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The 52307 working face with large mining height in Daliuta coal mine is chosen as the research background, where there is the special mining condition in the overburden structure with a buried depth of more than 150 m and only one layer of key structure in Shendong mining area. Using the methods of similarity simulation experiment and theoretical analysis, the overburden movement law based on the arch mechanical model of plane contact block is systematically researched. The research results indicate that before the initial weight, the main key layer appears layered fracture in the mining process, and its lower rock layer becomes a part of the collapse zone. Before the initial weight, the upper key layer forms a “fixed supported beam” structure. When the beam reaches the limit length, shear failure occurs in the middle position; during the periodic weight, the upper key layer breaks into the plane contact block arch structure close to the same size. Relying on the friction between the contact planes, it has a certain displacement but does not collapse completely. The load transmitted from overburden is transmitted to the rear of the gob through the semiarch characteristics of the structure; the sliding instability and rotary deformation instability of the plane contact block arch structure are analyzed. The fracture of the key layer lags behind the mining position of the working face by a certain distance, due to the influence of the fracture angle of collapse zone in the advancing process of working face. The research results provide an important guiding significance for prediction and prevention for dynamic disaster of rock strata in working face with large mining height.

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The paper introduced testing method of mean time between failures, did site test of mean time between failures in four coal mines to the same coal mine monitoring system, and got mean time between failures of main equipments of the monitoring system. It concluded: the values of mean time between failures of intrinsic safety power, gas sensor, CO sensor and wind speed sensor are relatively small, and these equipments should be the focus of future design and improvement; the monitoring system can achieve the index suggested in AQ 6201—2006 that mean time between failures should be not less than 800 hours; statistical results show that line fault of underground coal mine occurs frequently.

Aim: To determine whether etomidate (ET) has a protective effect on retinal ganglion cells (RGCs) injured with hydrogen peroxide (H 2 O 2 ) and to explore the potential mechanism underlying the antioxidative stress effect of ET., Methods: Cultured RGCs were identified by double immunofluorescent labeling of microtubule-associated protein 2 and Thy1.1. An injury model of H 2 O 2 -induced RGCs oxidative stress was established in vitro . Cells were pretreated with different concentrations of ET (1, 5, and 10 µmol/L) for 4h, followed by further exposure to H 2 O 2 at 1000 µmol/L. Cell counting kit 8 and Annexin V/propidium iodide assays were applied to detect the viabilities and apoptosis rates of the RGCs at 12, 24, and 48h after H 2 O 2 stimulation. The levels of nitric oxide, malondialdehyde, and glutathione in culture media were measured at these time points. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot were performed to observe the effects of ET on the messenger RNA and protein expression of inducible nitric oxide synthase (iNOS), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), glutathione peroxidase 1 and the level of conjugated acrolein in RGCs at 12, 24, and 48h after H 2 O 2 stimulation and in the retina at 12h after optic nerve transection (ONT)., Results: The applications of 5 and 10 µmol/L of ET significantly increased the viability of RGCs. Results from qRT-PCR indicated a decrease in the expression of iNOS and an increase in the expressions of Nrf2 and HO-1 in ET-pretreated RGCs at 12, 24 and 48h after H 2 O 2 stimulation, as well as in ET-treated retinas at 12h after ONT. Western blot analysis revealed a decrease in the expression of iNOS and levels of conjugated acrolein, along with an increase in the expressions of Nrf2 and HO-1 in ET-pretreated RGCs in vitro and ET-treated retinas in vivo ., Conclusion: ET is a neuroprotective agent in primary cultured RGCs injured by H 2 O 2 . The effect of ET is dose-dependent with the greatest effect being at 10 µmol/L. ET plays an antioxidant role by inhibiting iNOS, up-regulating Nrf2/HO-1, decreasing the production of acrolein, and increasing the scavenge of acrolein., Competing Interests: Conflicts of Interest: Zhao X, None; Fan DG, None; Zhang XC, None; You SW, None; Kuang F, None; Wu MM, None., (International Journal of Ophthalmology Press.)

Purpose: We aimed to provide anatomical data and mechanical tensile properties for the rectus femoris tendon to determine if it is a feasible substitute for the anterior cruciate ligament during knee joint reconstruction., Methods: The length and width of the quadriceps femoris tendon were measured from ten adult cadavers (20 knees; age =48±2 years). The anatomic features of the patellar insertion on the quadriceps femoris tendon were also documented. The rectus femoris tendon and anterior cruciate ligament were harvested from an additional five fresh specimens (10 knees; age =41±3 years). To minimize dehydration, each specimen was wrapped in saline-moistened paper towels and stored at -10°C. We imposed tensile stresses on a total of twenty samples in a sample-driven machine at 10 mm/min until the specimens failed., Results: The inserted and discrete widths of the rectus femoris tendon were 3.20±0.33 and 1.28±0.25 cm, respectively. The length of the tendon tissue was 6.96±0.80 cm and the length of mixing zone was 3.81±0.53 cm. The average thickness of the upper pole of the patella was 2.22±0.14 cm. In mechanical tensile properties, the unit modulus and unit maximum load of the rectus femoris tendon were both 63% of the anterior cruciate ligament., Conclusions: Based on its anatomical and mechanical tensile properties, the rectus femoris tendon is a feasible donor site to reconstitute the anterior cruciate ligament.

Sudden cardiac death (SCD) is the most common death mode. No test has been able to accurately predict SCD. This article reviews the risk factors and warning signs of SCD with an attempt to effectively prevent SCD events.