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This article aims to investigate the impact of frequency sequence on mechanical responses of sandstone exposed to multi-level compressive cyclic loading. Two modes were used with three levels of low frequencies (0.1, 0.2, and 0.4 Hz) in incremental or decremental sequences. The analysis was made on rock deformation, energy characteristics and stress–strain phase shift. The experimental results show that frequency sequence has a significant effect on various types of mechanical properties. The decremental frequency causes a greater growth in axial strain at maximum cyclic stress than at the minimum stress. The input and elastic energy are enhanced under incremental frequency sequence, while decremental frequency results in a higher occurrence ratio of phase lag, particularly in the radial direction. These experimental findings can help to deepen the understanding of rock fatigue from the view of frequency sequence. [ABSTRACT FROM AUTHOR]

This work aims to experimentally investigate the behaviour of sandstone drilled from an underground coal mine exposed to low-frequency cyclic loading with distinct loading/unloading rates, namely differential cyclic loading (DCL). Three loading modes with different loading/unloading rates were applied. The test results are presented and analysed in terms of dissipated energy ratio (DER), evolution of secant elastic moduli, stress–strain hysteresis and acoustic emission (AE) behaviours. The correlation between DER and maximum cyclic load level is revealed, and a novel method to predict the strength of the rock sample is proposed based on statistics of DER at failure. The hardening behaviour is observed during cyclic loading, which is characterized by gradual enhancement of the secant elastic moduli. The stress–strain hysteresis is determined, which shows that phase shift between stress–strain is loading/unloading rate-dependent. The evolution of AE counts and energy is documented and discussed with respect to the dissipated energy. The results indicate that patterns of AE evolution and Kaiser effect are both influenced by cyclic loading paths. [ABSTRACT FROM AUTHOR]

Rock structural deterioration induced by coupled freeze–thaw and stress disturbance are a great concern for jointed rock mass during rock constructions in cold regions. Previous studies focused on fracture evolution of intact rock or flawed rock under freeze–thaw–static loads, but the coupling effect of freeze–thaw and cyclic loads on the pre-flawed hollow-cylinder rock is not well understood. This work investigated the influence of freeze–thaw on rock microstructure change and fatigue mechanical behaviors. Testing results show that rock strength, volumetric strain, and lifetime decrease with increasing F–T number. The stiffness degradation caused by cyclic loads is also impacted by the previous freeze–thaw damage. Additionally, the AE ring count and energy count decrease with the increase of F–T treatment. Large fracture signals are captured for rock that has smaller F–T cycles and at the stress-increasing moment. The AE b-value increases with F–T cycles, and it decreases rapidly near rock failure. Spectral analysis indicates that large-scaled cracking is prone to form for a sample having high F–T cycles. Moreover, 2D CT images reveal the differential crack network pattern at rock bridge segments and how it is affected by the previous freeze–thaw damage. The crack coalescence and hole collapse patterns and the associated structural deterioration of the rock bridge segment are obviously influenced by the F–T treatment. Highlights: Fracture behaviors of pre-flawed hollow-cylinder granite under freeze-thaw-fatigue loads were analyzed. Cyclic freeze-thaw weathering influences rock microstructure and geomechanical properties. Acoustic emission parameters and spectral analysis reveals the impact of F-T on rock progressive failure. The crack coalescence and hole collapse patterns are obviously influenced by the F-T treatment. [ABSTRACT FROM AUTHOR]

Rock mass containing central locked segments is susceptible to freeze–thaw weathering and could result in rock instability and even serious geological hazards. This work conducts uniaxial compression and acoustic emission synchronization tests to experimentally investigate the rock bridge deformation and failure characteristics of central locked samples drilled from plateaus in China. The influences of freeze–thaw cycles and rock bridge angle on the fracturing and acoustic emission pattern were characterized. Results show that the physical and mechanical parameters deteriorate in varying degrees with the increase of freeze–thaw cycles. The compression stress curves display as fluctuation trend and multiple stress drops, indicating that the rock bridge improves the plastic properties of samples. The points of stress drops are in good agreement with sudden increment of acoustic emission count curve. The acoustic emission count and released acoustic emission energy decrease with the increase of freeze–thaw cycles. The damage model established based on acoustic emission parameters reflects the process of crack propagation and coalescence of central locked sample subjected to freeze–thaw cycles during uniaxial compression. Damage variable evolution rate decreases with increasing of freeze–thaw cycles. The damage evolution rate and the associated crack growth rate is the smallest for a rock with bridge angle of 30 °. [ABSTRACT FROM AUTHOR]

This article presents the results for cyclic uni/triaxial tests on the deeply seated granite samples drilled from a −915 m deep tunnel in Sanshandao (SSD) gold mine. The monotonic and cyclic tests were carried out to observe the mechanical responses of the granite samples under different loading regimes. The disparities concerning the strain evolution and compressive strength of granite samples considering monotonic and cyclic uniaxial and triaxial loading are presented. Deformation behaviour, dissipated energy, and hysteresis are documented and evaluated. Quantitative correlations between strain evolution and cyclic stress levels are revealed. The amount of energy transformation during uniaxial and triaxial cyclic loading is determined. The impacts of confining pressure level on ultimate strain, energy dissipation, and stress-strain phase shift are presented. The mechanical responses of the granite samples subjected to different stress paths and loading strategies are summarised, and corresponding interpretations are given to clarify the differences of mechanical behaviour encountered in distinct loading methods. [ABSTRACT FROM AUTHOR]

