Challenges and political solutions for steel recycling in China

The circular economy is an essential component of China's sustainable development. To promote the recycling of end-of-life products, the government has adopted various policies. Steel scrap is an important resource for steelmaking. Yet, the Chinese iron and steel industry uses less scrap to produce new steel compared to other large steelmaking countries. This article examines the reasons, why steel recycling is still relatively weak in China and what measures the government takes to improve the situation. We found that limited availability of scrap, high scrap prices, inadequate steelmaking capacities, industry fragmentation and unclear responsibilities for manufacturers are the main obstacles for steel recycling in China. The government is trying to improve steel recycling through tax incentives, import facilitation, support for supply, industry reorganization, and recycling parks, but with modest results.     

Potential dissemination mechanism of the tetC gene in Aeromonas media from the aerobic biofilm reactor under oxytetracycline stresses

The tetC gene has been found to be one of the most widely distributed tetracycline resistance (tet) genes in various environmental niches, but the detailed dissemination mechanisms are still largely unknown. In the present study, 11 tetC-containing Aeromonas media strains were isolated from an aerobic biofilm reactor under oxytetracycline stresses, and the genome of one strain was sequenced using the PacBio RSII sequencing approach to reveal the genetic environment of tetC. The tetC gene was carried by an IS26 composite transposon, named Tn6434. The tetC-carrying Tn6434 structure was detected in all of the A. media strains either in a novel plasmid pAeme2 (n=9) or other DNA molecules (n=2) by PCR screening. The NCBI database searching result shows that this structure was also present in the plasmids or chromosomes of other 13 genera, indicating the transferability of Tn6434. Inverse PCR and sequencing confirmed that Tn6434 can form a circular intermediate and is able to incorporate into a preexisting IS26 element, suggesting that Tn6434 might be responsible for the dissemination of tetC between different DNA molecules. This study will be helpful in uncovering the spread mechanism of tet genes in water environments.     

Conceptualizing controversies in the EU circular bioeconomy transition

The transition towards a circular bioeconomy (CBE) in the European Union is not without contestation. In particular, research has highlighted potential trade-offs of the large-scale production of bio-resources, for instance with environmental quality goals. To date, however, it remains underexplored in the CBE literature how controversies develop throughout a transition process. To address this gap, this paper explores where controversies are situated in a transition, how they change throughout, and how they influence the transition process. First, we suggest that controversies can be situated on and between different system layers within a transition. Second, we offer an explanation of how controversies evolve, as actors confirm, integrate, disintegrate and polarize underlying storylines. Third, these controversies can have both productive and unproductive outcomes while they unfold throughout a transition. We illustrate this understanding with the example of biorefineries as CBE key technology and discuss a research agenda on controversies in sustainability transitions.     

拉氏中值定理的发现与证明

给出了拉氏中值定理的发现过程和一个新的证明方法．     

绿色消费模式与循环经济相关性的探讨

绿色消费是循环经济在消费领域的具体形式,它要求人们的消费活动必须有利于环境保护、资源利用和人的整体素质的提高。绿色消费模式是人类发展模式的一次历史性转变,是一种人与自然相互协调的消费观,既强调消费的重要作用,又强调消费和再生产其他环节与环境的动态平衡,有利于取得人类社会和自然的协调发展。     

络合萃取法处理高浓度H酸废水

研究了用络合萃取法回收H酸废母液中染料中间体的多种影响因素，得出了最佳工艺参数。实验结果表明，通过萃取工艺，H酸废母液中染料中间体回收率可达90％以上，萃余液中CODcr d (1000-3000)mg/L之间，此工艺可使废母液中的回收物浓缩5－10倍，萃取剂可以再生回用。