Identification of a Mathematical Model for the Prediction of Platelet Damage Accumulation in Artificial Organs: A Preliminary Study

2007 ◽  
Author(s):  
Matteo Nobili ◽  
Jawaad Sheriff ◽  
Umberto Morbiducci ◽  
Alberto Redaelli ◽  
Danny Bluestein
Keyword(s):  
Platelet Activation ◽  
Damage Accumulation ◽  
Heart Valves ◽  
Implantable Devices ◽  
Artificial Organs ◽  
Model Parameters ◽  
Reliable Technique ◽  
Prosthetic Devices ◽  
High Incidence ◽  
Preliminary Study

Platelets are the pre-eminent cell involved in hemostasis and thrombosis. In recent years it has been demonstrated that flow-induced platelet activation is a major cause for the relatively high incidence of thromboembolic complications in mechanical heart valves (MHVs) [1,2].The platelet activation state (PAS) assay has proved to be a reliable technique for the experimental measurement of procoagulant activity [3]. A Predictive numerical model for platelets damage accumulation could provide critical information for thrombogenicity optimization of implantable prosthetic devices. This would lead to improving the safety and efficacy of implantable devices. Reliable models able to predict this phenomenon are still lacking. The aim of this work is an attempt to bridge this gap. A model for describing the activation of formed elements in blood requires establishing a correlation between mechanical loading, exposure time and the phenomenological response of these elements to it. A physically consistent phenomenological model is used [4] and genetic algorithms (GAs) [5], have been successfully applied to the tuning of the model parameters by correlating its predictions to PAS measurements conducted in a Hemodynamic Shearing Device (HSD) by exposing platelets to prescribed shear stress loading waveforms.

Platelet Damage Accumulation and Recovery due to Hemodynamic Shear Stresses: An In Vitro Study

2008 ◽  
Author(s):  
Jawaad Sheriff ◽  
Jolyon Jesty ◽  
Danny Bluestein
Keyword(s):  
Shear Stress ◽  
Damage Accumulation ◽  
Heart Valves ◽  
In Vitro Study ◽  
Shear Stresses ◽  
Special Importance ◽  
Prosthetic Devices ◽  
Recovery Potential ◽  
Low Shear

It is well established that shear stress exposure activates platelets, and it has been shown that this flow-induced activation contributes significantly to thromboembolic complications in mechanical heart valves (MHVs) [1]. In addition, the platelet activation state (PAS) assay has been demonstrated to be an efficient technique to measure procoagulant activity [2]. However, there is a lack of reliable models to predict platelet damage accumulation. Such a tool allows thrombogenicity optimization of implanted prosthetic devices. Prior to developing this tool, certain aspects of platelet behavior in response to shear stress must be elucidated. Of special importance for developing accountable damage accumulation models is the recovery potential of platelets during repeated passages through devices, when not exposed to the elevated stresses characterizing blood flow in these devices. To accomplish this, PAS measurements were conducted in a Hemodynamic Shearing Device (HSD), where platelets were exposed to prescribed waveforms with alternating periods of high and low shear stresses.

Molecular Dynamics Simulation of Neutron Damage in β-SIC

1998 ◽  
Vol 540 ◽  
Author(s):  
J.M. Perlado ◽  
L. Malerba ◽  
T. Diaz De La Rubia
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Point Defects ◽  
Damage Accumulation ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Temperature Sensitive ◽  
Neutron Damage ◽  
Preliminary Study ◽  
Threshold Displacement

AbstractMolecular Dynamics (MD) simulations of neutron damage in β-SiC have been performed using a modified version of the Tersoff potential. The Threshold Displacement Energy (TDE) for Si and C atoms at 300 K has been determined along directions [001], [110], [111] and [ 1 1 1 ]. The existence of recombination barriers, which allow the formation of metastable, temperature-sensitive defects even below the threshold, has been observed. Displacement cascades produced by both C- and Si-recoils of energies spanning from 0.5 keV up to, respectively, 5 keV and 8 keV have also been simulated at 300 K and 1300 K. Their analysis, together with the analysis of damage accumulation (∼3.4×10-3 DPA) at 1300 K, reveals that the two sub-lattices exhibit opposite responses to irradiation: whereas only a little damage is produced on the “ductile” Si sub-lattice, many point-defects accumulate on the much more “fragile” C sub-lattice. A preliminary study of the nature and clustering tendency of these defects is performed. The possibility of disorder-induced amorphization is considered and the preliminary result is that no amorphization takes place at the dose and temperature simulated.

