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Abstract To investigate the effects of high temperature and carbon fiber-bar reinforcement on the dynamic mechanical properties of concrete materials, a muffle furnace was used to treat two kinds of specimens, plain and carbon fiber-bar reinforced concrete, at high temperatures of 25, 200, 400 and 600 °C. Impact compression tests were carried out on two specimens after high-temperature exposure using a Hopkinson pressure bar (SHPB) test setup combined with a high-speed camera device to observe the crack extension process of the specimens. The effects of high temperature and carbon fiber-bar reinforcement on the peak stress, energy dissipation density, crack propagation and fractal dimension of the concrete were analyzed. The results showed that the corresponding peak strengths of the plain concrete specimens at 25, 200, 400, and 600 °C were 88.37, 93.21, 68.85, and 54.90 MPa, respectively, and the peak strengths after the high-temperature exposure first increased slightly and then decreased rapidly. The mean peak strengths corresponding to the carbon fiber-bar reinforced concrete specimens after high-temperature action at 25, 200, 400, and 600 °C are 1.13, 1.13, 1.21, and 1.19 times that of plain concrete, respectively, and the mean crushing energy consumption densities are 1.27, 1.31, 1.73, and 1.59 times that of plain concrete, respectively. The addition of carbon fiber-bar reinforcement significantly enhanced the impact resistance and energy dissipation of the concrete structure, and the higher the temperature was, the more significant the increase. An increase in temperature increases the number of crack extensions and width, and the high tensile strength of the carbon fiber-bar reinforcement and the synergistic effect with the concrete material reduce the degree of crack extension in the specimen. The fractal dimension of the concrete ranged from 1.92 to 2.68, that of the carbon fiber-bar reinforced concrete specimens ranged from 1.61 to 2.42, and the mean values of the corresponding fractal dimensions of the plain concrete specimens after high-temperature effects at 25, 200, 400, and 600 °C were 1.19, 1.21, 1.10, and 1.11 times those of the fiber-reinforced concrete specimens, respectively. The incorporation of carbon fiber-bar reinforcement reduces the degree of rupture and fragmentation of concrete under impact loading and improves the safety and stability of concrete structures.

Abstract In order to investigate the effects of strain rate and water saturation on the energy dissipation and crack growth of tuff, uniaxial compression tests were carried out on dry and water saturated tuff with different strain rates using an electro-hydraulic servo press and a 50 mm diameter split Hopkinson pressure rod (SHPB) device. High-speed camera and Image J image analysis software were used to obtain the crack growth process of the specimen under impact load, and fractal dimension was introduced to quantitatively study the crack growth degree. The results show that more than 90% of the energy is stored in the specimen as elastic energy when it reaches the peak stress under static load. The average total energy of water-saturated specimens is 67.55% of that of dry specimens. The average energy dissipation density of water-saturated specimens under 0.3 MPa, 0.4 MPa and 0.5 MPa air pressure is 0.79, 0.91 and 0.92 times of that of dry specimens, respectively. Water-saturated specimens will deteriorate and thus reduce their energy storage and energy absorption effects. The reflected energy, transmitted energy, absorbed energy and incident energy are linear, logarithmic and linear functions, respectively, and the energy absorptivity and specific energy absorptivity of water-saturated specimens are lower than those of dry specimens. Due to the existence of “stefan” effect, the increase of energy dissipation density of water-saturated specimen at high strain rate is greater than that of dry specimen. The mean fractal dimension of water-saturated specimens under 0.3 MPa, 0.4 MPa and 0.5 MPa is 1.09, 1.05 and 1.16 times that of dry specimens. At the same strain rate, the number and width of cracks in water-saturated specimens are larger than that in dry specimens. Water-saturated behavior reduces the energy absorption capacity of tuff, increases the fractal dimension of crack growth, and significantly reduces the resistance of water-saturated rock to external loads.

Abstract To increase the efficiency of deep-hole blasting driving in mine rock tunnels, an innovative pattern of wedge cutting blasting with hole-inner delay was proposed. First, the blasting mechanisms of conventional and innovative wedge cutting patterns were theoretically investigated. The results showed that the resistance from large upper rock blocks and the clamping action from the surrounding rock were the major challenges of conventional cutting methods. For the innovative cutting pattern, under the conversion of the spatial distribution and release sequence of blasting energy, the first blasting of the upper charge can strengthen the breaking of the upper rock mass and create a new free surface, which provides favorable conditions for the delayed blasting of the bottom charge. Second, finite element models of two cutting patterns were established and solved, and the simulation results visually revealed the propagation of a stress wave. Critically, the stress strength in the upper cavity increased by 66–83% under the action of the upper charge, which was conducive to the breaking of the upper rock mass and the generation of a new free surface. Therefore, the rock mass in the bottom cavity can be readily broken and discharged. Ultimately, field applications were executed in a rock tunnel. Compared with a conventional cutting pattern, the proposed innovative cutting pattern can prominently increase the cycle advance and hole utilization and greatly reduce the unit consumption of explosives and detonators. This research confirms the usability of the innovative wedge cutting pattern with hole-inner delay in deep-hole blasting driving of rock tunnels.

