As a contributing factor in the dynamic failure(bumping) of coal pillars,a bump-prone coal seam has been described as one that is ‘‘uncleated or poorly cleated,strong...that sustains high stresses."Despite exte...As a contributing factor in the dynamic failure(bumping) of coal pillars,a bump-prone coal seam has been described as one that is ‘‘uncleated or poorly cleated,strong...that sustains high stresses."Despite extensive research regarding engineering controls to help reduce the risk for coal bumps,there is a paucity of research related to the properties of coal itself and how those properties might contribute to the mechanics of failures. Geographic distribution of reportable dynamic failure events reveals a highly localized clustering of incidents despite widespread mining activities. This suggests that unique,contributing geologic characteristics exist within these regions that are less prevalent elsewhere. To investigate a new approach for identifying coal characteristics that might lead to bumping,a principal component analysis(PCA) was performed on 306 coal records from the Pennsylvania State Coal Sample database to determine which characteristics were most closely linked with a positive history of reportable bumping. Selected material properties from the data records for coal samples were chosen as variables for the PCA and included petrographic,elemental,and molecular properties. Results of the PCA suggest a clear correlation between low organic sulfur content and the occurrence of dynamic failure,and a secondary correlation between volatile matter and dynamic failure phenomena. The ratio of volatile matter to sulfur in the samples shows strong correlation with bump-prone regions,with a minimum threshold value of approximately 20,while correlations determined for other petrographic and elemental variables were more ambiguous. Results suggest that the composition of the coal itself is directly linked to how likely a coal is to have experienced a reportable dynamic failure event. These compositional controls are distinct from other previously established engineering and geologic criteria and represent a missing piece to the bump prediction puzzle.展开更多
Based on the safety coefficient method,which assigns rock failure criteria to calculate the rock mass unit,the safety coefficient contour of surrounding rock is plotted to judge the distribution form of the fractured ...Based on the safety coefficient method,which assigns rock failure criteria to calculate the rock mass unit,the safety coefficient contour of surrounding rock is plotted to judge the distribution form of the fractured zone in the roadway.This will provide the basis numerical simulation to calculate the surrounding rock fractured zone in a roadway.Using the single factor and multi-factor orthogonal test method,the evolution law of roadway surrounding rock displacements,plastic zone and stress distribution under different conditions is studied.It reveals the roadway surrounding rock burst evolution process,and obtains five kinds of failure modes in deep soft rock roadway.Using the fuzzy mathematics clustering analysis method,the deep soft surrounding rock failure model in Zhujixi mine can be classified and patterns recognized.Compared to the identification results and the results detected by geological radar of surrounding rock loose circle,the reliability of the results of the pattern recognition is verified and lays the foundations for the support design of deep soft rock roadways.展开更多
The permeability evolution of rock during the progressive failure process is described. In combination with the strength degradation index, the degradation formulas of s and a, which are dependent on the plastic confi...The permeability evolution of rock during the progressive failure process is described. In combination with the strength degradation index, the degradation formulas of s and a, which are dependent on the plastic confining strain component, the material constants of Hock-Brown failure criterion are presented, and a modified elemental scale elastic-brittle-plastic constitutive model of rock is established. The rela- tionship between volumetric strain and permeability through tri-axial compression is investigated. Based on the above, a permeability evolution model is established. The model incorporates confining pressure- dependent degradation of strength, dilatancy and corresponding permeability evolution. The model is implemented in FLAC by the FISH function method. The permeability evolution behavior of rock is inves-tigated during the progressive failure process in a numerical case. The results show that the model is cap- able of reproducing, and allowing visualization of a range of hydro-mechanical responses of rock. The effects of confining pressure on degradation of strength, dilatancy and permeability evolution are also reflected.展开更多
