The electron density distribution in pyridinium and bipyridylium compounds and its relevance to their adsorption by expanding lattice clays

Abstract

Charge distributions in 1, 1'‐ethylene‐2, 2'‐bipyridylium (diquat), 1,1'‐dimethyl‐4,4'‐bipyridylium (paraquat) and 1‐methylpyridinium organocations were calculated by a Complete Neglect of Differential Overlap semi‐empirical quantum mechanical procedure. The data show that the positive charges in the organocations are distributed around the molecules and are greatest in the positions ortho and para to the heterocyclic nitrogen atoms. Earlier interpretations of the mechanisms of adsorption of paraquat and diquat by soils and clays assumed that the charges were located in the heterocyclic nitrogen atoms. Here some consideration is given to the influence of the charge delocalizations on the processes of adsorption by montmorillonite and vermiculite clay preparations.     

Quantification of the interactions between Ca,Hg and extracellular polymeric substances (EPS) of sludge

The interactions between metals (Ca²⁺ and Hg²⁺) and extracellular polymeric substances (EPS) extracted from the aerobic and anaerobic sludge in wastewater treatment reactors were investigated using a combination of zeta potential measurement and 3-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analysis. Results show that Ca²⁺ had no substantial effects on the EEM fluorescence spectra of the EPS, but their zeta potentials increased with the increasing Ca²⁺ dosage. However, Hg²⁺ had a significant effect on the EEM fluorescence spectra of the EPS, while their zeta potentials seemed not to be affected by the dose of Hg²⁺. The interactions between Hg²⁺ and EPS were elucidated using the fluorescence quenching with PARAFAC analysis, while the interactions between Ca²⁺ and EPS were evaluated by the zeta potential technique. The binding constants for Hg²⁺ and EPS were two orders of magnitude higher than those for Ca²⁺ and EPS, suggesting that the binding mechanisms between Ca²⁺ and EPS were different from those between Hg²⁺ and EPS. The results might be useful for understanding the roles of EPS in bacterial self-protection against heavy metals and the aggregate formation mechanisms through ionic bridging interactions.     

产油微藻培养与回收的关键技术研究进展

寻找廉价而高效的替代原料是实现生物柴油产业化的关键所在.微藻以含油量高、生长周期短、环境适应能力强、生物产量高等优点,有望成为一种极具潜力的生物柴油生产原料.然而,目前尚存在微藻培养低效成本高和微藻回收效率低两大难题.综述了微藻培养与回收过程中的关键技术,并对存在的两大难题及其改进技术进行了详细的探讨.最后,总结并展望了微藻培养、回收技术未来的发展趋势.     

论园林树木栽培学(各论)的精讲教学法

园林树木栽培学是一门实践性很强的有关园林绿化领域的专业课、必修课.1995年以来,本人在园林树木栽培学各论教学中尝试重点讲解、课堂点评的教学方法,取得了较好的教学效果.     

石墨炉法测定铅的基体改进剂的选择

通过一系列实验,选择了石墨炉法测定铅的最佳基体改进剂,并确定了使用该基体改进剂的最佳灰化温度和原子化温度。     

A New Approach to Plant Diversity Assessment Combining HPLC Data, Simplex Mixture Design and Discriminant Analysis

The quantitative assessment of plant diversity and its monitoring with time represent a key environmental issue for management and conservation of natural resources. Assessment of plant diversity could be based on chemical analyses of secondary metabolites (e.g. flavonoids, terpenoids), because of the substantial quantitative and qualitative between-individual variability in such compounds. At a geographical scale, the plant populations become widely dispersed, and their monitoring from numerous routine individual analyses could become restricting. To overcome such constraint, this study develops a multivariate calibration model giving the relative frequency of a particular taxon from a simple high-performance liquid chromatography (HPLC) analysis of a plant mixture. The model was built from a complete set of mixtures combining different taxons, according to an experimental design (Scheffé’s matrix). For each mixture, a reference HPLC pattern was simulated by averaging the individual HPLC profiles of the constitutive taxons. The calibration models, based on Bayesian discriminant analysis (BDA), gave statistical relationships between the contributions of each taxon in mixtures and reference HPLC patterns of these mixtures. Finally, these models were validated on new mixtures by using outside plants. This new biodiversity survey approach is illustrated on four chemical taxons (four chemotypes) of Astragalus caprinus (Fabaceae). The more differentiated the taxon, the better predicted its contributions (in mixtures) were by BDA calibration model. This new approach could be very useful for a global routine survey of plant diversity.     

考虑纵横弯曲的空间杆系有限元计算

在普通刚架有限元计算模型的基础上 ,推导出了考虑空间纵横弯曲有限元的单元刚度矩阵和形函数 ,单元刚度矩阵和形函数考虑了轴力的影响。并以此编制了“kjgj”有限元软件 ,软件考虑了轴力引起的二阶效应。用平面和空间算例进行验证 ,单根杆件只剖分一个单元计算得到的精度可以达到商业软件剖分多个单元达到的精度。     

工科学生工程安全素质培养的探索与实践

高等学校工科学生的社会职业定位是工程师,工程师的主要工作是从事工程的规划、设计、实施、运行和管理,其工程行为对工程安全具有至关重要的影响。随着现代工程向大型化、综合化和复杂化方向发展,工程安全已成为人类社会面临的重大问题,解决工程安全问题的根本途径之一是加强和改进高等工程教育,致力于提高工科学生的工程安全素质培养。对工科学生的工程安全素质培养,各高校可根据自己的专业优势和服务需求面而独具特色,以适应社会对工程安全人才多样性要求。湖南科技大学在工科学生的培养中,从培养目标的改革中加强了对工程安全素质的要求;从培养内容的改革中加强了对工程安全知识的传授;从培养方法的改革中加强了对工程安全技能的训练;各项改革中的措施在实践中取得令人满意的效果。     

Pluralism,The Ethical Matrix,and Coming to Conclusions

The ethical matrix approach was developed by Prof Ben Mepham and his colleagues at the University of Nottingham in the early 1990s. Since then the approach has received increasing attention and has been used by several researchers in different projects related to assessing ethical impacts of different food production technologies and other policy options of societal concern. The ethical matrix is sometimes understood simply as a checklist of ethical concerns, but might also be seen as a guide to coming to conclusions on moral questions. The problem I discuss in this paper relates to how using the ethical matrix method as a decision guide can be combined with respecting pluralism. The aim of the paper is to suggest a framework making it possible to – at the same time – enhance public justification of judgments and respect pluralism. I argue that pluralism is fundamental to the ethical matrix approach; I distinguish between intuitionist principled pluralism and societal value pluralism; and I show how both kinds of pluralism imply restrictions on how conclusions can be made. No substantive moral decision principles can be allowed. Still, I argue, decision principles of a more epistemological or procedural character can be acceptable even within pluralism. The pragmatist principle of inquiry is defended as an account of moral problem solving compatible with both principled pluralism and value pluralism. When an ethical matrix is used within such a participatory inquiry process substantive conclusions can be drawn.