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Papers by mostafa abbasi

Propósitos y Representaciones, 2021

The results showed that among the factors affecting entrepreneurship, the economic factor is the ... more The results showed that among the factors affecting entrepreneurship, the economic factor is the most influential factor in the study area. The results also showed that rural entrepreneurship is one of the suitable fields for creating employment in agricultural and non-agricultural sectors and one of the important factors in achieving sustainable development in rural areas.

Journal of Medical and Biological Engineering, 2018

Arthrodesis, or fusion of subtalar joints (STJs), is a well-accepted and a routine treatment in t... more Arthrodesis, or fusion of subtalar joints (STJs), is a well-accepted and a routine treatment in the end stage of ankle injuries or disorder, such as arthritis or fractures. Arthrodesis can restore daily life function quickly at the expense of limiting joint motion. A triple arthrodesis (TA) consists of the surgical fusion of the talocalcaneal (TC), talonavicular (TN), and calcaneocuboid (CC) joints in the foot. This study aimed at investigating the effects of TA on strain distribution around tibia near the ankle joint. A finite element (FE) model, generated using computed tomography (CT) images of the human ankle, was then used to estimate stress distribution on the ankle joint surface. Axial load was applied to a human cadaveric ankle before and after TA, and load patterns were determined in various anatomical positions by measuring strain distribution around the tibia. Therefore, the effects of fusion were investigated by comparing strain distribution obtained from experiment and ...

Bulletin of the Iranian Mathematical Society, 2021

Journal of Cleaner Production, 2021

Abstract In recent years, microalgae have received a lot of attention as an alternative feedstock... more Abstract In recent years, microalgae have received a lot of attention as an alternative feedstock for biofuel production due to numerous advantages such as fast growth rate, high lipid and carbohydrate content, and lack of competition with food production. However, one of the main barriers preventing the commercialization of biofuel production from microalgae is related to the supply chain management issues, and research efforts in the industry and academic communities have been put into this area to deliver solutions. This paper provides a comprehensive and systematic review of studies in the context of the microalgae-to-biofuel supply chain to investigate problems that must be addressed to develop a reliable supply chain for real-world applications. Firstly, an introduction of biofuel production from microalgae and the general structure of the microalgae-based biofuel supply chain are presented. Secondly, decision-making levels in the microalgae biofuel supply chain along with associated supply chain decisions are discussed. Thirdly, the different sources of uncertainty that affect the performance of the supply chain as well as optimization approaches for dealing with uncertainty are reviewed. Finally, conclusions and directions for further research are outlined.

Propósitos y Representaciones, 2021

Entrepreneurship is an important instrument in planning and realizing rural community development... more Entrepreneurship is an important instrument in planning and realizing rural community development. Owing to current problems in societies, focusing on the rural entrepreneurship is of utmost importance. Entrepreneurship by creating new opportunities for employment and income plays an important role in improving socioeconomic conditions of villages. The aim of this study is to assess the factors influencing the development of rural entrepreneurship in a case study of villages in Torbat-e Heydarieh, Kadkan district. The research method was descriptive-analytic, and the data collection method was library and field studies. For data analysis, One-sample t-test with principal component analysis was used. The statistical population of the study was the villagers of Kadkan district of Torbat-e Heydarieh, from which 240 people were asked to complete a questionnaire. The validity of the questionnaire was evaluated using the Content and face validity with expert judgement. Reliability of the ...

