Publications

2026

1. LVSilentMI

   Computational investigation of the effect of pre-existing silent myocardial infarction on acute myocardial infarction

   Md Shah Wali Ullah, Jijo Derick Abraham, Samayala Rahman Oyshie, and 1 more author

   Computers in Biology and Medicine, 2026

   Abs DOI

   Recent clinical studies have reported that the pre-existence of unnoticed silent myocardial infarction (SMI) in patients hospitalized with acute myocardial infarction (AMI) significantly worsens morbidity and increases mortality. SMI patients exhibit infarcts of different sizes and locations. This condition occurs in conjunction with left ventricular (LV) hypertrophy. The distinct roles of these abnormalities on LV functions and their contribution to AMI prognosis are poorly understood. To address these gaps, this study utilizes a coupled finite element (FE) framework to investigate the effect of the size and location of isolated SMI and AMI on LV performance. Furthermore, the influence of the simultaneous occurrence of SMI and hypertrophy alongside AMI is evaluated. The results show that under the simulation conditions, the peak global longitudinal strain is influenced by the variation in the location and size of the SMI and AMI. However, ejection fraction (EF), end-diastolic pressure (EDP), and peak global circumferential strain are influenced by the size of the SMI. The findings indicate that the presence of pre-existing SMI and hypertrophy will notably impair the EF and global circumferential strain, resulting in worse morbidity in an AMI patient.

2025

1. BoilingR

   Nanoscale boiling and bubble dynamics of R152a/R1234ze(E) blends: Insights from molecular dynamics simulations

   Md. Aminul Islam, Sheikh Mohammad Shavik, and Mohammad Nasim Hasan

   International Communications in Heat and Mass Transfer, 2025

   Abs DOI

   Phase change characteristics of refrigerant blends is essential due to their wide applications and environmental relevance. This work investigates nanoscale boiling in R152a/R1234ze(E) blends using non-equilibrium molecular dynamics (NEMD) simulations under controlled heating (80–200 K/ns). Five compositions (0 %, 33 %, 50 %, 67 %, and 100 % R152a) are analyzed in a three-phase domain comprising liquid and vapor over a platinum wall with linearly increasing temperature to induce necessary phase change. Key characteristics—atomic kinetics, net evaporation, wall heat flux, bubble nucleation/growth, and near-wall temperature—are examined across blend ratios and heating conditions. Increasing R152a enhances boiling performance with a significant change in boiling mode. Significant enhancement in net evaporation number, bubble volume growth rate and time-average heat flux is noticed with the increase in R152a for all heating rates. However, blend of 67 % R152a demonstrates thermal performance comparable to pure R152a at low as well as high heating rates, but lags at moderate rates. Interfacial analysis shows the interfacial thermal resistance of R1234ze(E) is approximately 34 % lower than that of R152a although the bulk thermal resistance of R1234ze(E) is higher. Moreover, increase in R152a in the refrigerant blend enhanced its interfacial thermal resistance. This contrast enables optimal heat transfer in mixed compositions. Specifically, the 67 % R152a blend benefits from favorable molecular distribution, balancing interfacial and bulk transport properties for improved phase change behavior. These findings provide insights into tuning refrigerant blends for efficient heat transfer in nanoscale boiling systems.

2. LiquidNaHT

   Heat Transfer Dynamics of Liquid Sodium: Nanoscale Insights into Phase Change Characteristics and Leidenfrost Effects

