人体体温下UHMWPE人工髋臼材料压缩性能的试验研究

模拟人体体温下对超高分子量聚乙烯（UHMWPE）人工髋臼材料进行了压缩力学性能的试验研究,并与室温下的试验结果进行了对比.当由室温22℃升高到体温37℃和40℃时,其屈服应力呈明显的下降趋势,分别下降了23.1%和31.9%,由体温37℃升高到40℃时,二者仅差3℃,其屈服应力亦下降了11.5%.同时还对不同加载速度下UHMWPE试件压缩变形过程进行了红外辐射温度的监测与分析.不同加载速度下试件压缩变形过程中的红外辐射温度均有明显升高,加载时间越长,试件平均红外辐射温度越高.试验结果分析表明,不能忽视植入人体后UHMWPE人工髋臼局部受压时温度的升高,特别不能忽视植入人体后在人体体温作用下其力学性能的改变和下降,人体体温的作用是UHMWPE人工髋臼出现过早失效的原因之一.本试验研究为UHMWPE材料在人体环境中的应用研究提供了参考.     

Acrylic‐Based Polyurethane/Silica Hybrids Prepared by Acid‐Catalyzed Sol–Gel Process: Structure and Mechanical Properties

Summary: Silica sols were first prepared based on different ratios of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) by an acid‐catalyzed sol–gel process, and then incorporated into acrylic‐based polyurethanes. The structures and morphologies of silicone‐oxo clusters were studied by ²⁹Si NMR, SAXS, and scanning electron microscopy (SEM), whereas the mechanical properties of polyurethane/silica hybrids were characterized by DMA and tensile tests. The silicone‐oxo clusters in both silica sol and polyurethane hybrids became denser and larger at a higher molar ratio of TEOS/MTES and higher silica content, and the silica‐oxo clusters of polyurethane/silica hybrids even became more compact and larger than those of silica sols, increasing the elastic modulus and tensile strength of polyurethane/silica hybrids.

Typical structure of silica sol prepared from the hydrolysis and condensation of TEOS and MTES with acid as the catalyst.     

Mechanical heart valve prostheses:: identification and evaluation (erratum)

Mechanical heart value prostheses have been in use since the 1950s. Many prostheses have been used for a while and then discontinued. Today, there are a large number and variety of prostheses in use and an even larger variety that are in place in patients. These may be explanted at any time for a number of reasons. It is essential for the practicing pathologist to be able to identify the prosthesis and be aware of some of its reported complications and modes of failure. This article, and a second one on bioprosthetic heart valves, is designed as a ready reference guide to heart valve prostheses, their important identifying features, their common complications, and modes of failure. It should help in the accurate identification of explanted prosthetic valves and more definitive reports. This accuracy of identification as well as tracking of abnormalities noted will, we hope, permit the identification of new failure modes and the recording of causes of failure of new (or even modified) prosthetic heart valves.     

微机控制的韧带动态力学特性测试系统

本系统是为自动测试人体韧带或类似组织的动态力学特性试验而研制的。在试验时,受控的加载过程和数据采集过程同时进行。系统向韧带试件提供一个快速的匀速可控的拉伸载荷,模拟人体剧烈运动的实况,同时实时采集力和变形的数据。系统还提供对所采集数据的分析手段,从而得到力、变形、应力、应变、弹性模量和变形能等参数之间的关系,并可以图形和文字形式输出。系统亦可将各数据文件转换为其它应用软件包可接受的形式,以便利用标准商品软件包的数据和图象处理能力。系统采用菜单提示的人机对话方式进行监控。     

机械通气气管插管吸痰方法探讨

目的探讨不同的吸痰方法,从而有效地清除气管插管患者的呼吸道分泌物。方法对47例气管插管病人均采用常规法和呛咳法两种方法吸痰,呛咳法要求:吸痰管带负压进入气管插管,随吸痰管插入深度调节负压,适时安全吸痰,适度气道湿化。常规法按临床一般方法进行吸痰。将两种方法吸出的痰量,痰液性状及吸痰前后20min血氧饱和度(SpO2)进行比较。结果两种方法在吸出的痰量,痰液性状和SpO2方面存在着显著差异(P<0.05,P<0.01),呛咳法吸出的痰多且粘稠。吸痰后SpO2明显高于吸痰前和常规法。结论呛咳法吸痰能充分吸出气道深部的痰液,可以有效防止气道阻塞,改善通气功能。     

