Propagation form of internal cracks induced by continuous casting soft reduction and control strategy for internal quality

The propagation form of internal cracks induced by continuous casting soft reduction and the control strategy for enhancing the internal quality of 45 steel through industrial trials and a three-dimensional flow-heat transfer-solidification coupling model were investigated.The results showed that the internal cracks induced by soft reduction exhibited a characteristic of being"coarse in the middle and fine at both ends",and displayed an elliptical arc distribution on the loose side of the strand cross section.The cracks originated within the brittle temperature range and propagated inward to the liquid impenetrable temperature and outward to the zero ductility temperature or below.The control strategy for enhancing the internal quality of the 45 steel strand through soft reduction is to adjust the casting speed or the reduction zone appropriately,ensuring that the central solid fraction of the reduction zone falls within the range of 0.33-0.99.At this point,a reasonable reduction amount is allocated to eliminate the center shrinkage cavities and center segregation,even if it results in minor reduction-induced cracks.

Clustering and Expression Analysis of Chitinases in Maize and Rice

Chitinases play an important role in regulating plant growth and development, especially defending themselves from fungal pathogens. It is important to do the biological analyses in crops. In this study, the result showed that the chitinases were distributed into the whole genome in rice, and nearly the whole genome in maize expect for Chromosome 9. The clustering results showed that one out of three chitinases from maize and rice belonged to new groups, which were separated from those in the conformed Classes I-VII. The identification of most amino acid sequences was very low among the chitinases from rice and/or maize. It was inferred that the chitinases with different functions were relatively stable during plant evolution. The relationship of chitinases expression between leaf blade and anther was positively significant in maize, but not significant in rice. Additionally, the ratio of chitinases with up- or down-regulated expression in sensitive maize under Fusarium moniliforme inoculation was different from that in sensitive rice under Magnaporthe grisea inoculation. It might be result from different tissues infected by different fungi. The number of chitinases from resistant maize was less than that from sensitive maize, which inferred that the resistant pathways on F. moniliforme should be not only chitin induced Pathogen-associated molecular PTI （patterns-triggered immunity） pathway, but also might include other PTI pathways that improve tolerance to F. moniliforme. The analysis of expression pattern of chitinases from maize and rice under fungi inoculation will be contributed into further research on the defense mechanism of fungi in crops.

机械损伤和昆虫取食对紫茎泽兰与本地同属植物防御表达和补偿作用的差异

入侵地群落中的本地草食昆虫取食可以影响植物生长的适合度,从而有助于抵抗外来植物入侵。紫茎泽兰(Eupatorium adenophorum)是一种入侵性很强的外来物种,在中国南方许多省份已形成密集的单优群落。很多学者认为天敌逃逸是外来植物入侵的一个重要原因,但前期研究发现当地的几种广谱天敌能够取食紫茎泽兰。因此,本研究通过与本地同属植物异叶泽兰(E.heterophyllum)比较,来评估是否低水平的防御表达和高的生物量补偿促进了紫茎泽兰的成功入侵。本文分别比较了在广谱天敌棉铃虫(Helicoverpa armigera)取食和机械损伤情况下紫茎泽兰和异叶泽兰早期防御信号茉莉酸(JA)和茉莉酸-异亮氨酸(JA-Ile)、叶绿素荧光、非靶代谢组学特征以及补偿生长等方面的差异。研究结果表明,机械损伤和模拟取食能立即启动入侵植物紫茎泽兰和本地同属植物异叶泽兰的天敌防御,诱导两种植物特异性的生理反馈。异叶泽兰对组织损伤更为敏感,相比于入侵植物紫茎泽兰产生了更丰富的防御化合物。棉铃虫取食比机械损伤对防御诱导的影响更大;与异叶泽兰相比,紫茎泽兰具有较高的补偿生长能力,可以抵消生物量损失和防御成本的投入,受到的影响相对较小。较低的代谢防御和较高的补偿生长可能有助于紫茎泽兰的入侵成功。

Shifts in chemical and microbiological properties belowground of invader Ageratina adenophora along an altitudinal gradient

Tropical mountain ecosystems are usually colonized by numerous invasive plant species and represent an ideal‘natural laboratory’to study the effects of altitude on plant invasion.The aim of this study was to investigate the soil chemical and microbiological properties along an altitudinal gradient on a mountain colonized by the invader Ageratina adenophora.Rhizosphere soil of A.adenophora was collected over an altitudinal gradient(1400–2400 m)in Ailao Shan,China.We determined soil organic carbon(C),nutrient contents,enzyme activities,bacterial community composition as well as C and nitrogen(N)contents of the plant roots.Ecoenzymatic stoichiometric indices were calculated to estimate the relative C,N or P limitations of the microbial community.There was a significant effect of altitude on soil organic C in the rhizosphere,and a turning point in these measured variables was detected at an altitude of 2000 m.At low elevations,the rapid growth of invasive plants depleted the deficient phosphorus(P)in tropical soils,leading to microbial P limitation;at high elevations,microbes invested more energy to obtain C from resistant litter,leading to microbial C limitation.Bacterial beta diversity and soil pH contributed most to the altitudinal differences in ecoenzymatic stoichiometry,and Proteobacteria and Acidobacteria were the dominant bacterial phyla that determined the nutrient uptake status of microorganisms.These results demonstrate how microbial nutrient acquisition belowground of A.adenophora along an altitudinal gradient,which could contribute to further knowledge about the effects of altitude on biological invasion.