骨陷窝-微管代谢和生理功能的研究应用与进展

背景:个体在进行生理活动时,可以引起骨细胞周围间隙内液体的流动,这种液体流动对骨细胞代谢和发挥机械信号转导功能十分重要。目的:总结近年来关于骨结构和生理功能的研究进展,进一步阐明生理性负荷影响骨组织的机制。方法:应用计算机检索Pub Med数据库检索2009年1月至2015年12月关于骨微结构,骨代谢和骨细胞机械信号转导相关的文章,检索词为"osteocyte;mechanical load,permeability,lacunarcanalicularsystem,interstitialfluid flow,mechanotransduction,signaling pathways",通过对资料初审,排除较旧或者研究方法错误的文献报道,共搜集到符合纳入标准的文献40篇。结果与结论:骨组织可以迅速适应机械环境的变化,保证在骨功能性活动区有足够的骨量,即通过感受受力状态的改变,调节骨的吸收和形成,这和骨细胞的生理特点密切相关。骨细胞位于矿化的骨基质中,周围独特的微环境使其可以感受个体生理性活动产生的机械刺激,并将这种机械信号转化为化学信号进而调节骨的吸收或形成。当生理性机械负荷作用于骨组织时,会引起骨陷窝-微管系统内液体流动,即压力诱导性液体流动,这种液体运动通过2种机制影响骨细胞:调节骨细胞代谢,参与骨细胞机械信号转导过程。总之,生理性的机械负荷对于维持骨健康和调节骨适应有重要意义。

跳跃冲击诱导核因子κB对骨质代谢的调节机制及效果分析

背景:骨质疏松症是近年来致力于预防医学的一个重要议题,运动介入对于骨质健康扮演积极的关键角色。但不同运动类型对个体骨质含量及骨密度的影响存有显著差异,厘清这些差异的原因及其相关机制很有必要。目的:针对跳跃冲击诱发核因子κB信号通路变化从而影响骨质代谢的调控机制进行分析,从而为运动介入提高骨质代谢效率及预防骨质疏松等代谢性疾病提供理论基础及实践参考。方法:利用ELSEVIER,Springer,EBSCO,CNKI,万方数据、维普中文期刊服务平台以及台湾学术文献等数据库;以“跳跃冲击、发炎反应、跳跃运动、机械性负荷、骨质疏松症、骨代谢、骨重塑、骨质密度、运动训练、抗阻训练、冲击性训练、核因子-κB”及对应英文词组等搜寻相关文献,检索2018年12月前发表的文献。结果与结论:跳跃冲击动作能引起强烈机械性负荷刺激,它对整体腿部骨骼及受力较显著区域的骨质含量及骨密度皆有明显效果;跳跃冲击能提高身体内核因子κB的活化阈值,冲击载荷的地面反作用力对肌肉与骨骼所产生的损伤而诱发核因子κB的活化,不仅促使体内炎症反应,亦促使组织新生,以适应外在冲击变化;骨质代谢与炎症反应两者间是否通过核因子κB作为重要连结因子,将对骨疾病治疗产生重大影响,亦可借运动对核因子κB所产生的适应性,降低核因子κB于体内的活化,达到降低炎症反应与骨吸收功能。提示足够强度的跳跃冲击对局部骨骼产生显着的骨生成促进作用,除了增加局部骨密度与骨质含量,同时也会增进骨骼组织的生物力学特性;跳跃冲击诱发炎症反应可能与核因子κB信号通路高度相关,并借此影响单核球的分化与细胞融合,从而操控运动过程中的骨代谢走向。

Thermal-mechanical properties of short carbon fiber reinforced geopolymer matrix composites subjected to thermal load

Short carbon fiber preform reinforced geopolymer composites containing different contents of α-Al2O3 filler （Cr（a-Al2O3）/geopolymer composites） were fabricated, and the effects of heat treatment temperatures up to 1 200 ℃ on the thermal-mechanical properties were studied. The results show that the thermal shrinkage in the direction perpendicular to the lamination of the composites gradually increases with the increase of the heat treatment temperatures from room temperature （25 ℃ ） to 1000 ℃. However, the composites in the direction parallel to the lamination show an expansion behavior. Beyond 1 000℃, in the two directions the composites exhibit a larger degree of shrinkage due to the densification and crystallization. The mechanical properties of the composites show the minimum values in the temperature range from 600 to 800 ℃ as the hydration water of geopolymer matrix is lost. The addition of α-Al2O3 particle filler into the composites clearly increases the onset crystalline temperature of leucite （KAlSi2O6） from the amorphous geopolymer matrix. In addition, the addition of α-Al2O3 particles into the composites can not only help to keep volume stable at high temperatures but also effectively improve the mechanical properties of the composites subjected to thermal load to a certain extent. The main toughening mechanisms of the composites subjected to thermal load are attributed to fiber pulling-out.

Morphological Evolution of a Void under Thermal and Mechanical Loads

A model for the morphological evolution of a void under thermal and mechanical loads is established, and the thermodynamics potential of the model is given based on energy principle. Thus, the path and the bifurcation condition of the morphological evolution of the void are described, which gives some insight into the reliability of the interconnect under combined thermal and mechanical loads.

Two coplanar cracks in a functionally graded piezoelectric material strip under mechanical and transient thermal loadings

In this paper,the fracture problem of a functionally graded piezoelectric material strip(FGPM strip) containing two coplanar cracks perpendicular to its boundaries is considered.The problem is solved for an FGPM strip that is suddenly heated from the bottom surface under static mechanical loading.The top surface is maintained at the initial temperature.The crack faces are supposed to be completely insulated.Material properties are assumed to be exponentially dependent on the distance from the bottom surface.By using the Laplace and Fourier transforms,the thermoelectromechanical fracture problem is reduced to a set of singular integral equations,which are solved numerically.The stress intensity factors for the cases of the two embedded cracks,two edge cracks,and an embedded crack and an edge crack are computed and presented as a function of the normalized time,the nonhomogeneous and geometric parameters.

Influence of Intertube Additional Atoms on Sliding Behaviors of Double-Walled Carbon Nanotube

The effects of intertube additional atoms on （DWCNTs） are investigated using molecular dynamics （MD） the sliding behaviors of double-walled carbon nanotubes simulation method. The interaction between carbon atoms is modeled using the second-generation reactive empirical bond-order potential coupled with the Lennard-Jones potential. The simulations indicate that intertube additional atoms of DWCNT can significantly enhance the load transfer between neighboring tubes of DWCNT. The improvement in load transfer is guaranteed by the addition of intertube atoms which are covalently bonded to the inner and outer tubes of DWCNT. The results also show that the sliding behaviors of DWCNT are strongly dependent of additional atom numbers. The results presented here demonstrate that the superior mechanical properties of DWCNT can be realized by controlling intertube coupling. The general conclusions derived from this work may be of importance in devising high-performance CNT composites.