Carbon dots (CDs) are carbon-based zero-dimensional nanomaterials with characteristic sizes of less than 10 ​nm. Recently, bioactive CDs have made remarkable achievements in wound healing, bone and cartilage repair, neural regeneration, and myocardium regeneration owing to their unique physicochemical properties and excellent biocompatibility, which have significantly promoted the advancement of tissue engineering. Herein, we summarize the applications of bioactive CDs in tissue engineering. First, we briefly introduce the characteristics and synthesis methods of bioactive CDs. Subsequently, we review the applications of bioactive CDs in wound healing, bone and cartilage tissue engineering, neural tissue engineering, and cardiac tissue engineering in detail. Finally, we discuss the challenges and prospects of bioactive CDs in tissue engineering.

Abstract Plant secondary metabolites can protect organisms against oxidative stress caused by adverse environmental conditions. Cinnamomum camphora (L.) J. Presl contains plentiful terpenoids and is subdivided into 5 chemotypes. To develop natural antioxidants using the plant terpenoids, the terpenoid composition and antioxidant abilities of methanol, ethyl acetate, n-hexane and petroleum ether extracts from linalool and eucalyptol chemotypes were investigated, and the solvent effects on in vitro antioxidant activity of 8 main terpenoids were analyzed. Meanwhile, the in vivo effects of two strong antioxidant terpenoids were evaluated. For the two chemotypes, the 4 solvents exhibited the same extracting effects on the terpenoid types, but methanol extracts contained the highest content of terpenoids, which should contribute to their strongest scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals. In linalool and eucalyptol chemotype extracts, linalool, eucalyptol, ocimene, α-pinene, D-limonene, terpinene, β-pinene and longifolene were the 8 main terpenoids. Among the 4 solvents, the 8 terpenoids showed the strongest free radical-scavenging activity with methanol as the reaction medium, which might result from strong-polarity methanol easily activating C = C unsaturated bonds in these compounds. This might also contribute to the strongest scavenging activity of methanol extracts against free radicals. Among these main components, ocimene and longifolene separately showed the strongest activity in scavenging DPPH and ABTS free radical. In in vivo assay, the two compounds significantly lowered the reactive oxygen species (ROS) levels in Chlamydomonas reinhardtii, a single-celled model organism, under H2O2 stress, and the lowering effects gradually enhanced with increasing the compound concentration, resulting in the corresponding promoting effect on the algal growth. At the same concentration, longifolene showed the strongest effect on protecting the algal cells against oxidative stress. Therefore, methanol was suitable for extracting terpenoids in natural antioxidant development, and ocimene and longifolene were two strong antioxidant terpenoids without cell toxicity, with the latter having stronger in vivo antioxidant activity. Graphical Abstract

The efficient extraction of gas from low-permeability coal seams is an urgent problem in coal mine safety production. The traditional gas extraction technology generally suffers from problems that limited penetration enhancement or extraction effect, low construction efficiency, large workload, etc. Thus, it is especially urgent and important to explore the new technology applicable to efficient underground gas extraction. In this paper, based on the principle of hydraulic fracturing to increase permeability, we innovatively propose a technique to enhance the effect of hydraulic fracturing to increase permeability and further improve the efficiency of gas extraction using the gas desorption activity of native microorganisms in coal seams. Herein, the composition of the primary microbial community of a coal seam in Xinji No.2 mine was analyzed by bacterial and archaeal 16SrDNA amplicon sequencing, the community structure of the main functional microorganisms was clarified, the optimal combination of functional microorganisms for organic matter degradation in coal seam under anaerobic culture conditions was obtained. Besides the Biolog microplate technology was used to screen the nutrients of the excitation carbon source to stimulate the rapid decomposition of coal organic matter by microorganisms and to define the optimal ratio of the excitation carbon source to microorganisms. Finally, the effect of this technology on the application of coal seam fracturing and gas extraction was tested through field industrial tests, revealing that the extraction effect of this technology was more significant than that of the common coal seam perforation extraction technology. The results of this paper provide a new technical idea for gas extraction from low permeability coal seams, which is an important reference value for subsequent similar studies.

Oncogene E6 plays a critical role in the development and progression of esophageal cancer caused by human papillomavirus (HPV) infection. Alpha‐ketoglutarate (AKG) is a key metabolite in the tricarboxylic acid cycle and has been widely used as a dietary and anti‐ageing supplement. In this study, we found that treating esophageal squamous carcinoma cells with a high dose of AKG can induce cell pyroptosis. Furthermore, our research confirms that HPV18 E6 inhibits AKG‐induced pyroptosis of esophageal squamous carcinoma cells by lowering P53 expression. P53 downregulates malate dehydrogenase 1 (MDH1) expression; however, MDH1 downregulates L‐2‐hydroxyglutarate (L‐2HG) expression, which inhibits a rise in reactive oxygen species (ROS) levels—as L‐2HG is responsible for excessive ROS. This study reveals the actuating mechanism behind cell pyroptosis of esophageal squamous carcinoma cells induced by high concentrations of AKG, and we posit the molecular pathway via which the HPV E6 oncoprotein inhibits cell pyroptosis.