Journal of the Mechanical Behavior of Biomedical Materials, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Solution Chemistry, 2018

Polyethylene glycols have become more popular alternate reaction media due to interesting propert... more Polyethylene glycols have become more popular alternate reaction media due to interesting properties like non-toxicity, bio-degradability, and full miscibility with water and organic solvents. Binary mixtures of polyethylene glycols with common solvents can be useful to tune their physical and chemical properties and to facilitate chemical and physical processes. In this study, solvatochromic parameters were spectrophotometrically determined for binary solvent mixtures of poly(ethylene glycol)-400 (PEG-400) with methanol, 2-propanol, 1-butanol, dimethyl sulfoxide, N,N-Dimethylformamide, and dichloromethane under ambient conditions, over the whole range of mole fractions. The solvatochromic parameters showed different trends in protic and aprotic solvents mixed with PEG-400. Methanol/PEG-400 mixtures showed special properties in polarity and polarizability so that the mixtures are more dipolar/polarizable than their pure components. Positive or negative deviations from ideal behavior confirmed that the indicators were involved in a preferential solvation process in the solvent mixtures. These deviations from ideality can be attributed to strong solvent-solvent interactions in the binary mixtures.

Journal of Molecular Liquids, 2019

Abstract Deep eutectic solvents (DESs) are a new class of ionic liquids which have been applied i... more Abstract Deep eutectic solvents (DESs) are a new class of ionic liquids which have been applied in many chemical reactions therefore, the investigation of their physicochemical properties such as hydrogen bond property and ion delocalization, are important. We measured solvatochromic parameters of three different DESs, namely urea-choline chloride (reline), ethylene glycol-choline chloride (ethaline), and glycerol-choline chloride (glyceline) and their binary mixtures with different mole fractions of poly ethylene glycol (PEG 400) as co-solvent. Solvatochromic results showed that the reline has the biggest polarity in these three DESs, but the lowest in hydrogen bond donor and acceptor abilities. In binary mixtures of DESs with PEG 400, π* and α values are decreasing with increasing the mole fraction of PEG 400 which is in good agreement with these parameters in mixed solvents. Molecular dynamic simulations confirmed that there are hydrogen bonds between urea, ethylene glycol, glycerol and choline chloride in pure DESs, and their amount calculated in all DESs and also with some mole fractions of PEG 400. Moreover, delocalization of chloride in DESs, were calculated for all compositions by MD simulations analysis. Also, MD simulations confirmed result of the experimental finding and preferential solvation model.

GEOPHYSICS, 2018

The inversion of prestack seismic data using amplitude variation with offset (AVO) has received i... more The inversion of prestack seismic data using amplitude variation with offset (AVO) has received increased attention in the past few decades because of its key role in estimating reservoir properties. AVO is mainly governed by the Zoeppritz equations, but traditional inversion techniques are based on various linear or quasilinear approximations to these nonlinear equations. We have developed an efficient algorithm for nonlinear AVO inversion of precritical reflections using the exact Zoeppritz equations in multichannel and multi-interface form for simultaneous estimation of the P-wave velocity, S-wave velocity, and density. The total variation constraint is used to overcome the ill-posedness while solving the forward nonlinear model and to preserve the sharpness of the interfaces in the parameter space. The optimization is based on a combination of Levenberg’s algorithm and the split Bregman iterative scheme, in which we have to refine the data and model parameters at each iteration....

GEOPHYSICS, 2018

Seismic velocity analysis is one of the most crucial and, at the same time, the most laborious ta... more Seismic velocity analysis is one of the most crucial and, at the same time, the most laborious tasks during seismic data processing. This becomes even more difficult and time-consuming when nonhyperbolicity has to be considered in the velocity analysis. Nonhyperbolic velocity analysis provides very useful information during the processing and interpretation of seismic data. The most common approach for considering anisotropy during velocity analysis is to describe the moveout based on a nonhyperbolic equation. The nonhyperbolic moveout equation in vertically transverse isotropic (VTI) media is defined by two parameters: normal moveout (NMO) velocity [Formula: see text] and anellipticity [Formula: see text] (or horizontal velocity [Formula: see text]). We have developed a new approach based on polynomial chaos (PC) expansion for automating nonhyperbolic velocity analysis of common-midpoint (CMP) data in VTI media. For this purpose, we use the PC expansion to approximate the nonhyperb...

