particle dynamics (SDPD) and exploits the multiscale features of SDPD to account for thermal fluctuations. The LHMM is validated using different flow configurations and fluid types, showing its flexibility in modeling complex fluids at the microscale.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Engineering, Manufacturing
J. Lee, M. Duhovic, T. Allen, D. May, P. Kelly
Summary: Transverse impregnation variants of LCM processes, including RTP and CRTM, show fast fill times and the model developed in this study simulates these processes accurately, considering factors like process time, fluid pressure, stress, and fiber volume fraction distribution. Assumptions like quasi-steady flow and uniform through-thickness deformation lead to significant errors in manufacturing process predictions, especially for transverse processes involving direct tool compaction of the fiber preform.
COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING
(2023)
Article
Cardiac & Cardiovascular Systems
Neal M. Duggal, Ienglam Lei, Xiaoting Wu, Keith D. Aaronson, Francis D. Pagani, Hugo Y. -K. Lam, Paul C. Tang
Summary: This study examined the differences in myocardial transcriptome signatures among patients with different degrees of mitral regurgitation (MR) pre-left ventricular assist device (LVAD) implantation. The results showed that patients with moderate-severe MR have increased expression of inflammation-related genes and reduced expression of cellular proliferation genes, which may have important implications for myocardial recovery.
JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY
(2023)
Article
Engineering, Multidisciplinary
Andreas Hessenthaler, Robert D. Falgout, Jacob B. Schroder, Adelaide de Vecchi, David Nordsletten, Oliver Roehrle
Summary: A time-periodic MGRIT algorithm is proposed in this paper to reduce the time-to-solution of numerical algorithms by exploiting time periodicity. It is shown that this algorithm can achieve the same solution as sequential time-stepping but with significantly reduced time. The algorithm enables faster turnaround and allows for the solution of more complex and realistic problems.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2022)
Article
Cardiac & Cardiovascular Systems
Harminder Gill, Joao Fernandes, Omar Chehab, Bernard Prendergast, Simon Redwood, Amedeo Chiribiri, David Nordsletten, Ronak Rajani, Pablo Lamata
Summary: Uni-dimensional Doppler echocardiography data is the primary method for quantitatively assessing aortic stenosis, with transvalvular pressure drop being a crucial indicator of hemodynamic burden. Advanced techniques in velocity data acquisition and computational analysis have improved the accuracy and reproducibility of measurements. Three-dimensional imaging modalities allow angle-independent valve interrogation and calculation of more precise measures of the transvalvular pressure drop. This manuscript explores the fundamental physics principles underlying aortic stenosis evaluation and discusses modern techniques that may offer more accurate grading and inform appropriate management.
TRENDS IN CARDIOVASCULAR MEDICINE
(2023)
Article
Cardiac & Cardiovascular Systems
Adelaide de Vecchi, Alessandro Faraci, Joao Filipe Fernandes, David Marlevi, Hannah Bellsham-Revell, Tarique Hussain, Nidhin Laji, Bram Ruijsink, James Wong, Reza Razavi, David Anderson, Caner Salih, Kuberan Pushparajah, David Nordsletten, Pablo Lamata
Summary: This study proposed a method to assess the conduit and reservoir functions of the aorta in congenital vascular conditions and applied it to study the aorta in pre-Fontan hypoplastic left heart syndrome patients. The reconstructed neo-aorta in these patients showed good conduit function but impaired reservoir function, while the native descending HLHS aorta displayed enhanced reservoir function but impaired conduit function. This non-invasive and comprehensive assessment has potential clinical relevance in congenital vascular conditions.
JOURNAL OF CARDIOVASCULAR TRANSLATIONAL RESEARCH
(2022)
Article
Cardiac & Cardiovascular Systems
David Marlevi, Jorge Mariscal-Harana, Nicholas S. Burris, Julio Sotelo, Bram Ruijsink, Myrianthi Hadjicharalambous, Liya Asner, Eva Sammut, Radomir Chabiniok, Sergio Uribe, Reidar Winter, Pablo Lamata, Jordi Alastruey, David Nordsletten
Summary: This study aimed to explore aortic function in dilated cardiomyopathy (DCM) and found that subjects with reduced left ventricular systolic function had significantly reduced aortic relative pressure, increased aortic stiffness, and significantly delayed time-to-pressure peak duration. Aortic stiffness and aortic volumetric size were identified as key determinants of aortic relative pressure in DCM.
JOURNAL OF CARDIOVASCULAR TRANSLATIONAL RESEARCH
(2022)
Article
Engineering, Biomedical
Will Zhang, Gerhard Sommer, Justyna A. Niestrawska, Gerhard A. Holzapfel, David Nordsletten
Summary: Residual stress plays a critical role in modulating stress distributions in soft biological tissues and maintaining cell mechanobiological stress environment. This study analyzes the effects of viscoelasticity on residual stress and highlights the importance of viscoelastic approaches in accurately analyzing the residual stress distribution in soft biological tissues.