The structural stability of engineering rock mass under dynamic disturbance is directly associated with the fracture mechanics properties in engineering practice. Fully understanding the rock’s fracture mechanical behavior and crack evolution caused by stress concentration at the crack tip in engineering rock mass under dynamic load can offer useful insight into the rock’s dynamic fracture mechanism. A dynamic test using split-Hopkinson pressure bar (SHPB) test system was performed on a single prefabricated fissure sandstone centrally cracked Brazilian disk (CCBD) specimens. Based on the theory of fracture mechanics and one-dimensional stress wave theory, the dynamic crack initiation criterion of CCBD specimen is proposed, and the regression model of sandstone’s dynamic fracture toughness under the coupling effect of fissure angle and strain rate is established by using response surface methodology (RSM). The influence of strain rate and fissure angle on stress wave characteristics, dynamic tensile mechanical behavior, and fracture mechanics characteristic was investigated in this study. The findings demonstrate that: (1) The fissure angle plays a pivotal role in determining the failure mode of sandstone. As the fissure angle increases, three distinct failure modes emerge in the sandstone specimens, while variations in strain rate have minimal impact on the fracture mode of these specimens. (2) Alterations in the fissure angle result in changes to the waveform of transmitted waves. When the fissure angle is below 30°, the transmitted wave exhibits “double peak” characteristics; when it exceeds 30°, a “single peak” waveform is observed. This phenomenon can be attributed to diffraction principles governing incident waves. (3) When the impact pressure is 0.2 MPa, the peak load initially exhibits an increase followed by a decrease, with the peak load reaching its maximum at a fracture angle of 60°; when the impact pressures are 0.3 and 0.5 MPa, there exists a negative correlation between the peak load and the fissure angle. (4) The influence of strain rate on sandstone’s fracture resistance is predominant, with alterations in fissure angle exerting an auxiliary effect on this property. The research results can provide a theoretical and experimental basis for dynamic disaster prevention in urban underground space.

The excessive destruction of surrounding rock in deep tunnel will change the original environmental state and destroy the natural ecological balance. Research on the dynamic response characteristics and damage thresholds of rock masses in deep environments plays a crucial role in determining the excavation range of blasted rock and establishing safety construction scheme. This study employs numerical simulation techniques to investigate the dynamic response characteristics of surrounding rock under different ground stress conditions. By introducing the dynamic ultimate tensile strength criterion, critical fracture stress threshold, and maximum damage radius of rock under coupled dynamic-static loading conditions are determined. The research shows that under uniaxial ground stress condition, increasing ground stress inhibits damage to the surrounding rock and the extension of cracks in the excavation area, while imposing restrictions on the attenuation rate of explosive stress. Under bidirectional equal ground stress condition, an increase in lateral pressure coefficient inhibits the development of damage zones along the excavation contour, yet enhances the extension of cracks in the maximum principal stress direction. Moreover, when lateral pressure coefficient becomes excessively large, the attenuation rate of explosive stress significantly increases. Based on the threshold values of peak particle velocity (PPV), the functional relationship is established to predict safety criteria for deep blasting excavation.

Deep-hole bench blasting is the primary method for aggregate extraction in mines. However, factors such as complex geological conditions and suboptimal blasting parameters often result in uneven rock fragmentation and high fines content. This not only increases the cost and energy consumption of subsequent aggregate processing but also has adverse environmental implications. In this study, based on the Changjiu Shenshan limestone aggregate mining project in China, large-scale blasting experiments were conducted to investigate the influence of rock properties and blasting parameters on the size distribution of post-blast fragments and fines content. The results of the blasting experiments indicate that by controlling the size of the crushing zone and adjusting explosive performance, it is possible to significantly reduce fines content while improving mining efficiency. Recommended values for drilling and blasting parameters have been proposed based on geological conditions to more effectively control the generation of fines. The results highlight the importance of optimizing blasting parameters and charge structure for large-scale mining operations to achieve uniform rock fragmentation and low fines content. By adopting explosive performance adjustment methods based on reasonable control of the crushing zone, improving explosive performance can improve the economic benefits of mining operations, reduce energy consumption, and contribute to environmental protection.

To research the mechanical damage and failure mechanism of axially carbonated mortar under impact loading, dynamic uniaxial compression tests are used on specimens of different carbonization ages using a Hopkinson compression bar (SHPB) test apparatus. The effects of impact pressure and carbonation age on the longitudinal wave velocity, peak stress, energy dissipation, fractal dimension and fracture morphology of mortar materials are obtained. The failure mechanism of axially carbonized mortar is revealed. The results show that at the same carbonization age, the peak stress increases with gradually increasing impact pressure, and the strain rate effect is obvious. Under 0.65 MPa impact load, the peak stress of the values of the compressive strength of carbonated specimens for ages 3 d∼28 d are 4.97∼34.79% higher than those of the uncarbonated specimens. Carbonization increases the longitudinal wave velocity and peak stress. With increasing impact air pressure and carbonation age. the crushing energy density of mortar material increases, and although the increase significantly decreases. Carbonization reduces the fractal dimension of the specimen and enhances the deformation resistance of the specimen under an external load. With increasing ''carbonization reinforcement layer'' effect and decreasing impact air pressure, the failure mode of the specimen gradually changes from crushing failure to splitting tensile failure, and the degree of fragmentation decreases.