Journal of biomechanics, Jan 25, 2018

Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment option for patien... more Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment option for patients deemed at high and intermediate risk for surgical aortic valve replacement. Similar to surgical aortic valves (SAVs), transcatheter aortic valves (TAVs) undergo calcification and mechanical wear over time. However, to date, there have been limited publications on the long-term durability of TAV devices. To assess longevity and mechanical strength of TAVs in comparison to surgical bioprosthetic valves, three-dimensional deformation analysis and strain measurement of the leaflets become an inevitable part of the evaluation. The goal of this study was to measure and compare leaflet displacement and strain of two commonly used TAVs in a side-by-side comparison with a commonly used SAV using a high-resolution digital image correlation (DIC) system. 26-mm Edwards SAPIEN 3, 26-mm Medtronic CoreValve, and 25-mm Carpentier-Edwards PERIMOUNT Magna surgical bioprosthesis were examined in a custo...

The Annals of thoracic surgery, Jan 5, 2017

Leaflet thrombosis after valve-in-valve (ViV) procedure has been increasingly recognized. This st... more Leaflet thrombosis after valve-in-valve (ViV) procedure has been increasingly recognized. This study aimed to investigate the flow dynamics aspect of leaflet thrombosis by quantifying the blood stasis on the noncoronary and coronary leaflets of a surgical aortic valve (SAV) and a transcatheter aortic valve (TAV) in a ViV setting. Two computational models, representing a SAV and a TAV in ViV setting, were developed in a patient-specific geometry. Three-dimensional flow fields were obtained through a fluid-solid interaction modeling approach to study the difference in blood residence time (BRT) on the coronary and noncoronary leaflets. Longer BRT was observed on the TAV leaflets compared with the SAV, specifically near the leaflet fixed boundary. Particularly, at the end of diastole, the areas of high BRT (≥1.2 seconds) on the surface of the TAV model leaflets were four times larger than those of the SAV model. The distribution of BRT on the three leaflets exhibited a similar pattern ...

Journal of the American College of Cardiology, 2016

2016 21st Conference on Electrical Power Distribution Networks Conference (EPDC), 2016

Preventive maintenance and inspection using thermography operation in distribution networks of Al... more Preventive maintenance and inspection using thermography operation in distribution networks of Alborz province has been studied in this paper. Conditions like high energy consumption, fast growth of energy demand because of several industrial towns , immigration of people to this region and converting this region to one of the largest industrial zone of Islamic Republic of Iran in addition to environmental conditions, all caused power losses and age reduction in distribution networks equipments. Considering above mentioned conditions and our experts' high load of work for operating and maintaining the old installations in addition with their efforts for avoiding the blackouts, objectives of the Alborz Electric Power Distribution Co. (APPDC) for reducing the faults , black-outs and power losses caused rescheduling old preventive maintenance plans. In this project, more than 4300 Km middle voltage feeders and 12500 power transformer were inspected and 177726 loose connections were discovered. Fixing these loose connections resulted reducing 0.5% power losses and reduce the costs of operation up to 133,000 USD during one year.

Annals of biomedical engineering, Sep 5, 2016

Valvular hemolysis and thrombosis are common complications associated with stenotic heart valves.... more Valvular hemolysis and thrombosis are common complications associated with stenotic heart valves. This study aims to determine the extent to which hemodynamics induce such traumatic events. The viscous shear stress downstream of a severely calcified bioprosthetic valve was evaluated via in vitro 2D particle image velocimetry measurements. The blood cell membrane response to the measured stresses was then quantified using 3D immersed-boundary computational simulations. The shear stress level at the boundary layer of the jet flow formed downstream of the valve orifice was observed to reach a maximum of 1000-1700 dyn/cm(2), which was beyond the threshold values reported for platelet activation (100-1000 dyn/cm(2)) and within the range of thresholds reported for red blood cell (RBC) damage (1000-2000 dyn/cm(2)). Computational simulations demonstrated that the resultant tensions at the RBC membrane surface were unlikely to cause instant rupture, but likely to lead to membrane plastic fai...

