Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23111
S. Lieber
The number of heart valve replacements is increasing in the United States and worldwide due to aging of the population. This situation requires bioprosthetic heart valves with higher durability to reduce the rate of reoperation and the need for anticoagulation. However, introducing any improvement in the design of a heart valve requires ten years of validation in a clinical setup. A validated in-vitro fatigue testing system would significantly accelerate these innovations. The main objective of the proposed research is to: • Determine the dynamics of flow patterns and stresses in the vicinity of a bioprosthetic heart valve under pulsatile flow conditions. • Use the flow pattern information to validate an in-vitro fatigue testing system under physiological and accelerated conditions.
{"title":"Validation of Bench Durability of Bioprosthetic Heart Valves","authors":"S. Lieber","doi":"10.1115/imece2001/bed-23111","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23111","url":null,"abstract":"\u0000 The number of heart valve replacements is increasing in the United States and worldwide due to aging of the population. This situation requires bioprosthetic heart valves with higher durability to reduce the rate of reoperation and the need for anticoagulation. However, introducing any improvement in the design of a heart valve requires ten years of validation in a clinical setup. A validated in-vitro fatigue testing system would significantly accelerate these innovations. The main objective of the proposed research is to:\u0000 • Determine the dynamics of flow patterns and stresses in the vicinity of a bioprosthetic heart valve under pulsatile flow conditions.\u0000 • Use the flow pattern information to validate an in-vitro fatigue testing system under physiological and accelerated conditions.","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73686138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23033
Wei Lin, C. Rubin, Yi-Xian Qin
Osteoporosis is characterized by the non-traumatic fracture due to the deterioration of bone properties. Although there is a consensus that the loss of bone mass is the key factor to osteoporosis, the bone material strength and trabecular architecture are also important in the contribution to the whole bone strength. Ultrasound is mechanical in nature and it has the potential to assess the bone density as well as its mechanical stiffness. Ultrasound attenuation is one of the ultrasound parameters used to assess bone properties. Studies have shown that ultrasound attenuation is dependent on bone density [1,2] and is also indicative to the strength of trabecular bone [3,4]. Therefore, ultrasound attenuation has the potential to reveal bone properties. The objective of this study is to develop a frequency scanning method that can better extract the information of not only the bone quantity but also the bone quality.
{"title":"Measurment of Broadband Ultrasound Attenuation Using Tone Burst Frequency Scanning in Trabecular Bone Property Assessment","authors":"Wei Lin, C. Rubin, Yi-Xian Qin","doi":"10.1115/imece2001/bed-23033","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23033","url":null,"abstract":"\u0000 Osteoporosis is characterized by the non-traumatic fracture due to the deterioration of bone properties. Although there is a consensus that the loss of bone mass is the key factor to osteoporosis, the bone material strength and trabecular architecture are also important in the contribution to the whole bone strength. Ultrasound is mechanical in nature and it has the potential to assess the bone density as well as its mechanical stiffness. Ultrasound attenuation is one of the ultrasound parameters used to assess bone properties. Studies have shown that ultrasound attenuation is dependent on bone density [1,2] and is also indicative to the strength of trabecular bone [3,4]. Therefore, ultrasound attenuation has the potential to reveal bone properties. The objective of this study is to develop a frequency scanning method that can better extract the information of not only the bone quantity but also the bone quality.","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83830159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23130
C. Sadasivan, B. Lieber, D. Lopes, A. Ringer, L. Hopkins
The ultimate goal in the treatment of cerebral aneurysms is to exclude them from the intracranial circulation while preserving the parent artery. Recently, in vivo and in vitro experiments and clinical studies demonstrated that endovascular stenting is a significant and viable treatment option for cerebral aneurysms. Stents reduce the mass and momentum transport of blood from the parent artery into the aneurysm and alter both intra-aneurysmal flow and inflow-outflow patterns. The reduction of vorticity and flow stasis within the sac leads to thrombus formation and eventual exclusion of the aneurysm from the circulation. Digital subtraction angiography (DSA) has become an essential clinical tool for the diagnosis and treatment of aneurysms and is an important adjunct to stenting procedures.
