A NEW METHOD TO CONTROL THE REGIONAL STRATA MOVEMENT OF SUPER-THICK WEAK CEMENTATION OVERBURDEN IN DEEP MINING

In the western of china, the deep mining area with super-thick and weak cementation overburden is vast, sparsely populated and the ecological environment is extremely fragile. With the large-scale exploitation of deep coal resources, it is inevitable to face green mining problem, whose essence is the surface subsidence control. Therefore, it is necessary to study the control technology for the regional mining based on the evolution law of subsidence movement and energy-polling of super-thick and weak cementation overburden, and put forward the economically design scheme that can control strata movement and surface subsidence in a certain degree. Based on the key strata control theory, this paper puts forward the subsidence control scheme of partial filling -partial caving in multi-working face coordinated mining, and further studies its control mechanism through the numerical simulation and then analyzes the control effect of the strata movement and energy-polling in the fully caving mining, backfill mining, wide strip skip-mining and mixed filling mining method etc., the following conclusions are detailed as follows: (1) The maximum value of energy-polling occurs on the coal pillars or on both sides of goaf. With the width of goaf, the maximum value of energy-polling increases in a parabola. (2) In the partial filling-partial caving multiple working faces coordinated mining based on the main key stratum, the stress distribution of the composite backfill in the filling working face is parabolic, and it is high on both sides and low in the middle. Moreover, in the composite backfill, the stress concentration degree of a outside coal pillar is greater than that of the inside coal pillar. (3)The control mechanism of partial filling-partial caving harmonious mining based on main key layer structure is the double-control cooperative deformation system, formed by the composite backfill and the main and sub-key layers structure. They jointly control the movement and energy accumulation of overlying strata by greatly reducing the effective space to transmit upward, and absorb the wave subsidence trend of the overburden until it develops into a single flat subsidence basin. (4) Considering the recovery rate, pillar rate, area filling rate, technical difficulty and subsidence coefficient etc., the partial filling-partial caving multiple working faces coordinated mining based on the main key stratum is the most cost-effective mining method to control surface subsidence. This paper takes a guiding role in controlling the regional strata movement and surface subsidence of deep mining with super-thick and weak cementation overburden

MONITORING DYNAMIC GLOBAL DEFLECTION OF A BRIDGE BY MONOCULAR DIGITAL PHOTOGRAPHY

This study uses MDP (monocular digital photography) to monitor the dynamic global deflection of a bridge with the PST-TBP (Photographing scale transformation-time baseline parallax) method in which the reference system set near the camera is perpendicular to the photographing direction and does not need parallel to the bridge plane. A SONY350 camera was used to shoot the bridge every two seconds when the excavator was moving on the bridge and produced ten image sequences. Results show that the PST-TBP method is effective in solving the problem of the photographing direction being perpendicular to the bridge plane in monitoring the bridge by MDP. The PST-TBP method can achieve sub-pixel matching accuracy (0.3 pixels). The maximal deflection of the bridge is 55.34 mm which is within the bridge’s allowed value of 75mm. The MDPS (monocular digital photography system) depicts deflection trends of the bridge in real time, which can warn the possible danger of the bridge in time. It provides key information to assess the bridge health on site and to study the dynamic global deformation mechanism of a bridge caused by dynamic vehicle load. MDP is expected to be applied to monitor the dynamic global deflection of a bridge

The effect of parenting styles on Chinese undergraduate nursing students’ academic procrastination: the mediating role of causal attribution and self-efficacy

