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1.
Site-specific variation of collagen fibril orientations can affect cartilage stresses in knee joints. However, this has not been confirmed by 3-D analyses. Therefore, we present a novel method for evaluation of the effect of patient-specific collagen architecture on time-dependent mechanical responses of knee joint cartilage during gait. 3-D finite element (FE) models of a human knee joint were created with the collagen architectures obtained from T2 mapped MRI (patient-specific model) and from literature (literature model). The effect of accuracy of the implementation of collagen fibril architecture into the model was examined by using a submodel with denser FE mesh. Compared to the literature model, fibril strains and maximum principal stresses were reduced especially in the superficial/middle regions of medial tibial cartilage in the patient-specific model after the loading response of gait (up to ?413 and ?26%, respectively). Compared to the more coarsely meshed joint model, the patient-specific submodel demonstrated similar strain and stress distributions but increased values particularly in the superficial cartilage regions (especially stresses increased >60%). The results demonstrate that implementation of subject-specific collagen architecture of cartilage in 3-D modulates location- and time-dependent mechanical responses of human knee joint cartilage. Submodeling with more accurate implementation of collagen fibril architecture alters cartilage stresses particularly in the superficial/middle tissue.  相似文献   
2.
This study was undertaken to assess magnetic resonance imaging (MRI)-based radiocarpal surface contact models of functional loading in a clinical MRI scanner for future in vivo studies, by comparison with experimental measures from three cadaver forearm specimens. Experimental data were acquired using a Tekscan sensor during simulated light grasp. Magnetic resonance (MR) images were used to obtain model geometry and kinematics (image registration). Peak contact pressures (PPs) and average contact pressures (APs), contact forces and contact areas were determined in the radiolunate and radioscaphoid joints. Contact area was also measured directly from MR images acquired with load and compared with model data. Based on the validation criteria (within 25% of experimental data), out of the six articulations (three specimens with two articulations each), two met the criterion for AP (0%, 14%); one for peak pressure (20%); one for contact force (5%); four for contact area with respect to experiment (8%, 13%, 19% and 23%), and three contact areas met the criterion with respect to direct measurements (14%, 21% and 21%). Absolute differences between model and experimental PPs were reasonably low (within 2.5 MPa). Overall, the results indicate that MRI-based models generated from 3T clinical MR scanner appear sufficient to obtain clinically relevant data.  相似文献   
3.
污染场地土壤生态风险评估研究进展   总被引:1,自引:0,他引:1  
随着我国快速城市化以及产业结构的调整,遗留下了大量的污染场地,发展和实施污染场地土壤生态风险评估是进行大规模污染场地修复行动的必要条件。本文围绕污染场地土壤生态风险评估的科学原理、框架构建及技术方法等方面的关键问题: 1)评估框架的场地实际针对性;2)概念模型的不确定性;3)土壤复合污染毒性机制;4)评估终点筛选;5)评估方法和框架构建等展开讨论,指出土壤复合污染的制毒机制,即污染物生物有效性和联合效应是污染场地土壤生态风险评估的关键科学问题。耦合美国环保局四步法和欧盟层级法的“证据-权重法”评估框架适用于野外复杂环境条件下的土壤污染生态风险评估。建议今后重点开展以下5个方面的工作: 1)污染场地土壤生态风险评估技术框架与风险管控技术框架之间的联合;2)概念模型研究;3)基于过程的场地土壤污染物反应运移模型研究;4)场地土壤复合污染生态毒理学机制研究;5)生态系统高水平生态风险评估终点研究。旨在为形成我国本土污染场地土壤生态风险评估技术指南提供理论基础和构架。  相似文献   
4.
目的:探讨滑膜炎颗粒联合玻璃酸钠治疗创伤性膝关节滑膜炎的疗效及对患者血清炎症因子水平的影响。方法:选取2015年2月~2017年12月期间我院收治的创伤性膝关节滑膜炎患者216例为研究对象。根据随机数字表法将患者分为对照组(n=108)与研究组(n=108)。对照组患者给予玻璃酸钠治疗,研究组则在此基础上联合滑膜炎颗粒进行治疗,两组均治疗5周。比较两组治疗5周后(治疗后)的临床疗效及治疗前后血清白介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)、白介素-1β(IL-1β)水平,采用视觉模拟量表(VAS)评价患者治疗前后膝关节疼痛程度,美国特种外科医院量表(HSS)评价患者治疗前后膝关节功能,同时观察两组治疗期间不良反应发生情况。结果:研究组患者总有效率为92.59%(100/108),高于对照组患者的78.70%(85/108)(P0.05)。两组患者治疗后IL-6、TNF-α以及IL-1β水平均较治疗前降低,且研究组低于对照组(P0.05)。两组患者治疗后VAS评分较治疗前降低,且研究组低于对照组,HSS评分较治疗前升高,且研究组高于对照组(P0.05)。两组患者不良反应发生率对比差异无统计学意义(P0.05)。结论:滑膜炎颗粒联合玻璃酸钠治疗创伤性膝关节滑膜炎安全有效,可显著改善患者血清炎症因子水平以及膝关节功能,并减轻患者疼痛程度,具有一定的临床应用价值。  相似文献   
5.