Background: Male‐specifically inherited Y‐STRs have been widely used in population genetics and forensic investigations. Methods: We genotyped and analyzed Y chromosome haplotypes of 408 unrelated Tibeto‐Burman‐speaking Yi male individuals from Guizhou using Goldeneye® Y‐PLUS kit. Population comparisons between the Guizhou Yi and 67 reference groups were performed via the AMOVA, MDS, and phylogenetic relationship reconstruction. Results: A total of 389 alleles and 396 haplotypes could be detected, and the allelic frequencies ranged from 0.0025 to 0.9875. The haplotype diversity, random match probability, and discrimination capacity values were 0.9999, 0.0026, and 0.9900, respectively. The gene diversity (GD) of 36 Y‐STR loci in the studied group ranged from 0.0248 (DYS645) to 0.9601 (DYS385a/b). Our newly genotyped Yi samples show a close affinity with other Tibeto‐Burman speaking groups in China and Southeast Asia. Conclusions: The population stratification was almost consistent with the geographic distribution and language‐family, both among Chinese and worldwide ethnic groups. Our data may provide useful information for paternal lineage in the forensic application and population genetics, as well as evidence for archaeological and historical research. [ABSTRACT FROM AUTHOR]

• MSC model is proposed to replicate multi-level cyclic loading results. • Damage variable is stress-time dependent in numerical model. • Damage variable is characterized by reduction of bond diameter. • AE characteristics during cyclic loading are simulated based on PFC3D. Under the framework of the particle flow code (PFC), a three-dimensional multi-level stress corrosion model (MSC) is proposed to reproduce the mechanical behaviour of brittle geo-materials and concrete exposed to multi-level cyclic compressive loading. The damage induced by the variable cyclic load levels during consecutive loading stages in numerical simulations is quantitatively characterized by time-stress-dependent reducing of the bond diameter. The change of maximum or minimum load levels correspond to different evolution characteristics of the bond diameter. The simulation results with the adoption of the MSC model shows good consistency with laboratory testing. The MSC model is proved to replicate the mechanical characteristics of concrete samples subjected to cyclic loading with both, variable maximum and minimum load levels. A three-dimensional acoustic emission (AE) monitoring system is implemented into PFC3D. The cumulative AE energy collected during the simulation is designated as the released bond strain energy at bond breakage. The cumulative AE energy in the simulation shows good agreement with laboratory test results. [ABSTRACT FROM AUTHOR]

A nonlinear parallel-bonded stress corrosion (NPSC) model is proposed to simulate the fatigue characteristics of artificial rock (concrete) during cyclic loading. Numerical simulations of fatigue tests replicate the main mechanical features of concrete specimens subjected to cyclic loading observed in the laboratory. A nonlinear reduction speed of the bond diameter between two bonded particles represents the damage rate induced by the fatigue load. The damage rate is proportional to the maximum cyclic load level when the minimum cyclic load level is fixed. Compared with laboratory data, a logarithmic function of bond diameter in the NPSC model resulted in the best fit to simulate the fatigue behaviour of concrete. The simulation includes acoustic emission (AE) monitoring during fatigue tests. The axial strain of the assembly is governed by the evolution of bond breakages. The sum of released bond strain energy is documented as value proportional to cumulative AE energy. The simulation results show very similar evolution compared with laboratory data, which verifies the effectiveness of AE energy simulation. [ABSTRACT FROM AUTHOR]

Hysteresis energy-based failure indicators for concrete under cyclic loading conditions are proposed: hysteresis occurrence ratio (HOR) and hysteresis energy ratio (HER) considering the hysteresis characteristics and dissipated energy. A two-step approach to predict the failure of concrete is introduced. The first step: HOR has two critical values. These two critical values for the specific concrete used in our laboratory testing are 75% and 95%. In detail, when HOR is under 75%, the concrete has no risk to fail, when HOR is between 75% and 95%, the concrete has the possibility to fail, when HOR is larger than 95%, the concrete will fail very likely within the next few cycles. The second step contains two criteria: if HOR is larger than 75% and HER is larger than 0.3 at the same time, the concrete will fail. Different multi-level cyclic loading strategies have been designed to verify the effectiveness of these failure indicators and the failure prediction approach. First laboratory test results verified that HOR and HER are reliable failure indicators. [ABSTRACT FROM AUTHOR]

Based on dissipated energy approach (DEA), the energy dissipation characteristics of concrete samples subjected to uniaxial cyclic loading have been investigated. The effect of different cyclic load levels on energy dissipation is quantitatively analyzed by different damage indicators during cyclic fatigue tests. It is concluded that the cumulative speed of energy dissipation and increasing growth-rate of damage indicators in Continuum Damage Theory (CDT) follow an exponential function in relation to the maximum cyclic load level and follow a logarithmic function in relation to the minimum cyclic load level. The loading strategy has an effect on total energy dissipated during fatigue tests, in other words: Energy dissipation and damage evolution are stress path dependent. [ABSTRACT FROM AUTHOR]

