Introduction Atherosclerosis is a potentially life-threatening disease of large arteries that is strongly associated with systemic risk factors such as hypercholesterolemia,hypertension,smoking,and diabetes. However,a...Introduction Atherosclerosis is a potentially life-threatening disease of large arteries that is strongly associated with systemic risk factors such as hypercholesterolemia,hypertension,smoking,and diabetes. However,atherosclerosis develops as a展开更多
A proper landing posture is significant to the reduction of both the im-pact force acting on the human body and the injury at landing.In this paper theimpact force acting on human feet is studied.The subjects were 3 m...A proper landing posture is significant to the reduction of both the im-pact force acting on the human body and the injury at landing.In this paper theimpact force acting on human feet is studied.The subjects were 3 maleparachuters.The experiments were performed by means of high-speed photography and amotor analyzer.The experimental results are as follows:(1)When the subjectjumped from two platforms 1.0m and 1.5m in height,a vertical impact force onthe feet in half-squat posture was larger than in side spin posture.(2)When thesubject jumped from the platform 1.0m high,the feet gained a horizontal impactforce in the half-squat posture,larger than in the side spin posture.When thesubject jumped from the platform 1.5m high,the horizontal impact force pro-duced by both of the above-mentioned postures were just the same,which needsfurther research.(3)In terms of reducing the impact force acting on the feet,theside spin posture is better than the half-squat posture.展开更多
背景:脑卒中患者的异常步态严重影响了行走时的推进力,继发地降低了患者的行走速度、行走距离及稳定性,增加了患者的跌倒风险,严重影响患者的生活质量。目的:综述脑卒中偏瘫患者中推进力缺陷的相关研究,总结现有研究者对推进力缺陷的理...背景:脑卒中患者的异常步态严重影响了行走时的推进力,继发地降低了患者的行走速度、行走距离及稳定性,增加了患者的跌倒风险,严重影响患者的生活质量。目的:综述脑卒中偏瘫患者中推进力缺陷的相关研究,总结现有研究者对推进力缺陷的理解,并分析推进力与步态的关系,最后阐述并比较最新用于改善推进力缺陷的康复技术,为临床治疗提供参考。方法:通过计算机检索万方医学网、中国知网、Pub Med和Web of Science核心集数据库收录的相关文献。中文检索词为“推进力OR地面反作用力、脑卒中OR脑中风OR偏瘫、步态OR步行OR行走”,英文检索词为“propulsive force OR propulsive,Stroke OR cerebral infarction OR hemiplegia,walk*OR gait”。检索文献时限为2003-2023年,最终纳入71篇文献进行综述分析。结果与结论:(1)针对于髋、踝关节的训练可能对患者的步行功能更有效果,特别是应用柔性外骨骼机器人的训练,但以推进力作为脑卒中患者步行功能的预后指标仍然需要更加充足的证据。(2)与推进力相关的生物力学变量包括:支撑末期的髋关节后伸角度、踝关节跖屈力矩、膝关节的伸展。(3)偏瘫患者皮质脊髓束、小脑与皮质间的通路以及网状脊髓束的受损与推进力下降及步态不对称性相关。(4)推进力对正常步态的稳定性至关重要,推进力的减弱不利于步态稳定性;步态对称性与推进力、步长对称性、躯干位移以及下肢摆动能力相关,推进力是其中的关键因素;推进力可以作为量化偏瘫患者步态的指标,且以推进力评价步态利于行走的长远发展。(5)改善推进力缺陷的主要康复技术包括:下肢外骨骼机器人步行训练、结合功能性电刺激的跑步机训练、自适应速度跑步机训练、生物反馈技术以及全身振动训练,其中全身振动训练和生物反馈技术更有效。髋、膝、踝关节在推进力改善中的具体贡献及作用机制仍存在争议,但预计髋、踝关节的贡献更大。(6)以改善推进力作为康复的目标会有更加长远的行走功能发展,然而,脑卒中患者推进力缺陷的神经学研究基础、目前改善推进力的康复技术的长期疗效以及改善推进力的主要康复技术应用于何种病情的患者更合适,还需要未来的研究者来探索。展开更多
Excessive forces may cause root resorption and insufficient forces would introduce no effect in orthodontics. The objective of this study was to investigate the optimal orthodontic forces on a maxillary canine, using ...Excessive forces may cause root resorption and insufficient forces would introduce no effect in orthodontics. The objective of this study was to investigate the optimal orthodontic forces on a maxillary canine, using hydrostatic stress and logarithmic strain of the periodontal ligament（PDL） as indicators. Finite element models of a maxillary canine and surrounding tissues were developed. Distal translation/tipping forces, labial translation/tipping forces, and extrusion forces ranging from 0 to 300 g（100 g=0.98 N） were applied to the canine, as well as the force moment around the canine long axis ranging from 0 to 300 g·mm. The stress/strain of the PDL was quantified by nonlinear finite element analysis, and an