ACTA BIOMATERIALIA
(2022)
Article
Engineering, Multidisciplinary
Maximilian Balmus, Johan Hoffman, Andre Massing, David A. Nordsletten
Summary: In this work, a new stabilized approach for solving incompressible Navier-Stokes equations on fixed overlapping grids is proposed. The approach is based on the partition of unity finite element method and improves computational efficiency by lowering grid resolution requirements and allowing for velocity and pressure discretizations that do not satisfy the inf-sup condition. The authors provide implementation details and identify four key options to improve code efficiency. Through various tests, the new method demonstrates comparable accuracy to the single mesh boundary-fitted version of the same solver and shows a synergistic effect of the implementation options in reducing residual assembly time and achieving good load balancing properties.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2022)
Article
Anatomy & Morphology
Doyin S. Mansell, Eva Sammut, Vito D. Bruno, Raimondo Ascione, Jonathan C. L. Rodrigues, Harinderjit S. Gill, Katharine H. Fraser, Andrew N. Cookson
Summary: In a pig experimental model of myocardial infarction, a localized and layer-specific circumferential left ventricular strain metric has been found to indicate chronic changes in ventricular function post-infarction more effectively than ejection fraction. This study analyzed clinical volume indices, global strains, and the novel strain for a large human cohort to evaluate variations in ventricular function and morphology based on age, sex, and health status. Significant differences were observed between healthy and unhealthy populations, as well as between males and females. Care must be taken to correctly index critical values to age and sex when using regional circumferential strains for assessing cardiovascular health.
JOURNAL OF ANATOMY
(2023)
Review
Cardiac & Cardiovascular Systems
Ahmed Qureshi, Gregory Y. H. Lip, David A. Nordsletten, Steven E. Williams, Oleg Aslanidi, Adelaide de Vecchi
Summary: Atrial fibrillation (AF) is a major cause of ischemic stroke, and the left atrial appendage (LAA) is recognized as the primary source of embolism. Current stroke risk stratification methods mainly rely on clinical factors, rather than thrombogenic mechanisms. Cardiac imaging and image-based biophysical modeling have emerged as valuable tools for understanding thrombogenesis. However, neither technique alone is sufficient to fully assess thrombogenicity in AF. Future development integrating cardiac imaging, in-silico modeling, and machine learning approaches may improve personalized stroke risk stratification in AF patients.
FRONTIERS IN CARDIOVASCULAR MEDICINE
(2023)
Article
Engineering, Multidisciplinary
Will Zhang, Javiera Jilberto, Gerhard Sommer, Michael S. Sacks, Gerhard A. Holzapfel, David A. Nordsletten
Summary: Biomechanics is important in diagnosing and treating heart conditions. Computational models can provide personalized treatment options but require accurate constitutive equations for biomechanical behavior prediction. A fractional viscoelastic modeling approach that accurately captures the viscoelastic response of the human myocardium was previously developed. This approach has comparable computational costs and only requires two additional material parameters. In this study, the implementation of this approach in Finite Element Analysis was presented, numerical properties were examined, and the physiological implications were explored.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Engineering, Biomedical
Will Zhang, Majid Jadidi, Sayed Ahmadreza Razian, Gerhard A. Holzapfel, Alexey Kamenskiy, David A. Nordsletten
Summary: This study introduces a new viscoelastic constitutive model for the human femoropopliteal artery, which accurately describes its mechanical characteristics and time-dependent behavior. The model improves the accuracy of computational simulations and expands our knowledge of arterial mechanophysiology.
ACTA BIOMATERIALIA
(2023)
Article
Computer Science, Artificial Intelligence
E. Ferdian, D. Marlevi, J. Schollenberger, M. Aristova, E. R. Edelman, S. Schnell, C. A. Figueroa, D. A. Nordsletten, A. A. Young
Summary: The development of cerebrovascular disease is closely related to changes in intracranial flow and pressure. We developed a two-step approach using a deep residual network and physics-informed image processing to non-invasively quantify cerebrovascular hemodynamics. Our method showed good accuracy in estimating velocity and flow, as well as quantifying functional relative pressures. Additionally, we successfully applied our method to in-vivo volunteers, generating high-resolution intracranial flow images and reducing low-resolution bias in pressure estimation.
MEDICAL IMAGE ANALYSIS
(2023)
Article
Cardiac & Cardiovascular Systems
Joao Filipe Fernandes, Harminder Gill, Amanda Nio, Alessandro Faraci, Valeria Galli, David Marlevi, Malenka Bissell, Hojin Ha, Ronak Rajani, Peter Mortier, Saul G. Myerson, Petter Dyverfeldt, Tino Ebbers, David A. Nordsletten, Pablo Lamata
Summary: Non-invasive assessment of the distance to pressure recovery is possible using 4D Flow CMR tracking of blood flow momentum. Current clinical practices underestimate the pressure recovery distance in aortic stenosis, calling for re-evaluation of the methods that measure the hemodynamic burden caused by this condition.
JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE
(2023)
Meeting Abstract
Cardiac & Cardiovascular Systems
A. Qureshi, M. Balmus, G. Y. H. Lip, S. Williams, D. A. Nordsletten, O. Aslanidi, A. De Vecchi
EUROPEAN HEART JOURNAL
(2022)
Meeting Abstract
Cardiac & Cardiovascular Systems
M. Bonini, M. Hirschvogel, Y. Ahmed, H. Xu, A. Young, P. C. Tang, D. Nordsletten
JOURNAL OF HEART AND LUNG TRANSPLANTATION
(2022)