The existing cryptocurrency portfolio studies have relied heavily on historical asset returns and ignored the importance of the prediction information of asset returns, which leads to poor out-of-sample performance of the resulting portfolio strategies. To this end, we first crawl the tweets related to cryptocurrencies on Twitter, analyze tweets' sentiment, and construct sentiment indicators. Second, we use the historical trading data, daily Google Trends, and sentiment indicators to forecast the movement of cryptocurrency prices using Support Vector Machine (SVM). Third, we propose a portfolio optimization model by considering both the forecasting information and the global minimum variance model, and then derive the corresponding portfolio strategy. Finally, we compare the out-of-sample performance of the proposed strategy with classic portfolio strategies and the Cryptocurrency Index. The empirical results show that: on the one hand, the proposed multi-source data can effectively help forecast the cryptocurrency price movements; on the other hand, the proposed portfolio strategy outperforms traditional portfolio strategies regarding the out-of-sample Sharpe ratio, Sortino ratio, and certainty equivalent return, this proves that the proposed strategy can sufficiently combine information between history and future. More importantly, the above conclusions are well verified in the robustness test. [ABSTRACT FROM AUTHOR]

The mechanical response of rocks subjected to compressive differential cyclic loading (DCL) with various stress rates is rarely investigated via numerical simulation at the microscopic level. In this study, the behaviour of sandstone is numerically investigated via a 3D particle-based numerical model. A damage model is implemented based on the variation in bond diameter and succeeds in accurately reproducing the stress–strain relations obtained from laboratory tests. Three evolution patterns of bond diameter are used to duplicate the strain rates observed during the laboratory tests. A system similar to AE monitoring is run in simulations, and AE events are recorded, classified, and visualized according to the magnitude of released energy at bond failure. The effect of heterogeneous bond strengths on AE characteristics is discussed. A heterogeneous model is recommended for the realistic reproduction of the onset of cracking as well as stress dependency. A stress rate-induced phase shift in terms of the stress–strain relation is observed in both laboratory tests and numerical simulations. The damping effect is thoroughly considered in the numerical model. [ABSTRACT FROM AUTHOR]

• The evolution of natural stone masonry stiffness exposed to multi-level cyclic load is revealed. • A novel secant modulus-based failure prediction method is proposed. • A constitutive model is proposed to characterize stone deformation under multi-level fatigue load. Stiffness loss and catastrophic failure frequently occur in natural stone masonry subject to freeze–thaw action and cyclic stress, which may incur serious engineering disasters and casualties. This work strives to experimentally unveil the mechanical responses of a medium-grained building sandstone exposed to dual effects of freeze–thaw and cyclic stress. Testing results are presented from the insights of volumetric deformation, secant modulus evolution. A drop in secant modulus of the first cycle is observed in the failure cyclic loading stage, whereas all former stages exhibit a modulus increase. This precursor well applies to all samples which is freeze–thaw and stress level independent. The development of Poisson's ratio as well as stress level at onset of volume reversal are also presented. A theoretical modelling is put forward to characterize the axial and circumferential strains exposed to variable cyclic stress. The model shows decent effectiveness calibrated by testing results, the way to determine constants in models is introduced in detail, which can be used by readers in a broader range of construction materials. [ABSTRACT FROM AUTHOR]

This article aims to numerically investigate the mechanical behaviour of concrete Brazilian Disk (BD) samples when exposed to multi-level cyclic Brazilian loading. A numerical 3D particle-based model was successfully established to simulate the dynamic stress-controlled cyclic testing. A generalized model is proposed based on the time-dependent evolution of bond diameter. This model shows great effectiveness in terms of reproducing the stress-strain curves, axial strain evolution and displacement fields as observed during lab testing. An acoustic emission (AE) tracking algorithm was implemented in the model to characterize and visualize the released AE energy connected with micro fracturing. The AE energy is found to be stress-level dependent which is consistent with lab testing. The failure pattern in numerical simulation is also in line with lab results. The distinctions between cyclic compressive and cyclic Brazilian tests are discussed and summarized. [ABSTRACT FROM AUTHOR]

• AE behavior and P-wave speed of concrete are revealed in cyclic Brazilian test. • Deformation behavior of concrete is revealed in cyclic Brazilian test. • DIC measurement is performed in cyclic Brazilian test. This work aims to investigate the fatigue behaviour of concrete subjected to indirect cyclic tensile loading. A series of laboratory tests were performed based on Brazilian disk-shaped (BD) concrete samples. Two schemes of cyclic loading tests were designed by considering complex variations of maximum and minimum stresses. The effect of loading parameters, such as loading method, maximum and minimum stress, on sample deformation, acoustic emission (AE) characteristics, P-wave speed evolution and failure patterns were analysed. The features of AE behaviour and P-wave speed were compared between monotonic loading and indirect cyclic loading. Insight on the specific fatigue behaviour was obtained from AE hit counts, AE energy and P-wave speed degradation. The failure patterns of BD concrete samples are governed by the loading method as well as the stress paths. The stress paths have a direct and pronounced impact on the distribution of main and sub cracks on the surface of BD sample at failure. [ABSTRACT FROM AUTHOR]

