Academic literature on the topic 'Blood-vessels Electric properties Mathematical models'
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Journal articles on the topic "Blood-vessels Electric properties Mathematical models"
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Lv, Yanpeng, Yanfang Zhang, Jianwei Huang, Yunlong Wang, and Boris Rubinsky. "A Study on Nonthermal Irreversible Electroporation of the Thyroid." Technology in Cancer Research & Treatment 18 (January 1, 2019): 153303381987630. http://dx.doi.org/10.1177/1533033819876307.
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Background: Nonthermal irreversible electroporation is a minimally invasive surgery technology that employs high and brief electric fields to ablate undesirable tissues. Nonthermal irreversible electroporation can ablate only cells while preserving intact functional properties of the extracellular structures. Therefore, nonthermal irreversible electroporation can be used to ablate tissues safely near large blood vessels, the esophagus, or nerves. This suggests that it could be used for thyroid ablation abutting the esophagus. This study examines the feasibility of using nonthermal irreversible electroporation for thyroid ablation. Methods: Rats were used to evaluate the effects of nonthermal irreversible electroporation on the thyroid. The procedure entails the delivery of high electric field pulses (1-3 kV/cm, 100 microseconds) between 2 surface electrodes bracing the thyroid. The right lobe was treated with various nonthermal irreversible electroporation pulse sequences, and the left was the control. After 24 hours of the nonthermal irreversible electroporation treatment, the thyroid was examined with hemotoxylin and eosin histological analysis. Mathematical models of electric fields and the Joule heating-induced temperature raise in the thyroid were developed to examine the experimental results. Results: Treatment with nonthermal irreversible electroporation leads to follicular cells damage, associated with cell swelling, inflammatory cell infiltration, and cell ablation. Nonthermal irreversible electroporation spares the trachea structure. Unusually high electric fields, for these types of tissue, 3000 V/cm, are needed for thyroid ablation. The mathematical model suggests that this may be related to the heterogeneous structure of the thyroid-induced distortion of local electric fields. Moreover, most of the tissue does not experience thermal damage inducing temperature elevation. However, the heterogeneous structure of the thyroid may cause local hot spots with the potential for local thermal damage. Conclusion: Nonthermal irreversible electroporation with 3000 V/cm can be used for thyroid ablation. Possible applications are treatment of hyperthyroidism and thyroid cancer. The highly heterogeneous structure of the thyroid distorts the electric fields and temperature distribution in the thyroid must be considered when designing treatment protocols for this tissue type.
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Łebkowski, Andrzej, and Wojciech Koznowski. "Analysis of the Use of Electric and Hybrid Drives on SWATH Ships." Energies 13, no. 24 (December 8, 2020): 6486. http://dx.doi.org/10.3390/en13246486.
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The article presents issues related to the possibility of using electric and hybrid systems to drive Small Waterplane Area Twin Hull (SWATH) vessels. Ships of this type have significantly less sway and heave compared to monohull crafts and catamarans. Thanks to the synergistic combination of the hydrodynamic properties of SWATH hull and electric drive systems, they can be an interesting proposition for use in transport of passengers and offshore wind farms service crews. The paper presents comparative test results of an electric drive system powered by Hybrid Energy Storage System, which are a combination of systems consisting of batteries (BAT), hydrogen fuel cells (FC) and diesel generators (D). For the presented configurations of propulsion systems, mathematical models taking into account the hydrodynamic resistance of the hull of the vessel have been developed and implemented in the Modelica simulation environment. The tests carried out for various configurations of the drive system have shown reduced energy consumption by the DIESEL-ELECTRIC drive system (by approx. 62%), as well as the reduction of harmful greenhouse gas emissions to the atmosphere (by approx. 62%) compared to the conventional DIESEL drive.
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Kuchumov, A. G., M. R. Kamaltdinov, A. R. Khairulin, M. V. Kochergin, and M. I. Shmurak. "Patient-specific 0D–3D modeling of blood flow in newborns to predict risks of complications after surgery." Health Risk Analysis, no. 4 (December 2022): 159–67. http://dx.doi.org/10.21668/health.risk/2022.4.15.
