The focus of this paper is the thick soft rock mass roof of the track roadway in the No. 3606 panel of the Chaili Coal Mine. Due to its substantial thickness, the soft rock mass roof of the roadway ...is susceptible to damage and deformation during the mining process. In order to preserve the integrity of the roadway roof, a full anchor cable support scheme is proposed after studying the mechanism of bolt-anchor cable support. The supporting parameters and feasibility of the scheme were determined through support experience and numerical simulation analyses in the field. Moreover, on-site monitoring and data analysis were conducted, revealing that the anchor cables and anchor bolts played a stable role in supporting the roadway. The displacement of the roadway’s roof and floor was minimal, as was the displacement of the two ribs. The overall deformation of the roadway was minor. Practice demonstrated that the full anchor cable support method was effective in supporting the immediate roof of thick soft rock.
The multifractal structure of shale pores significantly affects the occurrence of fluids and the permeability of shale reservoirs. However, there are few studies on the multifractal characteristics ...of shale pores that distinguish between organic and inorganic pores. In this study, we obtained the pore size distribution (PSD) of organic and inorganic shale pores separately by using a new NMR-based method and conducted a multifractal analysis of the structure of organic and inorganic shale pores based on PSD. We then investigated the geological significance of the multifractal characteristics of organic and inorganic shale pores using two multifractal characteristic parameters. The results showed that the structures of both organic and inorganic pores have multifractal characteristics. Inorganic pores have stronger heterogeneity and poorer connectivity compared to organic pores. The multifractal characteristics of inorganic pores significantly affect shale permeability and irreducible water saturation. Greater heterogeneity in the inorganic pore structure results in lower shale permeability and higher irreducible water saturation. Meanwhile, better connectivity leads to higher shale permeability and lower irreducible water saturation. The multifractal characteristics of organic pores significantly affect the shale adsorption capacity and have a weak impact on irreducible water saturation. Greater heterogeneity in the organic pore structure results in the shale having stronger adsorption capacity and higher irreducible water saturation The results also indicate that the multifractal characteristic parameters of inorganic pores can be regarded as an index for estimating the irreducible water saturation and flowback rate of fracturing fluid, and the multifractal characteristic parameters of organic pores can be regarded as an index for evaluating the quality of shale reservoirs.
To investigate the overburden movement and the side abutment pressure distribution concerning the variation in deep mines with varying coal seam thickness, this study focused on the No. 72 mining ...area of Tianchen Coal Mine and obtained the following results: Variations in coal seam thickness within a stope lead to increased immediate roof thickness. When the coal seam thickness is 8 m, the maximum immediate roof thickness reaches 18 m. The roof is composed of a “Combined short cantilever-Voussoir beam” structure. Displacement curves of overburden in coal seam thickness-varying stopes exhibit asymmetry, with the overburden closer to the coal seam being more asymmetric. After post-goaf stabilization, the peak side abutment pressure decreases with increasing coal seam thickness and shifts deeper into the coal wall. Concurrently, the ultimate equilibrium area width expands. With an increase in coal seam thickness from 4 m to 8 m, the peak side abutment pressures decreased from 44.98 MPa to 41.04 MPa. The peak position shifted from a distance of 9 m from the coal wall to 14 m, while the stress-relaxation area expanded from 3 m to 5 m. This research provides essential insights for safe and efficient mining in similar conditions.
The development of a simple, portable and accurate instrument used in the evaluation of in vitro cytotoxicity is particularly important and urgent in the field of toxicology research at present. In ...the current study, a miniature electrochemical detection system was constructed that integrated graphene oxide quantum dots and multiwall carbon nanotubes modified anodized screen printed carbon electrode (GOQDs/MWCNTs/SPCE*) with a mini reaction vessel, which reduced the consumption of sample from 500 to 80 μL. Four electrochemical signals could be detected in cells distinctly for the first time which were attributed to the oxidation of uric acid, guanine/xanthine, adenine and hypoxanthine, respectively. This miniature electrochemical detection system has better selectivity, sensitivity and its detection limits were lower than those of most electrochemical sensors. Furthermore it has been found that the level of purine nucleotide metabolism in BALB/3T3 cells and MCF-7 cells was different, which could be related to the different purine nucleotide metabolisms of cancer cells and non cancer cells. The simple, portable and miniature electrochemical detection system could be used as a convenient instrument for toxicology detection.
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•A miniature electrochemical detection system was constructed that reduced the consumption of sample from 500 to 80 μL.•Four electrochemical signals attributed to UA, G/X, A and HX could be detected in cells for the first time.•The level of purine nucleotide metabolism in BALB/3T3 cells and MCF-7 cells has been found different.
