Behavior of amorphous materials under hydrostatic pressures: A molecular dynamics simulation study

The atomic structural behavior of amorphous pure Ni under hydrostatic pressures has been investigated through a molecular dynamics simulation study based on a semi-empirical interatomic potential (MEAM). It was observed that the amorphous material crystallizes under hydrostatic compressive pressure but forms nanovoids under hydrostatic tensile pressure at room temperature. These results could be explained by the volume change effect on the nucleation energy barrier during crystallization. Consistent with this explanation, stress induced increase in the energy level (decrease of energy barrier) is proposed as the main reason for the mechanically driven nanocrystallization of amorphous materials.     

关于利用金属磁记忆方法进行应力定量化评价问题的讨论

对利用金属磁记忆检测技术在应力评价方面的研究现状进行总结,分析磁记忆检测原理和磁机械效应理论之间、应力磁化反转现象和接近定律之间的关系,认为金属磁记忆效应,是稳恒弱磁场激励下的一种力磁效应,符合磁机械效应理论的相关描述和结论。指出弱磁激励情况下力磁关系的非线性、以及检测结果易受众多干扰因素影响的特点,给利用磁记忆检测技术进行应力定量化评价带来实质性困难。磁记忆检测技术的优势,应在研究铁磁材料塑性阶段濒临损伤前的微观缺陷和信号异变的复杂关系以及应力集中和损伤综合作用下异变磁信号的快速和有效识别等方面。     

Potential of Long Non-Coding RNAs in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the leading cause of visual impairment in the aging population with poorly known pathogenesis and lack of effective treatment. Age and family history are the strongest AMD risk factors, and several loci were identified to contribute to AMD. Recently, also the epigenetic profile was associated with AMD, and some long non-coding RNAs (lncRNAs) were shown to involve in AMD pathogenesis. The Vax2os1/2 (ventral anterior homeobox 2 opposite strand isoform 1) lncRNAs may modulate the balance between pro- and anti-angiogenic factors in the eye contributing to wet AMD. The stress-induced dedifferentiation of retinal pigment epithelium cells can be inhibited by the ZNF503-AS1 (zinc finger protein 503 antisense RNA 2) and LINC00167 lncRNAs. Overexpression of the PWRN2 (Prader-Willi region non-protein-coding RNA 2) lncRNA aggravated RPE cells apoptosis and mitochondrial impairment induced by oxidative stress. Several other lncRNAs were reported to exert protective or detrimental effects in AMD. However, many studies are limited to an association between lncRNA and AMD in patients or model systems with bioinformatics. Therefore, further works on lncRNAs in AMD are rational, and they should be enriched with mechanistic and clinical studies to validate conclusions obtained in high-throughput in vitro research.     

Selective Cardiomyocyte Oxidative Stress Leads to Bystander Senescence of Cardiac Stromal Cells

Accumulation of senescent cells in tissues during normal or accelerated aging has been shown to be detrimental and to favor the outcomes of age-related diseases such as heart failure (HF). We have previously shown that oxidative stress dependent on monoamine oxidase A (MAOA) activity in cardiomyocytes promotes mitochondrial damage, the formation of telomere-associated foci, senescence markers, and triggers systolic cardiac dysfunction in a model of transgenic mice overexpressing MAOA in cardiomyocytes (Tg MAOA). However, the impact of cardiomyocyte oxidative stress on the cardiac microenvironment in vivo is still unclear. Our results showed that systolic cardiac dysfunction in Tg MAOA mice was strongly correlated with oxidative stress induced premature senescence of cardiac stromal cells favoring the recruitment of CCR2⁺ monocytes and the installation of cardiac inflammation. Understanding the interplay between oxidative stress induced premature senescence and accelerated cardiac dysfunction will help to define new molecular pathways at the crossroad between cardiac dysfunction and accelerated aging, which could contribute to the increased susceptibility of the elderly to HF.     