The strategic mineral W-Sn deposits in China are mainly concentrated in South China, and many rare metal mineralizations, such as Li, Rb, Be, Nb, Ta, etc., are often coproduced with them. However, the genetic relationship between them is unclear. Based on the analysis of research data related to granite-related rare metals and W-Sn deposits in South China, we believe that the two types of mineralization have a close spatio-temporal relationship at multiple scales, such as metallogenic belts, ore fields, deposits, and minerals. In addition, the ore-forming material source, mineralization process, and ore-controlling structures are similar, indicating that they may have derived from a same granitic mass and the mineralization usually have close genetic relationship with the high evolved granite. Therefore, the exploration and research data of W-Sn deposits in South China can be used to explore and study rare metal deposits.

Smooth surface blasting control technology is aimed at blasting the rock body until it is left with a smooth surface and to protect it from damage; the current air spaced axial uncoupled charge and air spaced radial uncoupled continuous charge are effective charging structures for smooth surface blasting. Reserved air spacing can effectively reduce the blast wave and the peak pressure of the explosive gas, improving the quasi-static pressure of the explosive gas under the action of rock surface blasting with fracture seam quality. In order to ensure the effect of surface blasting, small-diameter light surface holes are more often used; with the development of drilling machinery, the use of large-diameter light blast holes with an oversized uncoupled coefficient of loading structure effectively improves the efficiency of the construction and at the same time achieves better blasting results. However, according to the bursting assumption of obtaining the theory of light surface blasting in the application of large uncoupling coefficient loading, light surface blasting has certain limitations. In this regard, the bursting theory explores the air spacing uncoupling charge in line with the multi-faceted exponential expansion of the critical uncoupling coefficient and is in accordance with the following: the requirements of light surface blasting and the field loading structure; the derivation of the quasi-static pressure on the wall of the gunhole under the action of large uncoupling, uncoupling coefficient, and the parameters of the spacing between the gunholes; the establishment of the axial uncoupling coefficient and the radial uncoupling coefficient-equivalent relationship between the uncoupling coefficient and the theoretical relationship between the selection of the spacing between the holes; the uncoupling coefficient and the selection of the theoretical relationship between the spacing between the holes. This study reveals the mechanism by which different parameters of surface blasting can achieve good results in engineering practices. A slope in Guizhou is an example of sample calculations and the application of two different charging structures applied to field loading, which have achieved good surface blasting results.

To study the particle size distribution and energy variation law of hard coal under a load, an impact compression test of hard coal specimens under different impact loading conditions was carried out using a Φ50 mm diameter Separate Hopkinson Press Bar (SHPB) test system. We implemented the theory of dynamic impact energy of rock to establish the calculation expression of hard coal impact crushing energy dissipation, and we established the Weibull distribution model of a crushing body to analyze the impact velocity in relation to the particle size distribution of hard coal crushing and crushing energy consumption. The results demonstrate that due to the different original states of the specimens, the damage to the specimens under static action is in the mode of conjugate plane shear damage, single bevel shear damage, and tensile damage. The damage process of the specimen under impact load loading is divided into three stages: elastic deformation, elastic–plastic deformation, and plastic softening, while the increase in the strain rate caused the peak stress of the specimen to increase. The Weibull distribution can characterize the impact crushing size distribution of hard coal specimens very well. The parameter of coal rock crushing degree is a power function that is influenced by the impact velocity; the greater the impact velocity, the higher the coal rock crushing degree, but the characteristic index of coal rock crushing fluctuates with the increase in impact velocity. As the impact velocity increases, the incident energy and reflected energy increase linearly, while the transmitted energy increases first and then decreases. The dissipation energy of coal rock crushing also increases linearly with the impact velocity. There is no obvious regular change between the energy dissipation rate of coal rock and impact velocity during impact damage, and the dissipated energy of macroscopic crushing only accounts for 10~20% of the incident energy; most of the energy is used for damping loss and damage loss.