   Amio Pronoy Das Ritwik, Md. Sajib Ali, Sheikh Mohammad Shavik, and 1 more author

   Nanoscale and Microscale Thermophysical Engineering, 2025

   Abs DOI

   Liquid alkali metals hold great potential in applications requiring efficient heat transfer, such as nuclear power plants, solar energy systems, and process technology. Their high latent heat of vaporization and exceptional thermal conductivity make them promising alternatives to conventional heat transfer fluids like air, water, and molten salts. Understanding the phase change characteristics of liquid alkali metals under non-equilibrium heating conditions is crucial for optimizing their performance in such applications. This study employs molecular dynamics simulations to investigate the nanoscale phase transition behavior of a thin liquid sodium layer, a representative alkali metal, in contact with a gold surface. After initial equilibration, the wall temperature is increased linearly to a target value over various heating periods. Temporal changes in temperature, pressure, center of mass, and wall heat flux are monitored for qualitative heat transfer analysis, while average heat flux and evaporative mass flux provide quantitative evaluation. The results reveal diverse phase change modes, including an intriguing phenomenon where the liquid sodium film undergoes explosive boiling, resembling the “Leidenfrost” effect, even at temperatures significantly below its critical point. The onset time and wall temperature for explosive boiling vary across heating conditions, offering essential insights for preventing the “boiling crisis” in sodium-based thermo-fluid systems. These findings advance the understanding of phase change phenomena in liquid alkali metals and their implications for high-performance heat transfer applications.

2024

1. LVHFpEF-HO

   Computational investigation of the role of ventricular remodelling in HFpEF: The key to phenotype dissection

   Jijo Derick Abraham, Sheikh Mohammad Shavik, Travis R. Mitchell, and 3 more authors

   Computers in Biology and Medicine, 2024

   Abs DOI

   Recent clinical studies have reported that heart failure with preserved ejection fraction (HFpEF) can be divided into two phenotypes based on the range of ejection fraction (EF), namely HFpEF with higher EF and HFpEF with lower EF. These phenotypes exhibit distinct left ventricle (LV) remodelling patterns and dynamics. However, the influence of LV remodelling on various LV functional indices and the underlying mechanics for these two phenotypes are not well understood. To address these issues, this study employs a coupled finite element analysis (FEA) framework to analyse the impact of various ventricular remodelling patterns, specifically concentric remodelling (CR), concentric hypertrophy (CH), and eccentric hypertrophy (EH), with and without LV wall thickening on LV functional indices. Further, the geometries with a moderate level of remodelling from each pattern are subjected to fibre stiffening and contractile impairment to examine their effect in replicating the different features of HFpEF. The results show that with severe CR, LV could exhibit the characteristics of HFpEF with higher EF, as observed in recent clinical studies. Controlled fibre stiffening can simultaneously increase the end-diastolic pressure (EDP) and reduce the peak longitudinal strain (ell) without significant reduction in EF, facilitating the moderate CR geometries to fit into this phenotype. Similarly, fibre stiffening can assist the CH and ‘EH with wall thickening’ cases to replicate HFpEF with lower EF. These findings suggest that potential treatment for these two phenotypes should target the bio-origins of their distinct ventricular remodelling patterns and the extent of myocardial stiffening.

2022

1. BiVPAH

   Data-driven computational models of ventricular-arterial hemodynamics in pediatric pulmonary arterial hypertension

   Christopher Tossas-Betancourt, Nathan Y. Li, Sheikh M. Shavik, and 15 more authors

   Frontiers in Physiology, 2022

   Abs DOI

   Pulmonary arterial hypertension (PAH) is a complex disease involving increased resistance in the pulmonary arteries and subsequent right ventricular (RV) remodeling. Ventricular-arterial interactions are fundamental to PAH pathophysiology but are rarely captured in computational models. It is important to identify metrics that capture and quantify these interactions to inform our understanding of this disease as well as potentially facilitate patient stratification. Towards this end, we developed and calibrated two multi-scale high-resolution closed-loop computational models using open-source software: a high-resolution arterial model implemented using CRIMSON, and a high-resolution ventricular model implemented using FEniCS. Models were constructed with clinical data including non-invasive imaging and invasive hemodynamic measurements from a cohort of pediatric PAH patients. A contribution of this work is the discussion of inconsistencies in anatomical and hemodynamic data routinely acquired in PAH patients. We proposed and implemented strategies to mitigate these inconsistencies, and subsequently use this data to inform and calibrate computational models of the ventricles and large arteries. Computational models based on adjusted clinical data were calibrated until the simulated results for the high-resolution arterial models matched within 10% of adjusted data consisting of pressure and flow, whereas the high-resolution ventricular models were calibrated until simulation results matched adjusted data of volume and pressure waveforms within 10%. A statistical analysis was performed to correlate numerous data-derived and model-derived metrics with clinically assessed disease severity. Several model-derived metrics were strongly correlated with clinically assessed disease severity, suggesting that computational models may aid in assessing PAH severity.