• Monitor the changes of PYR, FUM and PA content in the fermentation process. • Bacterial community succession during the fermentation of gray sufu was tracked. • Dominant bacteria changes from Fusobacterium to Lactobacillus during fermentation. • Microbial interaction affects the metabolism of Propionibacterium. • Lactobacillus could be the key factors to reduce PA content in gray sufu. In order to explore the correlation between the production of propionic acid (PA) and the succession of bacterial community during the fermentation of gray sufu, high-throughput sequencing and HPLC (High Performance Liquid Chromatography) were used to monitor the changes of bacterial community and metabolite content. The abundance and metabolite concentration of Propionibacterium increased rapidly in the early stage of fermentation. In the middle stage, the abundance of Lactobacillus began to increase, while the pH decreased rapidly. In the late stage, the concentration of PA began to decrease, but it remained at a high level at the end of fermentation. Correlation analysis showed that Lactobacillus and Bacillus had a strong negative correlation with PA and its precursor. The results showed that Fusobacterium , Providencia , Lactobacillus and Bacillus could be the key factors to reduce the PA content. This study provides a new idea for the quality control of traditional fermented food. [ABSTRACT FROM AUTHOR]

Freeze-thaw-fatigue (FTF) testing was carried out on Tibet marble at lab-scale by considering various Freeze-Thaw (FT) cycles and multi-level cyclic loading. The aim is to investigate the evolution of deformation and damage related parameters as well as the hysteresis behavior. The test results show that an increase of FT cycles and fatigue load level both accelerate the damage rate of marble. A rock suffering more FT cycles shows a much larger axial strain rate, radial strain rate and increasing Poisson's ratio. The relation of axial strain rate, radial strain rate and Poisson's ratio rate versus fatigue load level can be fitted by an exponential function. A warning level is defined according to the evolution of radial strain and Poisson's ratio which can inform before dilation starts. Moreover, the hysteresis behavior of stress-strain is investigated. It has been proven, that the proposed two indexes, "advance ratio" and "lag ratio" are effective precursors for rock failure prediction if subjected to FTF actions. The drastic drop of the "advance ratio" and the increase of the "lag ratio" are the indicators for forthcoming failure. The recommended warning limits for "advance ratio" and "lag ratio" for the tested marble are 5% and 70%, respectively. [ABSTRACT FROM AUTHOR]

This work aims to reveal the fracture the damage evolution characteristics of fissure‐holes containing rock under multistage constant‐amplitude variable‐frequency cyclic loads. Testing results show that the peak strength and fatigue lifetime both increase as the fissure angle increases from 10° to 70°. However, the volumetric deformation, AE activities, and crack network scale get to a maximum for a sample having a 50° fissure angle. More small‐sized cracks were formed for rock having a high fissure angle, and the proportion of low‐frequency signal is relatively high. A damage evolution model was proposed based on AE rate, and an inverted "S"‐shaped curve reflects the damage propagation of the experimental data. Additionally, the highlighted internal crack network reveals the crack coalescence and hole spalling behaviors; three types of rock bridge coalescence modes of single tensile coalescence, double‐tensile coalescence, and double shear coalescence were identified. Highlights: Failure of pre‐flawed granite under multi‐level variable‐frequency (MLVF) cyclic loads was discussed.Fissure angle influences the rock deformation, lifetime, AE activities, and the final crack pattern.A damage evolution model was proposed by AE rate to describe three‐phase damage propagation.The crack coalescence behaviors were visualized and three coalescence modes were identified. [ABSTRACT FROM AUTHOR]

This work proposed a progressive-sectional failure model (PSFM) based on Particle Flow Code (PFC) to simulate top coal drawing process in longwall top coal caving (LTCC) mining. The progressive-sectional fracturing of top coal was reproduced in simulation. 4 drawing schemes are numerically performed by considering drawing sequences and strategies. The results of simulations were compared in terms of top coal drawn out mass, drawing body, top coal recovery ratio (TCRR), top coal loss, etc. The results show that TCRR in PSFM is closer to average TCRR based on 9 LTCC coal mines measured in-situ. The top coal loss in PSFM is larger than loose granular model (LGM). The top coal boundary (TCB) in PSFM shows a "step" subsidence and is different from that in LGM. The factors to influence initial drawing body (IDB) are comprehensively analysed. A new mathematical model was proposed to specifically characterize IDB in LTCC. The results show that new model is well consistent with simulation results and is much more effective and accurate than former models. [ABSTRACT FROM AUTHOR]

• The axial strain for cyclically loaded concrete specimens is inhomogeneous. • The energy dissipation for cyclically loaded concrete specimens is inhomogeneous. • A new definition of P-wave ratio is proposed as an effective fatigue failure precursor. • Monotonically loaded concrete show larger cracks than cyclic loading case. The mechanical behaviour of different parts (top, middle and bottom) of concrete exposed to monotonic and cyclic loading is investigated through laboratory testing. Strain evolution and energy dissipation are found inhomogeneous at different parts of the sample during compressive cyclic loading. The middle part of sample shows larger residual strain rate and dissipated energy than the top and bottom parts when larger load levels are applied. The disparity between the middle part and top/bottom parts reaches the peak value at peak strength. Based on two different cyclic loading strategies, it is concluded that the maximum load level has more pronounced effect on energy dissipation than the minimum load level. The evolution of P-wave speed during cyclic loading is also found inhomogeneous, a new definition of P-wave ratio is proposed as an effective fatigue failure precursor. The failure patterns of concretes subjected to monotonic and cyclic loading are presented, and it is shown that size and type of cracks is directly related to the loading methods. [ABSTRACT FROM AUTHOR]