In situ stress is one of the most important factors affecting surrounding rock stability classification of coal roadway. Most surrounding rock stability classification methods do not fully consider ...the influence of in situ stress. In this paper, the author applied a fuzzy clustering method to the classification of surrounding rock stability of coal roadway. Taking into account the complexity of the classification of surrounding rock, some factors such as the strength of surrounding rock, in situ stress, the main roof first weighting interval, the size of the chain pillar, and the immediate roof backfilled ratio are selected as the evaluation indexes. The weight coefficients of these evaluation indexes are determined by unary regression and multiple regression methods. Using fuzzy clustering and empirical evaluation method, the classification model of surrounding rock stability of coal roadway is proposed, which is applied to 37 coal roadways of Zibo Mining Group Ltd., China. The result is in good agreement with practical situation of surrounding rock, which proves that the fuzzy clustering method used to classify the surrounding rock in coal roadway is reasonable and effective. The present model has important guiding significance for reasonably determining the stability category of surrounding rock and supporting design of coal roadway.
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•A simple and sensitive electrochemical sensor based on RGOQDs was developed by electrodeposited.•RGOQDs could enhance the electrochemical response intensity of UA, X and G with a ...lower detection limits of 0.024μM.•The RGOQDs/GCE was used to evaluate the cytotoxicity of fluorene on MCF-7 cells for the first time.
Fluorene was one of the priority controlled polycyclic aromatic hydrocarbons (PAHs) and distributed abundantly in the environment, which has a great harmful on human body. It was very important to detect the cytotoxicity of fluorene with a rapid and accurate method. In this present work, a simple and ultrasensitive electrochemical biosensor was developed by electrodeposition of reduced graphene oxide quantum dots (RGOQDs) on glassy carbon electrode (GCE) for the first time. The electrochemical behaviors of uric acid (UA), xanthine (X) and guanine (G) were studied on RGOQDs/GCE by differential pulse voltammetry (DPV) with a limit of detection of 0.024μM, respectively. Then the electrochemical biosensor was used to evaluate the cytotoxicity of fluorene for MCF-7 cells based on the variation of G/X in MCF-7 cells solution. The result showed that fluorene exposed to MCF-7 cells at the concentration range of 0–0.05mM could promote cell proliferation, the concentration above 0.05mM exhibited inhibitory effect, which was verified by methyl-thiazolyl-tetrazolium (MTT) assay. The electrochemical biosensor based on RGOQDs/GCE could be used not only for evaluation the cytotoxicity of PAHs, but also for detection the physiological process related to intracellular purine nucleotide metabolism.
•This article summarized the development course of biodegradable cardiovascular stents.•The present in vivo experimental results of Mg-based stents were briefly reviewed.•The strategies for surface ...endothelialization of cardiovascular stents were summarized.•The recent advances in surface endothelialization of magnesium alloy stent materials were reviewed.•The key issues and future direction of magnesium alloy stents were proposed in the present article.
Magnesium and its alloy have good mechanical properties and biodegradability, and have become the hotspot of the next-generation biodegradable vascular stent materials. However, their rapid degradation in vivo and poor biocompatibility are still the bottlenecks of clinical applications for the cardiovascular stents. In particular, how to induce the repair and regeneration of the vascular endothelial with normal physiological functions on the surface of the magnesium alloy stent materials represents the key to its clinical application in the field of cardiovascular stents. It has been believed that it is an ideal way to completely solve the postoperative complications through constructing the multifunctional anti-corrosive bioactive coating on the magnesium alloy surface to induce the formation of vascular endothelium with normal physiological functions. However, how to construct a corrosion-resistant multifunctional bioactive coating with the good endothelial regeneration abilities on the magnesium alloy surface still faces a great challenge. This paper mainly focused on highlighting and summarizing the recent advances in the surface endothelialization of the magnesium alloy materials for the vascular stent, including the bio-inert coating, in-situ immobilization of bioactive molecules on the surface, polymer coating loaded with bioactive factors, novel multifunctional polymer coating, bioactive micropatterns, bioactive layer with glycocalyx-like structure, NO-releasing coating and bioactive sol-gel coating. The advantages and disadvantages of these strategies were discussed and analyzed. Finally, in the senses of future development and clinical application, this paper analyzed and summarized the development direction and prospect of surface endothelialization of the magnesium alloy vascular stents. It is anticipated that this review can give the new cues to the surface endothelialization of the cardiovascular magnesium alloy stents and promote future advancements in this field.
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