Journal of the American College of Cardiology, 2015

changed at times during the course of a procedure (although measurements were only made when a st... more changed at times during the course of a procedure (although measurements were only made when a steady state was achieved), the resulting repeated CO measurements were closely correlated (R¼0.93; ICC¼0.96). In regards to AVA, although there was good correlation in AVA calculated from repeated assumed VO2 CO (R¼0.85; ICC¼0.89) and TD CO (R¼ 0.93; ICC¼0.94), AVA based on direct VO2 CO was very reproducible (R¼0.99;ICC>0.99). CONCLUSIONS Cardiac output and AVA calculated from directly measured VO2 varies substantially from those based on assumed VO2 values and thermodilution, which are the default methods used in most CCL. Directly measured VO2-derived CO gives highly reproducible valve area measurements and may be more accurate.

Journal of Biomechanics, 2015

Transcatheter aortic valve replacement (TAVR) is an established treatment alternative to surgical... more Transcatheter aortic valve replacement (TAVR) is an established treatment alternative to surgical valve replacement in high-risk patients with severe symptomatic aortic stenosis. The current guidelines for TAVR are to upsize transcatheter aortic valve (TAV) relative to the native annulus to secure the device and minimize paravalvular leakage. Unlike surgical stented bioprosthetic valves where leaflets are attached to a rigid frame, TAVs must expand to fit within the native annulus. Fully-expanded circular TAVs have consistent leaflet kinematics; however, subtle variations in the degree of stent expansion may affect leaflet coaptation. The objective of this study was to determine the impact of incomplete TAV expansion on leaflet stress and strain distributions. In this study, we developed finite element models of a 23 mm homemade TAV expanded to diameters ranging from 18 to 23 mm in 1 mm increments. Through dynamic finite element simulations, we found that leaflet stress and strain distributions were dependent on the diameter of the inflated TAV. After complete expansion of the TAV to 23 mm, high stress and strain regions were observed primarily in the commissures during diastole. However, 2-3 mm incomplete TAV stent expansion induced localized high stress regions within the TAV commissures, while 4-5 mm incomplete stent expansion induced localized high stress regions within the belly of the TAV leaflets during the diastolic phase of the cardiac cycle. Increased mechanical stress and flexural deformation on TAV leaflets due to incomplete stent expansion may lead to accelerated tissue degeneration and diminished long-term valve durability.

Journal of the American College of Cardiology, 2014

Conclusions: Annular measurements from a 20 cc CTA protocol were statistically equivalent to a va... more Conclusions: Annular measurements from a 20 cc CTA protocol were statistically equivalent to a validated standard of 3D-TEE measurements. A very low dose protocol may play a very important role in pre-TAVR assessment for patients at high risk of CIN. TCT-670 Volume and distribution of aortic valve calcium and implications for aortic regurgitation after transcatheter aortic valve implantation

International Journal of Experimental and Computational Biomechanics, 2015

The goal of this study was to determine stress distribution in ankle joint by correlating with th... more The goal of this study was to determine stress distribution in ankle joint by correlating with the strain distribution and its trend around tibia adjacent to the joint. Using an in-house device, an ankle from a cadaver was kept stable and loaded in various positions: neutral, dorsiflexion, plantar flexion, inversion and eversion. A total of six strain gauges were mounted around the shaft of the tibia, near the tibiotalar joint. This arrangement allowed us to measure deformations in the shaft of tibia. Patient-specific ankle joint geometry was generated from computed tomography data. The finite element model (FEM) of the ankle was validated using the experimental data logged by the strain gauges, and used for obtaining stress on the joint surface. A strong correlation was observed between the FEM and experimentally measured strains in magnitude (R = 0.94, P = 0.008), consequently stress distribution over the joint surface was obtained. 46 A. Chitsazan et al.