Organic Polymer Biocompatibility and Toxicology

1972 ◽  
Vol 18 (9) ◽  
pp. 869-894 ◽  
Author(s):  
Fritz Bischoff
Keyword(s):  
Food Packaging ◽  
Heart Valves ◽  
Chemical Carcinogenesis ◽  
Artificial Organs ◽  
Organic Polymer ◽  
Degradation Reactions ◽  
Contraceptive Devices ◽  
Heart Assist Devices ◽  
Liquid Silicone ◽  
Artificial Kidneys

Abstract Adverse effects of organic polymers used for plasma extenders, tissue adhesives, bone cements, contraceptive devices, prostheses, artificial organs, food packaging, cooking, and laboratory ware are appraised. Parenteral polymer disintegration involves hydrolytic, redox, and degradation reactions. Accumulative toxicity of plasticizers, antioxidants, and monomers liberated from plastic containers warrants investigation. Main problems with heart-assist devices are clotting and blood destruction; with plasma extenders, thesaurismotic reactions; with acrylic bone glues, transitory hypotension; with artificial kidneys, loss of metabolic essentials; with silicone heart valves, uptake of lipids; with silicone chin implants, bone resorption; and with liquid silicone mammary amplification, lumpy breasts and mastitis. A polymer fume fever is linked with pyrolysis of polytetrafluoroethylene. Human solid-state carcinogenesis constitutes a calculated risk with polymer implants. In rodents, all solid polymers tested produced cancer; chemical carcinogenesis was induced by a polyvinyl chloride copolymer, vinyl chloride, polycaprolactam, liquid silicone, and some brands of polytetrafluoroethylene.

scholarly journals In Silico Performance of a Recellularized Tissue-Engineered Transcatheter Aortic Valve

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Christopher Noble ◽  
Joshua Choe ◽  
Susheil Uthamaraj ◽  
Milton Deherrera ◽  
Amir Lerman ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Heart Valves ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Fe Analysis ◽  
Model Parameters ◽  
Biaxial Testing ◽  
Principal Stresses

Commercially available heart valves have many limitations, such as a lack of remodeling, risk of calcification, and thromboembolic problems. Many state-of-the-art tissue-engineered heart valves (TEHV) rely on recellularization to allow remodeling and transition to mechanical behavior of native tissues. Current in vitro testing is insufficient in characterizing a soon-to-be living valve due to this change in mechanical response; thus, it is imperative to understand the performance of an in situ valve. However, due to the complex in vivo environment, this is difficult to accomplish. Finite element (FE) analysis has become a standard tool for modeling mechanical behavior of heart valves; yet, research to date has mostly focused on commercial valves. The purpose of this study has been to evaluate the mechanical behavior of a TEHV material before and after 6 months of implantation in a rat subdermis model. This model allows the recellularization and remodeling potential of the material to be assessed via a simple and inexpensive means prior to more complex ovine orthotropic studies. Biaxial testing was utilized to evaluate the mechanical properties, and subsequently, constitutive model parameters were fit to the data to allow mechanical performance to be evaluated via FE analysis of a full cardiac cycle. Maximum principal stresses and strains from the leaflets and commissures were then analyzed. The results of this study demonstrate that the explanted tissues had reduced mechanical strength compared to the implants but were similar to the native tissues. For the FE models, this trend was continued with similar mechanical behavior in explant and native tissue groups and less compliant behavior in implant tissues. Histology demonstrated recellularization and remodeling although remodeled collagen had no clear directionality. In conclusion, we observed successful recellularization and remodeling of the tissue giving confidence to our TEHV material; however, the mechanical response indicates the additional remodeling would likely occur in the aortic/pulmonary position.

scholarly journals Prediction of Damage Accumulation Effect of Wood Structural Members under Long-Term Service: A Machine Learning Approach

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1243
Author(s):  
Zheng Li ◽  
Duo Tao ◽  
Mengwei Li ◽  
Zhan Shu ◽  
Songshi Jing ◽  
...  
Keyword(s):  
Machine Learning ◽  
Damage Accumulation ◽  
Goodness Of Fit ◽  
Machine Learning Algorithms ◽  
Cycle Performance ◽  
Model Parameters ◽  
Timber Structures ◽  
Structural Members ◽  
Accumulation Effect

It is well known that wood structural members can stand a relatively heavy load in the short term but will gradually get weaker if the load is applied for a longer period. This phenomenon is caused by the damage accumulation effect in wood and should be appropriately considered during the design of timber structures. Although various formulation methods (also known as classical models) have been proposed to evaluate the damage accumulation effect in wood, the calibration of model parameters is very time-consuming. Our work proposes a novel method to deal with the damage accumulation effect in wood that involves the application of machine learning algorithms. The proposed algorithm considers a multi-objective optimization process with a combination of goodness-of-fit and complexity. Long-term experimental data of typical wood species are used for developing the machine learning based damage accumulation model. Compared with existing pre-formulated models, our model managed to reduce the complexity of the model structure and give sufficiently accurate and unbiased predictions. This study aims to provide a novel tool for evaluating the damage accumulation in wood structural members, and the proposed model can further support the life-cycle performance assessment of timber structures under long-term service scenarios.

