Influence of Fine Grains on the Bending Fatigue Behavior of Two Implant Titanium Alloys

By means of the ultrasonic surface impact (amplitude of 30 μm, strike number of 48,000 times/mm²), nanograins have been achieved in the surfaces of both Ti6Al4V(TC4) and Ti3Zr2Sn3Mo25Nb(TLM) titanium alloys, mainly because of the dislocation motion. Many mechanical properties are improved, such as hardness, residual stress, and roughness. The rotating–bending fatigue limits of TC4 and TLM subjected to ultrasonic impact are improved by 13.1% and 23.7%, separately. Because of the bending fatigue behavior, which is sensitive to the surface condition, cracks usually initiate from the surface defects under high stress amplitude. By means of an ultrasonic impact tip with the size of 8 mm, most of the inner cracks present at the zone with a depth range of 100~250 μm in the high life region. The inner crack core to TC4 usually appears as a deformed long and narrow α-phase, while the cracks in TLM specimens prefer to initiate at the triple grain boundary junctions. This zone crosses the grain refined layer and the deformed coarse grain layer. With the gradient change of elastic parameters, the model shows an increase of normal stress at this zone. Combined with the loss of plasticity and toughness, it is easy to understand these fatigue behaviors.     

移动医疗干预在男男性行为人群中的应用研究进展

近年来随着移动通信技术的快速发展,移动医疗在健康服务与公共卫生领域得到了广泛的应用,在AIDS预防控制方面也展现出巨大潜力。本文通过综述移动医疗用于MSM人群的干预,分析高危行为的变化,评价移动医疗在AIDS防控中的作用和意义。     

股权激励契约设计与公司盈余管理行为

以2006年公告股权激励方案的上市公司为研究对象，运用其股权激励方案公告后3年的相关数据，基于应计项目与线下项目盈余管理的双重计量视角，实证分析股权激励契约的设计对激励后公司盈余管理方式与强度的影响。研究发现：股权激励方案公告后，相关公司应计项目和线下项目的盈余管理都存在，且公司管理层倾向于实施应计项目盈余管理方式。相对于实施业绩股票模式的公司，实施股票期权模式公司的线下项目盈余管理会显著减少，而应计项目盈余管理减少不明显。激励规模越大，行权条件设计的越严格，无论是应计项目还是线下项目盈余管理均会增强。激励计划的有效期设计的越长，线下项目盈余管理会显著减少，应计项目盈余管理减少不明显。     

天麻素对大鼠骨骼肌细胞化学损伤的保护

背景:现代药理学研究表明,天麻的主要成分天麻素可以恢复大脑皮质兴奋与抑制过程间的平衡失调,产生镇静、安眠和镇痛等中枢抑制作用。目的:观察天麻素对L6大鼠成肌细胞化学损伤的保护作用。方法:用H2O2建立L6大鼠成肌细胞的化学损伤模型。DMEM培养液制备不同浓度的天麻素(1.562500,0.781250,0.390625g/L)预处理保护组的L6大鼠成肌细胞24h,然后用0.1mmol/LH2O2孵育80min,同时设置增殖组(用不同浓度的天麻素预处理,但不经H2O2处理),模型组(仅用H2O2处理),阳性对照组(仅有L6细胞悬液),阴性对照组(只有DMEM培养液),对照组既不用天麻素预处理,也不用H2O2孵育。结果与结论:MTT检测显示,增殖组和保护组L6大鼠成肌细胞存活率明显高于模型组;DAPI荧光标记细胞核为蓝色,模型组细胞荧光度较弱,且数目显著少于保护组;苏木精-伊红染色显示保护组的细胞核形状较规则,细胞轮廓较清晰,而模型组破损细胞较多;Bax和Bcl-2免疫荧光细胞化学结果表明,模型组促凋亡基因bax表达明显高于保护组,而抑制凋亡基因bcl-2的表达量完全相反;流式细胞仪检测显示保护组的凋亡率显著低于模型组(P<0.05)。提示天麻素对保护大鼠骨骼肌细胞化学损伤有显著效果。     

Laccase immobilization and surface modification of activated carbon fibers by bio-inspired poly-dopamine

In this study, we developed a new synthesis method for modifying activated carbon fibers (ACFs) by dopamine with oxidation-based self-polymerization (DA-ACFs). In addition, laccase was immobilized on the surface of unmodified ACFs (L-ACFs) and DA-ACFs (LDA-ACFs) via cross-linking after being incubated for 12 h at 5 °C. The surface composition and microstructure of the samples were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier-transform infrared reflection and thermo-gravimetric analysis. The optimized laccase concentration for preparing the samples was 2.0 g L⁻¹. The results demonstrated that the successful poly-dopamine modification increased the catalytic abilities of the ACFs in terms of biocompatibility and hydrophilicity. Compared with free laccase, the immobilized laccase exhibited significantly higher relative activity over a pH range of 3.5–6.5 and a temperature range of 30–60 °C; the thermo-stability increased, and 50% relative activity of the LDA-ACFs remained after 5 h at 55 °C. After six cycles of reuse, the relative activity of LDA-ACFs remained ≥60%, compared to 40% activity remaining for L-ACFs, and long-term storage stability was demonstrated. Moreover, the kinetic parameters (K_m) of the two immobilized laccases were both higher than that of free laccase, whereas the maximum velocities (V_max) were lower. These results indicate that the DA-ACFs are economical, simple, and efficient carries for enzyme immobilization, and can be suitable for further biotechnology and environmental applications.

In this study, we developed a new synthesis method for modifying activated carbon fibers (ACFs) by dopamine with oxidation-based self-polymerization (DA-ACFs).     

Microwave absorption properties of lightweight and flexible carbon fiber/magnetic particle composites

Hybridized-carbon-based materials with magnetic metals and oxides have attracted much attention because of their enhanced electromagnetic wave loss. In this study, magnetic particles were coated on the surface of carbon fibers by carbonizing in a nitrogen atmosphere. The morphology, structure, thermolysis, and wave-absorption performance of the carbon fiber/magnetic particle composite were determined. Results show that the in situ-formed magnetic particles (such as Fe₃O₄, NiFe₂O₄, CoFe₂O₄, and Ni₃Fe) are uniformly dispersed along the carbon-based fibers, which exhibit different wave absorption. The absorption of the carbon fiber/magnetic particle composite can be controlled by adjusting the species and concentration of the magnetic particle coating, which provides a new and effective way of endowing the magnetic-particle-coated carbon fibers with good microwave absorption properties.

Hybridized-carbon-based materials with magnetic metals and oxides have attracted much attention because of their enhanced electromagnetic wave loss.