2021

1. LVHFpEFGuccione

   Computational Modeling Studies of the Roles of Left Ventricular Geometry, Afterload, and Muscle Contractility on Myocardial Strains in Heart Failure with Preserved Ejection Fraction

   Sheikh Mohammad Shavik, Samuel Wall, Joakim Sundnes, and 5 more authors

   Journal of Cardiovascular Translational Research, Apr 2021

   DOI

2020

1. BiVAint

   Multiscale Modeling Framework of Ventricular-Arterial Bi-directional Interactions in the Cardiopulmonary Circulation

   Sheikh Mohammad Shavik, Christopher Tossas-Betancourt, C. Alberto Figueroa, and 2 more authors

   Frontiers in Physiology, 2020

   Abs DOI

   Ventricular-arterial coupling plays a key role in the physiologic function of the cardiovascular system. We have previously described a hybrid lumped-finite element (FE) modeling framework of the systemic circulation that couples idealized FE models of the aorta and the left ventricle (LV). Here, we describe an extension of the lumped-FE modeling framework that couples patient-specific FE models of the left and right ventricles, aorta and the large pulmonary arteries in both the systemic and pulmonary circulations. Geometries of the FE models were reconstructed from magnetic resonance (MR) images acquired in a pediatric patient diagnosed with pulmonary arterial hypertension (PAH). The modeling framework was calibrated with pressure waveforms acquired in the heart and arteries by catheterization as well as ventricular volume and arterial diameter waveforms measured from MR images. The calibrated model hemodynamic results match well with the clinically-measured waveforms (volume and pressure) in the LV and right ventricle (RV) as well as with the clinically-measured waveforms (pressure and diameter) in the aorta and main pulmonary artery. The calibrated framework was then used to simulate three cases, namely, 1) an increase in collagen in the large pulmonary arteries, 2) a decrease in contractility and 3) an increase in the total pulmonary arterial resistance, all characteristics of progressive PAH. The key finding from these simulations is that hemodynamics of the pulmonary vasculature and RV wall stress is more sensitive to vasoconstriction with a 10% of reduction in the lumen diameter of the distal vessels than a 67% increase in the proximal vessel’s collagen mass.

2. LVPerfusion

   Effects of myocardial function and systemic circulation on regional coronary perfusion

   Ravi Namani, Lik C. Lee, Yoram Lanir, and 3 more authors

   Journal of Applied Physiology, 2020

   PMID: 32078466

   Abs DOI

   Cardiac-coronary interaction and the effects of its pathophysiological variations on spatial heterogeneity of coronary perfusion and myocardial work are still poorly understood. This hypothesis-generating study predicts spatial heterogeneities in both regional cardiac work and perfusion that offer a new paradigm on the vulnerability of the subendocardium to ischemia, particularly at the apex. We propose a mathematical and computational modeling framework to simulate the interaction of left ventricular mechanics, systemic circulation, and coronary microcirculation. The computational simulations revealed that the relaxation rate of the myocardium has a significant effect whereas the contractility has a marginal effect on both the magnitude and transmural distribution of coronary perfusion. The ratio of subendocardial to subepicardial perfusion density (Qendo/Qepi) changed by −12 to +6% from a baseline value of 1.16 when myocardial contractility was varied by +25 and −10%, respectively; Qendo/Qepi changed by 37% when sarcomere relaxation rate, b, was faster and increased by 10% from the baseline value. The model predicts axial differences in regional myocardial work and perfusion density across the wall thickness. Regional myofiber work done at the apex is 30–50% lower than at the center region, whereas perfusion density in the apex is lower by only 18% compared with the center. There are large axial differences in coronary flow and myocardial work at the subendocardial locations, with the highest differences located at the apex region. A mismatch exists between perfusion density and regional work done at the subendocardium. This mismatch is speculated to be compensated by coronary autoregulation.NEW & NOTEWORTHY We present a model of left ventricle perfusion based on an anatomically realistic coronary tree structure that includes its interaction with the systemic circulation. Left ventricular relaxation rate has a significant effect on the regional distribution of coronary flow and myocardial work.

