Concentration dependence of hydrogen diffusion in α-iron from atomistic perspectives

Evaluation of hydrogen diffusion in structural materials is essential to predict the leakage and embrittlement of hydrogen storage applications. In this work, we investigate the atomic-scale diffusion of interstitial hydrogen (H) in α-iron (Fe) over a temperature range from 350 to 900 K with different H concentrations (0.01–5%), employing classical molecular dynamics (MD) simulations. The self-diffusivity of H atoms increases with increasing temperature and decreasing concentration. With low concentrations, the calculated diffusion properties agree well with prior experiments. However, with a higher concentration (≥1%), the H diffusivity at low temperatures deviates from a high-temperature Arrhenius behavior. Through the energetic and structural analysis, we suggest that this deviation is attributed to a reduced mobility due to increased energy barrier by other H interstitials. This work contributes to the effective design of H storage applications by identifying temperature and concentration effects on permeability and addressing possible microstructural transformation.     

Molecular modeling on HIF-2α–ARNT dimer destabilization caused by R171A and/or V192D mutations in HIF-2α

Oxygen homeostasis in normal and tumor cells is mediated by hypoxia-inducible factors (HIFs), which are active as heterodimer complexes, such as HIF-2α–aryl hydrocarbon receptor nuclear translocator (ARNT) and HIF-1α–ARNT. A series of mutations on the interfaces between HIF-2α and ARNT and on the domain–domain interface within HIF-2α has been reported to exert varying effects on HIF-2α–ARNT dimerization. In the present study, molecular dynamic simulations were conducted to evaluate HIF-2α mutations, namely R171A, V192D, and R171A/V192D, which are not involved in the interaction with ARNT but impede HIF-2α–ARNT dimerization. Our results indicate that these mutations induct local conformation leading to a shortened (by V192D) or widened (by R171A and R171A/V192D) Y91–E346 separation distance, where E346 and Y91 are located on the HIF-2α and interact with ARNT according to electrostatic and geometrical shape complementarity, respectively.     

一种教学用脑波分析耳机的设计与实现

笔者阐述了一种教学环境中使用的脑波分析耳机的工作原理和设计方法,其核心是对EEG脑电波信号的采集、滤波,运用时频谱和复杂度分析的方法进行综合分析提取精神状态特征,设计神经网络多层分类器对精神状态进行分类和识别,最后完成精神状态的自动检测和识别,以提高学生上课的注意力。     

α/β放射性气溶胶的小流量采样快速测量技术研究

针对放射性气溶胶监测仪的便携要求,设计了一套小流量采样快速测量系统和测量方法。采用累积采样累积测量的方式,联合利用能量甄别修正法与α/β比值法去除Rn子体的干扰,实现小流量采样条件下的α/β放射性气溶胶的同时监测。通过对探测下限的分析,表明该方法可满足应急监测的需求,为便携式α/β放射性气溶胶监测仪设计提供了参考。     

α粒子与酒精联合作用致肝细胞恶性转化的影响

研究α粒子和酒精联合作用对肝细胞恶性转化生物效应的影响,为系统评价α粒子辐射风险提供实验依据。通过建立辐射和酒精联合作用细胞模型,分析比较α粒子辐射、酒精单因素与两者复合对人正常肝细胞的细胞周期、迁移和侵袭等恶性转化生物特征及相关基因mRNA水平表达的影响。与对照组比较,复合因素作用的细胞发生迁移和侵袭的细胞数量明显增多,在mRNA水平抑癌相关基因p53和细胞粘附蛋白相关基因cdh1表达量明显降低,原癌相关基因mdm2表达量明显升高,复合因素作用下肝细胞发生明显的恶性转化趋势。辐射和酒精均能诱导肝细胞发生恶性转化,肝细胞经α粒子辐照后再受酒精作用其发生恶性转化的风险高于单纯接受α粒子辐照的细胞,酒精增加了α粒子辐照后肝细胞恶性转化风险,可能与影响肝细胞表面E型粘连蛋白的表达有关,导致细胞之间粘连性降低,促进细胞发生迁移和侵袭。因此,在评价α粒子内照射对健康的影响时需要考虑职业人员的饮酒习惯。     

一种通过渐进拟合外推计算α放射性比值的方法

根据α能谱中常见的238Pu与239Pu+240Pu能峰难以完全分开且238Pu拖尾较为严重的情况,采用一种渐进拟合外推的解谱方法来计算各能峰的峰面积,进而计算α放射性比值。渐进拟合外推方法基于峰拖尾计数逐渐减少时整个能峰的面积越来越逼近能峰面积真值这一总趋势特点,进行拟合外推而得到能峰的总面积。在30多个能谱中的使用结果表明,这一方法是准确和可靠的。     

Methacrylate-functionalized POSS as an efficient adhesion promoter in olefin-based adhesives

This study aims to investigate the effects of methacrylate-functionalized polyhedral oligomeric silsesquioxane (MA-POSS) on polyolefin-based adhesives. The so called adhesive was synthesized by the cooligomerization of 1-decene/9-decene-1-ol monomers using a Ti amine bis-phenolate catalyst, [Ti{2,2′-(OC₆H₂-4,6-^tBu₂)₂NHC₂H₄NH(OⁱPr)₂], which was subsequentlyacrylated via a simple reaction with methacryloyl chloride. Different weight fractions of MA-POSS nanoparticles were solution blended with synthesized adhesive and undergone curing reaction with blue light. Observation of a unique tan δ peak in dynamic mechanical thermal analysis (DMTA) curve was clear evidence that two employed moieties were miscible and only one hybrid polymeric phase was created. Most noticeably, significant increase in mechanical parameters was detected in the lower inclusion compositions, 0.2-1 wt% of MA-POSS, where flexural strength and flexural modulus were increased up to 99 and 110%, respectively. Furthermore, thermal stability of the synthesized nanocomposite enhanced dramatically by increasing MA-POSS weight fraction. Influence of employed nanoparticles on adhesion properties of synthesized nanocomposites was evaluated with tensile shear bond strength and pull off analysis. According to the adhesion results, the MA-POSS causes an adhesion promotion on the fabricated adhesive/POSS nanocomposites.     

Polyacrylonitrile/α-Fe2O3 Hybrid Photocatalytic Composite Adsorbents for Enhanced Dye Removal

The potential of a novel α-Fe₂O₃/polyacrylonitrile (PAN) hybrid composite adsorbent to eliminate methylene blue (MB) from aqueous solution was evaluated. PAN was selected as the base composite. The presence of α-Fe₂O₃ as nanophotocatalyst on the surface of PAN introduced an efficient photocatalytic hybrid composite adsorbent for degrading MB. Effects of α-Fe₂O₃ nanopowder loading, pH, temperature, MB initial concentration, solar light, and contact time were investigated. Langmuir, Freundlich, and Temkin isotherms were applied to analyze the adsorption behavior. The Freundlich equation provided the best correlation with experimental data. Pseudo-first-order, pseudo-second-order, and intraparticle models were employed. Thermodynamic studies indicated an endotherm and spontaneous adsorption process in a defined temperature range.     

CVD涂层α-Al2O3织构制备技术研究

采用化学气相沉积法在硬质合金基体上沉积具有不同织构择优的α-Al2O3涂层,通过扫描电子显微镜(SEM)、X射线衍射(XRD)分别对其微观组织和机械性能进行分析。研究结果表明,通过改善过渡层的氧化气氛,氧化铝的过渡层结构为针状物,成功制备不同织构的氧化铝涂层,涂层结合力良好。