应力诱发马氏体相变对TiNi形状记忆合金疲劳过程影响的原位实验观察

利用长距离显微镜（QRMS）对经过精细抛光的试样表面进行观察，原位研究了TiNi形状记忆合金中应力诱发马氏体相变（SIMT）和逆相变对疲劳行为的影响。，包括对应力－应变响应和疲劳裂纹萌生和裂纹扩展规律的影响，并与普通金属的疲劳行为进行了对比。结果表明：TiNi形状记忆合金可逆的应力诱发马氏体相变有利于改善疲劳性能，然而也正是反复发生的SIMT引起 的滑移导致了疲劳裂纹的萌生。此外，在实验中还观察到若干反常的疲劳行为，如恒△K加载时裂纹扩展速率对裂纹长度的依赖性，裂纹扩展时的分叉以及疲劳试样表面出现的大量二次裂纹等现象。     

SrAl2O4:Eu2+材料的发光性能研究

制备了发光性能良好的SrAl2O4:Eu^2 材料，对其激光光谱、发射光谱和长余辉曲线进行了测试与分析讨论，结果表明长余辉衰减符合函数L＝ct^a（a＝0.754）形式。讨论SrAl2O4:Eu^2 材料的长余辉机理，指出长余辉应来自陷阱对空穴的俘获与缓慢释放。发现了SrAl2O4:Eu^2 材料的力至发光性能并分析了其可能原因。     

Ti-5553合金在轻气炮冲击下的变形行为

利用一级轻气炮装置,以不同速度的飞片对Ti-5553合金进行冲击加载;采用光学显微镜和透射电子显微镜观察并分析微观组织和变形行为;结合XRD和定量金相研究方法进行分析和计算。结果表明,Ti-5553合金在轻气炮冲击下会发生位错滑移、形变孪生和应力诱发马氏体相变(stress-induced martensite,SIM),形成α″相。α″相的生成量受轻气炮冲击速度的影响,随着冲击速度的增大,形成的α″含量呈明显上升趋势,当轻气炮冲击速度由380 m/s上升到560 m/s时,单位面积α″线的长度LA由39.18 mm/mm~2上升到52.65 mm/mm~2。     

Laser ablation-deposited PZT thin films for piezoelectric microsensors and microactuators

Abstract

We report on growth and deposition process optimization of laser ablation-deposited Pb(Zr_0.53Ti_0.47)O₃ thin films for application in piezoelectric microdevices. Films were grown on three different substrates: (100) cut LaAlO₃ single crystals, Pt/Ti/SiO₂/Si, and Pt/Ti/Si_3+xN₄/Si. On all three substrates, a deposition temperature of 620°C yielded perovskite films with good ferroelectric hysteresis properties. La_0.5Sr_0.5CoO₃ bottom and top electrodes were used for all films. PZT films on Pt/Ti/SiO₂/Si showed a variation of texture with film thickness. Thin membranes of PZT on Si_3+xN₄ were also fabricated.     

奥贝球铁承受抛丸冲击载荷时的变化

研究了奥贝球铁表面承受钢丸冲击时所产生的变化，在此基础上分析了表面层奥氏体发生应力诱发马氏体相变的机制，结果表明，奥贝球铁具有较高的加工硬化特性     

应力诱导引发马来酸酐官能化LLDPE的研究

采用提高双螺杆挤出机螺杆转速的应力诱导引发方法和添加引发剂与提高螺杆转速的复合引发方法,研究了线型低密度聚乙烯(LLDPE)与马来酸酐(MAH)的官能化反应;考察了官能化产物(LLDPE-g-MAH)对PET/铝箔复合薄膜T型粘合接头剥离强度的影响。结果表明:提高螺杆转速可抑制LLDPE在官能化过程中的交联副反应,制得具有较高接枝(嵌段)率、较好熔体流动速率和较低凝胶质量分数的官能化产物(Gd=0.30%~0.65%,MFR=1.0 g/10 min~4.7 g/10 min,凝胶质量分数≤0.4%),与单纯采用引发剂方法相比,高剪切应力诱导引发方法和复合引发方法所得官能化产物均可明显提高PET/铝箔复合薄膜T型粘合接头剥离强度。