BackgroundAcademic procrastination is common among college students, but there is a lack of research on the influencing mechanism of academic procrastination among nursing students. The purpose of this study was to explore the influence of parental rearing patterns on academic procrastination of nursing students, and the mediating role of causal attribution and self-efficacy.MethodsUsing Parental Bonding Instrument, Aitken Procrastination Inventory, Multidimensional Multi-Attribution Causality Scale and General Self-Efficiency Scale, the data of 683 nursing undergraduates from two universities in China were collected. Moreover, path analysis for structural equation modeling via AMOS 26.0 to evaluate mediation path model.ResultsPositive parenting style was negatively associated with academic procrastination (r = –0.350) and negative parenting style was positively associated with academic procrastination (r = 0.402). Positive parenting style directly or indirectly predicted academic procrastination through the mediating effect of internal attributional style (β = –0.10, 95% CI: –0.18 to –0.04) and self-efficacy (β = –0.07, 95% CI: –0.11 to –0.03), and this mediating effect accounted for 41.46% of the total effect. Positive parenting style directly or indirectly predicted academic delay through the mediating effect of external attributional style (β = 0.12, 95% CI: 0.07 to 0.17) and self-efficacy (β = 0.05, 95% CI: 0.03 to 0.08), and this mediating effect accounted for 42.5% of the total effect. In addition, causal attribution and self-efficacy of nursing students play a chain intermediary role between parenting style and academic procrastination.ConclusionParents should give students more care and autonomy and reduce control. In addition, educators should give students attribution training, which is helpful to improve students’ self-efficacy and reduce academic procrastination

Prediction method of surface subsidence due to underground coal gasification under thermal coupling

Underground coal gasification (UCG) is an essential part of the low-carbon green coal mining technology system. The implementation of the “double carbon” goal of the coal industry has brought excellent development opportunities for UCG. However, UCG will also cause rock movement and surface deformation, resulting in serious threat to safety of ground buildings (structures) when use UCG to recover the “three under” coal that is difficult to mine by underground mining methods. How to accurately predict the subsidence considering characteristics of UCG has become one of the critical bottlenecks limiting the industrial application of UCG. Based on this, combined with the characteristics of ‘strip mining-surface mining’ backward UCG process, this paper explores the causes of surface subsidence caused by UCG under the thermal coupling, and concludes that the root of surface subsidence caused by UCG is the deflection of rock strata and the compression deformation of coking barrier coal pillar. Further, the calculation method of deflection deformation of UCG roof under thermal-mechanical coupling is established, and the yield model and compression calculation method of gasification coal pillar based on D-P criterion are proposed. Then, according to the principle of equivalent subsidence space, an accurate prediction model of surface subsidence of UCG under thermal coupling is constructed, and the effectiveness and accuracy of the new method are verified by the measured data of UCG in Ulanqab. The research results have important practical significance for promoting the recovery of difficult-to-mine “three under” coal resources and the industrialization for UCG

Vancomycin efficiency and safety of a dosage of 40–60 mg/kg/d and corresponding trough concentrations in children with Gram-positive bacterial sepsis

BackgroundOptimal vancomycin trough concentrations and dosages remain controversial in sepsis children. We aim to investigate vancomycin treatment outcomes with a dosage of 40-60 mg/kg/d and corresponding trough concentrations in children with Gram-positive bacterial sepsis from a clinical perspective.MethodsChildren diagnosed with Gram-positive bacterial sepsis and received intravenous vancomycin therapy between January 2017 and June 2020 were enrolled retrospectively. Patients were categorized as success and failure groups according to treatment outcomes. Laboratory, microbiological, and clinical data were collected. The risk factors for treatment failure were analyzed by logistic regression.ResultsIn total, 186 children were included, of whom 167 (89.8%) were enrolled in the success group and 19 (10.2%) in the failure group. The initial and mean vancomycin daily doses in failure group were significantly higher than those in success group [56.9 (IQR =42.1-60.0) vs. 40.5 (IQR =40.0-57.1), P=0.016; 57.0 (IQR =45.8-60.0) vs. 50.0 (IQR =40.0-57.6) mg/kg/d, P=0.012, respectively] and median vancomycin trough concentrations were similar between two groups [6.9 (4.0-12.1) vs.7.3 (4.5-10.6) mg/L, P=0.568)]. Moreover, there was no significant differences in treatment success rate between vancomycin trough concentrations ≤15 mg/L and >15 mg/L (91.2% vs. 75.0%, P=0.064). No vancomycin-related nephrotoxicity adverse effects occurred among all enrolled patients. Multivariate analysis revealed that a PRISM III score ≥10 (OR =15.011; 95% CI: 3.937-57.230; P<0.001) was the only independent clinical factor associated with increased incidence of treatment failure.ConclusionsVancomycin dosages of 40-60 mg/kg/d are effective and have no vancomycin-related nephrotoxicity adverse effects in children with Gram-positive bacterial sepsis. Vancomycin trough concentrations >15 mg/L are not an essential target for these Gram-positive bacterial sepsis patients. PRISM III scores ≥10 may serve as an independent risk factor for vancomycin treatment failure in these patients