Objective To investigate the effect of peroxisome proliferator-activated receptor-α(PPARα) and PPARγactivators on tumor necrosis factor-α(TNFα) expression in neonatal rat cardiac myocytes. Methods Primary culture...Objective To investigate the effect of peroxisome proliferator-activated receptor-α(PPARα) and PPARγactivators on tumor necrosis factor-α(TNFα) expression in neonatal rat cardiac myocytes. Methods Primary cultures of cardiac myocytes from 1- to 3-day-old Wistar rats were prepared, and myocytes were ex-posed to lipopolysaccharide (LPS) and varying concentrations of PPARαor PPARγactivator (fenofibrate or pioglitazone).RT-PCR and ELISA were used to measure TNFα, PPARα, and PPARγexpression in cultured cardiac myocytes. Transient tr-ansfection of TNFαpromoter with or without nuclear factor-kappaB (NF-κB) binding site to cardiac myocytes was performed. Results Pretreatment of cardiac myocytes with fenofibrate or pioglitazone inhibited LPS-induced TNFαmRNA and protein expression in a dose-dependent manner. However, no significant changes were observed on PPARαor PPARγmRNA expression when cardiac myocytes were pretreated with fenofibrate or pioglitazone. Proportional suppression of TNFαpromoter activity was observed when myocytes was transiently transfected with whole length of TNFαpromoter (-721/+17) after being stimulated with LPS and fenofibrate or pioglitazone, whereas no change of promoter activity was observed with transfection of TNFαreporter construct in deletion of NF-κB binding site (-182/+17). Conclusions PPARαand PPARγactivators may inhibit cardiac TNFαexpression but not accompanied by change of PPARαor PPARγmRNA expression. Therefore PPARαand PPARγactivators appear to play a role in anti-inflammation. The mechanism may partly be involved in suppression of the NF-κB pathway.展开更多
Background Inhibition of aging of vascular endothelial cells （VECs） may delay aging and prolong life. The goal of this study was to prepare anti-CD31 monoclonal antibody conjugated PEG-modified liposomes containing ...Background Inhibition of aging of vascular endothelial cells （VECs） may delay aging and prolong life. The goal of this study was to prepare anti-CD31 monoclonal antibody conjugated PEG-modified liposomes containing the AU-rich region connecting factor 1 （AUF1） gene （CD31-PILs-AUF1） and to explore the effects of targeting CD31-PILs-AUF1 to aging VECs. Methods The mean particle sizes of various PEGylated immunoliposomes （PILs） were measured using a Zetasizer Nano ZS. Gel retardation assay was used to confirm whether PILs had encapsulated the AUF1 plasmid successfully. Fluorescence microscopy and flow cytometry were used to quantify binding of CD31-PILs-AUF1 to target cells. Flow cytometry was also used to analyze the cell cycles of aging bEnd3 cells treated with CD31-PILs-AUF1. We also developed an aging mouse model by treating mice with D-galactose. Enzyme-linked immunosorbent assay （ELISA） was used to evaluate the levels of interleuldn-6 （IL-6） and tumor necrosis factor-or （TNF-ct）. The malondialdehyde （MDA） and the superoxide dismutase （SOD） levels were detected by commercial kits. Hematoxylin-eosin （HE） staining was used to determine whether treatment with CD31-PILs-AUF 1 was toxic to the mice. Results CD31-PILs-AUF 1 specifically could targeted bEnd3 VECs and increased the percentage of cells in the S and G2/M phases of aging bEnd3 cells. ELISA showed that content of the IL-6 and TNF-ct decreased in CD31-PILs-AUF1 group. The level of SOD increased, whereas MDA decreased in the CD31-PILs-AUF1 group. Additionally, CD31-PILs-AUF 1 was not toxic to the mice. Conclusion CD31-PILs-AUF 1 targets VECs and may delay their senescence.展开更多
