Platelet Activation in Artificial Heart Valves

A numerical framework is developed to perform multi-scale (hinge-to valve-scale) flow simulation and quantify the thrombogenic performance of prosthetic heart valves. This aim is achieved by 1) developing a parallel dynamic overset grid and combining it with the curvilinear immersed boundary (overset-CURVIB) method to reduce the computational cost; and 2) developing a framework for evaluating the thrombogenic performance of heart valves in terms of platelet activation. The dynamic overset grids are used to locally increase the grid resolution near immersed bodies, which are handled using a sharp interface immersed boundary method, undergoing large movements as well as arbitrary relative motions. The new framework extends the previous overset-CURVIB method with fixed overset grids and a sequential grid assembly to moving overset grids with an efficient parallel grid assembly. In addition, a new method for the interpolation of variables at the grid boundaries is developed which can drastically decrease the execution time and increase the parallel efficiency. This overset grid framework is integrated with a framework to quantify the platelet activation which is developed using a Eulerian frame of reference which calculates the activation over the whole computational domain (contrary to Largrangian methods which use limited number of particles). The new framework is verified and validated against experimental data, and analytical/benchmark solutions. This framework is used to compare the role of systole phase in the poor performance of bileaflet mechanical heart (BMHV) valve by using the bioprothtetic heart valve as a control. The results show that the activation in the bulk flow during the systole phase might play an essential role in poor hemodynamic performance of BMHVs. In addition, the contribution of bulk and hinge flows to the activation of platelets in BMHVs is quantified for the first time by performing simulations of the flow through a BMHV and resolving the hinge by overset grids. The total activation by the bulk flow is found to be several folds higher than that by the hinge/leakage flow. This is mainly due to the higher flow rate of the bulk flow which exposes much more platelets to shear stress than the leakage flow. For the future work, this framework is going to be applied for thrombogenic optimization of new designs of mechanical heart valves including trileaflet ones as well as patient-specific hemodynamic analysis of heart valves using fluid-structure interaction in more realistic geometries extracted from the medical images such as echocardiography

Heat transfer and turbulent simulation of nanomaterial due to compound turbulator including irreversibility analysis

In this research, combined turbulator was proposed to achieve good thermal performance. Steady turbulent flow of copper oxide nanofluid with homogeneous model was simulated involving k-ɛ model. Among various geometric parameters, height of turbulator (b) has been selected and its variation as well as Reynolds number was demonstrated in outputs. Exergy loss as well as flow and heat transfer was analyzed. Augmenting b is capable of increasing heat transfer. More disturbances can be seen with augmenting inlet velocity. Exergy loss is inversely proportional to increase of pumping power

Numerical simulation for entropy generation and hydrothermal performance of nanomaterial inside a porous cavity using Fe3O4 nanoparticles

Computational analysis of exergy loss of laminar nanomaterial flow by including magnetic effect has been implemented in current research. CVFEM was incorporated to solve the describing equations. The influences of Darcy, Hartmann numbers as well as buoyancy impact on irreversibility have been explored. Lower temperature of walls occurs with higher Rayleigh number. Stronger magnetic field produces resistance to nanofluid transportation which reduces the Nusselt number. Boundary layer reconstructs more with augment of Darcy number

Investigation of nanofluid conduction heat transfer within a triplex tube considering solidification

In current simulation, Galerkin approach was employed to achieve the best design of heat storage. Utilizing nanoparticles as well as mounting fins were promising ways to improve the efficiency of unit. The unsteady discharge process was analyzed in various time steps and outcomes were reported as contours, profiles and solid front. Acceleration in discharging means that more uniform process and better performance. Increasing the fin length is effective way to achieve greater discharging rate. Outcomes revealed that greater size of nanoparticles yielding higher performance when dp \u3c 40 nm

Ferrofluid irreversibility and heat transfer simulation inside a permeable space including Lorentz forces

In current paper, exergy simulation of free convection is scrutinized. In current mathematical framework, uniform magnetic field is adopted. In order to save the time, single phase model has been involved for nanofluid. Trend of Darcy, Hartmann and Rayleigh numbers on Bejan number, exergy loss and Nusselt number are captured through figures. Obtained outputs have indicated the growth of Nuave with the Darcy and Rayleigh numbers. A growth of Lorenz forces reflects greater exergy loss. To get the desired outcomes for application prospective, lower Hartmann number should be selected

Comparison of Common Monogenic Defects in a Large Predominantly Antibody Deficiency Cohort

Background: Predominantly antibody deficiencies (PADs) are the most common primary immunodeficiencies, characterized by hypogammaglobulinemia and inability to generate effective antibody responses. Objective: We intended to report most common monogenic PADs and to investigate how patients with PAD who were primarily diagnosed as suffering from agammaglobulinemia, hyper-IgM (HIgM) syndrome, and common variable immunodeficiency (CVID) have different clinical and immunological findings. Methods: Stepwise next-generation sequencing and Sanger sequencing were performed for confirmation of the mutations in the patients clinically diagnosed as suffering from agammaglobulinemia, HIgM syndrome, and CVID. Results: Among 550 registered patients, the predominant genetic defects associated with agammaglobulinemia (48 Bruton's tyrosine kinase [BTK] and 6 μ heavy chain deficiencies), HIgM syndrome (21 CD40 ligand and 7 activation-induced cytidine deaminase deficiencies), and CVID (17 lipopolysaccharides-responsive beige-like anchor deficiency and 12 atypical Immunodeficiency, Centromeric instability, and Facial dysmorphism syndromes) were identified. Clinical disease severity was significantly higher in patients with μ heavy chain and CD40 ligand mutations compared with patients with BTK (P = .003) and activation-induced cytidine deaminase (P = .009) mutations. Paralysis following live polio vaccination was considerably higher in patients with μ heavy chain deficiency compared with BTK deficiency (P < .001). We found a genotype-phenotype correlation among patients with BTK mutations regarding clinical manifestation of meningitis and chronic diarrhea. Surprisingly, we noticed that first presentations in most patients with Immunodeficiency, Centromeric instability, and Facial dysmorphism were respiratory complications (P = .008), whereas first presentations in patients with lipopolysaccharides-responsive beige-like anchor deficiency were nonrespiratory complications (P = .008). Conclusions: This study highlights similarities and differences in the clinical and genetic spectrum of the most common PAD-associated gene defects. This comprehensive comparison will facilitate clinical decision making, and improve prognosis and targeted treatment