Comparison of: (2S,4R)-4-[F-18]Fluoroglutamine, [C-11]Methionine, and 2-Deoxy-2-[F-18]Fluoro-D-Glucose and Two Small-Animal PET/CT Systems Imaging Rat Gliomas

Purpose: The three positron emission tomography (PET) imaging compounds: (2S,4R)-4-[F-18]Fluoroglutamine ([F-18]FGln), L-[methyl-C-11]Methionine ([C-11]Met), and 2-deoxy-2-[F-18]fluoro-D-glucose ([F-18]FDG) were investigated to contrast their ability to image orthotopic BT4C gliomas in BDIX rats. Two separate small animal imaging systems were compared for their tumor detection potential. Dynamic acquisition of [F-18]FGln was evaluated with multiple pharmacokinetic models for future quantitative comparison.Procedures: Up to four imaging studies were performed on each orthotopically grafted BT4C glioma-bearing BDIX rat subject (n = 16) on four consecutive days. First, a DOTAREM(R) contrast enhanced MRI followed by attenuation correction CT and dynamic PET imaging with each radiopharmaceutical (20 min [C-11]Met, 60 min [F-18]FDG, and 60 min [F-18]FGln with either the Molecubes PET/CT (n = 5) or Inveon PET/CT cameras (n = 11). Ex vivo brain autoradiography was completed for each radiopharmaceutical and [F-18]FGln pharmacokinetics were studied by injecting 40 MBq into healthy BDIX rats (n = 10) and collecting blood samples between 5 and 60 min. Erythrocyte uptake, plasma protein binding and plasma parent-fraction were combined to estimate the total blood bioavailability of [F-18]FGln over time. The corrected PET-image blood data was then applied to multiple pharmacokinetic models.Results: Average BT4C tumor-to-healthy brain tissue uptake ratios (TBR) for PET images reached maxima of: [F-18]FGln TBR: 1.99 +/- 0.19 (n = 13), [F-18]FDG TBR: 1.41 +/- 0.11 (n = 6), and [C-11]Met TBR: 1.08 +/- 0.08, (n = 12) for the dynamic PET images. Pharmacokinetic modeling in dynamic [F-18]FGln studies suggested both reversible and irreversible uptake play a similar role. Imaging with Inveon and Molecubes yielded similar end-result ratios with insignificant differences (p > 0.25).Conclusions: In orthotopic BT4C gliomas, [F-18]FGln may offer improved imaging versus [C-11]Met and [F-18]FDG. No significant difference in normalized end-result data was found between the Inveon and Molecubes camera systems. Kinetic modelling of [F-18]FGln uptake suggests that both reversible and irreversible uptake play an important role in BDIX rat pharmacokinetics.</p

Honokiol Crosses BBB and BCSFB, and Inhibits Brain Tumor Growth in Rat 9L Intracerebral Gliosarcoma Model and Human U251 Xenograft Glioma Model