软骨组织工程中力学因素的影响及应用

力学因素是软骨组织工程中的重要影响因素之一。近年来的研究表明，力学作用可以刺激细胞因子及激素的分泌，改变三维支架上培养的软骨细胞的新陈代谢，从而促进软骨组织的生长与重建。目前已经有诸多关于体外构建软骨组织的报道，但对于其中的力学因素的影响（包括力学因素对软骨细胞增殖的促进及力学刺激的传导机制等）还没有完全认识。就以上几方面做一综述，并简单介绍生物反应器在软骨组织工程中的应用。     

冠状动脉支架抗压缩性能的有限元分析

冠状动脉支架作为经皮穿刺冠状动脉成形术中保持病变血管畅通的核心器件。其对病变动脉壁的支撑作用如何是支架植入术成功的先决条件之一。依据冠脉支架抗压缩性能的实际测试原型，建立起对应的有限元模型，并利用此方法系统地研究了专利支架设计，其扩张尺度的不同和筋的尺寸变化对支架抵抗两平面压缩性能的影响。结果显示，随支架扩张直径的增大，其抵抗两平面压缩的作用减小，增加支架筋的宽度或厚度能够提高支架的抗压缩性能，且这两个方向尺寸的增加对提高抗压缩性能的作用相当。模拟与实验结果一致，表明有限元模拟可以在一定程度上替代支架原型测试工作。     

听骨检测实验装置

目的：探讨对人工听骨赝复物传音功能进行评价的客观方法。方法：用两块圆形的弹性膜来分别代替鼓膜和卵圆窗，两膜之间放置人工听骨，在人工外耳道侧给予纯音刺激，同时记录其声强，在卵圆窗膜处用激光测振仪测量卵圆窗膜的振动速度，通过比较振动速度的大小来比较人工听骨的传音特性。结果：模型“感觉阈曲线”和正常人听阈曲线对比，两者走势基本相同。结论：中耳机械模型是检验人工听骨传音特性并进行人工听骨赝复物客观评价理想的工具之一。     

具有三层管壁结构组织工程血管支架的生物力学性能

目的针对组织工程血管的体内培养技术路线，对所制备的具有三层管壁结构的组织工程血管支架的生物力学性能进行测试，并研究了壁厚对支架力学性能的影响，以保证后续的动物体内移植实验能顺利进行。方法采用涂敷，喷涂．滤沥的方法制备了具有三层管壁结构（多孔PLGA层．致密PU层．多孔PLGA层）的可降解组织工程血管支架，用自制的设备测试了其爆破强度和径向顺应性，并对血管支架进行了缝合强度的测试。结果所制备的厚度为0．295mm-0．432mm的三层结构血管支架的径向顺应性为3．80％／100mmHg-0．57％／100mmHg，爆破强度为160kPa～183kPa，缝合强度为0．63N／针～1．52N／针。结论支架的管壁厚度，尤其是中间层厚度，对支架的力学性能有重要影响。增大壁厚可导致径向顺应性急剧下降，爆破强度和缝合强度线性提高。在所制备的样品中，管壁厚度为0．295mm的支架其综合力学性能最优，可满足血管组织工程体内植入的力学性能要求。     

Tensile Tests of Collagen Fibers Obtained from the Rabbit Patellar Tendon

Tensile properties of collagen fibers of approximately 1 m in diameter were determined using a newly developed micro tensile test system for cells and fine fibrous biological tissues. The test system consists of a thermostatic test chamber, an inverted microscope, micromanipulators, a direct drive linear actuator, a cantilever-type load cell, and a video dimension analyzer (VDA). The fibers were isolated with a mechanical method from collagen fascicles (approximately 300 m in diameter) cut out from the rabbit patellar tendon. The ends of each fiber were attached to the tips of a pair of glass microtubes (15 to 20 m in outer diameter) using a cyanoacrylate adhesive. One of the microtubes was attached to the load cell; the other one was connected to the linear actuator which was utilized to stretch the fiber. Load applied to the fiber was measured with the load cell, while its elongation was determined with the VDA using the images of the edges of the adhesive as markers. Tangent modulus, tensile strength, and strain at failure of the tested fibers were 54.3± 25.1 MPa, 8.5± 2.6 MPa, and 21.6± 3.0%, respectively. These values were much different from those of collagen fascicles (300 m in diameter) cut out from the rabbit patellar tendon and also from those of the bulk patellar tendon (Trans. ASME, J. Biomech. Eng. 121, 124–294, 1999); for example, tensile strength and strain at failure of the fibers were approximately 50 and 200% of those of the fascicles, respectively. These results suggest that the mechanical interactions between fibers and between fibers and ground substances contribute much to the mechanical properties of collagen fascicles and bulk tendons.