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The development of trench-arc-backarc (TABA) systems is uniquely associated with modern-style plate tectonics on Earth. The Qilian orogenic belt in NW China records the evolution history of the Proto-Tethys Ocean at the transition time from the Proterozoic to Phanerozoic. This paper presents systematic studies of petrography, U–Pb chronology and geochemistry on various rocks from a middle-ocean ridge (MOR)-type ophiolite belt, active continental margin and back-arc basin in the Qilian orogenic belt to address the development of a modern-style TABA system. Arc magmas include felsic intrusions with ages of 531 to 477 Ma and felsic-mafic arc volcanic rocks with ages of 506 to 439 Ma, showing distinctive features of typical magmatic rocks formed at an Andean-type continental margin. The back-arc basin is recorded by a 490- to 448-Ma suprasubduction zone (SSZ)-type ophiolite with boninite, and Silurian turbidite flysch formation. We establish a three-stage tectonic history from the initiation of subduction to the formation of a mature Japan-Sea-type back-arc basin at the active continental margin in the Early Paleozoic era. (1) Northward subduction of Proto-Tethys Ocean initiated and the Andean-type continental arc developed at ~530 to 500 Ma with continual crustal thickening; (2) a tectonic transition occurred from an Andean-type active continental margin to a West Pacific-type active continental margin at ~500 to 490 Ma with rapid thinning of crust to ~35 km; and (3) mature ocean basins and back-arc-basin (BAB) ophiolites were formed in the back-arc extensional environment at ~490 to 450 Ma. [ABSTRACT FROM AUTHOR]

Monochamus alternatus , the dominant vector of Bursaphelenchus xylophilus (Aphelenchida: Aphelenchoididae), has caused immense damage to forest resources. In China, this vector was native to the southern regions but has spread northward recently. To adapt to more challenging environments in the northern winter, M. alternatus has evolved an intricate strategy for overwintering, which remains largely unknown. Herein, we compared the transcriptome data of the overwintering and non-overwintering larvae of M. alternatus larvae to investigate the molecular mechanisms in overwintering. A total of 53.10 GB clean bases and 28, 245 unigenes were obtained by RNA-seq. Analysis of 2597 upregulated and 2429 downregulated unigenes, as well as the enrichment of DEGs showed that many genes and pathways were jointly involved in the overwintering period. Besides, the accuracy of the RNA-seq data was tested by using qPCR experiment involving 13 selected genes. The results revealed that the overwintering process relied largely on the energy allocation trade-off. Specifically, overwintering M. alternatus inhibited energy-intensive activities, such as growth and molting, detoxification, and trehalose transport, and the reserved energy was skewed towards the synthesis of antifreeze compounds and immune response to cope with the deleterious effects of winter. [ABSTRACT FROM AUTHOR]

In this paper, the occurrence characteristics of the weak and weathered overburden, and hydrogeological features, are first analyzed in a research coal field. The overburden failure law and the development of ‘Three Zones’ are studied through physical model tests, and the rupture pattern and rock failure are analyzed in the conditions of mining under a weakly cemented roof with longwall top coal caving. When coal mining is 5 meters thick, the developmental height of the caving zone and the water flowing fractured zone is calculated as 21 meters and 58 meters, respectively. Based on the geological and mining conditions, through discrete element numerical simulation, the overburden failure law and characteristics of strata pressure behaviors were studied under the weak and weathered composite roof during coal mining. The results show that under the conditions of the weak and weathered composite roof in a thin bedrock working face, the fracture length of old roof pressure will decrease, the abutment stress in front of the working face will distribute within a range of 15 meters, the peak point of abutment pressure in front of the working face will vary from 5 to 15 meters. This is smaller than that of the working face of thick bedrock, but the strata behaviors of the working face are obvious. Based on the field monitoring results, the overburden failure law is analyzed; the feasibility of the model test and the numerical simulation is verified. The influence degree of coal layer safety mining is evaluated; the appropriate water control measures have been submitted purposefully, in order to ensure safe mining. [ABSTRACT FROM AUTHOR]