absolute stress range between 0.47 k Pa（capillary pressure） and 12.8 k Pa（80% of human systolic blood pressure） was considered to be optimal, whereas an absolute strain exceeding 0.24%（80% of peak strain during canine maximal moving velocity） was considered optimal strain. The stress/strain distributions within the PDL were acquired for various canine movements, and the optimal orthodontic forces were calculated. As a result the optimal tipping forces（40–44 g for distal-direction and 28–32 g for labial-direction） were smaller than the translation forces（130–137 g for distal-direction and 110–124 g for labial-direction）. In addition, the optimal forces for labialdirection motion（110–124 g for translation and 28–32 g for tipping） were smaller than those for distal-direction motion（130–137 g for translation and 40–44 g for tipping）. Compared with previous results, the force interval was smaller than before and was therefore more conducive to the guidance of clinical treatment. The finite element analysis results provide new insights into orthodontic biomechanics and could help to optimize orthodontic treatment plans.展开更多
The ever-growing research on lymphatic biology has clearly identified lymphatic vessels as key players that maintain human health through their functional roles in tissue fluid homeostasis,immunosurveillance,lipid met...The ever-growing research on lymphatic biology has clearly identified lymphatic vessels as key players that maintain human health through their functional roles in tissue fluid homeostasis,immunosurveillance,lipid metabolism and inflammation.It is therefore not surprising that the list of human diseases associated with lymphatic malfunctions has grown larger,including issues beyond lymphedema,a pathology traditionally associated with lymphatic drainage insufficiency.Thus,the discovery of factors and pathways that can promote optimal lymphatic functions may offer new therapeutic options.Accumulating evidence indicates that aside from biochemical factors,biomechanical signals also regulate lymphatic vessel expansion and functions postnatally.Here,we review how mechanical forces induced by fluid shear stress affect the behavior and functions of lymphatic vessels and the mechanisms lymphatic vessels employ to sense and transduce these mechanical cues into biological signals.展开更多
基金support from National Heart Lung and Blood Institute Grants P50-HL56985 and R01-HL61794
文摘Introduction Atherosclerosis is a potentially life-threatening disease of large arteries that is strongly associated with systemic risk factors such as hypercholesterolemia,hypertension,smoking,and diabetes. However,atherosclerosis develops as a
文摘A proper landing posture is significant to the reduction of both the im-pact force acting on the human body and the injury at landing.In this paper theimpact force acting on human feet is studied.The subjects were 3 maleparachuters.The experiments were performed by means of high-speed photography and amotor analyzer.The experimental results are as follows:(1)When the subjectjumped from two platforms 1.0m and 1.5m in height,a vertical impact force onthe feet in half-squat posture was larger than in side spin posture.(2)When thesubject jumped from the platform 1.0m high,the feet gained a horizontal impactforce in the half-squat posture,larger than in the side spin posture.When thesubject jumped from the platform 1.5m high,the horizontal impact force pro-duced by both of the above-mentioned postures were just the same,which needsfurther research.(3)In terms of reducing the impact force acting on the feet,theside spin posture is better than the half-squat posture.