Rock joints have obvious acoustic emission (AE) Kaiser effect and Felicity effect under multilevel cyclic shear conditions. The TFD-20H/50J rock shear apparatus was used to carry out cyclic loading and unloading joint shear tests, and the acoustic emission parameters and frequency spectrum characteristics of the whole shearing process were analyzed. The results show that, under the cyclic loading, the shear stress-displacement curve forms several cyclic hysteresis loops, and the number of loops increases with the increase of normal stress. With the cycles increase, the shear damage gradually increases, and the Felicity ratio gradually decreases. The Felicity ratio at the final shear failure moment is about 0.94~0.99. The ratio of the RA value (rise time/amplitude) and the average frequency value (RA-AF) is used to classify the cracking mode of the joint sample. There are two AE crack signal types (tensile type and shear type) during shear damage. The peak frequency is displayed as high, medium, and low three frequency bands, which are distributed in the range of 0~35 kHz, 35~122 kHz, and 122~300 kHz, respectively. Both low-frequency and high-frequency signals account for less than 10%, and medium-frequency signals account for more than 90%. The research of the AE monitoring signals of multilevel shear behaviors can help understand the shear-friction mechanisms of rock joints. [ABSTRACT FROM AUTHOR]

Mining-induced hydromechanical behavior of sandstone is critical to mining safety and disaster prevention. To investigate the evolution behavior of the mechanical and permeability properties of sandstone, mining-induced stress was imitated by increasing axial stress and decreasing confining stress, and a set of hydromechanical experiments were further performed, incorporating the effect of in situ stress, pore pressure, and mining stress. The results show the similar variation tendencies of the deformation and permeability of sandstone under different loading paths of in situ stress and pore pressure. Most sandstone samples maintain a compression state for the peak stress condition. The failure mode evolved from shear failure to shear–tension failure with the increase in in situ stress. The stress-relief effect significantly effects the permeability, since the permeability of sandstone increases exponentially with decreasing effective confining stress. The growth rate of permeability in Stage II is significantly greater than that in Stage I. One order of magnitude of permeability was presented at the peak stress situation. A fitting exponential model based on the alteration of effective confining stress was proposed to describe the permeability evolution dominated by the stress-relief effect, and the discovered permeability model can accurately describe the experimental results. The research results provide significant guidance for understanding the hydromechanical behavior and water hazard prevention for underground coal mines. [ABSTRACT FROM AUTHOR]

A new method was developed for the identification and determination of L-ergothioneine in cosmetics based on ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The pretreatment method, chromatographic column, chromatographic conditions, and mass spectrometric conditions of cosmetic samples were optimized. Methanol was chosen as the extraction solvent, 85% acetonitrile with 0.1% FA was selected as the mobile phase, and the Waters CORTECS UPLC hydrophilic interaction liquid chromatography (HILIC) column was chosen for the separation. The sample was extracted with methanol and filtered, then separated by HILIC and detected by triple-quadrupole mass spectrometry. The quantitation was done under the matrix calibration curve using the external standard method. The results showed good linear relationships in the range of 5–200 ng/mL, and the correlation coefficient was greater than 0.999 in cosmetic samples. The limit of detection was in the range of 25–50 μg/kg and the limit of quantitation was in the range of 50–100 μg/kg. The recoveries of the method spiked ranged from 85.3% to 96.2% and the relative standard deviation (RSD) was in the range of 0.84%–2.08% (n = 6). The method is simple, quick, and accurate for the determination of L-ergothioneine in cosmetics, and has great practical value. [ABSTRACT FROM AUTHOR]

This study proposed a novel bio-carbonation method to recycle water-based drill cutting (WDC) to prepare samples, which contains reactive magnesia (MgO) cement (RMC), ground granulated blast furnace slag (GGBS), and fly ash (FA), with the adoption of microbially induced carbonate precipitation (MICP). Through the investigation of some parameters (i.e., GGBS content, FA content, and curing time), the microstructures and strength development of bio-carbonated RMC-based WDC samples were evaluated. The preliminary results revealed that bio-carbonated RMC-based WDC samples outperformed the control group (i.e., without bio-carbonation) in terms of the 28-day strength (i.e., 9.8 MPa versus 4.4 MPa), which can be assigned to formation of the carbonates, that is, hydrated magnesium carbonates (HMCs). Further, in addition to the identification of HMCs, the microstructural analysis also revealed a continuous carbonate network due to the presence of HMCs, which accounts for the strength boost of samples. [ABSTRACT FROM AUTHOR]

Chen et al. [[6]] developed a method to obtain the size distribution characteristics of the real source from the apparent amplitude in doubly truncated distribution using rock acoustic emission (AE) tests. 10.3390/math10193490 9 Qiu J., Feng F. Effect of Different Tunnel Distribution on Dynamic Behavior and Damage Characteristics of Non-Adjacent Tunnel Triggered by Blasting Disturbance. With the increasing requirements for energy, resources and space, numerous rock engineering projects (e.g., mining, tunnelling, underground storage, geothermal energy, petroleum, water conservancy and hydropower) are more often being constructed and operated in large-scale environments with complex geology. [Extracted from the article]

