Unstable Pillar Failure under Soft Loading Condition

AbstractPillar rockburst is an unstable pillar failure and one of the most hazardous problems in the underground mining engineering of deep hard-rock mines. In order to study the mechanism of unstable pillar failure, laboratory tests, numerical simulation, and theoretical analysis are adopted. The disc spring group was used to realize the soft loading function of testing machine, where loading stiffness of testing machine can be adjusted by changing the number and combination mode of disc springs. The results show that the loading stiffness of testing machine has major effect on the post-peak failure behavior of rock specimen, which means that the elastic rebound of disc spring group determines the unstable failure characteristics of rock specimen. The sudden jump Δd of rock specimen deformation and the elastic energy release ΔW of disc spring group all increase with the decreased loading stiffness of testing machine, resulting in more severe rock unstable failure (pillar rockburst). The soft loading condition has buffering and delaying effects on rock failure, but it increases the unstable failure intensity of rock specimen. The numerical simulation reproduced the rock unstable failure and the elastic rebound behavior of disc spring group, which also illustrated the damage evolution process of rock unstable failure. The necessary condition of rock unstable failure and the analytical solution of sudden jump Δd and elastic energy release ΔW were derived based on catastrophe theory, which further verified the experimental results. This study reveals the physical essence of unstable pillar failure, which may help to under the mechanism of pillar rockburst and provide references for underground mining

MTR4 drives liver tumorigenesis by promoting cancer metabolic switch through alternative splicing.

The metabolic switch from oxidative phosphorylation to glycolysis is required for tumorigenesis in order to provide cancer cells with energy and substrates of biosynthesis. Therefore, it is important to elucidate mechanisms controlling the cancer metabolic switch. MTR4 is a RNA helicase associated with a nuclear exosome that plays key roles in RNA processing and surveillance. We demonstrate that MTR4 is frequently overexpressed in hepatocellular carcinoma (HCC) and is an independent diagnostic marker predicting the poor prognosis of HCC patients. MTR4 drives cancer metabolism by ensuring correct alternative splicing of pre-mRNAs of critical glycolytic genes such as GLUT1 and PKM2. c-Myc binds to the promoter of the MTR4 gene and is important for MTR4 expression in HCC cells, indicating that MTR4 is a mediator of the functions of c-Myc in cancer metabolism. These findings reveal important roles of MTR4 in the cancer metabolic switch and present MTR4 as a promising therapeutic target for treating HCC

Humic Substance Photosensitized Degradation of Phthalate Esters Characterized by 2H and 13C Isotope Fractionation

The photosensitized transformation of organic chemicals is an important degradation mechanism in natural surface waters, aerosols, and water films on surfaces. Dissolved organic matter including humic-like substances (HS), acting as photosensitizers that participate in electron transfer reactions, can generate a variety of reactive species, such as OH radicals and excited triplet-state HS (3HS*), which promote the degradation of organic compounds. We use phthalate esters, which are important contaminants found in wastewaters, landfills, soils, rivers, lakes, groundwaters, and mine tailings. We use phthalate esters as probes to study the reactivity of HS irradiated with artificial sunlight. Phthalate esters with different side-chain lengths were used as probes for elucidation of reaction mechanisms using 2H and 13C isotope fractionation. Reference experiments with the artificial photosensitizers 4,5,6,7-tetrachloro-2′,4′,5′,7′-tetraiodofluorescein (Rose Bengal), 3-methoxy-acetophenone (3-MAP), and 4-methoxybenzaldehyde (4-MBA) yielded characteristic fractionation factors (−4 ± 1, −4 ± 2, and −4 ± 1‰ for 2H; 0.7 ± 0.2, 1.0 ± 0.4, and 0.8 ± 0.2‰ for 13C), allowing interpretation of reaction mechanisms of humic substances with phthalate esters. The correlation of 2H and 13C fractions can be used diagnostically to determine photosensitized reactions in the environment and to differentiate among biodegradation, hydrolysis, and photosensitized HS reaction

Immunogenicity and protective potential of chimeric virus-like particles containing SARS-CoV-2 spike and H5N1 matrix 1 proteins

Coronavirus Disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), has posed a constant threat to human beings and the world economy for more than two years. Vaccination is the first choice to control and prevent the pandemic. However, an effective SARS-CoV-2 vaccine against the virus infection is still needed. This study designed and prepared four kinds of virus-like particles (VLPs) using an insect expression system. Two constructs encoded wild-type SARS-CoV-2 spike (S) fused with or without H5N1 matrix 1 (M1) (S and SM). The other two constructs contained a codon-optimized spike gene and/or M1 gene (mS and mSM) based on protein expression, stability, and ADE avoidance. The results showed that the VLP-based vaccine could induce high SARS-CoV-2 specific antibodies in mice, including specific IgG, IgG1, and IgG2a. Moreover, the mSM group has the most robust ability to stimulate humoral immunity and cellular immunity than the other VLPs, suggesting the mSM is the best immunogen. Further studies showed that the mSM combined with Al/CpG adjuvant could stimulate animals to produce sustained high-level antibodies and establish an effective protective barrier to protect mice from challenges with mouse-adapted strain. The vaccine based on mSM and Al/CpG adjuvant is a promising candidate vaccine to prevent the COVID-19 pandemic