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Abnormal developments of the cardiovascular system are common congenital malformations. Computational fluid dynamics and mathematical modeling can be used to perform quantitative predictive assessments of hemodynamic properties in varied conditions. This article addresses the development of a coupled 0D–3D model of blood flow in newborns to predict risks of complications after surgery. The 0D-model of systemic circulations is created by using the analogy between the blood flow in vessels and the flow of current through an electric circuit. A shunted section of the aorta and pulmonary artery is replaced with a 3D-model with two-way fluid-solid interaction (FSI).A section in a vessel with the aortic valve is examined in a separate 3D-model. Three-dimensional geometry is based on real CT-scans of a patient. The algorithm for coupling models of different levels relies on meeting the condition that pressures and volumetric blood flows are equal at the interaction boundary. We have developed an algorithm for identifying personal parameters from the results obtained by solving an optimization problem. Computational experiments with different individual geometry of the aorta and aortic valve made it possible to analyze blood flow velocities, near-wall stresses, flows, and valve deformations. Observable near-wall stresses can be considered risk factors that could cause calcification on valve leaflets and other valve diseases. Computational solutions in the “aorta – shunt – pulmonary artery” 3D-system allowed obtaining spatial distributions of velocities, pressures, near-wall stresses and other parameters that are significant in respect to probable pathology development. The developed approaches are primarily relevant for decision-making in surgical practice to predict risks of postoperative complications. In future, our plans are to develop the model so that it covers also saturation and oxygen exchange. This is necessary for assessing whether oxygen supply to the lungs is adequate.
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Antonova, N. M., V. K. Paskova, and I. V. Velcheva. "Blood rheological and electrical properties and relationships with the microvascular tone regulation in patients with diabetes mellitus type 2." Regional blood circulation and microcirculation 20, no. 1 (March 22, 2021): 25–33. http://dx.doi.org/10.24884/1682-6655-2021-20-1-25-33.
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Aim. The study aims to evaluate impairment of the rheological and electrical properties of blood, plasma viscosity and blood conductivity in patients with type 2 diabetes mellitus (T2DM) in comparison with the data of the control group of healthy individuals. It also aims to investigate the changes of the skin blood flow responses to cold stress in T2DM patients through wavelet analysis of the peripheral skin temperature pulsations and to estimate their relationships with the blood viscosity and blood conductivity parameters, obtained from the simulation of experimental data with mathematical equations.Materials and methods. The whole blood viscosity was measured by Contraves LS30 viscometer (Switzerland) at a steady flow in 9 healthy individuals and in 13 patients with type 2 diabetes mellitus. Time variation of whole blood conductivity σ under transient flow at rectangular and trapezium shaped Couette viscometric flow and under electric field of 2 kHz was determined. The amplitudes of the skin temperature pulsations (ASTP) were monitored by «Microtest» device («FM-Diagnostics», Russia). To analyze the temperature fluctuations, wavelet transformation analysis of the low amplitude oscillations of skin temperature in accordance with myogenic (0.05–0.14 Hz), neurogenic (0.02–0.05 Hz), and endothelial (0.0095–0.02 Hz) control mechanisms of the vascular tone (WAST method) was applied.Results. Blood viscosity was increased in the T2DM patients’ group, while blood conductivity decreased in comparison to controls. Two sigmoidal equations were applied to describe the kinetics of blood conductivity. Both models include conductivity indices (σ1 , σ2 , σ3 ) and time indices too. The Pearson correlations between these parameters and the ASTP in the frequency ranges, corresponding to the myogenic, neurogenic and endothelial mechanisms of the microcirculation tone regulation were analyzed. The correlation analysis revealed good ASTP–(σ1 , σ2 , σ3 ) relationships in the neurogenic range 3 minutes after the cold test, while the ASTP–(σ1 , σ2 , σ3 ) correlation in the myogenic frequency range before the cold test was negative (r<–0.8, p<0.5).Conclusion. The results complement the studies of the microvascular regulatory mechanisms and endothelial dysfunction in patients with type 2 diabetes mellitus, as well as their relationships with the rheological and electrical properties of blood.
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Bali, Rekha, Bhawini Prasad, and Swati Mishra. "A REVIEW ON MATHEMATICAL MODELS FOR NANOPARTICLE DELIVERY IN THE BLOOD." International Journal of Advanced Research 10, no. 04 (April 30, 2022): 130–46. http://dx.doi.org/10.21474/ijar01/14526.