The shale fracture permeability is critical in determining gas production and deep CO2 sequestration performance. Moreover, how shale fracture permeability evolves after interactions with supercritical carbon dioxide (Sc-CO2) should be understood to constrain the shale reservoir permeability and evaluate the long-term sealing ability of shale formations. In this research, we conducted soaking experiments with shale fractures and Sc-CO2 at various times and then measured the shale fracture permeability and hydraulic aperture evolution under different stress states. Additionally, we quantify the chemical compositions, pore characteristics, fracture surface roughness alternation through X-ray diffraction, nuclear magnetic resonance, scanning electron microscope, and optical profilometry techniques. Our results indicate that soaking with Sc-CO2 will dramatically increase the shale fracture permeability and aperture due to the calcite and dolomite dissolution. This free-face dissolution process will remove the mineral particles in the fracture surface, resulting in larger pores, peaks, and valleys in the fracture surfaces. This process may last for seven days, and after that, chemical reactions may terminate, and the rock-Sc-CO2 system turns stable. Our results explain how Sc-CO2 alters the shale fracture permeability through the chemical dissolution of specific minerals from a microscale analysis. [ABSTRACT FROM AUTHOR]

Lots of in-situ experience indicate that water spraying or injection to rock mass before excavation is an effective method for rock-burst prevention in deeply buried hard rock engineering projects. To investigate the underlying mechanisms of rock-burst prevention by watering, a series of uniaxial compression laboratory experiments were performed on three types of sandstone samples under oven-dried and water-saturated conditions. A high-speed camera was used to record the fracture processes of the samples during testing. Experimental results show that the presence of water plays a dramatic weakening role on the uniaxial compressive strength, Young's modulus, and energy storage capacity of the three sandstones. After water saturation, the failure pattern of rock sample becomes much gentler and less dynamic. Moreover, a simple mechanical model of a roadway containing zonal water-weakening rock mass was established to illuminate the local geo-stress regulation by water penetration. The mechanisms for rock-burst prevention by water are mainly due to the declining energy storage capacity and the lowered stress near the working face. [ABSTRACT FROM AUTHOR]

Background: Myelomatous pleural effusion (MPE), as a presentation of extramedullary infiltration of multiple myeloma (MM), is rare and currently associated with poor outcomes without effective therapy. The potential value of cytokine detection in pleural effusion to MPE has not been reported to date. Case Presentation: We herein report a case of refractory and relapsed multiple myeloma that developed bilateral MPE due to disease progression caused by intolerance to various chemotherapy regimens. Cytomorphology and flow cytometry were adopted for diagnosis confirmation. Chemotherapy containing immunomodulators combined with thoracic catheterization drainage was applied to the patient, showing a certain therapeutic effect. During the course of disease, the change of cytokine profile in pleural effusion was monitored by cytometric bead array (CBA) technology, revealing that cytokines related to tumor load such as interleukin 6 (IL-6) and interleukin 10 (IL-10) in pleural effusion decreased with the improvement of disease, while other cytokines such as interleukin 2 (IL-2), interleukin 4 (IL-4), interleukin 17A (IL-17A), tumor necrosis factor α (TNF-α), interferon γ (IFN-γ), granzyme A, granzyme B, perforin and granulysin increased with the improvement of disease. Conclusion: There is a prospect that cytokine level in pleural effusion may indicate treatment response of MPE, and in light of this case, immunomodulators may be utilized in treating patients suffering MPE. Due to limitations of our single case, we urge more groups to evaluate the potential role of cytokine profile in MPE. [ABSTRACT FROM AUTHOR]

Due to the lack of relevant investigation research on the evolution of mining stress in high stope of metal mines, the understanding of how to ensure the safety during mining process is not clear at all. In this paper, by monitoring the mining-induced pressure of the surrounding rock in the 16-2# stope of Lilou Iron Mine, the evolution of the mining-induced pressure of the subsequent filling and mining method of the high-stage empty field is obtained. The study shows that there are three stages of pressure change in the second-step stope of Lilou Iron Mine: I (stress rising stage), II (stable stage), and III (pressure relief stage), and the mining stress in the surrounding rock is transferred from the top to bottom. The stress transfer model of stope is proposed, and the variation of vertical stress versus the depth is fitted; the four horizontal sections are fitted, respectively. By establishing the three-dimensional numerical model and distributed excavation simulation, the time-space evolution of mining stress is obtained and compared with the in-site measuring result. The two results show high consistency, and the effectiveness of numerical simulation is verified. [ABSTRACT FROM AUTHOR]

