Some theoretical and practical aspects in the separation of humic substances by combined liquid chromatography methods

Permanent need to understand nature, structure and properties of humic substances influences also separation methods that are in a wide scope used for fractionation, characterization and analysis of humic substances (HS). At the first glance techniques based on size-exclusion phenomena are the most useful and utilized for relating elution data to the molecular mass distribution of HS, however, with some limitations and exceptions, respectively, in the structural investigation of HS. The second most abundant separation mechanism is reversed-phase based on weak hydrophobic interactions beneficially combined with the step gradients inducing distinct features in rather featureless analytical signal of HS. Relatively great effort is invested to the developments of immobilized-metal affinity chromatography mimicking chelate-forming properties of HS as ligands in the environment. Surprisingly, relatively less attention is given to the ion-ion interactions based ion-exchange chromatography of HS. Chromatographic separation methods play also an important role in the examination of interactions of HS with pesticides. They allow us to determine binding constants and the other data necessary to predict the mobility of chemical pollutants in the environment. HS is frequently adversely acting in analytical procedures as interfering substance, so more detailed information is desired on manifestation of its numerous properties in analytical procedures. The article topic is covered by the review emphasizing advances in the field done in the period of last 10 years from 2000 till 2010.     

国际理论与应用力学联合会的建立过程

本文依据历史资料,简述了国际理论与应用力学联合会(International Union of Theoretical and Applied Mechanics,IUTAM)的建立过程,以及中国力学学会 (Chinese Society of Theoretical and Applied Mechanics,CSTAM) 1980年加入国际理论与应用力学联合会的一些情况,供大家研究力学史时参考。     

基于中国大学MOOC和超星学习通平台的化学与社会课程在线教学实践

采用国家精品在线开放课程作为课程资源、超星学习通作为智慧教学工具,成功开展了化学与社会课程在线教学。实践表明,基于MOOC和超星学习通相结合的在线教学形式受到了学生的欢迎,参与积极性高,教学效果良好。     

Social welfare relations and irregular sets

Social welfare relations satisfying Pareto and equity principles on infinite utility streams have revealed a non-constructive nature, specifically by showing that in general they imply the existence of non-Ramsey sets and non-Lebesgue measurable sets. In [4, Problem 11.14], the authors ask whether such a connection holds with non-Baire sets as well. In this paper we answer such a question showing that several versions of Pareto principles acting on different utility domains imply the existence of non-Baire sets. Furthermore, we analyze in more details the needed fragments of AC and we start a systematic investigation of a social welfare diagram in a similar fashion done in the past decades concerning cardinal invariants and regularity properties of the reals. In doing that we use tools from forcing theory, such as specific tree-forcings (in particular variants of Silver and Mathias forcings) and Shelah's amalgamation.     

Hidden Lives. Early Childhood Care as an Academic: The Slow Burn

As the inaugural entry in the new series Hidden Lives, this Viewpoint Article highlights challenges in early childhood care faced by academicians. Research centers must adapt to societal shifts in family structure, uncertainty around research funding, expanded job responsibilities and upheavals brought about by the pandemic. These problems represent opportunities for change at the technological, cultural and policy levels. It is crucial that we recognize those in need and help where we can.