{"title":"Modeling of Angiographic Dye Washout From Cerebral Aneurysms Before and After Stenting: An Index for Stent Efficacy","authors":"C. Sadasivan, B. Lieber, D. Lopes, A. Ringer, L. Hopkins","doi":"10.1115/imece2001/bed-23130","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23130","url":null,"abstract":"\u0000 The ultimate goal in the treatment of cerebral aneurysms is to exclude them from the intracranial circulation while preserving the parent artery. Recently, in vivo and in vitro experiments and clinical studies demonstrated that endovascular stenting is a significant and viable treatment option for cerebral aneurysms. Stents reduce the mass and momentum transport of blood from the parent artery into the aneurysm and alter both intra-aneurysmal flow and inflow-outflow patterns. The reduction of vorticity and flow stasis within the sac leads to thrombus formation and eventual exclusion of the aneurysm from the circulation. Digital subtraction angiography (DSA) has become an essential clinical tool for the diagnosis and treatment of aneurysms and is an important adjunct to stenting procedures.","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84528083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23138
M. Olufsen, L. Lipsitz, A. Nadim
Dynamic changes in cerebral blood flow and the associated vascular responses accompanying posture change that enable the brain to maintain perfusion during hypotensive stress are not fully understood. The aim of this work is to use a lumped parameter model of cerebral blood flow to analyze changes in key parameters (systemic and cerebrovascular resistances) during posture change from sitting to standing. Such a model sheds light on vascular adaptation to hypotensive stress, and could ultimately help determine the changes in cerebral autoregulation that occur in aging, hypertension, and other clinical conditions.
{"title":"A Lumped Parameter Model for Cerebral Blood Flow Regulation","authors":"M. Olufsen, L. Lipsitz, A. Nadim","doi":"10.1115/imece2001/bed-23138","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23138","url":null,"abstract":"\u0000 Dynamic changes in cerebral blood flow and the associated vascular responses accompanying posture change that enable the brain to maintain perfusion during hypotensive stress are not fully understood. The aim of this work is to use a lumped parameter model of cerebral blood flow to analyze changes in key parameters (systemic and cerebrovascular resistances) during posture change from sitting to standing. Such a model sheds light on vascular adaptation to hypotensive stress, and could ultimately help determine the changes in cerebral autoregulation that occur in aging, hypertension, and other clinical conditions.","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"133 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76789234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23009
R. Roy, S. Kohles, V. Zaporojan, L. Bonassar
The current literature presents many techniques for analysis of the mechanical properties of articular cartilage [1]. By comparison few techniques are available for analysis of auricular cartilage which experiences a different mechanical environment than articular cartilage. Specifically, large deflection bending is a deformation mode that is most relevant to auricular cartilage, but has not been studied thoroughly in soft tissues. The goals of this study were to: 1) apply an elasticity model to three point bending data from normal and engineered auricular and costal cartilage; and 2) use this model to determine the tensile elastic moduli.
{"title":"Analysis of Bending Behavior of Native Auricular and Costal Cartilage and Tissue Engineered Constructs","authors":"R. Roy, S. Kohles, V. Zaporojan, L. Bonassar","doi":"10.1115/imece2001/bed-23009","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23009","url":null,"abstract":"\u0000 The current literature presents many techniques for analysis of the mechanical properties of articular cartilage [1]. By comparison few techniques are available for analysis of auricular cartilage which experiences a different mechanical environment than articular cartilage. Specifically, large deflection bending is a deformation mode that is most relevant to auricular cartilage, but has not been studied thoroughly in soft tissues. The goals of this study were to: 1) apply an elasticity model to three point bending data from normal and engineered auricular and costal cartilage; and 2) use this model to determine the tensile elastic moduli.","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"65 6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77319762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23098
F. Mizuno, A. Harada, T. Yamaguchi
Numerous attempts to adapt multimedia communication to medical care have been reported recently. It is our view that spiritual support is more important in medical care, while so-called high technology may be necessary for medical practice. Therefore, we proposed the concept of the Hyper Hospital [1–3], to offer patients a means of effective human communication during medical care. The Hyper Hospital is a medical system constructed on a computer and multimedia based-network, which patients use to participate in medical and care activities through improved communication media. It is sometimes difficult for physically handicapped patients, such as PMD (progressive muscular dystrophy), ALS (amyotrophic lateral sclerosis), and traumatic cervical injury patients, to operate a computer, because of their disabilities. Therefore, there is a serious digital divide between physically disabled patients and healthy people. To remedy this, various communication devices, such as those using winking, eye gaze, voice, and electrical biological signals (event-related potential [4–5], electrooculogram, etc.) have been proposed and tested. These are designed to enable seriously handicapped patients to use a computer without using the usual mechanical input devices, such as a keyboard, mouse, or joystick. Although an EEG (electroencephalogram) offers one source of such potential electrical biological signals, it produces a very weak electrical signal that contaminating noise makes difficult to process. On the other hand, the ocular potential generated by the dipolar potential of the eyeball has a much larger gain in potential than the EEG. Moreover, the ocular potential can be easily controlled by the user, and eye-movement ability remains largely intact, even after neurological diseases progress to a very advanced stage. Therefore, this report studied the development of an input interface for computers using an electrooculogram.
