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The objective of this work was to investigate the self-healing properties and mechanical damage characteristics of dissolved salt columns under different humidity and time conditions. Based on the results of electron microscope scanning and uniaxial mechanical tests, the microscopic element distribution of the ore and the microscopic morphology of the minerals were investigated, and the healing, mechanical, and damage properties of the specimens were analyzed, which revealed the microscopic reinforcement mechanism of the damage healing of the dissolved salt columns. The results showed that the healing reinforcement, compressive strength, and modulus of elasticity of dissolved salt columns under uniaxial compression show a tendency to increase, then decrease with the increase of humidity, and gradually increase with the increase of the maintenance time and reach the maximum value at 10% humidity and 30 days of maintenance time, which are 3.48, 8.07, and 650 MPa, respectively. The damage type of the healed specimen as a whole gradually transitioned from tensile damage to shear-slip type, indicating that the brittle damage characteristics of the specimen under loading became more and more significant. Based on the principle of strain equivalence, the damage evolution equation under uniaxial compression of solid potash dissolved salt columns describes the damage evolution law and destruction process of the specimen, and the results of the damage characterization of the dissolved salt columns are consistent with the change rule of the healing properties and mechanical properties with humidity and conservation time. Based on the fine morphological features of the dissolved salt column specimens after self-healing, three different self-healing microscopic mechanisms for damage recovery of solid potash dissolved salt columns are summarized, namely, healing of damaged microcracks based on diffusion, recrystallization healing of brine-filled microfractures, and healing adhesion of crystal particles in dissolved zones. These microstructures effectively transform cracks into isolated sections and play a key role in improving mechanical properties. In addition, the higher the humidity, the thicker adsorbed water film is produced on the fissure surface, which accelerates the transportation of materials on the fissure surface, and the healing rate of the dissolved salt columns increases. However, when the humidity is too high, it causes the evaporation of the liquid film to be less than the recharge of water vapor, which reduces the healing rate of the dissolved salt columns. Thus, suitable humidity produces a more pronounced healing effect than an environment maintained at a constant high humidity level. The research results can provide theoretical guidance for the filling mining of solid potassium salt.

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Under the context of territorial spatial planning in the new era, it is of great significance to analyze the future land use competition pattern to construct a sustainable and adaptive management strategy for territorial spatial development and utilization protection. Taking Shenyang, a megacity in Northeast China, as the case study area, and the geographic information system technologies and the patch-generation land use simulation (PLUS) model was used to simulate the land use competition pattern in 2030 under four scenarios. Meanwhile, the dynamic evolution of territorial spatial structure competition was monitored based on the perspective of agricultural, ecological, and construction land space. The results show that land use competition was driven by food security, economic growth, and ecological protection. The results showed that (1) the most frequent changes in cultivated land and construction land were found in 1980, 1990, 2000, 2010, and 2020, and their competitive advantage among land use types was obvious. As for the driving mechanism, the influencing effect of socioeconomic factors on land use type competition was more significant than that of natural factors. (2) The competitive dominance scenario of cultivated land protection and the synergistic dominance scenario of cultivated land, ecological, and construction could help optimize and control the land use competition pattern. (3) The information entropy and equilibrium index of the territorial spatial structure increase in both scenarios; the dominance index decreases, and the proportion of agricultural, ecological, and construction space is more coordinated. The results may assist a holistic understanding of land use change to coordinate the competition among agricultural, ecological, and construction space and facilitate the realization of high-quality territorial spatial development goals.

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The objective of this work was to investigate the damage characteristics and failure modes of gypsum rock under dynamic impact loading. Split Hopkinson pressure bar (SHPB) tests were performed under different strain rates. The strain rate effects on the dynamic peak strength, dynamic elastic modulus, energy density, and crushing size of gypsum rock were analyzed. A numerical model of the SHPB was established using the finite element software, ANSYS 19.0, and its reliability was verified by comparing it to laboratory test results. The results showed that the dynamic peak strength and energy consumption density of gypsum rock increased exponentially with strain rate, and the crushing size decreased exponentially with the strain rate, both findings exhibited an obvious correlation. The dynamic elastic modulus was larger than the static elastic modulus, but did not show a significant correlation. Gypsum rock fracture can be divided into crack compaction, crack initiation, crack propagation, and breaking stages, and is dominated by splitting failure. With increasing strain rate, the interaction between cracks is noticeable, and the failure mode changes from splitting to crushing failure. These results provide theoretical support for improvements of the refinement process in gypsum mines.