Propósitos y Representaciones, 2021

The results showed that among the factors affecting entrepreneurship, the economic factor is the ... more The results showed that among the factors affecting entrepreneurship, the economic factor is the most influential factor in the study area. The results also showed that rural entrepreneurship is one of the suitable fields for creating employment in agricultural and non-agricultural sectors and one of the important factors in achieving sustainable development in rural areas.

Journal of Medical and Biological Engineering, 2018

Arthrodesis, or fusion of subtalar joints (STJs), is a well-accepted and a routine treatment in t... more Arthrodesis, or fusion of subtalar joints (STJs), is a well-accepted and a routine treatment in the end stage of ankle injuries or disorder, such as arthritis or fractures. Arthrodesis can restore daily life function quickly at the expense of limiting joint motion. A triple arthrodesis (TA) consists of the surgical fusion of the talocalcaneal (TC), talonavicular (TN), and calcaneocuboid (CC) joints in the foot. This study aimed at investigating the effects of TA on strain distribution around tibia near the ankle joint. A finite element (FE) model, generated using computed tomography (CT) images of the human ankle, was then used to estimate stress distribution on the ankle joint surface. Axial load was applied to a human cadaveric ankle before and after TA, and load patterns were determined in various anatomical positions by measuring strain distribution around the tibia. Therefore, the effects of fusion were investigated by comparing strain distribution obtained from experiment and ...

Bulletin of the Iranian Mathematical Society, 2021

Journal of Cleaner Production, 2021

Abstract In recent years, microalgae have received a lot of attention as an alternative feedstock... more Abstract In recent years, microalgae have received a lot of attention as an alternative feedstock for biofuel production due to numerous advantages such as fast growth rate, high lipid and carbohydrate content, and lack of competition with food production. However, one of the main barriers preventing the commercialization of biofuel production from microalgae is related to the supply chain management issues, and research efforts in the industry and academic communities have been put into this area to deliver solutions. This paper provides a comprehensive and systematic review of studies in the context of the microalgae-to-biofuel supply chain to investigate problems that must be addressed to develop a reliable supply chain for real-world applications. Firstly, an introduction of biofuel production from microalgae and the general structure of the microalgae-based biofuel supply chain are presented. Secondly, decision-making levels in the microalgae biofuel supply chain along with associated supply chain decisions are discussed. Thirdly, the different sources of uncertainty that affect the performance of the supply chain as well as optimization approaches for dealing with uncertainty are reviewed. Finally, conclusions and directions for further research are outlined.

Propósitos y Representaciones, 2021

Entrepreneurship is an important instrument in planning and realizing rural community development... more Entrepreneurship is an important instrument in planning and realizing rural community development. Owing to current problems in societies, focusing on the rural entrepreneurship is of utmost importance. Entrepreneurship by creating new opportunities for employment and income plays an important role in improving socioeconomic conditions of villages. The aim of this study is to assess the factors influencing the development of rural entrepreneurship in a case study of villages in Torbat-e Heydarieh, Kadkan district. The research method was descriptive-analytic, and the data collection method was library and field studies. For data analysis, One-sample t-test with principal component analysis was used. The statistical population of the study was the villagers of Kadkan district of Torbat-e Heydarieh, from which 240 people were asked to complete a questionnaire. The validity of the questionnaire was evaluated using the Content and face validity with expert judgement. Reliability of the ...