{"title":"Development of an Input Interface Using Ocular Potential for Handicapped Users of Health Care Supporting Computer","authors":"F. Mizuno, A. Harada, T. Yamaguchi","doi":"10.1115/imece2001/bed-23098","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23098","url":null,"abstract":"\u0000 Numerous attempts to adapt multimedia communication to medical care have been reported recently. It is our view that spiritual support is more important in medical care, while so-called high technology may be necessary for medical practice. Therefore, we proposed the concept of the Hyper Hospital [1–3], to offer patients a means of effective human communication during medical care. The Hyper Hospital is a medical system constructed on a computer and multimedia based-network, which patients use to participate in medical and care activities through improved communication media. It is sometimes difficult for physically handicapped patients, such as PMD (progressive muscular dystrophy), ALS (amyotrophic lateral sclerosis), and traumatic cervical injury patients, to operate a computer, because of their disabilities. Therefore, there is a serious digital divide between physically disabled patients and healthy people. To remedy this, various communication devices, such as those using winking, eye gaze, voice, and electrical biological signals (event-related potential [4–5], electrooculogram, etc.) have been proposed and tested. These are designed to enable seriously handicapped patients to use a computer without using the usual mechanical input devices, such as a keyboard, mouse, or joystick. Although an EEG (electroencephalogram) offers one source of such potential electrical biological signals, it produces a very weak electrical signal that contaminating noise makes difficult to process. On the other hand, the ocular potential generated by the dipolar potential of the eyeball has a much larger gain in potential than the EEG. Moreover, the ocular potential can be easily controlled by the user, and eye-movement ability remains largely intact, even after neurological diseases progress to a very advanced stage. Therefore, this report studied the development of an input interface for computers using an electrooculogram.","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86856144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23038
A. Meghdari, A. Bahrami
During flexion/extension, of the head-neck system, cervical spine undergoes a stepwise motion from the upper to lower regions with a specific time lag. Motion of each vertebrae is composed of a translation and a rotation with respect to lower vertebrae, which may be considered as an absolute rotation about an axis called Instantaneous Axis of Rotation (IAR). Location of this axis is different between normal, and degenerated spines. In this research intersegmental force-moments are evaluated and compared in normal, degenerated, and fused subjects employing a biomechanical model of head-neck system based on IAR’s concept and the results are presented.
{"title":"Mathematical Modeling of Normal, Degenerated, and Fused Cervical Spines Using IAR’S Concept","authors":"A. Meghdari, A. Bahrami","doi":"10.1115/imece2001/bed-23038","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23038","url":null,"abstract":"\u0000 During flexion/extension, of the head-neck system, cervical spine undergoes a stepwise motion from the upper to lower regions with a specific time lag. Motion of each vertebrae is composed of a translation and a rotation with respect to lower vertebrae, which may be considered as an absolute rotation about an axis called Instantaneous Axis of Rotation (IAR). Location of this axis is different between normal, and degenerated spines. In this research intersegmental force-moments are evaluated and compared in normal, degenerated, and fused subjects employing a biomechanical model of head-neck system based on IAR’s concept and the results are presented.","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91122237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23024
M. D. Roberts, R. T. Hart
The adaptation of bone to its mechanical demands is often described as a feedback control system wherein some aspect of the tissue strain environment acts as a driving signal to initiate cellular-level formation and resorption processes on bone surfaces. While this description may be somewhat simplified, the control system view is useful for organizing ideas, experiments, and simulations of adaptation. In the past 25 years, several investigators have introduced mathematical models and (finite element-based) computer simulations of bone adaptation, using numerous candidate driving mechanical signals as proposed bone mass regulators [1]. These simulations generally use the finite element method — including the appropriate geometry, material description, and loading — to calculate the needed tissue strain parameter being considered as the specific regulation signal. Based on the adaptive response being simulated — geometric and/or material property changes — the finite element model is updated, and re-analyzed in a series of discrete time steps.