2019

1. BiVRVAD

   In-silico assessment of the effects of right ventricular assist device on pulmonary arterial hypertension using an image based biventricular modeling framework

   Sheikh Mohammad Shavik, Liang Zhong, Xiaodan Zhao, and 1 more author

   Mechanics Research Communications, 2019

   Abs DOI

   Pulmonary arterial hypertension (PAH) is a heart disease that is characterized by an abnormally high pressure in the pulmonary artery (PA). While right ventricular assist device (RVAD) has been considered recently as a treatment option for end-stage PAH patients, its effects on biventricular mechanics are, however, largely unknown. To address this issue, we developed an image-based modeling framework consisting of a biventricular finite element (FE) model that is coupled to a lumped model describing the pulmonary and systemic circulations in a closed-loop system. The biventricular geometry was reconstructed from the magnetic resonance images of two PAH patients showing different degree of RV remodeling and a normal subject. The framework was calibrated to match patient-specific measurements of the left ventricular (LV) and RV volume and pressure waveforms. An RVAD model was incorporated into the calibrated framework and simulations were performed with different pump speeds. Results showed that RVAD unloads the RV, improves cardiac output and increases septum curvature, which are more pronounced in the PAH patient with severe RV remodeling. These improvements, however, are also accompanied by an adverse increase in the PA pressure. These results suggest that the RVAD implantation may need to be optimized depending on disease progression.

2018

1. ArEvapPtS2018

   Thermal transport during thin-film argon evaporation over nanostructured platinum surface: A molecular dynamics study

   Mohammad Nasim Hasan, Sheikh Mohammad Shavik, Kazi Fazle Rabbi, and 2 more authors

   Proceedings of the Institution of Mechanical Engineers, Part N: Journal of Nanomaterials, Nanoengineering and Nanosystems, 2018

   Abs DOI

   Investigation of thermal transport characteristics of thin-film liquid evaporation over nanostructured surface has been conducted using molecular dynamics simulation with particular importance on the effects of the nanostructure configuration for different wall–fluid interaction strengths. The nanostructured surface considered herein comprises wall-through rectangular nanoposts placed over a flat wall. Both the substrate and the nanostructure are of platinum while argon is used as the evaporating liquid. Two different wall–fluid interaction strengths have been considered that essentially emulate both hydrophilic and hydrophobic wetting conditions for three different nanostructure configurations. The argon–platinum molecular system is first equilibrated at 90 K and then followed by a sudden increase in the wall temperature at 130 K that induces evaporation of argon laid over it. Comparative effectiveness of heat and mass transfer for different surface wetting conditions has been studied by calculating the wall heat flux and evaporative mass flux. The results obtained in this study show that heat transfer occurs more easily in cases of nanostructured surfaces than in case of flat surface. Difference in behavior of argon molecules during and after the evaporation process, that is, wall adsorption characteristics, has been found to depend on the surface wetting condition as well as on presence and configuration of nanostructure. A thermodynamic approach of energy balance shows reasonable agreement with the present molecular dynamics study.

