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In this paper, a gas roadway with multiple coal seams in southwest China is taken as the test site, and the separate-layer hydraulic fracturing and multilayers comprehensive hydraulic fracturing are carried out. This paper analyzes the whole process of coal seam fracturing development, discusses the influence of water injection volume in coal seam on subsequent drilling construction, and obtains the distribution law of gas content and water content of coal seam after fracturing, and the gas drainage effect. And the fracturing influence ranges of the two fracturing methods are obtained. The results show that the hydraulic fracturing in coal seam composes of five stages: stress accumulation, fracture initiation, fracture propagation, multiple fracture initiation and propagation, and fracture propagation completion. Compared with the multilayers comprehensive hydraulic fracturing, the average pressure of separate-layer hydraulic fracturing is slightly higher, but the total water injection volume is significantly less. The gas content and water content of coal seam after separate-layer hydraulic fracturing are lower and higher than those of comprehensive fracturing technology, respectively; and the initial gas drainage concentration of coal seam is also higher. In addition, the average gas drainage concentration of single hole and drilling field are 54.1% and 43%, increased by 14.9% and 9% compared with comprehensive fracturing technology. And the effective fracturing influence radius of separate-layer fracturing and multilayers comprehensive fracturing reaches about 50 m and 40 m, respectively. This indicates that the separate-layer hydraulic fracturing technology can significantly improve the effective influence range and effect of seam permeability improvement in coal seam group. Moreover, the separate-layer hydraulic fracturing technology can reduce the water injection volume in coal seam, decreasing the bad phenomena in the subsequent drilling construction of gas drainage borehole, such as sticking drilling.

Gas drainage through long seam boreholes is an effective method to prevent gas disasters in coal mines. In this paper, a multifield coupling model of gas migration in gas-bearing coal was first established. Then, a quantitative characterization method of gas drainage effect was put forward. Finally, the extraction effect of long boreholes was obtained under different layouts and drilling lengths. The research results show that, under the arrangement of long boreholes along the seam, the gas pressure around the borehole decreases significantly with the extraction time. There is no extraction blank in the middle of the working face. However, it is easy to cause uneven gas drainage in the combined arrangement of the long boreholes along the seam and the penetrating boreholes. Furthermore, it is found that the drainage volume of the long boreholes along the seam is similar to that of the joint layout under the same drainage time. As the length of the borehole increases, the influencing range of gas drainage increases. When the borehole lengths are 150 m and 240 m, the drainage volumes are about 1.31 and 2.50 times that of the 90 m boreholes, respectively. The research achievements could provide a specific reference for the layout of long boreholes along the bedding and the determination of reasonable parameters for gas drainage on site. [ABSTRACT FROM AUTHOR]

Stress is one of the main factors influencing coal and gas outbursts. The apparent effects of the crustal stress, the structural stress, and the mining-induced stress increase as the depth of mining increases. At present, there have been few studies of the relationship between the comprehensive analyses of the crustal stress, mining-induced stress, and coal gas. The in situ measurement of the relationship between stress-related behaviors and coal gas under the influence of mining was conducted through experimental analysis of surrounding rock support and coal and gas outburst control and optimization of surrounding rock support materials and system construction. The results showed that the mining-induced stress first increased to a peak value, then gradually decreased, and tended to stabilize as the footage progresses. Stress appears at 96 m ahead due to mining; after 57 m of advancing, there is a large increase until it passes through this area. The stress in front of the working face increases linearly, and the increase range is obviously larger than that of the coal body in a certain range on both sides. The support anchoring force gradually decreased and tended to be stable after rapidly increasing to a maximum value. The deep displacement of the roof increased linearly and tended to be stable after reaching an accumulated displacement which can reach 16-28 mm. The residual gas pressure in front of mining operations decreased rapidly, and beyond 15 m on each side of the roadway, it decreased significantly. The residual gas pressure and gas content were consistent with the gas desorption index of drill cuttings due to the influences of gas predrainage and mining. The stress along the direction of the roadway and the residual gas content, the residual gas pressure, and the gas desorption index of drill cuttings conform to the logarithmic functional relationship. The research results provide a basis for the comprehensive prevention and control of coal and gas outbursts from multiple angles considering stress, coal, and gas. [ABSTRACT FROM AUTHOR]

