关键词： 阵发性房颤   射频消融术   电活动   机械运动   血流动力学功能   立体心电图   应变率成像  

摘要： 心房在心脏中扮演着通道、储存器、助力泵三大功能,是心房实现血流动力学功能的重要组成部分,目前多数情况单独采用超声心动图评价心房的血流动力学功能,不能全面评价心房的电机械血流动力学。另外,随着心房颤动患者的增多,射频消融治疗心房颤动已成为一线治疗方法,临床上更需要全面评估心房的功能,为房颤患者术前准备和术后随访服务。本研究运用立体心电图结合超声心动图同步综合评价两组不同年龄健康人心房的电,机械,血流动力学功能,对比两组人群的心房情况,并且将对心房评价较好的指标进一步应用于房颤消融术前后的心房功能改善评估。将研究对象分为两组,第一组:选择20-30岁和50-60岁健康志愿者各30名,全部使用3D-ECG立体心电图仪、彩色多普勒超声心动图仪同步记录立体心电图、超声心动图。第二组:阵发性房颤患者共20例,年龄为40-70岁。同期入选20例接受体检的健康人员作为对照,且与阵发性房颤患者在年龄,性别,血压方面具有可比性。使用3D-ECG立体心电图仪、彩色多普勒超声心动图仪、射频消融仪、三维标测导航系统、心脏程序刺激仪、数字减影X线机、多通道电生理记录仪以及相关的射频消融导管、电极等器械。对所有患者(检查时为窦性心律)和对照人群应用3D-ECG立体心电图仪、彩色多普勒超声心动图仪进行详细检查。阵发性房颤患者进行射频消融术,并且在术后一、三、六月进行来院随访,复查3D-ECG立体心电图和彩色多普勒超声心动图。数据采用SPSS 19.0进行统计学处理,所有计量资料均以x±s表示,将健康人群作为一个整体采用pearson直线相关分析各测值之间的关系,两组间参数比较采用独立样本的t检验。以p<0.05作为差异显著性界限。本组实验的结果为:第一组:将全部志愿者作为整体进行统计显示:心房的p波向量环与容积参数均在正常范围,应变率成像分析发现心房左右房壁及间隔之间的机械运动不完全同步。相关性分析发现;心房的传导时间及振幅与心房的容积正相关,应变与心房容积相关,心房p振幅和机械运动无明显相关性,心房的收缩应变a与左右心房的总排空量及收缩排空量无相关。30-40岁与50-60岁健康群体间心房电活动和机械运动参数具有显著差异,血流动力学功能参数比较无显著区别。表明随着年龄的增加,健康人群的心房电活动,机械运动发生了改变,提示年龄增加心房壁基质出现改变,这将为心房发生心律失常提供了基础。血流动力学功能无明显改变,说明血流动力学功能在没有其他诱因下可以保持相对完整。第二组:房颤患者与对照群体间基线资料比较有显著差异,发现阵发性房颤p波间期延长,振幅增加,左房较对照组明显扩大,心房扩大伴随着心房收缩能力的减少,表现为应变率a值升高。同时心房顺应性降低:表现为应变率s下降,应变率e值升高。说明心房收缩、储存和管道功能相对于对照组均出现明显区别。术后一个月心房参数:相比房颤患者的基线心房心电图、超声心电图参数,术后心房传导、机械运动和形态开始改善。术后三个月心房参数:房颤患者的传导、机械运动和形态均出现明显改善,p波间期改善,振幅降低,左房、右房直径改善,容积改善。心房泵功能和顺应性改善,应变率a峰降低,s峰增加,e波下降。术后六个月心房参数:消融组p波间期和振幅改善更明显,左房、右房直径和容积进一步改善。心房泵功能和顺应性进一步改善,表现为应变率a波,s波,e波进一步明显改善。这表明心房的形态进行再重构,大多数收缩参数相比对照组得到了改善。研究发现机械参数较电活动和容积改善较早教明显,因此可以作为评价心房功能早期恢复较敏感的评价指标。综合考虑心房的情况,指标改善同健康对照、群体相比仍不理想,反映房颤患者的心房结构出现了持续性、不可逆的改变。实验结果表明:1.不同年龄组相比,年龄较大的健康人群的心房电活动和机械运动发生了改变,血流动力学功能无明显改变。2.联合立体心电图与心脏多普勒是同步评价心房的电传导、机械运动和血流动力学功能状况的简单方便工具,能更直观的表现心脏整体情况。3.本研究发现应用心电图联合应变率成像发现房颤患者消融术后心房电活动与心房机械功能出现了重构逆转。4.机械参数可以作为评价心房功能早期恢复较敏感的评价指标。