{"title":"Contour Based Implementation of Long Bone Adaptation","authors":"M. D. Roberts, R. T. Hart","doi":"10.1115/imece2001/bed-23024","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23024","url":null,"abstract":"\u0000 The adaptation of bone to its mechanical demands is often described as a feedback control system wherein some aspect of the tissue strain environment acts as a driving signal to initiate cellular-level formation and resorption processes on bone surfaces. While this description may be somewhat simplified, the control system view is useful for organizing ideas, experiments, and simulations of adaptation. In the past 25 years, several investigators have introduced mathematical models and (finite element-based) computer simulations of bone adaptation, using numerous candidate driving mechanical signals as proposed bone mass regulators [1]. These simulations generally use the finite element method — including the appropriate geometry, material description, and loading — to calculate the needed tissue strain parameter being considered as the specific regulation signal. Based on the adaptive response being simulated — geometric and/or material property changes — the finite element model is updated, and re-analyzed in a series of discrete time steps.","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80335201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23032
X. N. Dong, X. Guo
Age-related changes in microstructure and composition of bone tissue are becoming increasing important as people continue to live longer. The cortical porosity increases with age in both men and women [1]. Age related increases in Haversian canal size and Haversian canal number contribute to the increasing porosity of cortical bone for the elderly men and women [2, 3]. The number of osteoclastic resorption space is also greater in the old men than in the young men [3]. The increased porosity and the higher prevalence of giant Haverian canals have a markedly negative influence on the ability of the cortical shell to withstand mechanical loads associated with a fall [4].
{"title":"Predicting a Power Law Between Elastic Modulus and Porosity in Cortical Bone: A Micromechanics Model","authors":"X. N. Dong, X. Guo","doi":"10.1115/imece2001/bed-23032","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23032","url":null,"abstract":"\u0000 Age-related changes in microstructure and composition of bone tissue are becoming increasing important as people continue to live longer. The cortical porosity increases with age in both men and women [1]. Age related increases in Haversian canal size and Haversian canal number contribute to the increasing porosity of cortical bone for the elderly men and women [2, 3]. The number of osteoclastic resorption space is also greater in the old men than in the young men [3]. The increased porosity and the higher prevalence of giant Haverian canals have a markedly negative influence on the ability of the cortical shell to withstand mechanical loads associated with a fall [4].","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82760021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/bed-23113
H. Iwase, Hao Liu, S. Fujimoto, R. Himeno
We present a numerical study of dynamical blood flow in a left ventricle of human heart using Computational Fluid Dynamics (CFD). Three-dimensional shape of the left ventricle model was reconstructed using spline interpolation, based on a set of two-dimensional ultrasound echocardiogram images. Blood flow in the left ventricle was computed by solving the incompressible, unsteady Navier-Stokes equations in a manner of Finite Volume Method (FVM). In the present preliminary results the asymmetric intracardiac flow pattern is detected very similar to observed in vivo (Kilner, 2000) which shows a large vortex and a small vortex at diastole.
{"title":"Numerical Analysis of Blood Flow in a Left Ventricle","authors":"H. Iwase, Hao Liu, S. Fujimoto, R. Himeno","doi":"10.1115/imece2001/bed-23113","DOIUrl":"https://doi.org/10.1115/imece2001/bed-23113","url":null,"abstract":"\u0000 We present a numerical study of dynamical blood flow in a left ventricle of human heart using Computational Fluid Dynamics (CFD). Three-dimensional shape of the left ventricle model was reconstructed using spline interpolation, based on a set of two-dimensional ultrasound echocardiogram images. Blood flow in the left ventricle was computed by solving the incompressible, unsteady Navier-Stokes equations in a manner of Finite Volume Method (FVM). In the present preliminary results the asymmetric intracardiac flow pattern is detected very similar to observed in vivo (Kilner, 2000) which shows a large vortex and a small vortex at diastole.","PeriodicalId":7238,"journal":{"name":"Advances in Bioengineering","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84301222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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