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One of the ubiquitous causes of deaths are the Cardio Vascular Diseases or CVDs. The implementation of nanotechnology in the treatment of CVDs has evinced better bio-compatibility and enhanced cell interactions. This provides a strong potential for their mathematical modeling with the diseased blood vessels. In our current study we have reported various mathematical models used for the treatment of CVDs employing nanotechnology. Mathematical modeling provides a tool to comprehend the type, shape and size of the nanoparticles that can be employed as possible drug delivery systems. Mathematical models help to predict how nano-drugs have many improvements like expanded drug loading capacity and programmable pharmo-kinetic properties over the conventional drugs. The amalgamation of mathematical models with clinical data provides for designing these optimal therapies. This review encapsulates the current state of mathematical modeling approaches to treat CVDs using nanoparticle targeted drug delivery.
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Bali, Rekha, Bhawini Prasad, and Swati Mishra. "A REVIEW ON MATHEMATICAL MODELS FOR NANOPARTICLE DELIVERY IN THE BLOOD." International Journal of Advanced Research 10, no. 04 (April 30, 2022): 130–46. http://dx.doi.org/10.21474/ijar01/14526.
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One of the ubiquitous causes of deaths are the Cardio Vascular Diseases or CVDs. The implementation of nanotechnology in the treatment of CVDs has evinced better bio-compatibility and enhanced cell interactions. This provides a strong potential for their mathematical modeling with the diseased blood vessels. In our current study we have reported various mathematical models used for the treatment of CVDs employing nanotechnology. Mathematical modeling provides a tool to comprehend the type, shape and size of the nanoparticles that can be employed as possible drug delivery systems. Mathematical models help to predict how nano-drugs have many improvements like expanded drug loading capacity and programmable pharmo-kinetic properties over the conventional drugs. The amalgamation of mathematical models with clinical data provides for designing these optimal therapies. This review encapsulates the current state of mathematical modeling approaches to treat CVDs using nanoparticle targeted drug delivery.
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HERRERO, MIGUEL Á., ÁLVARO KÖHN, and JOSÉ M. PÉREZ-POMARES. "MODELLING VASCULAR MORPHOGENESIS: CURRENT VIEWS ON BLOOD VESSELS DEVELOPMENT." Mathematical Models and Methods in Applied Sciences 19, supp01 (August 2009): 1483–537. http://dx.doi.org/10.1142/s021820250900384x.
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In this work we present a comprehensive account of our current knowledge on vascular morphogenesis, both from a biological and a mathematical point of view. To this end, we first describe the basic steps in the known mechanisms of blood vessel morphogenesis, whose structure, function and unfolding properties are examined. We then provide a wide, although by no means exhaustive, account of mathematical models which are used to describe and discuss particular aspects of the overall biological process considered. We finally summarize the approaches presented, and suggest possible directions for future research. Details about some of the major signalling molecules involved are included in a first Appendix at the end of the paper. A second Appendix provides a brief overview of design principles for vascular nets, a subject that has deserved considerable attention over the years.
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Sánchez-Molina, David, Silvia García-Vilana, Jordi Llumà, Ignasi Galtés, Juan Velázquez-Ameijide, Mari Carmen Rebollo-Soria, and Carlos Arregui-Dalmases. "Mechanical Behavior of Blood Vessels: Elastic and Viscoelastic Contributions." Biology 10, no. 9 (August 26, 2021): 831. http://dx.doi.org/10.3390/biology10090831.
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The mechanical properties of the cerebral bridging veins (CBVs) were studied using advanced microtensile equipment. Detailed high-quality curves were obtained at different strain rates, showing a clearly nonlinear stress–strain response. In addition, the tissue of the CBVs exhibits stress relaxation and a preconditioning effect under cyclic loading, unequivocal indications of viscoelastic behavior. Interestingly, most previous literature that conducts uniaxial tensile tests had not found significant viscoelastic effects in CBVs, but the use of more sensitive tests allowed to observe the viscoelastic effects. For that reason, a careful mathematical analysis is presented, clarifying why in uniaxial tests with moderate strain rates, it is difficult to observe any viscoelastic effect. The analysis provides a theoretical explanation as to why many recent studies that investigated mechanical properties did not find a significant viscoelastic effect, even though in other circumstances, the CBV tissue would clearly exhibit viscoelastic behavior. Finally, this study provides reference values for the usual mechanical properties, as well as calculations of constitutive parameters for nonlinear elastic and viscoelastic models that would allow more accurate numerical simulation of CBVs in Finite Element-based computational models in future works.
