Gas formation and biological effects of biodegradable magnesium in a preclinical and clinical observation

Magnesium alloys are biodegradable metals receiving increasing attention, but the clinical applications of these materials are delayed by concerns over the rapid corrosion rate and gas formation. Unlike corrosion, which weakens mechanical properties, the gas formation issue has received little attention. Therefore, we evaluated the gas formation and biological effects for Mg implants through preclinical (immersed in Earle’s balanced salt solution and in vivo) and clinical studies. The immersion test examined the gas volume and composition. The in vivo study also examined gas volume and histological analysis. The clinical study examined the gas volume and safety after Mg screw metatarsal fixation. Gas was mainly composed of H₂, CO and CO₂. Maximum volumes of gas formed after 5 days for in vivo and 7 days in clinical study. Within the clinical examination, two superficial wound complications healed with local wound care. Osteolytic lesions in the surrounding metaphysis of the Mg screw insertion developed in all cases and union occurred at 3 months. Mg implants released gas with variable volumes and composition (H₂, CO, and CO₂), with no long-term toxic effects on the surrounding tissue. The implants enabled bone healing, although complications of wound breakdown and osteolytic lesions developed.     

铝合金在盐水环境中腐蚀性能的电化学研究

为了深入研究温度对铝合金材料的腐蚀行为和机理,采用盐水腐蚀方法研究了其在高温条件下的电化学特性及腐蚀机理.选用7A04和5A06铝合金作为研究对象,在质量分数为3.5%的氯化钠溶液中,利用增重法、蔡司显微镜并结合电化学测试方法研究了其在20~80 ℃范围内的腐蚀性能,分析了腐蚀产物的微观形貌,探讨了腐蚀机理.结果表明：两种铝合金试样的腐蚀速率均随温度升高而增大.在Tafel极化曲线图中,对于同一种铝合金,自腐蚀电位随腐蚀温度增加向负方向移动,自腐蚀电流密度和年腐蚀深度随腐蚀温度增加而减小.对同一腐蚀温度下的两种铝合金,5A06铝合金自腐蚀电位低于7A04铝合金,腐蚀电流密度和年腐蚀深度均小于7A04铝合金.电化学阻抗图谱中,两种铝合金在不同条件下的Nyquist图均存在一个容抗弧,极化电阻随腐蚀温度增加而减小.对于同一种铝合金,在3.5%氯化钠溶液中的腐蚀速率会随着温度的升高而增大;在同一腐蚀温度下,5A06铝合金比7A04铝合金更容易发生腐蚀,但腐蚀速率比7A04铝合金慢.     

The isothermal section of the La–Si–Mg system at 500 C

The isothermal section of the La–Si–Mg system at 500 ^°C was constructed in the whole concentration range by means of the SEM-EDXS and XRPD characterization of about forty alloys prepared by induction melting and then annealed. Phase equilibria are characterized by the following ternary phases: τ₁-La_2+xSi₂Mg_1−x (0≤x≤0.35,tP10-Mo₂FeB₂), τ₂-LaSi₂Mg₂ (tP5-CeSi₂Mg₂), τ₃-LaSi₂Mg (structure still unknown) and τ₄-La₆SiMg₂₃ (cF120-Zr₆SiZn₂₃). The high temperature binary phase LaMg₂ (cF24-MgCu₂) has been found to be stabilized at 500 ^°C probably by a small amount of Si. Phases in binary subsystems do not generally form extended ternary solid solutions except for (La_1−xMg_x)₃Si₂ (0≤x≤0.167,tP10-U₃Si₂). Crystal structures of phases τ₁-La_2+xSi₂Mg_1−x and (La_1−xMg_x)₃Si₂ are correlated, the former being a substitution derivative of the latter.     

基于溶出伏安法的水质重金属自动监测系统

基于线性扫描溶出伏安法研制了一套水质重金属自动监测系统,实现了水中铅、锌、砷、锑重金属元素的自动监测.介绍了系统的硬、软件设计,详细阐述了数据采集中虚假点识别和纠正算法、定量分析方法和富集电位等参数的配置.实验表明,该仪器具有检出限低、响应快、自动化程度高等优点,具有一定应用前景.     