2. LVAint

   High Spatial Resolution Multi-Organ Finite Element Modeling of Ventricular-Arterial Coupling

   Sheikh Mohammad Shavik, Zhenxiang Jiang, Seungik Baek, and 1 more author

   Frontiers in Physiology, 2018

   Abs DOI

   While it has long been recognized that bi-directional interaction between the heart and the vasculature plays a critical role in the proper functioning of the cardiovascular system, a comprehensive study of this interaction has largely been hampered by a lack of modeling framework capable of simultaneously accommodating high-resolution models of the heart and vasculature. Here, we address this issue and present a computational modeling framework that couples finite element (FE) models of the left ventricle (LV) and aorta to elucidate ventricular - arterial coupling in the systemic circulation. We show in a baseline simulation that the framework predictions of (1) LV pressure - volume loop, (2) aorta pressure - diameter relationship, (3) pressure - waveforms of the aorta, LV and left atrium (LA) over the cardiac cycle are consistent with the physiological measurements found in healthy human. To develop insights of ventricular-arterial interactions, the framework was then used to simulate how alterations in the geometrical or, material parameter(s) of the aorta affect the LV and vice versa. We show that changing the geometry and microstructure of the aorta model in the framework led to changes in the functional behaviors of both LV and aorta that are consistent with experimental observations. On the other hand, changing contractility and passive stiffness of the LV model in the framework also produced changes in both the LV and aorta functional behaviors that are consistent with physiology principles.

3. LVmuStructure

   Contribution of left ventricular residual stress by myocytes and collagen: existence of inter-constituent mechanical interaction

   Marissa R. Grobbel, Sheikh Mohammad Shavik, Emma Darios, and 3 more authors

   Biomechanics and Modeling in Mechanobiology, Feb 2018

   DOI
4. ArEvap2018

   Atomistic modelling of thin film argon evaporation over different solid surfaces at different wetting conditions

   Mohammad Nasim Hasan, Sheikh Mohammad Shavik, Khaled Mosharraf Mukut, and 2 more authors

   Micro & Nano Letters, 2018

   Abs DOI

   In the present study, non-equilibrium molecular dynamics (MD) simulations have been performed to reveal the effect of solid-liquid interfacial wettability on the evaporation characteristics of thin liquid argon film placed over the flat solid surface. The atomistic model considered herein comprises of a three-phase simulation domain having a solid wall over which liquid argon and argon vapour co-exist. Initially, the system is thermally equilibrated at 90 K for a while after which rapid increase in the solid wall temperature induces a phase change process, i.e. evaporation. Both hydrophilic and hydrophobic wetting conditions of the solid surface have been considered at an evaporation temperature of 130 K for three different surface materials such as platinum, silver, and aluminium. The simulation results show that both the surface wettability and surface material have a significant role in phase transition phenomena of thin liquid film, particularly the surface wettability for the present system configuration. The thermal transport phenomena between the wall and liquid thin film have been studied thoroughly and discussed in terms of wall heat flux, evaporative mass flux, upper bound of maximum possible heat flux etc. The results obtained in the present MD simulation study are compared with the macroscopic predictions based on classical thermodynamics. Interestingly, a very good agreement has been found indicating that macroscopic thermodynamics approach can predict the characteristic of phase change phenomena of nanoscale thin liquid film.

2017

1. LVActive

   Organ-level validation of a cross-bridge cycling descriptor in a left ventricular finite element model: effects of ventricular loading on myocardial strains