Actinobacteria are important producers of bioactive compounds. Extreme ecosystems cause evolution of novel secondary metabolic pathways of Actinobacteria and increase the possible discovery of new biological functions of bioactive compounds. Here, we isolated 65 Actinobacteria from rhizosphere soil samples of Opuntia stricta. An Actinobacteria strain (named SCA3-4) was screened against Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4, ATCC 76255). The strain produced pink–white aerial mycelia and brown substrate mycelium on Gause No. 1 agar. Biverticillate chains of cylindrical spores were observed by scanning electron microscopy (SEM). Based on alignment of 16 S rRNA sequences, a constructed phylogenetic tree showed that strain SCA3-4 shared a 99.54% similarity with Streptomyces lilacinus NRRL B-1968T. The morphological, biochemical, physiological, and molecular characteristics further indicated that strain SCA3-4 belongs to the Streptomyces sp. It can grow well on medium with the following antibiotics chloramphenicol, streptomycin, penicillin-G, gentamicin, erythromycin, nystatin or neomycin sulfate. The polymerase chain reaction (PCR) amplification of types I and II polyketide synthase genes (PKS-I and PKS-II) suggested its bioactive potential. Under treatment with 100 μg/ml of ethyl acetate extracts isolated from Streptomyces sp. SCA3-4, growth of Foc TR4 was inhibited and cell membrane was destroyed. Crude extracts also showed a broad-spectrum antifungal activity against 13 phytopathogenic fungi including Foc TR4 and displayed the lowest minimum inhibitory concentration (MIC) (0.781 μg/ml) against Colletotrichum fragariae (ATCC 58718). A total of 21 different compounds identified by gas chromatography–mass spectrometry (GC-MS) were composed of phenolic compound, pyrrolizidine, hydrocarbons, esters, and acids. Besides the known active compounds, Streptomyces sp. SCA3-4 possesses antimicrobial or other biological activities. Further attention will be paid on other compounds with no functional annotation, aiming at the discovery of new bioactive substances. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) represent a class of endogenous non-coding small RNAs that play important roles in multiple biological processes by degrading targeted mRNAs or repressing mRNA translation. Thousands of miRNAs have been identified in many plant species, whereas only a limited number of miRNAs have been predicted in M. acuminata (A genome) and M. balbisiana (B genome). Here, previously known plant miRNAs were BLASTed against the Expressed Sequence Tag (EST) and Genomic Survey Sequence (GSS), a database of banana genes. A total of 32 potential miRNAs belonging to 13 miRNAs families were detected using a range of filtering criteria. 244 miRNA:target pairs were subsequently predicted, most of which encode transcription factors or enzymes that participate in the regulation of development, growth, metabolism, and other physiological processes. In order to validate the predicted miRNAs and the mutual relationship between miRNAs and their target genes, qRT-PCR was applied to detect the tissue-specific expression levels of 12 putative miRNAs and 6 target genes in roots, leaves, flowers, and fruits. This study provides some important information about banana pre-miRNAs, mature miRNAs, and miRNA target genes and these findings can be applied to future research of miRNA functions. [ABSTRACT FROM AUTHOR]

The cover image is based on the Full Paper Preparation and characterization of magnetic hollow Fe3O4/P(GMA‐EGDMA)‐SO3H/Au‐PPy recyclable catalyst for catalytic reduction of 4‐nitrophenol by Na An et al., https://doi.org/10.1002/aoc.4739. [ABSTRACT FROM AUTHOR]

A highly effective and stable hollow Fe3O4/P(GMA‐EGDMA)‐SO3H/Au‐PPy catalyst was prepared. Monodisperse hollow Fe3O4 microspheres were synthesized using a hydrothermal method. As the catalyst support, magnetic hollow Fe3O4/P(GMA‐EGDMA) microspheres with core–shell structure were prepared by distillation precipitation polymerization. Then sulfonic acid groups (─SO3H) were introduced into the surface of the support by surface modification. Au3+ could be adsorbed by coordination with ─SO3H and underwent redox reactions with added pyrrole monomers. Finally, an Au–polypyrrole (PPy) layer was formed on the surface of the Fe3O4/P(GMA‐EGDMA)‐SO3H microspheres. The synthesized material was characterized using various techniques. Results indicated that the as‐prepared hollow Fe3O4/P(GMA‐EGDMA)‐SO3H/Au‐PPy catalyst had excellent catalytic activity and exhibited reusability for the reduction reaction of 4‐nitrophenol. In addition, the catalyst was reusable for at least ten successive cycles. A highly effective and stable hollow Fe3O4/P(GMA‐EGDMA)‐SO3H/Au‐PPy catalyst was prepared and characterized. The catalyst had excellent activity and exhibited reusability for the reduction reaction of 4‐nitrophenol. In addition, the catalyst was reusable for at least 10 successive cycles. [ABSTRACT FROM AUTHOR]