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The stability of cultivated land ecosystem is crucial to the green and high-quality development of agriculture. Revealing its spatio-temporal differentiation is an important scientific issue to improve the resilience of cultivated land and ensure food security. In this paper, Shenyang, a typical region of Lower Liaohe Plain, is the study area. Starting from the stress buffer response process of cultivated land ecosystem stability, USLE, RWEQ, SDI, RSEI and grey relational model are used to clarify the relationship between the three, and depict the temporal and spatial differentiation pattern of cultivated land ecosystem stability. The results showed that the external stress intensity of cultivated land in Shenyang decreased as a whole, but the stress intensity of cultivated land distributed in the northern and southeast hilly areas increased. Most of the endogenous buffer strength has been improved, and the buffer capacity of cultivated land in the northern hilly region has declined on a large scale. More than half of the response intensity to the effect has been improved, while the response intensity of cultivated land in the west and north has generally declined. The stability of cultivated land ecosystem in Shenyang has been improved for the most part, but in the hilly areas in the north and southeast, the stability in the lower reaches of Liaohe River plain in the south has declined. Terrain conditions and high-intensity cultivation patterns are the important reasons for the temporal and spatial differentiation of cultivated land ecosystem stability in the study area. The study clarified the dynamic process of cultivated land ecosystem stability and provided an important way to grasp the scientific law of stability change.

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KEY MESSAGE: Rf candidate genes were related to the super D05_PPR-cluster and verified to be individually nonfunctional. Restorer of fertility (Rf) genes of cytoplasmic male sterility (CMS) is commonly found to be PPR (pentatricopeptide repeat) genes, which are mostly located in a cluster of PPR genes with high similarity. Here, Homocap-seq was applied to analyze PPR clusters in 'three lines,' and we found broad variations within the D05_PPR-cluster in a restorer line and deduced that the D05_PPR-cluster was associated with fertility restoration. Genetic mapping of Rf and Homocap-seq analysis of three genotypes in the F2 population validated that the D05_PPR-cluster was the origin of Rf. Three Rf candidates were cloned that were the most actively expressed genes in the D05_PPR-cluster in the restorer line as revealed by their high-depth amplicons. However, further transgenic experiments showed that none of the candidates could restore fertility of the CMS line independently. Then, the members of the brand-new super D05_PPR-cluster in the restorer line, containing 14 full-length PPRs and at least 13 PPR homologous sequences, were identified by long-read resequencing, which validated the effectiveness of variation and expression prediction of Homocap-seq. Additionally, we found that several PPR duplications, including 2 of the 3 Rf candidates, had undergone site-specific selection as potentially important anther development-associated genes. Finally, we proposed that multiple PPRs were coordinately responsible for the fertility restoration of the CMS line.

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BACKGROUND: Cotton is the dominant textile crop and also serves as an important oil crop. An estimated 15% economic loss associated with cotton production in China has been caused by diseases, and no resistance genes have been cloned in this crop. Molecular markers developed from resistance gene homologues (RGHs) might be tightly linked with target genes and could be used for marker-assisted selection (MAS) or gene cloning. RESULTS: To genetically map expressed RGHs, 100 potential pathogenesis-related proteins (PRPs) and 215 resistance gene analogs (RGAs) were identified in the cotton expressed sequence tag database, and 347 specific primers were developed. Meanwhile, 61 cotton genome-derived RGA markers and 24 resistance gene analog polymorphism (RGAP) markers from published papers were included to view their genomic distribution. As a result, 38 EST-derived and 17 genome-derived RGH markers were added to our interspecific genetic map. These 55 markers were distributed on 18 of the 26 cotton chromosomes, with 34 markers on 6 chromosomes (Chr03, Chr04, Chr11, Chr17, Chr19 and Chr26). Homologous RGHs tended to be clustered; RGH clusters appeared on 9 chromosomes, with larger clusters on Chr03, Chr04 and Chr19, which suggests that RGH clusters are widely distributed in the cotton genome. Expression analysis showed that 19 RGHs were significantly altered after inoculation with the V991 stain of Verticillium dahliae. Comparative mapping showed that four RGH markers were linked with mapped loci for Verticillium wilt resistance. CONCLUSIONS: The genetic mapping of RGHs confirmed their clustering in cotton genome. Expression analysis and comparative mapping suggest that EST-derived RGHs participate in cotton resistance. RGH markers are seemed to be useful tools to detected resistance loci and identify candidate resistance genes in cotton.

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