两种术式治疗老年椎体骨质疏松性压缩骨折的循证思考

椎体成形术(PVP)与球囊扩张椎体后凸成形术(PKP)是目前临床上常用的治疗老年椎体骨质疏松性压缩骨折有效方法。针对两者的优缺点,利用比较治疗学相关原理和方法,从其生物力学、适应证、疗效、并发症及费用等方面进行比较,以获得启示,为临床实践提供指导。     

复杂胫骨平台骨折处理的临床决策

复杂胫骨平台骨折处理相当困难,治疗上存在着一系列矛盾,准确的骨折分型和软组织损伤情况评估,合理的手术入路和手术时机选择,重视复位、固定方式和方法及软组织保护,双下肢同时消毒包扎为术中快速的体位转换提供了方便,一系列临床决策极大地提高了复杂胫骨平台骨折的治疗水平。     

Educational struggles and political community in South Africa

Democracy is often said to rest on some form of deeper argument, some self-understanding amongst people as belonging to a common political community. This paper explores this issue in the situation of South Africa. The policies of Apartheid have left a legacy of a morally fractured society with little by way of a shared moral discourse, and the paper raises the question of whether the concepts of democracy and community which emerged out of educational struggles in South Africa might provide a basis for the development of a shared moral discourse. The answer provided in the paper is that, although such concepts cannot provide the basis for democracy at a national level, they do provide some hints of how schools might contribute to the emergence of a shared moral discourse, and, thus, the starting point for building a unified political community.     

PFNA、DHS与FHR治疗老年股骨粗隆间骨折的疗效比较

比较股骨近端防旋髓内钉（PFNA）、动力髋螺钉（DHS）与人工股骨头置换术（FHR）治疗老年股骨粗隆间骨折的临床疗效。对2005年6月～2012年6月收治且获得随访的65例老年股骨粗隆间骨折患者进行回顾性分析,其中男27例,女38例。根据治疗方式不同分为三组：PFNA 组21例,DHS 组22例,FHR 组22例。比较三组患者手术时间、术中出血量、术后引流量、负重时间、术后并发症发生情况及术后3个月、6个月、12个月髋关节 Harris 评分等。结果65例患者均获随访12个月～24个月（平均12．0个月＆#177;3．4个月）,三种方法中,手术时间及负重时间比较,FHR 组时间最短,差异有统计学意义（P＜0．05）;术中出血量比较,DHS 组最少,差异有统计学意义（P＜0．05）;髋关节功能比较,FHR 组优于PFNA 组及 DHS 组,差异有统计学意义（P＜0．05）;术后引流量及术后并发症三组比较差异无统计学意义（P ＞0．05）。因此,对老年股骨粗隆间骨折患者,采用 FHR 手术可使患者术后早期下床,改善患者生活质量。     

Plastic stability of bimetals composed of Ti-based metallic glass composite and pure titanium

The plastic stability of bimetals composed of a Ti-based metallic glass composite (MGC) and a pure titanium (PT) under tension has been investigated. The results reveal that the plastic stability of the MGC/PT bimetal is strongly dependent on the thickness fraction of the MGC: when the thickness fraction of the MGC decreases to a critical value, a homogeneous plastic deformation occurs in the MGC/PT bimetals, i.e. the strain localization and necking of the MGC is effectively suppressed. This unique phenomenon is explained using the normalized strain-hardening rate, and the quantitative relationship between the normalized strain-hardening rate of the MGC/PT bimetals and the thickness fraction of the MGC is thereby established.     

Critical Poisson’s ratio between toughness and brittleness

We have a new understanding on a unified fracture criterion based on two kinds of strain energy density. A definite expression which is a function of Poisson’s ratio to describe a crucial parameter in the unified fracture criterion is derived. The critical value of Poisson’s ratio between brittle and ductile materials can be derived as 2/7 which is verified by experimental data. Besides, the effect of Poisson’s ratio on the fracture loci in stress spaces is studied using unified fracture criterion. It is found that the decrease in Poisson’s ratio increases the asymmetry of fracture loci between tensile stress states and compressive stress states in principal stress spaces and between Lode parameters are 1 and ?1 in deviatoric-stress spaces. In addition, stress triaxiality has a great effect on the fracture behaviour with different Poisson’s ratios.     

Discontinuous cracking of TiN films on a steel substrate induced by an adhesive interlayer

ABSTRACT

The basic mechanisms governing the process of cracking of single-layer brittle films have been extensively explored through both simulations and experiments. However, the role that an adhesive interlayer plays in the cracking of the overlying brittle film remains unclear. By performing three-point bending experiments, we observed that the insertion of a 100?nm thick Ti interlayer changed the cracking behaviour of TiN films from a continuous pattern to a discontinuous pattern. The slight change in the microstructure of the film and the increase in film thickness arising from the addition of the Ti interlayer are unlikely to cause the observed cracking morphology. The combination of the different interface between the Ti and the steel substrate and the fracture of the Ti interlayer are responsible for the transition in the TiN film cracking morphologies.     

Behaviour of helium in UO2 single crystals: a transmission electron microscopy investigation

We have found that the structure of an Al-Ni-Co decagonal quasicrystal, which shows a diffraction pattern with many superlattice reflections (called a 'type I superlattice'), can be described as an ordered arrangement of two kinds of atomic columnar cluster with different orientations of their pentagonal symmetry. The fundamental lattice, which is constructed by connecting the clusters, is a rhombic quasiperiodic lattice with a bond length of about 2nm. The two kinds of cluster are placed at the lattice points in a definite manner such that the two connected clusters have different orientations.     

Scale-dependent fracture mode in Cu–Ni laminate composites

Fracture behavior of Cu–Ni laminate composites has been investigated by tensile testing. It was found that as the individual layer thickness decreases from 100 to 20 nm, the resultant fracture angle of the Cu–Ni laminate changes from 72° to 50°. Cross-sectional observations reveal that the fracture of the Ni layers transforms from opening to shear mode as the layer thickness decreases while that of the Cu layers keeps shear mode. Competition mechanisms were proposed to understand the variation in fracture mode of the metallic laminate composites associated with length scale.     

Influence of the restored work-hardening rate on ductility studied by X-ray computed tomography

Abstract

Void growth and coalescence in a model material containing an artificial three-dimensional void array (the estimated local void volume fraction was 1.1%) were investigated by X-ray computed tomography (=XCT). The initially tapered cylindrical voids became elongated along the principal straining direction by some amount of tensile plastic deformation, and then the work-hardening capacity in the intervoid matrix was restored by an intermediate annealing. The annealed model material was pulled in tension all the way up to fracture to see if the existing void coalescence models can predict the void coalescence strain.