目的:探讨低强度周期性静水压力对体外培养的人膝关节软骨细胞增殖、凋亡,以及细胞Ⅱ型胶原分泌表达的影响。方法:体外酶消化法分离培养成人膝关节正常软骨细胞,将培养的第3代软骨细胞分为两组:正常对照组、3.0MPa组压力实验组,应用多功能恒温体外细胞培养中高压静水压力加载装置加载低强度周期性压力,共5d,每天2h。Ⅱ型胶原免疫组织化学染色法和甲苯胺蓝染色法鉴定软骨细胞,流式细胞术检测细胞凋亡,四甲基偶氮唑蓝(MTT)法绘制细胞生长曲线,qRT-PCR、Western-Blot检测Ⅱ型胶原的分泌和表达。结果:软骨细胞Ⅱ型胶原免疫组织化学染色和甲苯胺蓝染色均显示为阳性。与正常对照组相比,3.0MPa组表现出促进软骨细胞增殖,抑制细胞凋亡,且Ⅱ型胶原的合成分泌明显升高(P0.05)。结论:通过体外模拟人生理情况下较低强度(3.0MPa)的周期性静水压力对人软骨细胞增殖、凋亡水平及周围基质分泌合成功能的影响,初步证实了较低强度压力有助于软骨自我修复和自身保护作用的发挥。  相似文献   
6.
In human gait analysis studies, the entire foot is typically modeled as a single rigid-body segment; however, this neglects power generated/absorbed within the foot. Here we show how treating the entire foot as a rigid body can lead to misunderstandings related to (biological and prosthetic) foot function, and distort our understanding of ankle and muscle-tendon dynamics. We overview various (unconventional) inverse dynamics methods for estimating foot power, partitioning ankle vs. foot contributions, and computing combined anklefoot power. We present two case study examples. The first exemplifies how modeling the foot as a single rigid-body segment causes us to overestimate (and overvalue) muscle-tendon power generated about the biological ankle (in this study by up to 77%), and to misestimate (and misinform on) foot contributions; corroborating findings from previous multi-segment foot modeling studies. The second case study involved an individual with transtibial amputation walking on 8 different prosthetic feet. The results exemplify how assuming a rigid foot can skew comparisons between biological and prosthetic limbs, and lead to incorrect conclusions when comparing different prostheses/interventions. Based on analytical derivations, empirical findings and prior literature we recommend against computing conventional ankle power (between shank-foot). Instead, we recommend using an alternative estimate of power generated about the ankle joint complex (between shank-calcaneus) in conjunction with an estimate of foot power (between calcaneus-ground); or using a combined anklefoot power calculation. We conclude that treating the entire foot as a rigid-body segment is often inappropriate and ill-advised. Including foot power in biomechanical gait analysis is necessary to enhance scientific conclusions, clinical evaluations and technology development.  相似文献   
7.
梁志伟  江新青  吴梅  魏新华  夏建东  郭媛 《生物磁学》2009,(13):2499-2501,2479
目的:探讨三维快速梯度回波水激励膝关节软骨成像序列(3D-FFE-WATS)相对于三维快速梯度回波预饱和反转恢复法脂肪抑制序列(3D-FFE-SPIR)在显示膝关节软骨方面的优势,选择显示膝关节软骨的最佳序列。方法:应用3D-FFE-WATS及3D-FFE-SPIR序列组合对20名志愿者及30例疑诊关节软骨损伤的单膝关节进行检查,获得膝关节各软骨的3D图像,并利用3D最大密度投影法(MIP)进行横断面和冠状面3D重建。分析上述2种序列对软骨病变的显示及检出能力,计算其对关节软骨的信噪比(SNR)和对比噪声比(CNR),并进行统计学分析。结果:两序列在显示膝关节软骨SNR方面,无统计学意义(P〉0.05);两种序列在显示软骨与关节液的CNR、软骨与骨皮质的CNR、软骨与骨髓的CNR、软骨与肌肉的CNR差异方面t值分别为(-30.619;2.348;-2.408;2.216),有统计学意义(P〈0.05)。结论:3D-FFE-WATS序列可作为膝关节软骨成像的首选序列。  相似文献   
8.
9.
This opinion piece offers a commentary on the four papers that address the theme of the development of self and other understanding with a view to highlighting the important contribution of developmental research to understanding of mechanisms of social cognition. We discuss potential mechanisms linking self–other distinction and empathy, implications for grouping motor, affective and cognitive domains under a single mechanism, applications of these accounts for joint action and finally consider self–other distinction in group versus dyadic settings.  相似文献   
10.
Previous studies evaluated 3D human jaw movements using kinematic analysis systems during mouth opening, but information on the reliability of such measurements is still scarce. The purpose of this study was to analyze within- and between-session reliabilities, inter-rater reliability, standard error of measurement (SEM), minimum detectable change (MDC) and consistency of agreement across raters and sessions of 3D kinematic variables during maximum mouth opening (MMO). Thirty-six asymptomatic subjects from both genders were evaluated on two different days, five to seven days apart. Subjects performed three MMO movements while kinematic data were collected. Intraclass correlation coefficient (ICC), SEM and MDC were calculated for all variables, and Bland-Altman plots were constructed. Jaw radius and width were the most reproducible variables (ICC > 0.81) and demonstrated minor error. Incisor displacement during MMO and angular movements in the sagittal plane presented good reliability (ICC from 0.61 to 0.8) and small errors and, consequently, could be used in future studies with the same methodology and population. The variables with smaller amplitudes (condylar translations during mouth opening and closing and mandibular movements on the frontal and transversal planes) were less reliable (ICC < 0.61) and presented larger SEM and MDC. Although ICC, SEM and MDC showed less between-session reproducibility than within-session and inter-rater, the limits of agreement were larger in inter-rater comparisons. In future studies care must be taken with variables collected on different days and with mandibular movements in the frontal and transversal planes.  相似文献   
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