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Strigel, R. M., D. J. Schutt, J. G. Webster, D. M. Mahvi, and D. Haemmerich. "An Electrode Array for Limiting Blood Loss During Liver Resection: Optimization via Mathematical Modeling." Open Biomedical Engineering Journal 4, no. 1 (February 4, 2010): 39–46. http://dx.doi.org/10.2174/1874120701004020039.
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Liver resection is the current standard treatment for patients with both primary and metastatic liver cancer. The principal causes of morbidity and mortality after liver resection are related to blood loss (typically between 0.5 and 1 L), especially in cases where transfusion is required. Blood transfusions have been correlated with decreased long-term survival, increased risk of perioperative mortality and complications. The goal of this study was to evaluate different designs of a radiofrequency (RF) electrode array for use during liver resection. The purpose of this electrode array is to coagulate a slice of tissue including large vessels before resecting along that plane, thereby significantly reducing blood loss. Finite Element Method models were created to evaluate monopolar and bipolar power application, needle and blade shaped electrodes, as well as different electrode distances. Electric current density, temperature distribution, and coagulation zone sizes were measured. The best performance was achieved with a design of blade shaped electrodes (5 × 0.1 mm cross section) spaced 1.5 cm apart. The electrodes have power applied in bipolar mode to two adjacent electrodes, then switched sequentially in short intervals between electrode pairs to rapidly heat the tissue slice. This device produces a ~1.5 cm wide coagulation zone, with temperatures over 97 ºC throughout the tissue slice within 3 min, and may facilitate coagulation of large vessels.
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Lee, J., E. P. Salathe, and G. W. Schmid-Schonbein. "Fluid exchange in skeletal muscle with viscoelastic blood vessels." American Journal of Physiology-Heart and Circulatory Physiology 253, no. 6 (December 1, 1987): H1548—H1556. http://dx.doi.org/10.1152/ajpheart.1987.253.6.h1548.
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A mathematical model of capillary-tissue fluid exchange in a viscoelastic blood vessel is presented, and the Landis occlusion experiment is simulated. The model assumes that the fluid exchange is governed by Starling's law and that the protein and red blood cells are conserved in the capillary. Before occlusion, in the steady flow state, the pressure in the capillary decreases from the arterial to venous end due to viscous dissipation. After occlusion a constant pressure is established along the capillary. We assume the capillary to be distensible with viscoelastic wall properties. Immediately following occlusion an instantaneous distension of the capillary occurs. The vessel continues to expand viscoelastically while fluid is filtered for a period of several minutes, until it reaches an equilibrium state. A full numerical solution of the governing equations has been obtained. We use this model to compute the distance variation between two labeled erythrocytes as obtained in the Landis occlusion experiment and compare the results with experimental data obtained recently for the spinotrapezius muscle in our laboratory. The new model can fit the experimental data better than previous models that neglect the distensibility of the capillaries.
Conference papers on the topic "Blood-vessels Electric properties Mathematical models"
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Kalyanam, Sureshkumar, Lance Hill, Gery Wilkowski, and Frederick Brust. "Computational Mechanics Based Validation of Crack Growth Approaches for Fracture Specimen Predictions." In ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-84898.
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Abstract The last several decades have seen growth in elastic-plastic fracture mechanics and the modeling of the behavior of structural steels employed in the nuclear, oil and gas, and other construction industries. Among these are a particular class of problems that provide challenges in modeling the physical behavior of structural steels using finite element modeling (FEM) approach that are based on microstructural damage and using parameters that depict the strain and stress states in the material region ahead of an existing crack. In this work, a recently experimented and investigated pipeline steel X80 material was modeled through two different fracture specimen geometries, namely single-edge-notch-tension, SEN(T) and compact-tension, C(T) to compare and contrast the predictions from two material damage models (microstructure and continuum based). The predictions from both these damage models that predict the ductile crack growth have been compared to the experimental findings of the crack growth (obtained using a d-c Electric Potential measurement technique), the corresponding load levels, and crack opening displacements (CODs). The points of similarity between the experimental measurements and the fracture surface observations of crack growth and the predictions from the FEM approach have been discussed. The same X80 material properties and damage model parameters were employed to predict the ductile crack growth in the two different fracture specimen geometries, SEN(T) and C(T) with a subtle change of one of the parameter values. This sheds light on the predictability of the crack initiation event and the subsequent ductile crack growth until failure using these damage models. The findings provide credence to the applicability of either model (after they are carefully tuned to arrive at optimized parameters) for piping materials while providing a framework for flaw evaluation methodologies. The investigation also opens the doors for regions where mesh regularization methods and modeling approaches along with mathematical relations can be developed to form a more efficient framework for modeling specimens with diverse constraints efficiently and develop material fracture resistance curves.
