Background:Traumatic brain injury can be caused by head impacts,but many brain injury risk estimation models are not equally accurate across the variety of impacts that patients may undergo,and the characteristics of ...Background:Traumatic brain injury can be caused by head impacts,but many brain injury risk estimation models are not equally accurate across the variety of impacts that patients may undergo,and the characteristics of different types of impacts are not well studied.We investigated the spectral characteristics of different head impact types with kinematics classification.Methods:Data were analyzed from 3262 head impacts from lab reconstruction,American football,mixed martial arts,and publicly available car crash data.A random forest classifier with spectral densities of linear acceleration and angular velocity was built to classify head impact types(e.g.,football,car crash,mixed martial arts).To test the classifier robustness,another 271 lab-reconstructed impacts were obtained from 5 other instrumented mouthguards.Finally,with the classifier,type-specific,nearest-neighbor regression models were built for brain strain.Results:The classifier reached a median accuracy of 96% over 1000 random partitions of training and test sets.The most important features in the classification included both low-and high-frequency features,both linear acceleration features and angular velocity features.Different head impact types had different distributions of spectral densities in low-and high-frequency ranges(e.g.,the spectral densities of mixed martial arts impacts were higher in the high-frequency range than in the low-frequency range).The type-specific regression showed a generally higher R2value than baseline models without classification.Conclusion:The machine-learning-based classifier enables a better understanding of the impact kinematics spectral density in different sports,and it can be applied to evaluate the quality of impact-simulation systems and on-field data augmentation.展开更多
To consider the head is a flexible multi-layer structure and the contact-impact is flexible, the Hertz Contact Law is unsuitable for analyzing the dynamic response of human head impacts elastic plane with initial spee...To consider the head is a flexible multi-layer structure and the contact-impact is flexible, the Hertz Contact Law is unsuitable for analyzing the dynamic response of human head impacts elastic plane with initial speed. In this paper, the process of head impacting with elastic plane is modeled as a response of vibrant system, and methods like mechanical network figure and mechanical impedance is taken to resolve this dynamic response problem. Based on the actual head structure, head is modeled as a vibrant model, which concludes the masses of scalp and bone in the impact area, the masses in the other part of the head and the brain, the stiffness of the head, and the damp coefficient of the scalp and brain. At the same time, the elastic plane is simplified as a vibrant model including mass, stiffness and damp. These two vibrant models are linked into one vibrant systematic model. In order to calculate the elastic deformation and the impact acceleration of the head, the models are transformed into mechanical girding figure at violent vibration point. The dynamic impact force of the system, the impact acceleration of the head, the elastic deformation of the plane and the fixed frequency of the system can be worked out by calculating the velocity impedance at the violent vibration point when the initial impact speed is known. The results fit the test data well, which proves that this method is available for the analysis of the dynamic response of the system under impact.展开更多