Journal of the Mechanical Behavior of Biomedical Materials, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Solution Chemistry, 2018

Polyethylene glycols have become more popular alternate reaction media due to interesting propert... more Polyethylene glycols have become more popular alternate reaction media due to interesting properties like non-toxicity, bio-degradability, and full miscibility with water and organic solvents. Binary mixtures of polyethylene glycols with common solvents can be useful to tune their physical and chemical properties and to facilitate chemical and physical processes. In this study, solvatochromic parameters were spectrophotometrically determined for binary solvent mixtures of poly(ethylene glycol)-400 (PEG-400) with methanol, 2-propanol, 1-butanol, dimethyl sulfoxide, N,N-Dimethylformamide, and dichloromethane under ambient conditions, over the whole range of mole fractions. The solvatochromic parameters showed different trends in protic and aprotic solvents mixed with PEG-400. Methanol/PEG-400 mixtures showed special properties in polarity and polarizability so that the mixtures are more dipolar/polarizable than their pure components. Positive or negative deviations from ideal behavior confirmed that the indicators were involved in a preferential solvation process in the solvent mixtures. These deviations from ideality can be attributed to strong solvent-solvent interactions in the binary mixtures.

Journal of Molecular Liquids, 2019

Abstract Deep eutectic solvents (DESs) are a new class of ionic liquids which have been applied i... more Abstract Deep eutectic solvents (DESs) are a new class of ionic liquids which have been applied in many chemical reactions therefore, the investigation of their physicochemical properties such as hydrogen bond property and ion delocalization, are important. We measured solvatochromic parameters of three different DESs, namely urea-choline chloride (reline), ethylene glycol-choline chloride (ethaline), and glycerol-choline chloride (glyceline) and their binary mixtures with different mole fractions of poly ethylene glycol (PEG 400) as co-solvent. Solvatochromic results showed that the reline has the biggest polarity in these three DESs, but the lowest in hydrogen bond donor and acceptor abilities. In binary mixtures of DESs with PEG 400, π* and α values are decreasing with increasing the mole fraction of PEG 400 which is in good agreement with these parameters in mixed solvents. Molecular dynamic simulations confirmed that there are hydrogen bonds between urea, ethylene glycol, glycerol and choline chloride in pure DESs, and their amount calculated in all DESs and also with some mole fractions of PEG 400. Moreover, delocalization of chloride in DESs, were calculated for all compositions by MD simulations analysis. Also, MD simulations confirmed result of the experimental finding and preferential solvation model.

GEOPHYSICS, 2018

The inversion of prestack seismic data using amplitude variation with offset (AVO) has received i... more The inversion of prestack seismic data using amplitude variation with offset (AVO) has received increased attention in the past few decades because of its key role in estimating reservoir properties. AVO is mainly governed by the Zoeppritz equations, but traditional inversion techniques are based on various linear or quasilinear approximations to these nonlinear equations. We have developed an efficient algorithm for nonlinear AVO inversion of precritical reflections using the exact Zoeppritz equations in multichannel and multi-interface form for simultaneous estimation of the P-wave velocity, S-wave velocity, and density. The total variation constraint is used to overcome the ill-posedness while solving the forward nonlinear model and to preserve the sharpness of the interfaces in the parameter space. The optimization is based on a combination of Levenberg’s algorithm and the split Bregman iterative scheme, in which we have to refine the data and model parameters at each iteration....

GEOPHYSICS, 2018

Seismic velocity analysis is one of the most crucial and, at the same time, the most laborious ta... more Seismic velocity analysis is one of the most crucial and, at the same time, the most laborious tasks during seismic data processing. This becomes even more difficult and time-consuming when nonhyperbolicity has to be considered in the velocity analysis. Nonhyperbolic velocity analysis provides very useful information during the processing and interpretation of seismic data. The most common approach for considering anisotropy during velocity analysis is to describe the moveout based on a nonhyperbolic equation. The nonhyperbolic moveout equation in vertically transverse isotropic (VTI) media is defined by two parameters: normal moveout (NMO) velocity [Formula: see text] and anellipticity [Formula: see text] (or horizontal velocity [Formula: see text]). We have developed a new approach based on polynomial chaos (PC) expansion for automating nonhyperbolic velocity analysis of common-midpoint (CMP) data in VTI media. For this purpose, we use the PC expansion to approximate the nonhyperb...