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Kalyanam, S., L. T. Hill, G. Wilkowski, Y. Hioe, and F. W. Brust. "Strain Based Damage Model Predictions of Ductile Crack Growth in Multiple Fracture Specimen Geometries." In ASME 2021 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/pvp2021-61172.
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Abstract Modeling damage and ductile crack growth in metallic materials has been of interest over the last four decades. Damage models of increasing complexity have been employed to characterize and predict the ductile crack growth in materials. A short review of the existing ductile crack growth models has been provided. Recently, a strain-based damage model has been advanced by researchers, which is capable of capturing the stress and strain states for the incipient damage within the material while being able to capture the triaxiality parameter. In this work a strain based ductile fracture damage model has been employed to model specimens with three different crack geometries, namely a single-edge notch tension SEN(T), compact-tension C(T), and outer diameter (OD) axial surface-cracked pipe. The predictions from the ductile crack growth model have been compared to experimental findings of the crack growth (obtained using a d-c Electric Potential measurement technique) and the corresponding load levels and crack opening displacements (CODs). The points of similarity between the experimental measurements and the fracture surface observations of crack growth and the predictions from the finite element modeling (FEM) approach have been discussed. The same X80 material properties and damage model parameters were employed to benchmark the ductile crack growth in two different SEN(T) specimens with differing normalized crack depths (crack/width ratios, a/W), a C(T) specimen (a/W = 0.5), and an OD SC pipe (a/t = 0.6) to shed light on the predictability of the crack initiation event and the subsequent ductile crack growth until failure. The findings provide credence to the applicability of the new approach for piping materials while providing a framework for flaw evaluation methodologies. The investigation also opens the doors for regions where mesh regularization methods and modeling approaches along with mathematical relations can be developed to form a more efficient framework for modeling specimens with diverse constraints efficiently.
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Prakash, Raghu V., C. Anish, and Dhinakaran Sampath. "Modeling Electric-Potential for a Crack Subjected to Corrosion Under Static and Cyclic Loading." In ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-85773.
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Abstract High strength steels are increasingly being used in applications such as ship hulls and oil and gas pipelines which are subjected to corrosive environment. These steel grades exhibit more than an order of magnitude higher crack growth rates in corrosive environments compared with the crack growth rates in air. A mathematical model is developed based on the slip dissolution mechanism to evaluate the chemistry and potential distributions in the occluded crack. The species distribution due to diffusion and ion migration is evaluated by considering the effect of ferrous hydroxide formation on the transport properties in the electrolyte. It is also found that the potential and pH drop in the crack is affected by the crack tip stress and strain fields. The dissolution of iron at the crack tip is enhanced by the pH drop. Both steady state and transient numerical studies are carried out to determine the evolving crack geometry. Thus, by considering reactions inside the crack, a better representation of the species and potential distributions can be obtained.
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Masi, Maurizio, Carlo Cavallotti, Gianluca Valente, and Marco Di Stanislao. "Multi-Scale and Multi-Hierarchy Modeling in Electronic Materials Processing (Keynote)." In ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1540.
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Modern material science and engineering rely on models based on fundamental laws to link material structure and properties to the many parameters that control the adopted production process. Unfortunately, the full comprehension of the main features characterizing the synthesis of these materials is complicated by the fact that chemical and physical events occur at length scales differing for even some orders of magnitudes. An example well suited to illustrate these aspects is represented by the solid films deposition by means of chemical vapor deposition processes. There, the characteristic length ranges from the nanometers up the centimeters, going by through the microns. The former is the scale at which the chemical phenomena can be described through quantum chemical methods, the latter is that where the overall reactor behavior can be depicted. The meso-scales are instead of interest to describe aspect interesting the collective surface behavior, like the description of the trench filling, the obtained film morphology or the various types of defects formation. Here, different mathematical models suitable to study the mentioned multi-scale phenomena and the hierarchy that can be adopted to their link will be reviewed with particular reference to silicon film deposition processes of interest for the microelectronic industry.
