骨延长的骨愈合原理

骨延长愈合与骨折愈合等多种多样的骨修复现象可能具有相同的细胞生物学基础,这个理论称为骨修复一元论.血管内皮细胞是启动骨修复的感受器,破骨细胞通过分泌骨形态发生蛋白(BMP)启动骨特异性修复.骨折间隙间断性的力学脉冲通过血管内皮细胞不断地转化为骨修复的生物学脉冲.在微损伤条件下,骨修复具有放大效应.保护下负重和功能锻炼是下肢骨骼延长术后的重要原则.     

骨折术后运动康复安全评定的几点体会

骨科学以运动系统疾病为对象,功能康复是骨科疾病治疗的最终目的。骨科治疗与康复是不可分割的整体。但骨科治疗与康复往往未能很好地结合,探索将两个学科有机地结合起来的安全运动康复评定的几点体会,制定出合理的运动处方,为较大限度地提高骨折疾病的功能疗效。     

Thermal shock resistance of brittle ceramic materials with embedded elliptical cracks

An analytical model is established for the prediction of the thermal shock resistance of a ceramic plate with an embedded elliptical crack with ideal thermal insulation. The thermal stress intensity factors at the crack fronts are formulated by fitting the thermal stress to a polynomial form in an un-cracked plate. The thermal shock resistance of sapphire ceramic is evaluated as an example. In addition, the numerical solution of thermal shock resistance suitable for practical engineering applications is provided. The model developed applies to any brittle material in high temperature applications.     

‘Crossing culture’: a multi‐method enquiry into consumer behaviour and the experience of cultural transition

Visitors, travellers and migrants have a range of reactions to ‘crossing culture’, ie moving from one cultural environment to another. This paper reports a two‐stage multi‐method study that examines how visitors' consumer behaviour and use of material possessions influence resolution of cultural fracture during periods of cultural transition. The research consisted of a quantitative survey (n = 598) and a qualitative ethnoconsumerist study of visitors to the UK. Analysis of the survey data shows that nationality is a poor indicator of crossing‐culture experiences. A Six Typology Model of Cultural Fracture identified six cluster groups using combinations of three types of cultural fracture experience: symbolic fracture, emotional fracture and functional fracture. The six clusters vary by consumer behaviour and possession use. The ethnoconsumerist study illustrates that consumer‐related activities and possession used together provide an important resource that visitors can use to make sense of crossing‐culture experiences. Product categories, retail formats and shopping conventions are also implicated in experiences of cultural fracture to varying degrees. The paper concludes by considering the limitations of importing a priori assumptions regarding nationality and ethnic differences in cross‐cultural consumer research, and discusses some of the potential benefits of multi‐method research in this context. Copyright © 2004 Henry Stewart Publications.     

单纯胸椎骨折合并迟发性血胸的诊治及临床特点

为了探讨单纯胸椎骨折合并迟发性血胸的临床特点及诊治方法,回顾分析了11例单纯胸椎骨折合并迟发性血胸患者的诊疗情况并总结其临床特点。结果显示,所有病例均获得明确诊断,10例通过胸穿治疗获得治愈,1例行割胸探查术。提示单纯胸椎骨折合并迟发性血胸临床较少见,伤后体温逐渐升高、胸闷、氧分压下降或剧烈咳嗽、翻身拍背后突然出现呼吸困难、发绀、大汗常为其临床特点,大多可通过保守治疗获得痊愈。     

椎体成形术和球囊扩张椎体后凸成形术治疗骨质疏松性椎体压缩骨折的对比研究

为对比分析椎体成形术（PVP）与球囊扩张椎体后凸成形术（PKP）治疗骨质疏松性椎体压缩骨折的临床疗效。共治疗患者45例。PVP25例,PKP20例。所有患者术后疼痛均明显减轻或消失,PVP组与PKP组两组相比,术后的伤椎及相邻椎间隙高度、脊柱后凸Cobb角及ODI评分差异有统计学意义（P〈0．05）。PKP能够更好的恢复骨折椎体的高度,矫正脊柱后凸畸形,改善脊柱功能,明显减少骨水泥渗漏,临床效果较PVP更为满意。     

Ductile fracture mechanism in fine-grained magnesium alloy

The ductile fracture mechanism in a fine-grained magnesium alloy has been investigated by transmission electron microscopy-focused ion beam techniques. In coarse-grained or conventional magnesium alloys, twins form at the very beginning of the deformation process, and crack propagation occurs through the twin boundaries. However, in the alloy used in this study, subgrain structures were found instead of twins at the crack tip. Nanoscale twins formed subsequently owing to large stress in the crack propagation route. The fine-grained alloys showed high fracture toughness resulting from resistance to the twins at the beginning of the deformation.     

Flaw tolerance promoted by dissipative deformation mechanisms between material building blocks

Novel high-performance composite materials often draw inspiration from natural materials such as bone or mollusc shells. A prime feature of such composites is that they are, like their natural counterparts, quasibrittle. They are tolerant to material flaws up to a certain characteristic flaw-tolerant size scale, exhibiting high strength and toughness, but start to behave in a brittle manner when sufficiently large flaws are present. Here, we establish that better flaw tolerance can be achieved by maximizing fracture toughness relative to the maximum elastic energy available in the material, and we demonstrate this concept with simple two-dimensional coarse-grained simulations where the transition from brittle to quasibrittle behaviour is examined.     

Deformation and failure of a heterogeneous high explosive

The deformation and failure of the pristine PBX 9501 high explosive are studied experimentally by combining Brazilian disk compression with the digital image correlation (DIC) technique. The Brazilian disk specimen was loaded by a pair of compressive forces across the diameter. The full-field deformation on the surface of the disk, during the loading process, was obtained using DIC on a series of random speckle images acquired during the test. In this series of experiments, we focused on the effect of temperature while keeping the loading speed quasi-static. Tests were conducted under three different temperatures, ?15°C, 23°C, and 50°C. For all testing conditions, it was observed that as the applied load reaches maximum, localized deformation starts at the two regions near the loading points. The localized deformation then proceeds along an irregular path toward the center of the specimen and coalesces. Finally, deformation of the Brazilian disk subjected to cyclic compressive load at ambient temperature was also measured and studied.