Relationship Among MRTA, DXA, and QUS

Dual-energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS) are the accepted modalities for the evaluation of fracture risk in the clinical setting. However, neither method provides a direct measurement of bone mechanics. In this study, we investigated a prototype device, known as a mechanical response tissue analyzer (MRTA), which provides direct mechanical measurements of mechanical properties of bone. A total of 56 healthy volunteers (20 men and 36 women) between the ages of 18 and 83 were recruited. The MRTA was used to measure the cross-sectional bending stiffness (EI) of the ulna bone. Axial speed of sound (SOS) at the ulna bone was determined by QUS; bone mineral content (BMC) and bone mineral density (BMD) were determined by DXA. Correlations, regression analysis, and analyses of variance (ANOVAs) were used to compare the three modalities. These analyses revealed that although there are strong linear relationships among the data collected by the various technologies, the bone properties reflected by MRTA are not fully explained by DXA and QUS. We conclude that the total information conveyed by MRTA measurements is unique. Further research is needed to delineate the different qualities of bone strength that are captured by MRTA, but not by DXA or QUS.     

替牙(牙合)时期前牙反(牙合)矫治中弓丝弯制的探讨

目的　探讨在“2× 4”矫治技术中弓丝弯制的方法及原理。方法　替牙牙合时期前牙反牙合患者 2 4例 ,使用粗弓丝 ,在其弓丝上弯制各种曲形 ,并根据不同错牙合类型 ,处理各种曲与牙齿、带环关系 ,防止出现磨牙旋转移动等异常。结果　 2～ 6个月纠正反牙合 ,2 4例替牙牙合时期反牙合患者得以早期矫治。结论　本方法矫治时间短 ,效果明显 ,操作简单 ,能够达到较为理想的矫治效果     

含钛合金及Ni-Cr合金与瓷粉结合强度的实验研究

目的:研究含钛合金(4%～6%)[熔附HeraCeramJC瓷粉(A1组)和Vita瓷粉(A2组)]、HeraCeram公司的Ni-Cr合金[熔附HeraCeramJC瓷粉(B1组)和Vita瓷粉(B2组)]及西北有色金属厂的Ni-Cr合金[熔附HeraCeramJC瓷粉(C1组)和Vita瓷粉(C2组)]的金-瓷结合强度,为临床工作提供参考。方法:运用三点弯曲法对各组的金-瓷结合强度进行测试,并对金-瓷结合界面进行电镜观察分析。结果:电镜显示各组瓷粉均与金属基体结合紧密,无明显气泡、中间层等缺陷。结合强度:A1组:(41.08±2.98)MPa,B1组:(46.05±3.16)MPa,C1组:(44.04±3.69)Mpa;A2组:(42.29±3.38)MPa,B2组:(42.05±3.26)MPa,C2组:(47.47±2.92)MPa。①HeraCeramJC瓷粉与3种合金结合的结合强度比较:B1>A1(P<0.05);B1>C1、C1>A1(P>0.05)。②Vita瓷粉与3种合金结合的结合强度比较:C2>A2、C2>B2(P<0.05);A2>B2(P>0.05)。结论:本实验表明临床常用的3种非贵合金与瓷粉的金-瓷结合强度均大于ISO所要求的基本值25MPa,但各组间还存在一定差异,为临床工作中根据患者的具体情况选择合适的烤瓷修复基底材料和瓷粉提供实验依据。     

兔胫骨应力性骨折过程中的生物力学研究

目的 探讨兔应力性骨折发生过程中胫骨生物力学指标的变化与应力性骨折发生的关系.方法 将36只雄性大耳白兔随机分为6组,进行跑跳训练,根据制定的分组训练时间,于训练任务完成后的第7、14、21、28、35天分别处死动物.光镜下观察胫骨病理变化;生物力学机上行胫骨三点弯曲生物力学测试,描记载荷-变形曲线,并根据该曲线及相应参数分析胫骨生物力学性能.结果 实验组动物训练第2、3、4、5周后最大载荷与对照组动物相比之差异均有统计学意义(P＜0.05).实验组动物第1、2、3、4、5周后载荷与变形量之比与对照组动物相比之差异均有统计学意义(P＜0.05),最大应力和弹性模量与对照组动物相比之差异则均无统计学意义(P＞0.05).结论 应力性骨折的发生是一个由骨细胞直接参与的破骨细胞性重吸收大于成骨细胞性骨形成的生理过程;胫骨结构力学性能的改变是由胶原纤维紊乱、骨皮质厚度降低等所造成,从而导致应力性骨折的发生.     