农业废弃物作为吸附剂去除水中重金属研究

农业废弃物主要由纤维素和木质素组成,是一种潜在的重金属吸附剂。文中归纳了几种农业废弃物吸附剂及其改性方法,阐述了改性农业废弃物吸附重金属的机理,讨论了pH、重金属离子初始浓度、吸附剂用量、反应温度等因素对改性农业废弃物吸附能力的影响,并展望了改性农业废弃物的应用前景。     

GENOTOXICITY IN CHIRONOMUS KIIENSIS (CHIRONOMIDAE: DIPTERA) AFTER EXPOSURE TO POLLUTED SEDIMENTS FROM RIVERS OF NORTH PENINSULAR MALAYSIA: IMPLICATION FOR ECOTOXICOLOGICAL MONITORING

Rapid industrialization and urbanization has led to increasing input of chemical contaminants into the aquatic environment of Malaysia. Despite the threat civilization poses to the biota, there are still very few relevant studies on ecotoxicological testing of river ecosystems. To overcome this knowledge gap, we examined lethal and genotoxic effects of sediments from different rivers of the northern Malaysia against Chironomus kiiensis, a group well represented in the aquatic fauna of this region. We exposed the larvae to sediments from Selama River (SR), Permatang Rawa River (PRR) and Kilang Ubi River (KUR) at various durations (0, 6, 12, 24 and 48 h). The larval mortality was monitored, whereas DNA damage in survivors' cells was determined using the comet assay. Pollution level indexed by the amounts of heavy metals and other organic contaminants in the sediment showed progressive increases from SR to PRR to KUR. Highly polluted sediments (PRR to KUR) were detrimental to C. kiiensis larvae, most of which did not survive following exposure for long periods. DNA analyses revealed greater damages in nuclei derived from larvae maintained on polluted sediments, in particular, those from KUR. The effects on the genomic material of C. kiiensis larvae occurred in a time‐dependent manner, with damage level increasing as exposure time progressed. Our results highlight the genotoxic properties of polluted sediments. More importantly, this study showed that C. kiiensis larvae could respond to different levels of pollution with respect to exposure time. It is concluded that C. kiiensis larvae is a potential candidate for river ecotoxicological monitoring. Copyright © 2012 John Wiley & Sons, Ltd.     

太湖流域蔬菜复合污染及生物富集特征研究

在太湖流域（苏南地区）无锡、常州、镇江3市农业活动区蔬菜及其对应土壤中PAEs化合物和Cd、Zn、Cu、Ni 4种重金属进行检测分析基础上,探讨了蔬菜复合污染分布及污染物的生物富集特征。结果表明,流域蔬菜中PAEs以DMP、DEEP、DNP含量较高,分别为：0.01～10.10mg/kg,ND-8.28mg/kg,ND-2.85mg/kg,重金属以Zn含量最高,为1.86～14.24mg/kg;蔬菜对应土壤中PAEs以DNOP、DMEP、DNP、DMP含量较高,分别为：0.13～44.7mg/kg,0.47～50.42mg/kg,0.48～64.7mg/kg,19.46～533.6mg/kg,重金属也以Zn含量最高,为31.02～43.73mg/kg;蔬菜富集规律分析发现,BMPP、DNHP、DNOP及重金属Cd在蔬菜中的富集系数较大。     

钛白副产硫酸亚铁制备超细透明氧化铁黄研究

以钛白粉厂副产物硫酸亚铁为原料,以氨水为沉淀剂,采用空气氧化法制备超细透明氧化铁黄.分别研究了影响晶种形成和晶体生长的主要影响因素.通过优化实验,得出了最佳工艺条件.晶种制备阶段：温度为30℃,空气流量为2L/min,溶液的pH为4～6,搅拌速度为400r/min,Fe2＋浓度为1mol/L.晶体生长阶段：温度为85℃,空气流量为2L/min,溶液pH为4～6.     

Evaluation of metal-doped manganese oxide octahedral molecular sieves in catalytic reduction of NOx from cigarette mainstream smoke

A series of Ag, Cu and Co-doped manganese oxide octahedral molecular sieves (OMS-2) were synthesized and evaluated to remove nitrogen oxides (NO _x ) from cigarette mainstream smoke. The three kinds of catalysts were added to cigarettes for studying the capabilities of reducing NO _x from cigarette mainstream smoke. The catalysis and reduction of NO in laboratory were studied. A mechanism for NO _x catalytic reduction from burning cigarettes with the catalysts adding to cigarettes was described. The catalysts show excellent catalytic activity for NO _x removal, especially the Ag-doped OMS-2 catalyst. 0.5% (mass fraction) Ag-doped OMS-2 catalyst has the best ability to remove NO _x from cigarette mainstream smoke. The use of Ag-doped OMS-2 as catalyst for removing carcinogenic compounds from cigarette smoke will be an effective strategy to protect the environment and public health.