背景:由身体接触性运动或交通事故造成的脑震荡远比人们想象的更为严重与常见,近年来引起了媒体、医学界及体育界的广泛关注与高度重视。目的:采用文献计量学方法对有限元方法在脑震荡领域的研究热点与趋势进行可视化分析,从而为中国在...背景:由身体接触性运动或交通事故造成的脑震荡远比人们想象的更为严重与常见,近年来引起了媒体、医学界及体育界的广泛关注与高度重视。目的:采用文献计量学方法对有限元方法在脑震荡领域的研究热点与趋势进行可视化分析,从而为中国在该领域的研究提供一定的参考。方法:基于Web of Science核心集数据库进行文献检索,检索主题词策略为(TS=(Concussion)) AND TS=(Finite element),利用CiteSpace 6.2.R4可视化工具对纳入文献的作者、国家、机构、关键词及被引文献等进行可视化分析。结果与结论:(1)共计纳入215篇文献,发文量与被引量总体上呈上升趋势;学科分布涉及生物医学工程、生物物理学、运动科学、临床神经学及神经科学等学科,呈现多学科交叉融合的趋势;发文量最多的作者是来自爱尔兰都柏林大学的Gilchrist M,发文量最多的机构是渥太华大学,发文量最多的国家是美国。(2)通过关键词分析发现研究的热点聚焦于脑损伤模型的建立用来模拟和预测脑震荡的损伤;脑震荡损伤机制的解析;防护设备和装置的优化设计。(3)通过文献共被引分析发现脑损伤的预测与评估是该领域的知识基础亦是研究热点。(4)有限元方法运用在脑震荡领域的研究热点主要围绕头部损伤预测为主题展开,结合探索大脑损伤机制以及防护装备的设计与改进。(5)随着人工智能与材料学的进步,未来有限元方法在脑震荡损伤领域的研究热点将集中于脑损伤模型、测试方法与防护装备的改进。展开更多
Background:Considering the potential cumulative effects of repetitive head impact(HI)exposure,we need sensitive biomarkers to track shortand long-term effects.Circulating small extracellular vesicles(sEVs)(<200 nm)...Background:Considering the potential cumulative effects of repetitive head impact(HI)exposure,we need sensitive biomarkers to track shortand long-term effects.Circulating small extracellular vesicles(sEVs)(<200 nm)traffic biological molecules throughout the body and may have diagnostic value as biomarkers for disease.The purpose of this study was to identify the microRNA(miRNA)profile in circulating sEVs derived from human plasma following repetitive HI exposure.Methods:Healthy adult(aged 18-35 years)soccer players were randomly assigned to one of 3 groups:the HI group performed 10 standing headers,the leg impact group performed 10 soccer ball trapping maneuvers over 10 min,and the control group did not participate in any soccer drills.Plasma was collected before testing and 24 h afterward,and sEVs were isolated and characterized via nanoparticle tracking analysis.Next-generation sequencing was utilized to identify candidate miRNAs isolated from sEVs,and candidate microRNAs were analyzed via quantitative polymerase chain reaction.In silico target prediction was performed using TargetScan(Version 7.0;targetscan.org)and miRWalk(http://mirwalk.umm.uni-heidelberg.de/)programs,and target validation was performed using luciferase reporter vectors with a miR-7844-5p mimic in human embryonic kidney(HEK)293T/17 cells.Results:Plasma sEV concentration and size were not affected across time and group following repetitive HI exposure.After 24 h,the HI read count from next-generation sequencing showed a 4-fold or greater increase in miR-92b-5p,miR-423-5p,and miR-24-3p and a 3-fold or greater decrease in miR-7844-5p,miR-144-5p,miR-221-5p,and miR-22-3p.Analysis of quantitative polymerase chain reaction revealed that leg impact did not alter the candidate miRNA levels.To our knowledge,miR-7844-5p is a previously unknown miRNA.We identified 8 miR-7844-5p mRNA targets:protein phosphatase 1 regulatory inhibitor subunit 1B(PPP1R1B),LIM and senescent cell antigen-like domains 1(LIMS1),autophagy-related 12(ATG12),microtubule-associated protein 1 light chain 3 beta(MAP1LC3B),integrin subunit alpha-1(ITGA1),mitogenactivated protein kinase 1(MAPK1),glycogen synthase kinase 3b(GSK3b),and mitogen-activated protein kinase 8(MAPK8).Conclusion:Collectively,these data indicate repetitive HI exposure alters plasma sEV miRNA content,but not sEV size or number.Furthermore,for the first time we demonstrate that previously unknown miR-7844-5p targets mRNAs known to be involved in mitochondrial apoptosis,autophagy regulation,mood disorders,and neurodegenerative disease.展开更多
跨介质航行体入水瞬间会受到巨大的冲击载荷,极易导致结构破坏甚至内部器件失灵。为发展有效的降载方法,本文基于VOF(Volume of Fluid)多相流模型,研究头部喷气航行体入水过程的载荷特性和流体动力特性,分析喷气压力、喷气高度对降载效...跨介质航行体入水瞬间会受到巨大的冲击载荷,极易导致结构破坏甚至内部器件失灵。为发展有效的降载方法,本文基于VOF(Volume of Fluid)多相流模型,研究头部喷气航行体入水过程的载荷特性和流体动力特性,分析喷气压力、喷气高度对降载效果的影响,并探索头部喷气降载方法有效性的入水速度范围。研究结果表明,头部喷气使自由液面下凹形成空腔,并能极大地降低航行体所受阻力和冲击力,延缓了航行体撞水时间,从而实现冲击载荷控制;喷气压力和喷气高度对入水空泡形态及冲击压力峰值的影响都不大,合理的选择既能达到降载效果又能节约喷气量;入水速度为50 m/s时,降载量高达76.51%,但当入水速度为300 m/s时,降载量仅为39.92%。因此,针对高亚声速跨介质入水问题,需进一步探索主被动相结合的复合降载方法。展开更多