The propagation law of blast stress waves in jointed rock masses is closely related to the characteristics of the joint filling medium. The water content and thickness of the filling medium affect the propagation characteristics of the blast stress wave in the joint surface. Based on similarity theory, mortar-red clay-mortar composite specimens with different moisture contents (36%, 39%, 42%, and 45%) and medium thicknesses (3 mm, 6 mm, and 9 mm) were prepared with red clay as the filling medium. The dynamic uniaxial compression test of the specimen under different strain rates was carried out by using a variable cross-section split Hopkinson compression bar with a diameter of 50 mm. The effects of strain rate, moisture content, and medium thickness on the stress wave propagation characteristics, dynamic stress-strain curve, peak stress, crushing energy consumption density, and crushing characteristics of mortar-red clay-mortar composite specimens were analyzed. The results show that the blocking effect of joints on stress waves increases significantly with increasing filling medium thickness and water content. With increasing strain rate, the peak stress and energy of the composite specimen increase and there is an obvious strain rate effect. With the increase in the thickness and moisture content of the filling medium, the peak stress, dynamic elastic modulus, energy consumption density per unit volume, and crushing degree of the specimen gradually decrease and the nonlinear deformation is more obvious. There is a good linear relationship between the peak stress and the thickness and moisture content of the filling medium. The existence of joints greatly weakens the damage effect of stress waves on the specimens behind the joints, and with the increase in the thickness and water content of the filling medium, the degree of damage to the specimens behind the joint surface decreases under the same impact pressure and the weakening effect becomes increasingly significant.

Concrete is widely used in bridge foundation, water supply, and drainage engineering. On the one hand, the saturated concrete is always in the saturated state. In the cold winter, northeast China and the alpine region suffer from freezing disaster. On the other hand, it has to continue to bear the dynamic load action of vehicles and running water, which makes the stress state of saturated concrete more complicated under the coupling action of low temperature and dynamic load. In order to study the mechanical properties and fracture characteristics of saturated concrete under the coupling effect of low temperature and dynamic load, the impact compression tests of concrete under normal temperature 20°C, -5°C, -10°C, and -15°C were carried out with a diameter of 74 mm split Hopkinson pressure bar (SHPB). The stress-strain characteristics, energy dissipation, and failure modes of specimens under different low temperatures were studied. From a detailed point of view, the failure mechanism of low-temperature water-saturated concrete is expounded. The results show that under the same dynamic load, the dynamic stress-strain curve of saturated concrete changes obviously with the change of low temperature. The dynamic compressive strength of the natural specimen at room temperature is high while that of the water-saturated specimen is low, and the dynamic compressive strength is opposite at low temperature. At the same temperature, the energy time-history curves of concrete in the saturated state are different from those in the natural state, mainly in the plastic section. The energy time-history curves of saturated concrete are different at different temperatures, and the energy dissipation rate of saturated concrete increases linearly with the decrease of temperature. Under the experimental conditions, the dynamic strength of saturated concrete increases linearly with the decrease of temperature, and the peak strain of saturated concrete decreases linearly with the increase of temperature. With the decrease of temperature, the fragmentation of saturated concrete under the impact of the same air pressure gradually increases, and the integrity of the specimen gradually improves. Low temperature can improve the impact resistance of saturated concrete, which is consistent with the failure law of natural state concrete. The water-saturated low-temperature state of the concrete void is filled with ice crystal particles; for low-temperature water-saturated concrete in the impact of the dynamic load, the microstructure is affected by the ice crystal structure which is not easy to change; the specimen along the axial force direction microdefect development produces a crack, the crack along the parallel to the pressure direction of cracking, through the two ends of the specimen, and finally produces axial splitting tensile damage. The research results have important theoretical significance for the safety design of low temperature saturated concrete structures.

In order to study the impact of the blasting vibration of subway tunnels on adjacent buildings, taking the tunnel mining method construction of the section between Zhifang Street Station and Metro Town Station of Wuhan Metro Line 27 as the engineering background, the blasting scheme is optimized by reducing the maximum single section charge, multi-section and densifying the surrounding holes. The HHT method and wavelet analysis are used to evaluate the advantages and disadvantages of the optimization scheme from the perspective of energy. The results show that the peak velocity of the blasting vibration is significantly reduced and the frequency is significantly increased after the blasting scheme is optimized. After the blasting scheme is optimized, when the working face is directly below the external wall of the building, the peak vibration velocity is the largest; from the back of the working face to the front of the working face, the peak velocity of the surface particle vibration first increases and then decreases. The frequency band of the optimized blasting vibration signal energy distribution is wider and the energy is more dispersed. This study can provide some practical experience for the design and construction of similar projects.

Considering the low efficiency of cutting blasting in hard rock mine tunnels, a novel solution of increasing the charge diameter of the cutting holes was put forward. To investigate the influence of the charge diameter on the cutting blasting results, three different working conditions of Φ 32 mm, Φ 42 mm, and Φ 50 mm blasting holes combined with Φ 27 mm, Φ 35 mm, and Φ 45 mm cartridges, respectively, were taken as the investigation objects. At first, the theoretical destruction ranges of single cutting holes under the three different charge diameters were computed. The computed results showed that the destruction range of the cutting holes could be expanded by increasing the charge diameter, which would be beneficial to the destruction of the rock far away from the cutting holes in the cutting cavity. Subsequently, numerical simulations of cutting blasting under the three different charge diameters were performed to display the dynamic propagation process of the blasting stress wave. Importantly, the stress field intensity in the cutting cavity was enhanced significantly with the charge diameter. The stronger stress field intensities generated by the larger diameter charges were more conducive to breaking the rock in the cutting cavity into small fragments that were easy to be discarded. Ultimately, a hard rock vertical slope was used instead of the driving face to carry out the cutting blasting experiments, and the hole utilizations of the cutting blasting were 70.4%, 82.0%, and 94.0%, respectively, under the three different charge diameters, from small to large. The experimental results forcefully substantiated that a higher cutting blasting efficiency could be achieved by increasing the charge diameter of cutting holes in hard rock mine tunnels.