Modelling HA protein-mediated interaction between an influenza virus and a healthy cell: pre-fusion membrane deformation.

We present a mathematical model for pre-fusion interaction between an influenza virus and a healthy cell. Our model describes the role played by hemagglutinin (HA) protein clusters in bringing the viral membrane into close contact with the host cell membrane as a first step of the fusion process between the two membranes. The viral membrane is modelled as a lipid bilayer with bending rigidity. Using the calculus of variations, we compute the deformation of the viral membrane under the influence of HA protein clusters. Our numerical results support the hypothesis of dimple formation in the fusion site proposed in the literature. The asymmetric nature of the protein molecules due to various reasons such as tilting is the primary cause for the dimple formation. We discuss the effects of spontaneous curvature, the protein cluster radius, fusion-site size and the bending moment exerted by the protein cluster. We also examine the effects of membrane tension and the presence of a host cell on the dimple shape. Our results support previous experimental observations.     

PVA／PAA水凝胶纤维的电刺激响应性能

以过硫酸胺为引发剂,在PVA水溶液中原位聚合丙烯酸单体,得到的PVA／PAA混合水溶液在凝固浴硫酸胺饱和水溶液中纺丝制备了物理缠结和氢固定网络形式的PVA／PAA水凝胶纤维。该纤维于NaCl溶液中在直流电场作用下具有电流－刺激敏感性,表现为溶胀、收缩、弯曲行为。纤维的弯曲速度和最大弯曲度随电场强度和凝胶网络中PAA含量的增加而增大,随电解质溶液离子强度的变化出现临界最大值。纤维向负极弯曲的过程中,在电场下自由离子和反庆子迁移引起的渗透压主导作用,弯曲过程主要是溶胀弯曲;向正极弯曲过程中,由于电化学反应和电场作用下产生的PH梯度导致凝胶网络构像变化主导作用,弯曲主要是收缩弯曲;弯曲由负极向正极转化过程中,两种机理对弯曲的影响相对平衡。     

运动锻炼对长骨截面几何形态和力学性质的影响

本文通过成年大耳白兔６周的大强度跑跳运动，对胫骨全骨进行三点抗弯和扭转试验，发现大强度运动可明显提高胫骨的抗弯和抗扭强度，胫骨的截面内外长短径、轴惯性矩、抗弯和抗扭截面模量明显加大，使截面更加合理。     

ANSYS疲劳分析在接骨板选型评估中的应用

目的 通过对比股骨远端接骨板中A型、B型锁定加压接骨板(locking compression plate, LCP)的疲劳强度,为测试其弯曲强度及疲劳性能时对接骨板选型提供理论评估方法。方法 通过对不同类型接骨板进行弯曲强度性能测试与疲劳性能测试,再结合ANSYS Workbench对接骨板总变形、von Mises应力及疲劳使用寿命进行有限元分析。结果 A型接骨板疲劳强度比B型接骨板高30.7%,A型接骨板应力比B型接骨板要低,A型接骨板最低疲劳使用寿命比B型接骨板要高17%。结论 A型接骨板的疲劳性能比B型接骨板良好,故A型接骨板的失效可能性比B型接骨板的可能性要低。研究结果为测试新研发的两种接骨板各种性能时对不同接骨板选型辅助提供参考。     

具有一般截面形状的平面复合曲梁正应力分析

分析工程中对于由多种材料组合而成的一般截面形状平面曲梁在载荷作用下的强度问题.在截面形状不变的假设基础上,导出了其正应力的计算公式.作为特殊情况,该梁在对称弯曲时的相应公式也可以从上述公式得到,最后给出了计算实例.     

Microstructure and Mechanical Behavior of Porous Ti–6Al–4V Processed by Spherical Powder Sintering

Reducing the stiffness of titanium is an important issue to improve the behavior of this material when working together with bone, which can be achieved by generating a porous structure. The aim of this research was to analyze the porosity and mechanical behavior of Ti–6Al–4V porous samples developed by spherical powder sintering. Four different microsphere sizes were sintered at temperatures ranging from 1300 to 1400 °C for 2, 4 and 8 h. An open, interconnected porosity was obtained, with mean pore sizes ranging from 54.6 to 140 µm. The stiffness of the samples diminished by as much as 40% when compared to that of solid material and the mechanical properties were affected mainly by powder particles size. Bending strengths ranging from 48 to 320 MPa and compressive strengths from 51 to 255 MPa were obtained.