The migration and distribution of oil in oil-bearing coal significantly influence the gas drainage and gas-outburst control during mining activity. To quantitative describe the oil/gas migration and morphology in mining-induced fractured, the triaxial seepage experiment was conducted considering the mining-induced redistributed stress, and the self-developed online low field nuclear magnetic resonance triaxial seepage system (LF-NMR) was employed. The stress-fracture-seepage field evolution was monitored and corresponding coupling mechanism was analyzed based on the T 2 spectrum, MRI and stress-strain response. The pore-fracture was composed of macropore (>10 m s), mesopore (1–10 m s) and micropore (0.01–1 m s), and experienced rapid compaction, stable reduction and rebound stage, which was mainly contributed by the macropore. The coal experienced compression, elastic, elastic-plastic, plastic-failure state with the increase of vertical stress, and continuously created tensile stress-dependent, tensile stress and shear stress-dependent, and shear stress-dependent pore-fracture structure under the confined pressure of 18 MPa, 10/14 MPa, and 2/6 MPa. The vertical stress triggered the pore-fracture development, and confined pressure controlled the pore-fracture distribution and morphology. As the unloading of confined pressure, the horizontal deflection of fracture angle was increased, fracture size was decreased, and the conductivity channel for oil/gas migration experienced "compacting channeling " (10–18 MPa), "optimal channeling" (10 MPa) and "gas channeling " (2–10 MPa) with corresponding oil recovery of 35 %, 40 % and 20 %. The gas drainage experienced lower stable state, dynamic peak state, and re-lower state, and the maximum methane concentration of 70 % and discharge of 0.9 m3/min presented ahead of the mining face around 20 m in engineering practice. The findings provide insight into the co-mining of coal, gas and oil. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the water saturation effects on the thermal infrared radiation (IRR) characteristics of rock materials during deformation and fracturing processes. Three kinds of rocks, namely sandstone, granite, and marble, were adopted for tests. Uniaxial compression tests were carried out on oven-dried and water-saturated rock samples. The evolution of IRR temperature on rock surface was monitored and recorded with the aid of an infrared thermographic camera. Test results show that the IRR temperature of saturated samples is apparently higher than that of dry ones subjected to the same axial stress. After water saturation, the heating rate in elastic deformation phase, the IRR temperature increment at peak stress, and the IRR temperature on the new-formed fracture surface have a significant growth compared to dry condition. These indicate that the presence of water facilitates the release of thermal energy. The sensitivities of the heating rates in elastic deformation phase to water saturation are very distinct for the three rocks. This is possibly resulted from the mineral composition of rock types, especially the proportion of calcite and swelling clay minerals. The IRR temperature increment at peak stress for rock not only depends on the moisture condition, but is also relevant to the uniaxial compressive strength. [ABSTRACT FROM AUTHOR]

• The abrasive parameters of three construction rocks are analysed. • Cerchar test was conducted by using a special instrumented West apparatus. • Cerchar abrasion ratio is a meaningful parameter to evaluate rock abrasivity. • Cerchar abrasive parameters and their effecting factors are summarized. The Cerchar test method and its index, the so-called Cerchar abrasivity index, are most commonly used to determine the abrasivity of rocks and other geo-materials for construction. Recently, with the aid of a new test device, various abrasive parameters can be obtained from the Cerchar test. In this article, several abrasive parameters such as scratching force, scratching energy and scratching specific energy are determined using a special instrumented West apparatus. Three typical rock materials for construction (granite, sandstone and slate) are selected to study the correlation of Cerchar abrasive parameters with rock intrinsic properties. The research results show that the Cerchar abrasion ratio is a meaningful parameter to quantify not only the rock abrasivity, but also the rock-stylus interaction, as well as the stylus wear and the scratching effectivity. [ABSTRACT FROM AUTHOR]

Ferroptosis was reported to be involved in cerebral ischemia-reperfusion injury (CIRI), on which the effects of berberine (BBR) remain unclear. Moreover, based on the critical role of gut microbiota in pleiotropic actions of BBR, we hypothesized that BBR can suppress CIRI-induced ferroptosis by modulating the gut microbiota. In this study, the results showed that BBR obviously attenuated the behavioral deficits of CIRI mice, accompanied with the improved survival rate and neuron damages, as phenocopied by dirty cage experiment. The typical morphological changes in ferroptotic cells and biomarkers of ferroptosis were attenuated in BBR- and its fecal microbiota-treated mice, accompanied by reduced malondialdehyde and reactive oxygen species, and the increased glutathione (GSH). BBR was found to alter the gut microbiota of CIRI mice with decreased abundance of Muribaculaceae , Erysipelotrichaceae , Helicobacteraceae , Streptococcaceae and Tannerellaceae, but elevated Bacteroidaceae and Enterobacteriaceae. KEGG analysis based on the 16S rRNA results indicated that multiple metabolic pathways including ferroptosis and GSH metabolism, were altered by BBR. Oppositely, the antibiotics administration counteracted the protective properties of BBR. Summarily, this study revealed the therapeutic potential of BBR on CIRI via inhibiting neuronal ferroptosis, in which upregulated glutathione peroxidase 1 (GPX1) was possibly involved. Moreover, the BBR-modulated gut microbiota was shown to play the critical role in the underlying mechanism. [ABSTRACT FROM AUTHOR]

• DEM based fluid-driven fracture propagation behavior in coal rock is simulated using PFC2D. • Intersection mode of HF and NP in coal subjected to distinct geo stress and approaching angle during hydraulic fracturing is analyzed and compared with other rock masses. • Low approaching angles of natural plane in coal can facilitate the generation of more complex hydro-fractures. • High injection rate and less in-situ stress difference is more conducive to branch and random distribution of hydraulic fractures near borehole in coal rock. To better understand the propagation characterizations of hydraulic fracture (HF) in coal with natural planes (NP), a fully coupled fluid flow-DEM method is employed, and a series of numerical simulations are carried out. The impact of the NP approaching angle (the angle between NP and the horizontal direction), in-situ geo-stress, the fluid flow injection rate on the fracture propagation behavior and breakdown pressure is analyzed. It is concluded that three interaction modes can be simulated, and the existence of NPs with low strength and approaching angles can facilitate the development of more complex fracture networks in coal rock. Intersection mode of HF and NP in coal subjected to different approaching angle is more sensitive comparing to other rock masses. Distinct injection rates, in-situ stress difference of NP also play a key role in determining HF morphology and its interaction mode with NP. The findings in this study may provide a numerical reference for optimizing the design of hydraulic fracturing in coal. [ABSTRACT FROM AUTHOR]