Abstract In this study, using the Climate Model Intercomparison Project 5 (CMIP5) simulations and by empirical orthogonal function (EOF) analysis, the first mode of variability in interannual surface air temperature (SAT) in Antarctica (EOF1) was examined for the period between 1979–2004 and 2051–2099 during the austral summer. The ensemble mean of EOF1 of the CMIP5 models shows a positive SAT anomaly over the northern Antarctic Peninsula (AP) and a negative SAT anomaly over Eastern Antarctica (EA) in both periods. A poleward expansion of the AP positive anomaly and an increase in the negative anomaly over interior EA are expected in 2051–2099, resulting in a larger difference of interannual SAT between interior EA and the AP in 2051–2099 than in 1979–2004. The increasing difference in the interannual SAT is consistent with a larger magnitude of the SAM‐related circulation anomalies in the future.

The Qin-Hang Metallogenic Belt (QHMB), an important metallogenic belt in South China, hosts Cu and W–Sn polymetallic deposits. The Tongshanling ore field in the QHMB is characterized by the coexistence of Cu- and W-bearing polymetallic deposits, which are related to granodiorite and granite porphyry. This study examined whole-rock geochemistry, geochronology, and Sr–Nd–Hf isotopes to determine the genetic relationship between diverse ore-related granitoids (i.e., granodiorite and granite porphyry) and Cu–W metallogeny in the Tongshanling ore field. Zircon LA-ICP-MS U–Pb dating shows that the granodiorite and granite porphyry in the Tongshanling ore field were emplaced at 163.7 ± 0.4 Ma to 154.7 ± 0.6 Ma and 161.1 ± 0.3 Ma, respectively. Geochemically, the granodiorites are classified as oxidized I-type, while the highly evolved granite porphyry is reduced A-type. The Lu–Hf isotopic composition of the granodiorites is characterized by εHf(t) values ranging from –10.49 to –4.99 (average = –7.17), with corresponding TDMC ages ranging from 1524 to 1877 Ma (average = 1682 Ma). In contrast, the granite porphyry has higher εHf(t) values (–3.60 to –1.58, average = –2.78) and younger TDMC (1310–1438 Ma, average = 1387 Ma). The εNd(t) values of granodiorite are −8.06 to −7.37 and the two-stage model ages (TDM2) are 1543–1598 Ma, while the granite porphyry has higher εNd(t) values (−3.0 to −3.4) and younger TDM2 ages (1195–1223 Ma). The results show that the granodiorite and granite porphyry were formed from partial melting of different Mesoproterozoic basement rocks under varying degrees of crust–mantle interaction. Granite porphyry underwent well-recorded fractional crystallization. Compared to the Cu-forming granodiorite, the W-forming granite porphyry has a higher differentiation index, higher crystallization temperatures of zircon (average = 708 °C versus 631 °C), and lower oxygen fugacity (median ΔFMQ = –2.21 versus –1.77).

To acquire a satisfying cutting effect during medium-length hole blasting driving of rock tunnels, an improved wedge cutting blasting method with supplementary blasting of the center holes was proposed. Initially, the cavity forming mechanism of the improved cutting method was analyzed theoretically. The results suggested that cutting hole blasting could realize the ejection of rock within the range from free face to critical cutting depth, and hence reduce the restraining force of the center hole blasting, and the supplementary blasting of the center holes could further accomplish the expulsion of the residuary rock. Subsequently, simulation of the improved cutting method was implemented to exhibit the stress wave evolution and reveal the stress field distribution. The simulation results indicated that cutting hole blasting could cause the preliminary failure of the residuary rock, and center hole blasting could strengthen the stress field intensity in 1.8–2.5 m in order to aggravate the destruction of the residuary rock. Hence, the residuary rock could be broken into small fragments that were easy to expel out. Finally, a field application experiment was conducted in a coal mine rock tunnel. Using the improved wedge cutting method instead of the conventional wedge cutting method, the full-face blasting driving efficiency was obviously enhanced and the overall blasting driving expense was significantly reduced, which forcefully confirmed the engineering usefulness of the improved wedge cutting method in the medium-length hole blasting driving of rock tunnels.

It is important to guarantee the safety of adjacent underground structures during the foundation pit blasting excavation of modern city construction. The blasting excavation construction of a large, deep foundation pit near an existing metro station of Guangzhou Metro Line 3 is used as the example in this study. Based on blasting vibration field test results, the influence of blasting dynamic load on the lining of an adjacent metro tunnel is numerically analyzed in simulation using Fast Lagrangian Analysis of Continua 3D (FLAC3D), and the relationships between the blasting vibration velocity and stress and the displacement of the metro tunnel lining are obtained. The results show that the stress of lining structure is within the allowable range under the experimental blasting conditions, the lining displacement increases linearly with the applied dynamic vibration velocity, and the vertical displacement of the lining is more obviously affected than the horizontal displacement by the dynamic load. This study can be used as a basis for the control of blasting vibration in a complex urban environment. Its practical application shows that the proposed blasting plan and parameters are reasonable and effective.