文摘As a contributing factor in the dynamic failure(bumping) of coal pillars,a bump-prone coal seam has been described as one that is ‘‘uncleated or poorly cleated,strong...that sustains high stresses."Despite extensive research regarding engineering controls to help reduce the risk for coal bumps,there is a paucity of research related to the properties of coal itself and how those properties might contribute to the mechanics of failures. Geographic distribution of reportable dynamic failure events reveals a highly localized clustering of incidents despite widespread mining activities. This suggests that unique,contributing geologic characteristics exist within these regions that are less prevalent elsewhere. To investigate a new approach for identifying coal characteristics that might lead to bumping,a principal component analysis(PCA) was performed on 306 coal records from the Pennsylvania State Coal Sample database to determine which characteristics were most closely linked with a positive history of reportable bumping. Selected material properties from the data records for coal samples were chosen as variables for the PCA and included petrographic,elemental,and molecular properties. Results of the PCA suggest a clear correlation between low organic sulfur content and the occurrence of dynamic failure,and a secondary correlation between volatile matter and dynamic failure phenomena. The ratio of volatile matter to sulfur in the samples shows strong correlation with bump-prone regions,with a minimum threshold value of approximately 20,while correlations determined for other petrographic and elemental variables were more ambiguous. Results suggest that the composition of the coal itself is directly linked to how likely a coal is to have experienced a reportable dynamic failure event. These compositional controls are distinct from other previously established engineering and geologic criteria and represent a missing piece to the bump prediction puzzle.
基金provided by the National Natural Science Foundation of China(Nos.51322401,51309222,51323004,51579239 and 51574223)the Opening Project Fund of Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation(No.CDPM2014KF03)+2 种基金the State Key Laboratory for GeoMechanics Opening Project Fund of Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and MitigationDeep Underground Engineering,China University of Mining&Technology(No.SKLGDUEK1305)China Postdoctoral Science Foundation(Nos.2014M551700and 2013M531424)
文摘Based on the safety coefficient method,which assigns rock failure criteria to calculate the rock mass unit,the safety coefficient contour of surrounding rock is plotted to judge the distribution form of the fractured zone in the roadway.This will provide the basis numerical simulation to calculate the surrounding rock fractured zone in a roadway.Using the single factor and multi-factor orthogonal test method,the evolution law of roadway surrounding rock displacements,plastic zone and stress distribution under different conditions is studied.It reveals the roadway surrounding rock burst evolution process,and obtains five kinds of failure modes in deep soft rock roadway.Using the fuzzy mathematics clustering analysis method,the deep soft surrounding rock failure model in Zhujixi mine can be classified and patterns recognized.Compared to the identification results and the results detected by geological radar of surrounding rock loose circle,the reliability of the results of the pattern recognition is verified and lays the foundations for the support design of deep soft rock roadways.
基金the National Natural Science Foundation of China (Nos.51274079,51274110 and 51574139)the Natural Science Foundation of Hebei Province (No.E2013208148)
文摘The permeability evolution of rock during the progressive failure process is described. In combination with the strength degradation index, the degradation formulas of s and a, which are dependent on the plastic confining strain component, the material constants of Hock-Brown failure criterion are presented, and a modified elemental scale elastic-brittle-plastic constitutive model of rock is established. The rela- tionship between volumetric strain and permeability through tri-axial compression is investigated. Based on the above, a permeability evolution model is established. The model incorporates confining pressure- dependent degradation of strength, dilatancy and corresponding permeability evolution. The model is implemented in FLAC by the FISH function method. The permeability evolution behavior of rock is inves-tigated during the progressive failure process in a numerical case. The results show that the model is cap- able of reproducing, and allowing visualization of a range of hydro-mechanical responses of rock. The effects of confining pressure on degradation of strength, dilatancy and permeability evolution are also reflected.
基金Supported by the National Nature Science Foundation of China (30270551) and Military "10.5"Foundation (02M012).