BACKGROUND: Gliosarcoma is one of the most common malignant brain tumors, and anti-angiogenesis is a promising approach for the treatment of gliosarcoma. However, chemotherapy is obstructed by the physical obstacle formed by the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCSFB). Honokiol has been known to possess potent activities in the central nervous system diseases, and anti-angiogenic and anti-tumor properties. Here, we hypothesized that honokiol could cross the BBB and BCSFB for the treatment of gliosarcoma. METHODOLOGIES: We first evaluated the abilities of honokiol to cross the BBB and BCSFB by measuring the penetration of honokiol into brain and blood-cerebrospinal fluid, and compared the honokiol amount taken up by brain with that by other tissues. Then we investigated the effect of honokiol on the growth inhibition of rat 9L gliosarcoma cells and human U251 glioma cells in vitro. Finally we established rat 9L intracerebral gliosarcoma model in Fisher 344 rats and human U251 xenograft glioma model in nude mice to investigate the anti-tumor activity. PRINCIPAL FINDINGS: We showed for the first time that honokiol could effectively cross BBB and BCSFB. The ratios of brain/plasma concentration were respectively 1.29, 2.54, 2.56 and 2.72 at 5, 30, 60 and 120 min. And about 10% of honokiol in plasma crossed BCSFB into cerebrospinal fluid (CSF). In vitro, honokiol produced dose-dependent inhibition of the growth of rat 9L gliosarcoma cells and human U251 glioma cells with IC(50) of 15.61 µg/mL and 16.38 µg/mL, respectively. In vivo, treatment with 20 mg/kg body weight of honokiol (honokiol was given twice per week for 3 weeks by intravenous injection) resulted in significant reduction of tumor volume (112.70±10.16 mm(3)) compared with vehicle group (238.63±19.69 mm(3), P = 0.000), with 52.77% inhibiting rate in rat 9L intracerebral gliosarcoma model, and (1450.83±348.36 mm(3)) compared with vehicle group (2914.17±780.52 mm(3), P = 0.002), with 50.21% inhibiting rate in human U251 xenograft glioma model. Honokiol also significantly improved the survival over vehicle group in the two models (P<0.05). CONCLUSIONS/SIGNIFICANCE: This study provided the first evidence that honokiol could effectively cross BBB and BCSFB and inhibit brain tumor growth in rat 9L intracerebral gliosarcoma model and human U251 xenograft glioma model. It suggested a significant strategy for offering a potential new therapy for the treatment of gliosarcoma

STUDY ON FAILURE MECHANISM OF STRIP FOUNDATION BUILDINGS CAUSED BY SURFACE HORIZONTAL DEFORMATION IN MINING AREA

The surface deformation caused by underground coal mining will cause great damage to the surface buildings. Especially for the strip foundation buildings, the surface horizontal deformation will cause the walls to crack and open, threatening the safe use of buildings. However, there is lacking research on the failure mechanism of strip foundation buildings caused by surface horizontal deformation. Therefore, it is particularly important to study the mechanism. In this paper, a mechanical model of additional stress distribution in the strip foundation under surface horizontal deformation is established. Based on the model, the internal stress variation characteristics of the longitudinal wall of strip foundation buildings are studied with different factors: friction coefficient, surface curvature, foundation load and foundation length under the surface horizontal deformation. The internal stress variation of the transverse wall of the strip foundation buildings is analysed. The theory is verified by numerical simulation and a case study from Fengfeng coalmine China. Finally, the protection methods of the strip foundation buildings under the surface horizontal deformation are proposed

Feasibility of Coupling PS System with Building Protection in an Ultrasoft Strata Colliery

To guarantee the stability of a building complex above a planned mining district with ultrasoft strata, strip mining technology (SMT) was applied to control the displacement and deformation caused by underground exploitation. This study attempts to design a reasonable pillar width to establish a stable pillar-support (PS) system composed of ground buildings with coal pillars underneath. Based on the stratigraphic structure of ultrasoft strata and in situ measurement data of mining subsidence monitoring, this study takes an ultrasoft strata colliery in western Henan province, central China, as an example to examine the technical and economical feasibility of the proposed PSsyst under two mining scenarios. The major results indicated that the initial design of pillar width would be 120 m under scenario 1, with expected damage of only 450 mm maximum subsidence predicted by probability integration method (PIM); while under scenario 2, the cost of compensation for buildings’ mining-induced damage would increase to CNY 61.31 million with an expected output of 7.629 million tons of raw coal. Moreover, the protection rate of the residential area in the proposed postmining area of scenario 1 can reach as much as 6.91% comparing to the fully mechanized coal winning technology in scenario 2. Overall, the proposed PSsyst will bring good benefits both economically and environmentally and should be worth promoting as a reference for similar geological and mining conditions in the future