   Sheikh Mohammad Shavik, Samuel T. Wall, Joakim Sundnes, and 2 more authors

   Physiological Reports, 2017

   Abs DOI

   Abstract Although detailed cell-based descriptors of cross-bridge cycling have been applied in finite element (FE) heart models to describe ventricular mechanics, these multiscale models have never been tested rigorously to determine if these descriptors, when scaled up to the organ-level, are able to reproduce well-established organ-level physiological behaviors. To address this void, we here validate a left ventricular (LV) FE model that is driven by a cell-based cross-bridge cycling descriptor against key organ-level heart physiology. The LV FE model was coupled to a closed-loop lumped parameter circulatory model to simulate different ventricular loading conditions (preload and afterload) and contractilities. We show that our model is able to reproduce a linear end-systolic pressure volume relationship, a curvilinear end-diastolic pressure volume relationship and a linear relationship between myocardial oxygen consumption and pressure–volume area. We also show that the validated model can predict realistic LV strain-time profiles in the longitudinal, circumferential, and radial directions. The predicted strain-time profiles display key features that are consistent with those measured in humans, such as having similar peak strains, time-to-peak-strain, and a rapid change in strain during atrial contraction at late-diastole. Our model shows that the myocardial strains are sensitive to not only LV contractility, but also to the LV loading conditions, especially to a change in afterload. This result suggests that caution must be exercised when associating changes in myocardial strain with changes in LV contractility. The methodically validated multiscale model will be used in future studies to understand human heart diseases.

2. ArEvap2017

   Phase Change Characteristics of Ultra-Thin Liquid Argon Film over different Flat Substrates at High Wall Superheat for Hydrophilic/Hydrophobic Wetting Condition: A Non-Equilibrium Molecular Dynamics Study

   Mohammad Nasim Hasan, SM Shavik, KF Rabbi, and 2 more authors

   Journal of Chemical Engineering, Aug 2017

   Abs DOI

   Non-equilibrium molecular dynamics simulations have been conducted to understand the effect of solid-liquid interfacial wettability and surface material on the phase change phenomena of the thin liquid argon film placed over flat substrate at high wall superheat. The molecular system consists of a three phase simulation domain involving solid wall, liquid argon and argon vapor. After the system is thermally equilibrated at 90K and kept in equilibrium for a while, a high wall superheat (250K that is far above the critical temperature of argon) is induced at the liquid boundary so that the liquid undergoes ultrafast heating. Both hydrophilic and hydrophobic surfaces were considered in the present study in order to observe the effect of surface wettability on phase change characteristics for three different solid substrate materials namely, Platinum (Pt), Silver (Ag) and Aluminium (Al). Results obtained in the present study are discussed in terms of transient atomic distribution inside system domain, heat flux characteristics across the solid-liquid interface together with evaporative mass flux from liquid argon. Simulation results show that, depending on the surface wetting condition, the phase change process appears to be very different (explosive/ diffusive) for all three substrate materials under consideration. Among three materials considered herein, Al is found to offer the least favourable condition for phase change process while Pt and Ag show similar heat and mass transfer characteristics for both hydrophilic and hydrophobic wetting conditions. Surface wettability effect is found to be more prominent than the effect of substrate material in thin film liquid phase change phenomena.

2015

1. ArEvapPtS2015

   Molecular Dynamics Study of Effect of Different Wetting Conditions on Evaporation and Rapid Boiling of Ultra-thin Argon Layer Over Platinum Surface

   S.M. Shavik, Mohammad Nasim Hasan, A.K.M. Monjur Morshed, and 1 more author

   Procedia Engineering, 2015

   The 6th BSME International Conference on Thermal Engineering

   Abs DOI

   Molecular dynamics simulations have been conducted to reveal the effect of solid-liquid interfacial wettability on the boiling phenomena of the thin liquid argon film placed over solid platinum wall. The three phase molecular system is comprised of solid platinum wall, liquid argon and argon vapor. Initially the three phase system is thermally equilibrated at 90K and after the attainment of equilibrium the temperature of solid platinum wall is suddenly increased which resembles ultrafast pulse heating. Two different degree of superheat have been considered to characterize the boiling phenomena, namely, evaporation for low degree of superheat and rapid or explosive boiling for high degree of superheat in which temperature of the wall was far above the critical temperature of argon. The solid-liquid interfacial wettability is varied to observe its effect on boiling and thus simulations are run for hydrophilic, hydrophobic and neutral surfaces. The simulation results show that surface wettability has a significant role on both cases of boiling phenomena. The nucleation of bubbles and formation of vapor films occurs more quickly for increased solid-liquid interfacial wettability. The study shows that hydrophilic surface is the most favorable surface condition for bubble nucleation.