To overcome the problems of poor cutting effects in hard rock roadways, a cut blasting technique with large diameter charges was developed; that is, the cut holes employ 50 mm diameter blast holes and 45 mm diameter explosive sticks, while the other holes adopt 42 mm diameter blast holes and 35 mm diameter explosive sticks. First, the effect of charge diameter on damage range and cut cavity formation was analyzed. Next, simulation of wedge cut for different charge diameters was conducted to reveal the stress wave developments and compare the stress field intensities. Finally, field tests were conducted to verify the viability of this technique. The results indicate that large diameter charges can increase the damage range around cut holes to improve the fragmentation degree of the rock mass in the cut cavity and significantly enhance the cavity formation power to better expel the rock mass fragments. The stress wave evolution of wedge cut was visualized using numerical simulations, which confirmed that the use of large diameter charges in cut holes increases the stress field intensity in the cut cavity and hence increases the damage degree of the rock mass. In this study, the use of a large diameter charge for cut blasting increased the average footage by 0.30 m, and the average utilization rate of blast holes increased by 12.5%. Therefore, the cutting effects in hard rock roadways can be improved by using large diameter charges, which increase the blasting footage and the utilization rate of blast holes.

Aiming at the dynamic mechanical properties of weakly cemented fine sandstone in the rich water-bearing strata in western China under dynamic loading, a 50 mm rod diameter separation Hopkinson pressure bar (SHPB) test was used to study the Paleogene fine sandstone in a coal mine in Ningxia. The system carried out the impact compression tests of −15°C, −20°C, and −30°C and the average strain rate of 28 s−1–83 s−1 and obtained the dynamic compressive strength of the frozen fine sandstone specimens under different test conditions. The strain curve and the fracture morphology were analyzed for the relationship between dynamic peak stress, peak strain, dynamic strength growth coefficient (DIF), and fracture morphology and strain rate. The results show that the peak stress of frozen fine sandstone increases from the decrease of freezing temperature under the same average strain rate. The peak stress of the specimen increases from the increase in the average strain rate of the same freezing temperature. The failure modes of specimen are mainly divided into axial splitting tensile failure and compression crushing failure. To the splitting tensile failure and the compression crushing failure, the main factors determining the two failure modes are the strain rate, while the temperature affects the severity of the impact damage. In the load strain rate and temperature range, the DIF of the frozen fine sandstone is linearly correlated with the strain rate, and the lower the temperature, the slower the growth rate of the DIF.

Rocks in deep coal mines are usually in varying degrees of damage state before they are destabilized by impact loads such as rock bursts. For the problem of the mechanical properties and energy evolution of damaged rocks under impact loads, the authors use static loads with different cyclic load thresholds to act on sandstone specimens to make them in distinct degrees of damage. Then, the rock mechanics system (MTS-816) and the Split Hopkinson pressure bar (SHPB) are employed to perform uniaxial compression and impact dynamics tests on sandstones with different degrees of damage. The results show that, from the perspective of mechanical properties, the uniaxial compressive strength and dynamic compressive strength of the damaged sandstone gradually decrease with the increase of the upper limit of the cycle threshold and both obey the growth law of the quadratic function, and the dynamic strength increase factor (DIF) also decreases with the increase of the cyclic load threshold. In terms of energy, with the increment of the cyclic load threshold, the number of cracks in the damaged sandstone is large and the scale is enormous. Due to the effect of cracks, when the incident energy is a fixed value, the transmission energy decreases with the increase of the damage degree and the change law of the reflection energy is the opposite. The systematic study of the dynamic mechanical properties and energy evolution law of the damaged sandstone provides some reference for the prevention and mechanism research of rock bursts.

Deep mine rocks are often subjected to rock burst induced by dynamic load. The existence of initial holes will reduce the mechanical properties of rocks and affect the stability and safety of the tunnel excavating. In order to study the effect of the ratios of inner and outer diameter on disc specimen dynamic mechanical properties and failure modes, we use cylindrical sandstone specimens of Φ50 × 25 mm to process center holes of different diameters, and a series of dynamic splitting test were carried out with a system of split Hopkinson pressure bar (SHPB) with the diameter of Φ50 mm when the pressure is 0.15 MPa, 0.3 MPa, and 0.5 MPa. The results show that (1) the dynamic tensile stress-time-history curve exhibited double peak phenomena, and the second peak value is less than the first peak value, (2) the dynamic tensile stress peaks decrease nonlinearly with the increasing of the ratios of inner and outer diameter, and the dependence is more obvious when the pressure is higher, and (3) there is a tensile crack running along the loading direction in the failure modes of the five samples with the ratio of inner to outer diameter under three kinds of impact pressure. Under the same impact pressure, when the ratio of inner diameter to outer diameter is greater than the critical ratio of inner diameter to outer diameter, there is an obvious empty hole effect; that is, the sample develops secondary tensile cracks that develop from the upper and lower ends of the pore disc to the center of the inner hole. With the increase of the ratio of inner diameter to outer diameter, the width of the penetration crack increases. With the increase of impact pressure, the critical ratio of inner diameter to outer diameter decreases gradually. The research results have certain significance for understanding the mechanical properties of porous rocks.