Electrocatalytic Activity of Palladium Nanocatalysts Supported on Carbon Nanoparticles in Formic Acid Oxidation

采用化学还原法制备了碳纳米粒子支撑的钯纳米结构(Pd-CNP). 透射电镜表征显示在Pd-CNP纳米复合物中，金属Pd呈菜花状结构，粒径约20~30 nm。它们由许多更小的Pd纳米粒子（3~8 nm）组成. 电化学研究表明，虽然Pd-CNP的电化学活性面积比商业Pd黑低40%（可能原因是部分Pd表面被一层碳纳米粒子覆盖），但其对甲酸氧化却表现出更好的电催化活性：质量比活性和面积比活性都比Pd黑高几倍. 催化活性增强的原因可能是碳纳米粒子支撑的Pd纳米结构具有特殊的层次化结构，可以形成更多的活性位，以及表面位更利于反应进行.Palladium nanostructures were deposited onto carbon nanoparticle surface by a chemical reduction method. Transmission electron microscopic studies showed that whereas the resulting metal-carbon (Pd-CNP) nanocomposites exhibited a diameter of 20 to 30 nm, the metal components actually showed a cauliflower-like surface morphology that consisted of numerous smaller Pd nanoparticles (3 to 8 nm). Electrochemical studies showed that the effective surface area of the Pd-CNP nanoparticles was about 40% less than that of Pd black, possibly because the Pd nanoparticles were coated with a layer of carbon nanoparticles; yet, the Pd-CNP nanocomposites exhibited marked enhancement of the electrocatalytic activity in formic acid oxidation, as compared to that of Pd black. In fact, the mass- and surface-specific activities of the former were about three times higher than those of the latter. This improvement was likely a result of the enhanced accessibility of the Pd catalyst surface and the formation of abundant active sites of Pd on the carbon nanoparticle surface due to the hierarchical structure of the metal nanocatalysts.This work was supported, in part, by the National Science Foundation (CHE–1012256 and DMR–0804049) and by the ACS-Petroleum Research Fund (49137–ND10). J. H. was supported, in part, by a research fellowship from the China Scholarship Council. TEM work was performed as a User Project at the National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, which is supported by the US Department of EnergyThis work was supported, in part, by the National Science Foundation (CHE–1012256 and DMR–0804049) and by the ACS-Petroleum Research Fund (49137–ND10). J. H. was supported, in part, by a research fellowship from the China Scholarship Council. TEM work was performed as a User Project at the National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, which is supported by the US Department of Energy作者联系地址：1. 加利福尼亚大学化学与生物化学系，美国 圣克鲁兹 95064; 2. 西北工业大学凝固技术国家重点实验室，陕西 西安710072Author's Address: 1. Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States; 2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China通讯作者E-mail：[email protected]

Seismic Performance Assessment and Retrofit of Rectangular Bridge Piers with Externally Encased Circular Steel Jacket

In this paper, the experimental results of four bridge piers retrofitted with externally encased steel jackets are presented in detail. These piers have a 1/5 scale factor and were designed according to the current seismic design codes for bridges in China that contains no provision on good ductility and seismic performance for piers. Design variables include concrete strength, axial load level, volume of transverse reinforcement and so on. Tests on all four piers are completed in two stages. First, all piers are tested under cyclic loading to an excessively damaged state and their seismic performance is assessed. Then these piers are retrofitted with externally encased circular steel jackets and retested to total failure under the same loading condition. Ductility, strength, energy dissipation capacity and the lateral jacket strain are investigated. Test results indicate that retrofitting rectangular bridge piers with steel jackets can significantly improve the displacement ductility and energy dissipation capacity due to the firm confinement provided by the jacket and can also increase the strength and stiffness of the piers to some degrees

A coupled thermal-hydrological-mechanical damage model and its numerical simulations of damage evolution in apse

This paper proposes a coupled thermal–hydrological–mechanical damage (THMD) model for the failure process of rock, in which coupling effects such as thermally induced rock deformation, water flow-induced thermal convection, and rock deformation-induced water flow are considered. The damage is considered to be the key factor that controls the THM coupling process and the heterogeneity of rock is characterized by the Weibull distribution. Next, numerical simulations on excavation-induced damage zones in Äspö pillar stability experiments (APSE) are carried out and the impact of in situ stress conditions on damage zone distribution is analysed. Then, further numerical simulations of damage evolution at the heating stage in APSE are carried out. The impacts of in situ stress state, swelling pressure and water pressure on damage evolution at the heating stage are simulated and analysed, respectively. The simulation results indicate that (1) the v-shaped notch at the sidewall of the pillar is predominantly controlled by the in situ stress trends and magnitude; (2) at the heating stage, the existence of confining pressure can suppress the occurrence of damage, including shear damage and tensile damage; and (3) the presence of water flow and water pressure can promote the occurrence of damage, especially shear damage