• The dynamic properties of burst-prone coal are influenced by fissure angle. • The crack evolution behavior of burst-prone coal with single fissure is obtained. • The dissipated energy evolution of burst-prone coal with single fissure is studied. The dynamic properties of burst-prone coal are directly associated with the prevention of outburst in engineering practice. In this study, the mechanical responses and crack evolution under dynamic disturbance was investigated by considering the effect of a single prefabricated fissure. The tests were performed via the modified split Hopkinson pressure bar (SHPB) test system, an ultra-dynamic strain acquisition system and a high-speed camera system were employed. The results show that the peak load is positively correlated with the fissure angle, characterized by the increase of 1.85 to 2.3 kN with an N-shape. The main macrocracks propagated and coalesced along the end-point of fracture and loading direction, while that occurred at the middle of the fracture and parallel expanded to the loading direction under fissure angle of 90°. The main cracks are wing cracks at fissure angle of 0°, 15° and 30°, and anti-wing cracks presented under fissure angle of 45° and 60° condition. The fractal dimension increases from 1.54 to 1.67 for the decrease of fissure angle. The evolution of dissipated energy was characterized by S-shape and exhibited a four-phase pattern, the maximum value of 16 J is recorded at fissure angle of 30°and the corresponding minimum value is 11.5 J at fissure angle of 45°. The experimental results provide a reference to the prevention of coal burst in engineering practice. [ABSTRACT FROM AUTHOR]

Underground rock structures are frequently subjected to water erosion and dynamic disturbance simultaneously. Herein, in order to study the coupled effects of water and high strain rate on the mechanical behavior and microstructures of sandstone, we conducted a series of dynamic unconfined compressive tests on oven-dried and water-saturated sandstone core samples using a split Hopkinson pressure bar. Test results revealed that, three macroscopic final patterns, namely unbroken, axial split and pulverization, were observed. At given strain rates, the presence of water weakens the dynamic peak stress and the dissipated energy density (the ratio of energy dissipation to residual axial strain) of rock sample but enhances the elastic modulus regardless of the failure pattern. Additionally, the saturated sample owns a higher rate dependence of dynamic strength compared to the dry one under the explored range of strain rate (43.9–156.7 s−1), which indicates that water-weakening on rock strength gradually attenuates with the increase of strain rate. Interestingly, thin sections analysis microscopically showed that the failure of dry samples is characterized by the intra-granular fracturing in larger quartz grains while that of saturated samples by the inter-granular fracturing. The underlying mechanisms were interpreted with two micro-mechanical damage models. • Dynamic compression tests are performed on dry and saturated rocks. • Water presence weakens the peak stress and the dissipated energy density but enhances the elastic modulus. • The rate dependence in strength of saturated samples is greater than that of dry samples. • The micro-damage mechanisms of dry and saturated samples under dynamic loading are different. [ABSTRACT FROM AUTHOR]

• As the number of wetting-drying cycles increases, the density and P-wave velocity of sandstone gradually decrease and the porosity increases. • The density and interconnectivity of the internal microcracks increase with wetting-drying cycles. • Under the same loading rate, the fracture toughness and energy dissipation of rock decreases as the increasing cyclic number. • The primary mechanisms for the rock deterioration after wetting-drying cycles are the dissolution of calcite and the intergranular cracking induced by clay swelling. Rocks are usually subjected to cyclic wetting-drying due to the periodical changes in moist condition. To investigate the effect of wetting-drying cycles on the fracture behavior of sandstone, notched semi-circular bending tests were performed on sandstone samples after every ten cycles (a total of 50 cycles) under both quasi-static and dynamic loading conditions. Tests results indicate that both of fracture toughness and energy dissipation of sandstone significantly decrease with the increase of cycle number. Moreover, the microstructural characteristics reveal that after cyclic wetting-drying treatments, the calcite cementation between grains gradually dissolves and the density and width of inter-granular fracture increase, which could be responsible for the deterioration of rock mechanical properties. [ABSTRACT FROM AUTHOR]

• Loading frequency has almost no influence on dissipated energy for a single cycle. • Total dissipated energy is related to the total cycle number. • Two hysteresis indexes are proposed to predict fatigue failure of coal sample. • The damage evolution of coal sample subjected to cyclic loading is inhomogeneous. This paper documents investigations of the fatigue behaviour of strong burst-prone coal in terms of energy dissipation, hysteresis and micro-seismicity. The energy dissipation characteristics of the coal subjected to multi-level-frequency cyclic loading were studied. Two hysteresis indexes were proposed according to the stress-strain relation during cyclic loading. These two indexes are effective as twin precursors to predict the fatigue failure of coal samples. The effect of frequency on energy dissipation rate was studied. With the aid of an AE monitoring system and a high speed camera, 3D distribution of AE events and failure patterns were obtained. The damage evolution of coal samples subjected to cyclic loading is not homogenous due to the stiffness effect of the loading platen. The failure patterns captured by high speed camera are consistent with the results characterized by the spatial distribution of the AE events. [ABSTRACT FROM AUTHOR]