关键词： CROSSLINKED polymers   MOLECULAR dynamics   DEFORMATIONS (Mechanics)   COLLOIDS   BIOMATERIALS   MOLECULAR structure  

摘要： Networks combining physical and covalent chemical cross-links can exhibit a large amount of dissipated inelastic energy along with high stretchability during deformation. We present our analysis of the influence of the extent of covalent cross-linking on the inelasticity of hydrogels. Four model networks, which are similar in structure but strongly differ in elasticity, have been studied. The aim was the identification of a key structural factor responsible for observing a hysteresis or an elastic deformation. In the employed molecular dynamics study this factor is derived from the underlying structure of each particular hydrogel network. Several structural characteristics have been investigated like the extent of damage to the network, chains sliding, and the specific properties of load-bearing chains. By means of such a key factor, one can predict the deformation behavior (hysteresis or elasticity) of some material, provided a precise description of its structure exists and it resembles any of the four types of a network. The results can be applied in the design of bio-inspired materials with tailored properties.

关键词： zinc oxide   nanoindentation   residual stress   nanoscratching   molecular dynamics  

摘要： Molecular dynamics is used to simulate the mechanical behaviour of zinc oxide under nanoscratching and nanoindentation. The effects of indenter speed and substrate temperature on the structure-phase formation, slip vector, radial distribution function, and residual stresses are investigated. Simulation results show that the dislocation loops nucleate and propagate, forming a body-centred tetragonal lattice structure along the slip direction due to high local stress. Furthermore, the dislocation loops nucleate and propagate due to the resolved shear stress along the 45 degrees slip direction under nanoscratching. The average mean biaxial stress and the normal stress of the O layers are -9.35 and -4.36 GPa, respectively, and those of the Zn layers are -0.80 and -0.30 GPa, respectively. This may be attributed to the energetic O atoms, with which unstable atoms have high activation.

关键词： Alloys   Microstructure   Mechanical properties   Heat treatment  

摘要： The precipitation kinetics and the mechanical behavior in a solution treated and aged dual phase stainless steel (DSS) are investigated. X-ray diffraction, transmission and scanning electron microscopy techniques are used to characterize the microstructure and to identify its constituents. The precipitation kinetics analysis shows that the ferrite to sigma phase transformation follows the modified Johnson Mehl Avrami (JMA) model containing an impingement parameter c that is adjusted to 0.3. Activation energies calculation leads to conclude that interface reaction is the main mechanism that controls the sigma phase formation. Detailed analysis of the extent of the different tensile deformation domains reveals the significant contribution of both sigma phase particles and dislocation accumulation to the strain hardening of the material. (C) 2014 Elsevier B.V. All rights reserved.

关键词： EPOXY resins   LIGHT -- Scattering   AMINES   MATERIALS -- Mechanical properties   CHEMICAL kinetics   IN situ microanalysis  

摘要： The cure kinetics of epoxy cured with an amine hardener is investigated using a combination of light scattering techniques. Concurrent Raman and Brillouin scattering are used to monitor the formation of epoxy networks over time in terms of both the structural connectivity of the network and the evolution of chemical bonding configurations. The relationship between the elastic properties of the network and the degree of cure was found to depend on the cure temperature and the resinhardener stoichiometry. A numerical model was created to determine the degree of cure and elastic modulus as a function of time and cure conditions. Accordingly, the modulus of the epoxy comprises two contributions: one directly related to the concentration of covalent bonds that form and another one due to nonbonding interactions that arise as the network relaxes into an optimally packed configuration.