文摘背景:脑卒中患者的异常步态严重影响了行走时的推进力,继发地降低了患者的行走速度、行走距离及稳定性,增加了患者的跌倒风险,严重影响患者的生活质量。目的:综述脑卒中偏瘫患者中推进力缺陷的相关研究,总结现有研究者对推进力缺陷的理解,并分析推进力与步态的关系,最后阐述并比较最新用于改善推进力缺陷的康复技术,为临床治疗提供参考。方法:通过计算机检索万方医学网、中国知网、Pub Med和Web of Science核心集数据库收录的相关文献。中文检索词为“推进力OR地面反作用力、脑卒中OR脑中风OR偏瘫、步态OR步行OR行走”,英文检索词为“propulsive force OR propulsive,Stroke OR cerebral infarction OR hemiplegia,walk*OR gait”。检索文献时限为2003-2023年,最终纳入71篇文献进行综述分析。结果与结论:(1)针对于髋、踝关节的训练可能对患者的步行功能更有效果,特别是应用柔性外骨骼机器人的训练,但以推进力作为脑卒中患者步行功能的预后指标仍然需要更加充足的证据。(2)与推进力相关的生物力学变量包括:支撑末期的髋关节后伸角度、踝关节跖屈力矩、膝关节的伸展。(3)偏瘫患者皮质脊髓束、小脑与皮质间的通路以及网状脊髓束的受损与推进力下降及步态不对称性相关。(4)推进力对正常步态的稳定性至关重要,推进力的减弱不利于步态稳定性;步态对称性与推进力、步长对称性、躯干位移以及下肢摆动能力相关,推进力是其中的关键因素;推进力可以作为量化偏瘫患者步态的指标,且以推进力评价步态利于行走的长远发展。(5)改善推进力缺陷的主要康复技术包括:下肢外骨骼机器人步行训练、结合功能性电刺激的跑步机训练、自适应速度跑步机训练、生物反馈技术以及全身振动训练,其中全身振动训练和生物反馈技术更有效。髋、膝、踝关节在推进力改善中的具体贡献及作用机制仍存在争议,但预计髋、踝关节的贡献更大。(6)以改善推进力作为康复的目标会有更加长远的行走功能发展,然而,脑卒中患者推进力缺陷的神经学研究基础、目前改善推进力的康复技术的长期疗效以及改善推进力的主要康复技术应用于何种病情的患者更合适,还需要未来的研究者来探索。
基金Project supported by the National Natural Science Foundation of China(Nos.51375453 and 51775506)the Natural Science Foundation of Zhejiang Province(No.LY18E050022),China
文摘Excessive forces may cause root resorption and insufficient forces would introduce no effect in orthodontics. The objective of this study was to investigate the optimal orthodontic forces on a maxillary canine, using hydrostatic stress and logarithmic strain of the periodontal ligament（PDL） as indicators. Finite element models of a maxillary canine and surrounding tissues were developed. Distal translation/tipping forces, labial translation/tipping forces, and extrusion forces ranging from 0 to 300 g（100 g=0.98 N） were applied to the canine, as well as the force moment around the canine long axis ranging from 0 to 300 g·mm. The stress/strain of the PDL was quantified by nonlinear finite element analysis, and an absolute stress range between 0.47 k Pa（capillary pressure） and 12.8 k Pa（80% of human systolic blood pressure） was considered to be optimal, whereas an absolute strain exceeding 0.24%（80% of peak strain during canine maximal moving velocity） was considered optimal strain. The stress/strain distributions within the PDL were acquired for various canine movements, and the optimal orthodontic forces were calculated. As a result the optimal tipping forces（40–44 g for distal-direction and 28–32 g for labial-direction） were smaller than the translation forces（130–137 g for distal-direction and 110–124 g for labial-direction）. In addition, the optimal forces for labialdirection motion（110–124 g for translation and 28–32 g for tipping） were smaller than those for distal-direction motion（130–137 g for translation and 40–44 g for tipping）. Compared with previous results, the force interval was smaller than before and was therefore more conducive to the guidance of clinical treatment. The finite element analysis results provide new insights into orthodontic biomechanics and could help to optimize orthodontic treatment plans.
基金This work was supported by NUHS internal funding and the Ministry of Education(Project 594 ID:MOE2019-T2-1-136)to VA and the National Medical Research Council(Y-IRG grant)to HYL。
文摘The ever-growing research on lymphatic biology has clearly identified lymphatic vessels as key players that maintain human health through their functional roles in tissue fluid homeostasis,immunosurveillance,lipid metabolism and inflammation.It is therefore not surprising that the list of human diseases associated with lymphatic malfunctions has grown larger,including issues beyond lymphedema,a pathology traditionally associated with lymphatic drainage insufficiency.Thus,the discovery of factors and pathways that can promote optimal lymphatic functions may offer new therapeutic options.Accumulating evidence indicates that aside from biochemical factors,biomechanical signals also regulate lymphatic vessel expansion and functions postnatally.Here,we review how mechanical forces induced by fluid shear stress affect the behavior and functions of lymphatic vessels and the mechanisms lymphatic vessels employ to sense and transduce these mechanical cues into biological signals.