In Vitro Thrombogenicity Testing of Artificial Organs

1998 ◽  
Vol 21 (9) ◽  
pp. 548-552 ◽  
Author(s):  
R. Paul ◽  
O. Marseille ◽  
E. Hintze ◽  
L. Huber ◽  
H. Schima ◽  
...  
Keyword(s):  
Heart Valves ◽  
Early Stage ◽  
Thrombus Formation ◽  
Testing Procedure ◽  
Artificial Organs ◽  
Coagulation System ◽  
In Vitro Testing ◽  
Animal Testing ◽  
Thrombogenic Potential

Thromboembolic complications remain as one of the main problems for blood contacting artificial organs such as heart valves, bloodpumps and others. In vitro evaluation of thrombogenesis in prototypes has not previously been part of the standard evaluation of these devices. In comparison to hemolysis testing, evaluation of the thrombogenic potential is more difficult to perform because of the complexity of the blood coagulation system. We present an in vitro testing procedure that allows the accelerated examination of the thrombogenic potential of different types of blood pumps. Additionally, first results are presented that indicate the reliability of the accelerated clotting test for mechanical heart valves. Results for the centrifugal pump BioMedicus and two microaxial pumps have shown typical thrombus formation at locations such as bearings. The results indicate that the accelerated clotting test is an excellent addition to the much more expensive animal testing of artificial organs or assist devices. In vitro testing permits studies of thrombus formation to be performed at an early stage and at low costs and also facilitates a more precise investigation of device areas known to be potential hot spots for thrombus formation.

scholarly journals Adhesion and biofilm formation of Candida albicans on native and Pluronic-treated polystyrene

Biofilms ◽  
2005 ◽  
Vol 2 (1) ◽  
pp. 63-71 ◽  
Author(s):  
K. E. Wesenberg-Ward ◽  
B. J. Tyler ◽  
J. T. Sears
Keyword(s):  
Candida Albicans ◽  
Biofilm Formation ◽  
Pluronic F127 ◽  
Artificial Organs ◽  
Confocal Scanning Laser Microscopy ◽  
Mechanical Trauma ◽  
Biofilm Growth ◽  
Prosthetic Devices ◽  
Initial Adhesion ◽  
Defined Culture

Candida albicans forms part of the normal human flora whose growth is usually restricted by the normal flora bacteria and the host's immune system. It is an opportunistic fungal pathogen that causes infections in immunocompromised individuals, mechanical trauma victims and iatrogenic patients. Candida albicans can ingress the human host by adhering to a plastic surface (i.e. prosthetic devices, catheters, artificial organs, etc.) that is subsequently implanted, and forms a protective biofilm that provides a continuous reservoir of yeast to be hematogenously dispersed. In order for the medical profession to battle device-related infections, initial adhesion and biofilm formation of C. albicans needs to be better understood. There has been some skepticism as to whether the initial adhesion events bear any relationship to subsequent biofilm formation. Thus, to better comprehend the relationship between the initial adhesion rates and growth rate and biofilm formation, these events were studied on two different, well-defined culture surfaces, native polystyrene and Pluronic F127-conditioned polystyrene. The adhesion studies determined that Pluronic F127 adsorption dramatically reduced the adhesion of C. albicans to polystyrene. The biofilm growth studies, analyzed by confocal scanning laser microscopy, revealed that Pluronic F127 decreased the biofilm surface coverage, cluster group size, thickness and the presence of hyphal elements over the untreated polystyrene. These findings indicate that the effect of a material's surface chemistry on the initial adhesion process has a direct influence on subsequent biofilm formation.

A Preliminary Study of Microcapsule Suspension for Hemolysis Evaluation of Artificial Organs

1999 ◽  
Vol 23 (3) ◽  
pp. 274-279 ◽  
Author(s):  
Osamu Maruyama ◽  
Takashi Yamane ◽  
Naoki Tsunemoto ◽  
Masahiro Nishida ◽  
Tatsuo Tsutsui ◽  
...  
Keyword(s):  
Artificial Organs ◽  
Preliminary Study

Simulation of Nitrate Concentration Affected from Land Use Changes in the Lower Part of Yom River Basin,Thailand: A Preliminary Study

2014 ◽  
Vol 931-932 ◽  
pp. 738-743
Author(s):  
Satika Boonkaewwan ◽  
Srilert Chotpantarat
Keyword(s):  
Land Use ◽  
River Basin ◽  
Swat Model ◽  
Land Use Changes ◽  
Sediment Concentration ◽  
Model Parameters ◽  
The North ◽  
Optimal Values ◽  
Preliminary Study ◽  
Year 2000

The Lower Yom River Basin is located in the north of Thailand. This study carried out to calibrate and validate using SWAT model in terms of streamflow and sediment concentration hydrographs (Year 2000-2012) for 3 RID streamflow gauging stations (the Royal Irrigation Department). The nitrates concentrations simulate have been influenced of land use changes during last ten years. Optimal values of model parameters derived from calibration and validation processes, which showed well fitted between observed and simulated results. In the last decade, particular in Lower Yom River, the land use change gradually transformed to be more paddy field and has been increased 127.48 km2 (approx. 0.87% increase), followed by urban area, which has been increased 196.66 km2 (approx. 1.35% increase), respectively. Average monthly concentration of nitrate increased 38.28 mg/l (approx.13.40 % increase), 43.17 mg/l (approx.12.00% increase), 43.02 mg/l (approx. 8.60% increase) at station Y.6, Y.4 and Y.17, respectively. Accordingly, on the basis of the results presented in this study, land use changes can significantly affect on concentrations of nitrate.

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