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Pandey, Ajit K., Isaac Chang, Matthew R. Myers, and Rupak K. Banerjee. "Finite Element Analysis of Radio-Frequency Ablation in a Reconstructed Realistic Hepatic Geometry." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32046.
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Radio-frequency (RF) ablation is a minimally invasive procedure that has the potential for widespread use in hepatic cancer therapy. In the procedure, RF current is applied to the tissue, resulting in the conversion of electrical to heat energy and thus, a rise in temperature, with the goal of eventual tumor necrosis. Potential complications from the procedure include insufficient heating of large tumors, resulting in tumor recursion, as well as excessive thermal damage to healthy tissue. Mathematical models are valuable in predicting the temperature rise within the organ during RF ablation, thereby enhancing the success rate of the procedure. Eventually, models can be used to guide ablation procedures, by predicting the optimal set of operational parameters e.g., catheter probe geometry and placement, given patient-specific information. The present study focuses on the analysis of temperature rise within a reconstructed model of a realistic three-dimensional (3D) section of a porcine liver during RF ablation. This study calculates the effect of blood flow through arteries as well as perfusion through the liver on the time-dependent temperature distribution near the RF ablation probe (Figure 1). For a time duration of 30 min of an ablation procedure, a temperature of about 80°C could be achieved over a diameter of about 4 cm with the present RF probe. As an initial step, the present study includes isotropic hepatic tissue and blood properties.
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Wan, William, Laura Hansen, and Rudolph L. Gleason. "A 3-D Constrained Mixture Model for Vascular Growth and Remodeling." In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206778.
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It is known that arteries adapt and remodel to changes in their loading conditions. Evolution of mechanical properties of blood vessels is associated with numerous chronic and acute conditions such as hypertension and coronary thrombosis. In addition, treatments such as bypass surgery create loading conditions not seen in normal arteries. Blood vessels used in coronary bypass grafts experience abnormal loading conditions in both circumferential and axial directions. Blood vessels remodel by altering structural components to restore homeostatic values of stress. Such changes may include smooth muscle cell proliferation, migration and collagen synthesis, degradation, and remodeling. While biaxial mechanical tests and organ culture experiments provide values for global variables such as mean stresses and total thickness, mathematical models can help describe local mechanical properties at locations throughout the vessel wall. Experimental observations suggest that constituents of arteries turnover at different rates; thus, it is important that models are able to track individual constituents of the artery separately. Here, we present a 3D constrained mixture model for growth and remodeling of arteries exposed to large changes in flow, pressure, and axial stretch -induced.
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Hossain, Md Shahadat, Bhavin Dalal, Ian S. Fischer, Pushpendra Singh, and Nadine Aubry. "Modeling of Blood Flow in the Human Brain." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30554.
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The non-Newtonian properties of blood, i.e., shear thinning and viscoelasticity, can have a significant influence on the distribution of Cerebral Blood Flow (CBF) in the human brain. The aim of this work is to quantify the role played by the non-Newtonian nature of blood. Under normal conditions, CBF is autoregulated to maintain baseline levels of flow and oxygen to the brain. However, in patients suffering from heart failure (HF), Stroke, or Arteriovenous malformation (AVM), the pressure in afferent vessels varies from the normal range within which the regulatory mechanisms can ensure a constant cerebral flow rate, leading to impaired cerebration in patients. It has been reported that the change in the flow rate is more significant in certain regions of the brain than others, and that this might be relevant to the pathophysiological symptoms exhibited in these patients. We have developed mathematical models of CBF under normal and the above disease conditions that use direct numerical simulations (DNS) for the individual capillaries along with the experimental data in a one-dimensional model to determine the flow rate and the methods for regulating CBF. The model also allows us to determine which regions of the brain would be affected relatively more severely under these conditions.
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Naga Siva Kumar, G., and Sushanta K. Mitra. "Modeling of Dielectrophoresis for Myoglobin Molecules in a Microchannel With Parallel Electrodes." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-10765.
