Physical and numerical investigations of target stratum selection for ground hydraulic fracturing of multiple hard roofs

Ground hydraulic fracturing plays a crucial role in controlling the far-field hard roof,making it imperative to identify the most suitable target stratum for effective control.Physical experiments are conducted based on engineering properties to simulate the gradual collapse of the roof during longwall top coal caving(LTCC).A numerical model is established using the material point method(MPM)and the strain-softening damage constitutive model according to the structure of the physical model.Numerical simulations are conducted to analyze the LTCC process under different hard roofs for ground hydraulic fracturing.The results show that ground hydraulic fracturing releases the energy and stress of the target stratum,resulting in a substantial lag in the fracturing of the overburden before collapse occurs in the hydraulic fracturing stratum.Ground hydraulic fracturing of a low hard roof reduces the lag effect of hydraulic fractures,dissipates the energy consumed by the fracture of the hard roof,and reduces the abutment stress.Therefore,it is advisable to prioritize the selection of the lower hard roof as the target stratum.

Platelet-rich fibrin-induced bone marrow mesenchymal stem cell differentiation into osteoblast-like cells and neural cells

Bone marrow mesenchymal stem cells were allowed to develop for 14 days in a platelet-rich fibrin environment.Results demonstrated that platelet-rich fibrin significantly promoted bone marrow mesenchymal stem cell proliferation.In addition,there was a dose-dependent increase in Runt-related transcription factor-2 and bone morphogenetic protein-2 mRNA expression,as well as neuron-specific enolase and glial acidic protein.Results showed that platelet-rich fibrin promoted bone marrow mesenchymal stem cell proliferation and differentiation of osteoblast-like cells and neural cells in a dose-dependent manner.

miR-21 promotes the differentiation of hair folliclederived neural crest stem cells into Schwann cells

Hair follicle-derived neural crest stem cells can be induced to differentiate into Schwann cells in vivo and in vitro. However, the underlying regulatory mechanism during cell differentiation remains poorly understood. This study isolated neural crest stem cells from human hair folli-cles and induced them to differentiate into Schwann cells. Quantitative RT-PCR showed that microRNA （miR）-21 expression was gradually increased during the differentiation of neural crest stem cells into Schwann cells. After transfection with the miR-21 agonist （agomir-21）, the differentiation capacity of neural crest stem cells was enhanced. By contrast, after transfection with the miR-21 antagonist （antagomir-21）, the differentiation capacity was attenuated. Further study results showed that SOX-2 was an effective target of miR-21. Without compromising SOX2 mRNA expression, miR-21 can down-regulate SOX protein expression by binding to the 3′-UTR of miR-21 mRNA. Knocking out the SOX2 gene from the neural crest stem cells significantly reversed the antagomir-21 inhibition of neural crest stem cells differentiating into Schwann cells. The results suggest that miR-21 expression was increased during the differentiation of neural crest stem cells into Schwann cells and miR-21 promoted the differentiation through down-regu-lating SOX protein expression by binding to the 3′-UTR of SOX2 mRNA.

Betaine improves growth performance, liver health, antioxidant status, breast meat yield, and quality in broilers fed a mold- contaminated corn-based diet

Betaine has been demonstrated to improve growth performance and antioxidant status of animals under various stress conditions.However,there is no literature on the effects of betaine in animals exposed to mycotoxins,which are among the most prevalent contaminants in feed.Therefore,this study was conducted to evaluate the influence of dietary betaine on broilers fed a diet based on mold-contaminated corn(MCC).A total of 192 Ross 308 male broiler chicks at 1 d of age were randomly divided into 4 groups with 6 replicates and fed an MCC-based diet supplemented with 0,250,500,and 1,000 mg/kg betaine,respectively.Betaine increased average daily gain(linear,P=0.030)and decreased feed conversion ratio(linear,P=0.027)of broilers during d 1-21,and decreased feed conversion ratio during d 22-42(linear,P=0.012;quadratic,P<0.001)and d 1-42(linear,P=0.003;quadratic,P=0.004),whereas feed intake was not affected.Total cholesterol(linear,P=0.024),alanine aminotransferase(quadratic,P<0.001)and alkaline phosphatase(linear,P=0.007;quadratic,P=0.025)activities in serum were decreased by betaine.Betaine linearly increased breast muscle yield(P=0.003)and pH24 h(P=0.008),and decreased drip loss(P=0.022).Betaine increased(linear,P=0.025;quadratic,P=0.016)total superoxide dismutase activity in breast muscle and reduced malondialdehyde content in serum(linear,P=0.006),liver(quadratic,P=0.006)and breast muscle(linear,P=0.003).Moreover,the zearalenone concentrations in breast muscle were linearly decreased by betaine(P=0.006).It was concluded that betaine could improve growth performance,liver health,antioxidant status,and breast meat yield and quality,and reduce zearalenone residue in broilers fed the MCC-based diet,especially at 500 or 1,000 mg/kg.

An Experimental Analysis of Stability in Human Walking

Biped locomotion has excellent environment adaptability due to natural selection and evolution over hundreds of millions years. However, the biped walking stability mechanism is still not clear. In this paper, an experimental analysis of walking stability in human walking is carried out by using a motion capture system. A new stability analysis method is proposed based on Zero Moment Point （ZMP） and Sliding Time Window （STW）. The influences of ground friction coefficient, ground slope angle and contact area of support polygon on human walking stability are investigated. The experiment is carried out with 12 healthy subjects, and 53 passive reflective markers are pasted to each subject to obtain moving trajectory and to calculate lower limb joint variation during walking. Experimental results show that ground friction coefficient, ground slope angle and contact area have significant effects on the stride length, step height, gait cycle and lower limb joint angles. When walking with small stability margin, subjects modulate gait to improve the stability, such as shortening stride length, reducing step height, and increasing the gait cycle. These results provide insights into the stability mechanism of human walking, which is beneficial for locomotion control of biped robots.

From illite/smectite clay to mesoporous silicate adsorbent for efficient removal of chlortetracycline from water

A series of mesoporous silicate adsorbents with superior adsorption performance for hazardous chlortetracycline（CTC） were sucessfully prepared via a facile one-pot hydrothermal reaction using low-cost illite/smectite（IS） clay,sodium silicate and magnesium sulfate as the starting materials.In this process,IS clay was ＂teared up＂ and then ＂rebuilt＂ as new porous silicate adsorbent with high specific surface area of 363.52 m^2/g（about 8.7 folds higher than that of IS clay） and very negative Zeta potential（- 34.5 mV）.The inert Si- O- Si（Mg,Al） bonds in crystal framework of IS were broken to form Si（Al）- O^- groups with good adsorption activity,which greatly increased the adsorption sites served for holding much CTC molecules.Systematic evaluation on adsorption properties reveals the optimal silicate adsorbent can adsorb 408.81 mg/g of CTC（only 159.7 mg/g for raw IS clay） and remove 99.3%（only 46.5%for raw IS clay） of CTC from 100 mg/L initial solution（pH 3.51;adsorption temperature 30℃;adsorbent dosage,3 g/L）.The adsorption behaviors of CTC onto the adsorbent follows the Langmuir isotherm model,Temkin equation and pseudo second-order kinetic model.The mesopore adsorption,electrostatic attraction and chemical association mainly contribute to the enhanced adsorption properties.As a whole,the high-efficient silicate adsorbent could be candidates to remove CTC from the wastewater with high amounts of CTC.