Journal of biomechanics, Jan 25, 2018

Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment option for patien... more Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment option for patients deemed at high and intermediate risk for surgical aortic valve replacement. Similar to surgical aortic valves (SAVs), transcatheter aortic valves (TAVs) undergo calcification and mechanical wear over time. However, to date, there have been limited publications on the long-term durability of TAV devices. To assess longevity and mechanical strength of TAVs in comparison to surgical bioprosthetic valves, three-dimensional deformation analysis and strain measurement of the leaflets become an inevitable part of the evaluation. The goal of this study was to measure and compare leaflet displacement and strain of two commonly used TAVs in a side-by-side comparison with a commonly used SAV using a high-resolution digital image correlation (DIC) system. 26-mm Edwards SAPIEN 3, 26-mm Medtronic CoreValve, and 25-mm Carpentier-Edwards PERIMOUNT Magna surgical bioprosthesis were examined in a custo...

The Annals of thoracic surgery, Jan 5, 2017

Leaflet thrombosis after valve-in-valve (ViV) procedure has been increasingly recognized. This st... more Leaflet thrombosis after valve-in-valve (ViV) procedure has been increasingly recognized. This study aimed to investigate the flow dynamics aspect of leaflet thrombosis by quantifying the blood stasis on the noncoronary and coronary leaflets of a surgical aortic valve (SAV) and a transcatheter aortic valve (TAV) in a ViV setting. Two computational models, representing a SAV and a TAV in ViV setting, were developed in a patient-specific geometry. Three-dimensional flow fields were obtained through a fluid-solid interaction modeling approach to study the difference in blood residence time (BRT) on the coronary and noncoronary leaflets. Longer BRT was observed on the TAV leaflets compared with the SAV, specifically near the leaflet fixed boundary. Particularly, at the end of diastole, the areas of high BRT (≥1.2 seconds) on the surface of the TAV model leaflets were four times larger than those of the SAV model. The distribution of BRT on the three leaflets exhibited a similar pattern ...

Journal of the American College of Cardiology, 2016

2016 21st Conference on Electrical Power Distribution Networks Conference (EPDC), 2016

Preventive maintenance and inspection using thermography operation in distribution networks of Al... more Preventive maintenance and inspection using thermography operation in distribution networks of Alborz province has been studied in this paper. Conditions like high energy consumption, fast growth of energy demand because of several industrial towns , immigration of people to this region and converting this region to one of the largest industrial zone of Islamic Republic of Iran in addition to environmental conditions, all caused power losses and age reduction in distribution networks equipments. Considering above mentioned conditions and our experts' high load of work for operating and maintaining the old installations in addition with their efforts for avoiding the blackouts, objectives of the Alborz Electric Power Distribution Co. (APPDC) for reducing the faults , black-outs and power losses caused rescheduling old preventive maintenance plans. In this project, more than 4300 Km middle voltage feeders and 12500 power transformer were inspected and 177726 loose connections were discovered. Fixing these loose connections resulted reducing 0.5% power losses and reduce the costs of operation up to 133,000 USD during one year.

Annals of biomedical engineering, Sep 5, 2016

Valvular hemolysis and thrombosis are common complications associated with stenotic heart valves.... more Valvular hemolysis and thrombosis are common complications associated with stenotic heart valves. This study aims to determine the extent to which hemodynamics induce such traumatic events. The viscous shear stress downstream of a severely calcified bioprosthetic valve was evaluated via in vitro 2D particle image velocimetry measurements. The blood cell membrane response to the measured stresses was then quantified using 3D immersed-boundary computational simulations. The shear stress level at the boundary layer of the jet flow formed downstream of the valve orifice was observed to reach a maximum of 1000-1700 dyn/cm(2), which was beyond the threshold values reported for platelet activation (100-1000 dyn/cm(2)) and within the range of thresholds reported for red blood cell (RBC) damage (1000-2000 dyn/cm(2)). Computational simulations demonstrated that the resultant tensions at the RBC membrane surface were unlikely to cause instant rupture, but likely to lead to membrane plastic fai...