关键词： Cancer arylthioindole QSAR tubulin G-QSAR inhibitor  

摘要： Background: A number of microtubule disassembly blocking agents and inhibitors of tubulin polymerization have been elements of great interest in anti-cancer therapy, some of them even entering into the clinical trials. One such class of tubulin assembly inhibitors is of arylthioindole derivatives which results in effective microtubule disorganization responsible for cell apoptosis by interacting with the colchicine binding site of the beta-unit of tubulin close to the interface with the a unit. We modelled the human tubulin beta unit (chain D) protein and performed docking studies to elucidate the detailed binding mode of actions associated with their inhibition. The activity enhancing structural aspects were evaluated using a fragment-based Group QSAR (G-QSAR) model and was validated statistically to determine its robustness. A combinatorial library was generated keeping the arylthioindole moiety as the template and their activities were predicted. Results: The G-QSAR model obtained was statistically significant with r2 value of 0.85, cross validated correlation coefficient q2 value of 0.71 and pred_r2 (r2 value for test set) value of 0.89. A high F test value of 65.76 suggests robustness of the model. Screening of the combinatorial library on the basis of predicted activity values yielded two compounds HPI (predicted pIC50 = 6.042) and MSI (predicted pIC50 = 6.001) whose interactions with the D chain of modelled human tubulin protein were evaluated in detail. A toxicity evaluation resulted in MSI being less toxic in comparison to HPI. Conclusions: The study provides an insight into the crucial structural requirements and the necessary chemical substitutions required for the arylthioindole moiety to exhibit enhanced inhibitory activity against human tubulin. The two reported compounds HPI and MSI showed promising anti cancer activities and thus can be considered as potent leads against cancer. The toxicity evaluation of these compounds suggests that MSI is a promis

关键词： Mechanochemistry   Solid state reactions   Critical loading conditions   Kinetics analysis   Rietveld method  

摘要： We have addressed a new study by mechanical alloying on the nominally immiscible Cu50Fe50 system with the aim of relating the solid state transformation process, with formation of a disordered unstable solid solution having the face centered cubic habit, to parameters reflecting the impulsive, discontinuous nature of the process. The milling set-up, tools and powder were adjusted in order to ensure completely anelastic hits. Phase analysis, structure and microstructure parameters of such powder system have been followed accurately in the course of the kinetics by X-ray Diffraction using the Rietveld method. The experimental kinetics data points of the amount of transformed solid solution show a typical sigmoidal behavior. It was assumed that dissolution only occurs in the volumes of material that have undergone the necessary critical loading conditions, which is accounted by a discrete series expansion. The mass fraction effectively processed at each collision can be regarded as an apparent rate constant for the microstructural refinement and phase transformation processes. Analysis of model curves fitting the experimental data suggests that it takes up an average of 6 impacts of coupled powder particles to drive the system to the new unstable nano-crystalline state. (C) 2013 Elsevier B.V. All rights reserved.

关键词： 安全操作   动力机械   操作工   规程   内燃机   水箱盖  

摘要： 1内燃机摇车启动时，应五指并拢握紧摇柄，从下向上提动，禁止从上向下硬压或连续摇转。用手拉绳启动时，不准将绳绕在手上。 2．内燃机需打开水箱盖时，应防止蒸汽或水喷出烫伤人。

关键词： 机械活化淀粉   丙烯酰胺   丙烯酸   反相乳液   接枝共聚   反应动力学  

摘要： 淀粉接枝共聚物是一种新型功能性材料。以机械活化淀粉（mSt）为接枝母体,丙烯酰胺（AM）和丙烯酸（AA）为接枝单体,研究了在淀粉/单体/乳化剂/油/水反相乳液体系中引发机械活化淀粉与丙烯酰胺/丙烯酸接枝共聚反应的动力学,考察了引发剂浓度[I]、单体浓度[M]、淀粉乳浓度[mSt]和乳化剂浓度[E]等因素对表观聚合速率Rp的影响。结果表明,在本文考察范围内动力学关系式为Rp∝[mSt]1.5[M]1.7[I]0.9[E]0.92,单体浓度和淀粉乳液浓度对聚合反应速率影响显著,聚合反应速率随体系温度升高而加快,在45~60℃范围内,聚合反应的表观活化能为89.5kJ/mol,聚合过程中单基终止与双基终止反应同时存在。

关键词： 多体动力学   机械工程   端点振动  

摘要： 本文研究多动体力学在机械工程领域的应用,运用多体动力学的模型建立作为基础,主要包含本模型坐标系的建立、模型元素、动力学方程和管理体系的分析等。另外运用了在柔性机械臂振动控制、工业机器人动力分析中多体动力学的应用的实例来说明了它如何应用于机械工程领域中的高精度制造与位置跟随。