Fluid percussion-induced traumatic brain injury models have been widely used in experimental research for years. In an experiment, the stability of impaction is inevitably affected by factors such as the appearance of...Fluid percussion-induced traumatic brain injury models have been widely used in experimental research for years. In an experiment, the stability of impaction is inevitably affected by factors such as the appearance of liquid spikes. Management of impact pressure is a crucial factor that determines the stability of these models, and direction of impact control is another basic element. To improve experimental stability, we calculated a pressure curve by generating repeated impacts using a fluid percussion device at different pendulum angles. A stereotactic frame was used to control the direction of impact. We produced stable and reproducible models, including mild, moderate, and severe traumatic brain injury, using the MODEL01-B device at pendulum angles of 6°, 11° and 13°, with corresponding impact force values of 1.0 ± 0.11 atm（101.32 ± 11.16 k Pa）, 2.6 ± 0.16 atm（263.44 ± 16.21 k Pa）, and 3.6 ± 0.16 atm（364.77 ± 16.21 k Pa）, respectively. Behavioral tests, hematoxylin-eosin staining, and magnetic resonance imaging revealed that models for different degrees of injury were consistent with the clinical properties of mild, moderate, and severe craniocerebral injuries. Using this method, we established fluid percussion models for different degrees of injury and stabilized pathological features based on precise power and direction control.展开更多
基金supported by the Pac-12 Conference’s Student-Athlete Health and Well-Being Initiative,the National Institutes of Health (R24NS098518)Stanford Department of Bioengineering。
文摘Background:Traumatic brain injury can be caused by head impacts,but many brain injury risk estimation models are not equally accurate across the variety of impacts that patients may undergo,and the characteristics of different types of impacts are not well studied.We investigated the spectral characteristics of different head impact types with kinematics classification.Methods:Data were analyzed from 3262 head impacts from lab reconstruction,American football,mixed martial arts,and publicly available car crash data.A random forest classifier with spectral densities of linear acceleration and angular velocity was built to classify head impact types(e.g.,football,car crash,mixed martial arts).To test the classifier robustness,another 271 lab-reconstructed impacts were obtained from 5 other instrumented mouthguards.Finally,with the classifier,type-specific,nearest-neighbor regression models were built for brain strain.Results:The classifier reached a median accuracy of 96% over 1000 random partitions of training and test sets.The most important features in the classification included both low-and high-frequency features,both linear acceleration features and angular velocity features.Different head impact types had different distributions of spectral densities in low-and high-frequency ranges(e.g.,the spectral densities of mixed martial arts impacts were higher in the high-frequency range than in the low-frequency range).The type-specific regression showed a generally higher R2value than baseline models without classification.Conclusion:The machine-learning-based classifier enables a better understanding of the impact kinematics spectral density in different sports,and it can be applied to evaluate the quality of impact-simulation systems and on-field data augmentation.