Journal of the American College of Cardiology, 2015

changed at times during the course of a procedure (although measurements were only made when a st... more changed at times during the course of a procedure (although measurements were only made when a steady state was achieved), the resulting repeated CO measurements were closely correlated (R¼0.93; ICC¼0.96). In regards to AVA, although there was good correlation in AVA calculated from repeated assumed VO2 CO (R¼0.85; ICC¼0.89) and TD CO (R¼ 0.93; ICC¼0.94), AVA based on direct VO2 CO was very reproducible (R¼0.99;ICC>0.99). CONCLUSIONS Cardiac output and AVA calculated from directly measured VO2 varies substantially from those based on assumed VO2 values and thermodilution, which are the default methods used in most CCL. Directly measured VO2-derived CO gives highly reproducible valve area measurements and may be more accurate.

Journal of Biomechanics, 2015

Transcatheter aortic valve replacement (TAVR) is an established treatment alternative to surgical... more Transcatheter aortic valve replacement (TAVR) is an established treatment alternative to surgical valve replacement in high-risk patients with severe symptomatic aortic stenosis. The current guidelines for TAVR are to upsize transcatheter aortic valve (TAV) relative to the native annulus to secure the device and minimize paravalvular leakage. Unlike surgical stented bioprosthetic valves where leaflets are attached to a rigid frame, TAVs must expand to fit within the native annulus. Fully-expanded circular TAVs have consistent leaflet kinematics; however, subtle variations in the degree of stent expansion may affect leaflet coaptation. The objective of this study was to determine the impact of incomplete TAV expansion on leaflet stress and strain distributions. In this study, we developed finite element models of a 23 mm homemade TAV expanded to diameters ranging from 18 to 23 mm in 1 mm increments. Through dynamic finite element simulations, we found that leaflet stress and strain distributions were dependent on the diameter of the inflated TAV. After complete expansion of the TAV to 23 mm, high stress and strain regions were observed primarily in the commissures during diastole. However, 2-3 mm incomplete TAV stent expansion induced localized high stress regions within the TAV commissures, while 4-5 mm incomplete stent expansion induced localized high stress regions within the belly of the TAV leaflets during the diastolic phase of the cardiac cycle. Increased mechanical stress and flexural deformation on TAV leaflets due to incomplete stent expansion may lead to accelerated tissue degeneration and diminished long-term valve durability.

Journal of the American College of Cardiology, 2014

Conclusions: Annular measurements from a 20 cc CTA protocol were statistically equivalent to a va... more Conclusions: Annular measurements from a 20 cc CTA protocol were statistically equivalent to a validated standard of 3D-TEE measurements. A very low dose protocol may play a very important role in pre-TAVR assessment for patients at high risk of CIN. TCT-670 Volume and distribution of aortic valve calcium and implications for aortic regurgitation after transcatheter aortic valve implantation

International Journal of Experimental and Computational Biomechanics, 2015

The goal of this study was to determine stress distribution in ankle joint by correlating with th... more The goal of this study was to determine stress distribution in ankle joint by correlating with the strain distribution and its trend around tibia adjacent to the joint. Using an in-house device, an ankle from a cadaver was kept stable and loaded in various positions: neutral, dorsiflexion, plantar flexion, inversion and eversion. A total of six strain gauges were mounted around the shaft of the tibia, near the tibiotalar joint. This arrangement allowed us to measure deformations in the shaft of tibia. Patient-specific ankle joint geometry was generated from computed tomography data. The finite element model (FEM) of the ankle was validated using the experimental data logged by the strain gauges, and used for obtaining stress on the joint surface. A strong correlation was observed between the FEM and experimentally measured strains in magnitude (R = 0.94, P = 0.008), consequently stress distribution over the joint surface was obtained. 46 A. Chitsazan et al.