Models of Neurotoxicity: Extrapolation of Benchmark Doses in Vitro

In risk assessment, no observed exposure level (NOAEL) and benchmark dose (BMD) are usually derived either from epidemiological studies in humans or from animal experiments. In many in vitro studies, concentration-effect/response curves have been analyzed using different mathematical models finalized to the identification of EC50. In the present article, we propose a model to fit dose-response curves in vitro. The BMD approach has been used to compare the cell viability (MIT assay) of different rat (C6 and PC12, glial and neuronal, respectively) and human cell lines (D384 and SK-N-MC, glial and neuronal, respectively) after 24-hour exposure to the following neurotoxic substances: manganese chloride (MnCl2), methyl-mercury (Me-Hg), and the enantiomers of styrene oxide (SO). For all rat and human cell lines, the potency of the examined compounds was: MnCl2 < S-SO < R-SO < Me-Hg. A preliminary comparison with in vivo toxicity data for these substances gave rise to consistent results. Whereas a reasonable agreement between in vitro and in vivo data has been found for Mn and styrene oxide, a wide scatter of LOAEL has been reported for Me-Hg and these appear to be either much higher or lower than the BMD for the MIT assay we observed in vitro.     

The EPA Health Risk Assessment of Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

This paper describes the U.S. Environmental Protection Agency's assessment of potential health risks associated with the possible widespread use of a manganese (Mn)-based fuel additive, methylcyclopentadienyl manganese tricarbonyl (MMT). This assessment was significant in several respects and may be instructive in identifying certain methodological issues of general relevance to risk assessment. A major feature of the inhalation health risk assessment was the derivation of Mn inhalation reference concentration (RfC) estimates using various statistical approaches, including benchmark dose and Bayesian analyses. The exposure assessment component used data from the Particle Total Exposure Assessment Methodology (PTEAM) study and other sources to estimate personal exposure levels of particulate Mn attributable to the permitted use of MMT in leaded gasoline in Riverside, CA, at the time of the PTEAM study; on this basis it was then possible to predict a distribution of possible future exposure levels associated with the use of MMT in all unleaded gasoline. Qualitative as well as quantitative aspects of the risk characterization are summarized, along with inherent uncertainties due to data limitations.     

钙钛矿锰氧化物为基体的二相复合体低场室温高磁电阻研究

综述了国内外对钙钛矿锰氧化物为基体的二相复合体低场磁电阻研究现状,提出了钙钛矿锰氧化物低场室温高磁电阻实现的新途径。     

钙钛矿锰氧化物颗粒边界异质改性及低场磁电阻效应研究

综述了近几年钙钛矿锰氧化物磁电性质及CMR效应研究进展;综述了低场磁电阻研究现状,着重阐述了通过对钙钛矿锰氧化物的颗粒界面异质改性,实现低场磁电阻的方法,并提出利用A位稀土掺杂钙钛矿锰氧化物与金属颗粒复合实现低场磁电阻的设想。     

锰、铈氧化物气凝胶的制备和其对CO氧化的催化性能

以无机盐为原料通过超临界干燥法制得了锰、铈氧化物气凝胶 ,初步考察了该气凝胶对 CO氧化的催化活性 .结果显示以超临界干燥法可以制得 1 0纳米以下的锰、铈氧化物纳米粒子 ,该纳米粒子对 CO氧化呈现出良好的催化活性 ,氧化锰和氧化铈之间存在着协同效应 .     

反思环境资本化——以XS土家族苗族自治县的矿业发展为例

XS土家族苗族自治县在锰矿开发过程中获得了经济增长的同时,引发了一系列的生态环境、社会文化问题。这些问题从根本上而言是环境资本化的一种表现,而环境资本化的危险在于过度简化自然的功能至经济功能。在此意义上,XS面临的环境资本化所带来的系列问题既是个人困扰,同时也是公众议题。两者都包含着某些应被珍视的价值受到了威胁:对个人而言,是生活安全与生命健康;对群体而言,是文化的失衡与传统的失落。应对环境资本化需同时考虑个人困扰与公众议题两个方面,即:既关注个体的生存合理性,也要关注社会结构的优化。     

土壤中有效态锰的浸取与测定

采用La-Zr涂覆石墨管、石墨炉原子吸收分光光度法对土壤中有效态锰的浸取与测定的条件进行了研究。经试验，该法对有效态锰的精密度为5.48%；回收率在93.5%-97.4%之间。测定了一组土样，结果满意。     

催化动力学光度法测定痕量锰的研究

研究了在碱性介质中，锰（Ⅱ）催化高碘酸钾氧比镁试剂Ⅱ褪色指示反应及其动力学条件，建立了测定锰的新方法，方法的检测限为6．67×10－10g／mL，线性范围为0～1．0μg／25mL。本法简单灵敏，选择性较好。用于茶叶中锰（Ⅱ）的含量测定，结果满意。     

单扫描极谱法测定环境水样中微量锰

在0.01mol·L-1硼砂溶液中,Mn（Ⅱ）于-1.53V（vs·SCE）处产生灵敏的极谱波,Mn（Ⅱ）浓度在0.012～12.0μg·mL-1范围内与导数波高呈良好线性关系,检出限为0.008μg·mL-1,样品加标回收率为94～98％,相对标准偏差小于2.8％,该方法准确、简便、选择性好.     

与光合作用Ⅱ相关的锰簇合物的水氧催化理论计算

锰簇合物在植物及一些菌类和藻类的光合作用中具有非常重要的作用,主要用于催化光产生水氧的反应。本文总结了二十多年来,光合作用Ⅱ水氧化产氧的机制的功能探讨以及国外对锰簇合物水氧催化理论计算的研究,利用DFT方法对理论模型的构建及计算。