文摘Objective To investigate the effect of peroxisome proliferator-activated receptor-α(PPARα) and PPARγactivators on tumor necrosis factor-α(TNFα) expression in neonatal rat cardiac myocytes. Methods Primary cultures of cardiac myocytes from 1- to 3-day-old Wistar rats were prepared, and myocytes were ex-posed to lipopolysaccharide (LPS) and varying concentrations of PPARαor PPARγactivator (fenofibrate or pioglitazone).RT-PCR and ELISA were used to measure TNFα, PPARα, and PPARγexpression in cultured cardiac myocytes. Transient tr-ansfection of TNFαpromoter with or without nuclear factor-kappaB (NF-κB) binding site to cardiac myocytes was performed. Results Pretreatment of cardiac myocytes with fenofibrate or pioglitazone inhibited LPS-induced TNFαmRNA and protein expression in a dose-dependent manner. However, no significant changes were observed on PPARαor PPARγmRNA expression when cardiac myocytes were pretreated with fenofibrate or pioglitazone. Proportional suppression of TNFαpromoter activity was observed when myocytes was transiently transfected with whole length of TNFαpromoter (-721/+17) after being stimulated with LPS and fenofibrate or pioglitazone, whereas no change of promoter activity was observed with transfection of TNFαreporter construct in deletion of NF-κB binding site (-182/+17). Conclusions PPARαand PPARγactivators may inhibit cardiac TNFαexpression but not accompanied by change of PPARαor PPARγmRNA expression. Therefore PPARαand PPARγactivators appear to play a role in anti-inflammation. The mechanism may partly be involved in suppression of the NF-κB pathway.
基金This work was supported by grants from the Guangxi Natural Science Foundation （No. 2015GXNSFAA139217 and 2016GXNSFAA380231）, a grant from The Scientific Research Fund of Guangxi Education Department （No. YB2014057） entitled ＂AU-rich region connecting factor 1 targeted vascular endothelial cells for anti-aging＂, a grant from the Youth Foundation in Guangxi Medical Univer- sity （No. GXMUYSF201328）, a grant from the Undergraduate Innovative plan in Guangxi （No. 201510598012）, and a grant from the Guangxi Education Department Grant entitled ＂Innovation Project of Guangxi Graduate Educa- tion＂.
文摘Background Inhibition of aging of vascular endothelial cells （VECs） may delay aging and prolong life. The goal of this study was to prepare anti-CD31 monoclonal antibody conjugated PEG-modified liposomes containing the AU-rich region connecting factor 1 （AUF1） gene （CD31-PILs-AUF1） and to explore the effects of targeting CD31-PILs-AUF1 to aging VECs. Methods The mean particle sizes of various PEGylated immunoliposomes （PILs） were measured using a Zetasizer Nano ZS. Gel retardation assay was used to confirm whether PILs had encapsulated the AUF1 plasmid successfully. Fluorescence microscopy and flow cytometry were used to quantify binding of CD31-PILs-AUF1 to target cells. Flow cytometry was also used to analyze the cell cycles of aging bEnd3 cells treated with CD31-PILs-AUF1. We also developed an aging mouse model by treating mice with D-galactose. Enzyme-linked immunosorbent assay （ELISA） was used to evaluate the levels of interleuldn-6 （IL-6） and tumor necrosis factor-or （TNF-ct）. The malondialdehyde （MDA） and the superoxide dismutase （SOD） levels were detected by commercial kits. Hematoxylin-eosin （HE） staining was used to determine whether treatment with CD31-PILs-AUF 1 was toxic to the mice. Results CD31-PILs-AUF 1 specifically could targeted bEnd3 VECs and increased the percentage of cells in the S and G2/M phases of aging bEnd3 cells. ELISA showed that content of the IL-6 and TNF-ct decreased in CD31-PILs-AUF1 group. The level of SOD increased, whereas MDA decreased in the CD31-PILs-AUF1 group. Additionally, CD31-PILs-AUF 1 was not toxic to the mice. Conclusion CD31-PILs-AUF 1 targets VECs and may delay their senescence.