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Myoglobin is one of the important cardiac markers, whose concentration increases from 90 pg/ml to over 5000 pg/ml in the blood serum of heart attack patients. Separation and detection of myoglobin play a vital role in deciding the cardiac arrest in advance, which is the challenging part of ongoing research. In the present study, one of the electrokinetic approach i.e., dielectrophoresis (DEP) is chosen to manipulate the myoglobin molecule in aqueous solution. A generalized theoretical expression is developed for the dielectrophoretic force acting on an arbitrary shape of the particle. Dielectric myoglobin model is developed by approximating the shape of the molecule as sphere, oblate and prolate spheroids. Mathematical model for simulating dielectrophoretic behavior of a myoglobin molecule in a microchannel is developed. The microchannel consists of parallel array of electrodes at the bottom wall. Finite element based approach is considered to solve the problem. The variation in the Clausius-Mossotti factor with respect to the applied electric field frequency is observed for aqueous solution of myoglobin. The crossover frequency is obtained as 30 MHz for given properties, for all the shapes of molecule. Shifting of crossover frequency with conductivity of medium is observed. The simulation results indicate that, the electric field and DEP forces are maximum at the edges of the electrodes and minimum elsewhere. The results also indicate that, DEP force exponentially decayed along the height of the channel.
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Hossain, Md Shahadat, Shriram B. Pillapakkam, Bhavin Dalal, Ian S. Fischer, Nadine Aubry, and Pushpendra Singh. "Modeling of Blood Flow in the Human Brain." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64525.
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Under normal conditions, Cerebral Blood Flow (CBF) is related to the metabolism of the cerebral tissue. Three factors that contribute significantly to the regulation of CBF include the carbon dioxide and hydrogen ion concentration, oxygen deficiency and the level of cerebral activity. These regulatory mechanisms ensure a constant CBF of 50 to 55 ml per 100g of brain per minute for mean arterial blood pressure between 60–180 mm Hg. Under severe conditions when the autoregulatory mechanism fails to compensate, sympathetic nervous system constricts the large and intermediate sized arteries and prevents very high pressure from ever reaching the smaller blood vessels, preventing the occurrence of vascular hemorrhage. Several invasive and non-invasive techniques such as pressure and thermoelectric effect sensors to Positron Emission Tomography (PET) and magnetic resonance imaging (MRI) based profusion techniques have been used to quantify CBF. However, the effects of the non-Newtonian properties of blood, i.e., shear thinning and viscoelasticity, can have a significant influence on the distribution of CBF in the human brain and are poorly understood. The aim of this work is to quantify the role played by the non-Newtonian nature of blood on CBF. We have developed mathematical models of CBF that use direct numerical simulations (DNS) for the individual capillaries along with the experimental data in a one-dimensional model to determine the flow rate and the methods for regulating CBF. The model also allows us to determine which regions of the brain would be affected more severely under these conditions.
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Agianniotis, Aristotelis, Nikos Stergiopulos, Raymond P. Vito, Tarek Shazly, and Alexander Rachev. "A Theoretical Simulation of Maladaptive Remodeling in Response to Hypertension." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14462.
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Hypertension is a key risk factor for many adverse cardiovascular events. The sustained increase in pressure causes arterial remodeling, which results in long-term changes in the geometrical dimensions and mechanical properties of the vascular tissue. The remodeling response in experimental animal models of hypertension is often described according to the structurally determined change in lumen diameter. Depending on whether the process resulted in a decrease or increase in the diameter, remodeling is termed inward or outward, while depending on the increase, no change, or decrease in the amount of material, remodeling is hypertrophic, eutrophic, or hypotrophic [1]. Due to the multi-factorial and complex nature of remodeling, it is exceedingly difficult to evaluate the relative importance of any one factor in isolation. Predictive mathematical models based on continuum mechanics are powerful tools for studying the mechanical and remodeling response of blood vessels. So far, most theoretical studies addressed adaptive remodeling in response to sustained hypertension. An adaptive response manifests as preservation of the normotensive deformed diameter, change in residual strains and axial stretch ratio, and thickening of the arterial wall, such that the tensile wall stress and flow-induced shear stress remain at baseline values. Maladaptive remodeling could result from a variety of dysfunctional biological processes, and is characterized by the incomplete restoration of the baseline mechanical environment. This study is devoted to a theoretical simulation of some modes of maladaptive remodeling and aims to evaluate the relative importance of certain geometrical and mechanical factors in the remodeling response to hypertension.