Background: Plant chloroplast DNA (cpDNA) typically has a circular structure, including a large single-copy region (LSC), a small single-copy region (SSC) and two inverted repeats (IR1 and IR2). The organization of these four elementary regions LSC-IR1-SSC-IR2 is highly conserved across all plant cpDNAs. Only very a few structural variations (SVs) occurring at the elementary-region level have been reported. Results: In the present study, we assembled the full-length cpDNA of Dongxiang wild rice line 159 (DXWR159). Using the long PacBio subreads, we discovered a large inversion of SSC and a large duplication of IR in DXWR159 cpDNAs. The large inversion of SSC results in a reverse orientation of SSC. According to the orientation of SSC, the structures of cpDNAs can be classified into the forward SSC (SSC-F) and reverse SSC (SSC-R) types. As the most significant finding, both SSC-R and SSC-F type cpDNAs were detected in several seedlings of DXWR159 with a ratio of 1.2. The frequent inversion of SSC was named as SSC switching.Conclusions: The frequencies of Short tandem repeats (STRs) and large SVs in plant cpDNAs need to be intensely investigated for rediscovery. STRs may not be useful as molecular markers in phylogenetic studies, particularly at low taxonomic levels. We propose that: (1) SSC switching ubiquitous occurs in plant cpDNAs and is not a rarely occurring event; (2) SSC switching may be active or inactive by regulation at the molecular level; and (3) further investigation of the underlying mechanism may reveal novel and important functions associated with SSC switching.
With the increase of deep wells, high temperature and high pressure wells and complex wells, the demand for logging is also increasing. Wireline logging is an important technical means to obtain downhole data in the process of petroleum testing. This paper establishes a cable mechanics model by analyzing the main influencing factors of the cable force in the inclined well section or the vertical well section. Calculate the lifting power of the tool. Through logging calculation, the force change law of the downhole cable and tool string is obtained when the wellhead pressure changes.
Unlike conventional long-wall mining, the roofing activity is more intense when the long-wall face passes through the abandoned roadway. Technically, the coal pillar between the abandoned roadway and the long-wall face will suddenly fail with a certain critical value of its width, leading to the roof breaks in advance and other production-restricted problems because of the support loss, which will be a great threat to underground mining activities. In order to guarantee safe mining conditions, it is a great necessity to uncover how the roof breaks in advance and how to deal with it. From the stability maintaining of the key block perspective, this study looked at research from the 12404–1 long-wall face of Wulanmulun coal mine, China. The critical value of the coal pillar’s width was determined to be about 4.75 m by theoretical analysis, and likely, the appropriate supporting force of the abandoned roadway’s roof is about 1073 kN per meter. In this study, a numerical simulation method was adopted to study the ground pressure when the long-wall face is passing through the abandoned roadway. Correspondingly, a compound supporting technology involving the roof presplit technique, anchor cable supporting, and pumping pillar supporting was proposed for the roof of the abandoned roadway, and it practically worked well.
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