文摘To consider the head is a flexible multi-layer structure and the contact-impact is flexible, the Hertz Contact Law is unsuitable for analyzing the dynamic response of human head impacts elastic plane with initial speed. In this paper, the process of head impacting with elastic plane is modeled as a response of vibrant system, and methods like mechanical network figure and mechanical impedance is taken to resolve this dynamic response problem. Based on the actual head structure, head is modeled as a vibrant model, which concludes the masses of scalp and bone in the impact area, the masses in the other part of the head and the brain, the stiffness of the head, and the damp coefficient of the scalp and brain. At the same time, the elastic plane is simplified as a vibrant model including mass, stiffness and damp. These two vibrant models are linked into one vibrant systematic model. In order to calculate the elastic deformation and the impact acceleration of the head, the models are transformed into mechanical girding figure at violent vibration point. The dynamic impact force of the system, the impact acceleration of the head, the elastic deformation of the plane and the fixed frequency of the system can be worked out by calculating the velocity impedance at the violent vibration point when the initial impact speed is known. The results fit the test data well, which proves that this method is available for the analysis of the dynamic response of the system under impact.
文摘背景:由身体接触性运动或交通事故造成的脑震荡远比人们想象的更为严重与常见,近年来引起了媒体、医学界及体育界的广泛关注与高度重视。目的:采用文献计量学方法对有限元方法在脑震荡领域的研究热点与趋势进行可视化分析,从而为中国在该领域的研究提供一定的参考。方法:基于Web of Science核心集数据库进行文献检索,检索主题词策略为(TS=(Concussion)) AND TS=(Finite element),利用CiteSpace 6.2.R4可视化工具对纳入文献的作者、国家、机构、关键词及被引文献等进行可视化分析。结果与结论:(1)共计纳入215篇文献,发文量与被引量总体上呈上升趋势;学科分布涉及生物医学工程、生物物理学、运动科学、临床神经学及神经科学等学科,呈现多学科交叉融合的趋势;发文量最多的作者是来自爱尔兰都柏林大学的Gilchrist M,发文量最多的机构是渥太华大学,发文量最多的国家是美国。(2)通过关键词分析发现研究的热点聚焦于脑损伤模型的建立用来模拟和预测脑震荡的损伤;脑震荡损伤机制的解析;防护设备和装置的优化设计。(3)通过文献共被引分析发现脑损伤的预测与评估是该领域的知识基础亦是研究热点。(4)有限元方法运用在脑震荡领域的研究热点主要围绕头部损伤预测为主题展开,结合探索大脑损伤机制以及防护装备的设计与改进。(5)随着人工智能与材料学的进步,未来有限元方法在脑震荡损伤领域的研究热点将集中于脑损伤模型、测试方法与防护装备的改进。
基金National Institutes of Health(NIH)-National Institute of Neurological Disorders and Stroke(NINDS)R01(NS102157-01)National Institutes of Health(NIH)-National Institute of General Medical Sciences(NIGMS)P20(GM113125-01).
文摘Background:Considering the potential cumulative effects of repetitive head impact(HI)exposure,we need sensitive biomarkers to track shortand long-term effects.Circulating small extracellular vesicles(sEVs)(<200 nm)traffic biological molecules throughout the body and may have diagnostic value as biomarkers for disease.The purpose of this study was to identify the microRNA(miRNA)profile in circulating sEVs derived from human plasma following repetitive HI exposure.Methods:Healthy adult(aged 18-35 years)soccer players were randomly assigned to one of 3 groups:the HI group performed 10 standing headers,the leg impact group performed 10 soccer ball trapping maneuvers over 10 min,and the control group did not participate in any soccer drills.Plasma was collected before testing and 24 h afterward,and sEVs were isolated and characterized via nanoparticle tracking analysis.Next-generation sequencing was utilized to identify candidate miRNAs isolated from sEVs,and candidate microRNAs were analyzed via quantitative polymerase chain reaction.In silico target prediction was performed using TargetScan(Version 7.0;targetscan.org)and miRWalk(http://mirwalk.umm.uni-heidelberg.de/)programs,and target validation was performed using luciferase reporter vectors with a miR-7844-5p mimic in human embryonic kidney(HEK)293T/17 cells.Results:Plasma sEV concentration and size were not affected across time and group following repetitive HI exposure.After 24 h,the HI read count from next-generation sequencing showed a 4-fold or greater increase in miR-92b-5p,miR-423-5p,and miR-24-3p and a 3-fold or greater decrease in miR-7844-5p,miR-144-5p,miR-221-5p,and miR-22-3p.Analysis of quantitative polymerase chain reaction revealed that leg impact did not alter the candidate miRNA levels.To our knowledge,miR-7844-5p is a previously unknown miRNA.We identified 8 miR-7844-5p mRNA targets:protein phosphatase 1 regulatory inhibitor subunit 1B(PPP1R1B),LIM and senescent cell antigen-like domains 1(LIMS1),autophagy-related 12(ATG12),microtubule-associated protein 1 light chain 3 beta(MAP1LC3B),integrin subunit alpha-1(ITGA1),mitogenactivated protein kinase 1(MAPK1),glycogen synthase kinase 3b(GSK3b),and mitogen-activated protein kinase 8(MAPK8).Conclusion:Collectively,these data indicate repetitive HI exposure alters plasma sEV miRNA content,but not sEV size or number.Furthermore,for the first time we demonstrate that previously unknown miR-7844-5p targets mRNAs known to be involved in mitochondrial apoptosis,autophagy regulation,mood disorders,and neurodegenerative disease.
文摘跨介质航行体入水瞬间会受到巨大的冲击载荷,极易导致结构破坏甚至内部器件失灵。为发展有效的降载方法,本文基于VOF(Volume of Fluid)多相流模型,研究头部喷气航行体入水过程的载荷特性和流体动力特性,分析喷气压力、喷气高度对降载效果的影响,并探索头部喷气降载方法有效性的入水速度范围。研究结果表明,头部喷气使自由液面下凹形成空腔,并能极大地降低航行体所受阻力和冲击力,延缓了航行体撞水时间,从而实现冲击载荷控制;喷气压力和喷气高度对入水空泡形态及冲击压力峰值的影响都不大,合理的选择既能达到降载效果又能节约喷气量;入水速度为50 m/s时,降载量高达76.51%,但当入水速度为300 m/s时,降载量仅为39.92%。因此,针对高亚声速跨介质入水问题,需进一步探索主被动相结合的复合降载方法。
基金supported by a grant from the International S cience and Technology Cooperation Projects of China,No.2011DFG33430
文摘Fluid percussion-induced traumatic brain injury models have been widely used in experimental research for years. In an experiment, the stability of impaction is inevitably affected by factors such as the appearance of liquid spikes. Management of impact pressure is a crucial factor that determines the stability of these models, and direction of impact control is another basic element. To improve experimental stability, we calculated a pressure curve by generating repeated impacts using a fluid percussion device at different pendulum angles. A stereotactic frame was used to control the direction of impact. We produced stable and reproducible models, including mild, moderate, and severe traumatic brain injury, using the MODEL01-B device at pendulum angles of 6°, 11° and 13°, with corresponding impact force values of 1.0 ± 0.11 atm（101.32 ± 11.16 k Pa）, 2.6 ± 0.16 atm（263.44 ± 16.21 k Pa）, and 3.6 ± 0.16 atm（364.77 ± 16.21 k Pa）, respectively. Behavioral tests, hematoxylin-eosin staining, and magnetic resonance imaging revealed that models for different degrees of injury were consistent with the clinical properties of mild, moderate, and severe craniocerebral injuries. Using this method, we established fluid percussion models for different degrees of injury and stabilized pathological features based on precise power and direction control.