Deep rock bears dynamic loads such as machinery, blasting and disturbance in the mining process. The dynamic fracture mechanism of deep rock is a necessary prerequisite for engineering design and analysis. To study the dynamic fracture mechanism of rock under high in situ stress, deep mudstone and sandstone were selected as research objects. The dynamic mechanical properties and energy dissipation of mudstone sandstone were assessed by using a 50 mm diameter separated Hopkinson test device. According to the similarity criterion, the similarity of strength was assumed as primary factor to prepare similar model materials. Then, dynamic mechanical tests of these similar materials were carried out under dynamic compression splitting and active confining pressure. The results show that materials similar to mudstone and sandstone mainly show axial fracture tensile failure and crushing failure. Both the average strain rate dynamic strength and peak strain of these similar materials increase with increasing impact pressure, and the dynamic strength of similar materials increases exponentially with increasing strain rate. This result is consistent with the regularity of original rock. The dynamic splitting of mudstone-like materials is dominated by the failure of intermediate cracks, and sandstone-like materials also show secondary cracks in addition to intermediate splitting cracks. The dynamic peak strength of mudstone-like materials increases with increasing active confining pressure, and the dynamic peak strength of sandstone-like materials increases nearly twofold under the action of active confining pressure.

The protective effects of the oligomeric proanthocyanidins from lotus seedpod (LSPC) and probiotics (Lactobacillus rhamnosus LGG and Bifidobacterium Bb-12) were evaluated in Enterotoxigenic Escherichia coli (ETEC) infected diarrhea mice. In normal mice, LSPC, LGG and Bb-12 showed no intestinal injury effect. In the prophylactic groups fed with LSPC and probiotics for 10 days, diarrhea signs were significantly reduced. The marker of intestine barrier, inflammatory response and oxidant stress were significantly improved. In addition, LSPC and probiotics regulated the expressions of tight junction proteins and inflammatory mediators via MAPKs pathway. Furthermore, the combination of LSPC and probiotics (LGG and Bb-12) could significantly improve the effect of treating diarrhea alone. These findings suggested that LSPC could act as prebiotics combining with probiotics to improve the composition of intestinal microbes and further reduce ETEC-induced diarrhea consequences. It might provide a novel potential natural therapeutic agent to resist ETEC infected diarrhea disease.

In view of the devastating outcomes of fires and explosions, it is imperative to research the dynamic responses of concrete structures at high temperatures. For this purpose, the effects of the strain rate and high temperatures on the dynamic tension behavior and energy characteristics of high-strength concrete were investigated in this paper. Dynamic tests were conducted on high-strength concrete after exposure to the temperatures of 200, 400, and 600 °C by utilizing a 74 mm diameter split Hopkinson pressure bar (SHPB) apparatus. We found that the quasi-static and dynamic tensile strength of high-strength concrete gradually decreased and that the damage degree rose sharply with the rise of temperature. The dynamic tensile strength and specific energy absorption of high-strength concrete had a significant strain rate effect. The crack propagation law gradually changed from directly passing through the coarse aggregate to extending along the bonding surface between the coarse aggregate and the mortar matrix with the elevation of temperature. When designing the material ratio, materials with high-temperature resistance and high tensile strength should be added to strengthen the bond between the mortar and the aggregate and to change the failure mode of the structure to resist the softening effect of temperature.

BackgroundVoltage-gated Ca(v)1.2 calcium channels play a crucial role in Ca(2+) signaling. The pore-forming alpha(1C) subunit is regulated by accessory Ca(v)beta subunits, cytoplasmic proteins of various size encoded by four different genes (Ca(v)beta(1)-beta(4)) and expressed in a tissue-specific manner.Methods and resultsHere we investigated the effect of three major Ca(v)beta types, beta(1b), beta(2d) and beta(3), on the structure of Ca(v)1.2 in the plasma membrane of live cells. Total internal reflection fluorescence microscopy showed that the tendency of Ca(v)1.2 to form clusters depends on the type of the Ca(v)beta subunit present. The highest density of Ca(v)1.2 clusters in the plasma membrane and the smallest cluster size were observed with neuronal/cardiac beta(1b) present. Ca(v)1.2 channels containing beta(3), the predominant Ca(v)beta subunit of vascular smooth muscle cells, were organized in a significantly smaller number of larger clusters. The inter- and intramolecular distances between alpha(1C) and Ca(v)beta in the plasma membrane of live cells were measured by three-color FRET microscopy. The results confirm that the proximity of Ca(v)1.2 channels in the plasma membrane depends on the Ca(v)beta type. The presence of different Ca(v)beta subunits does not result in significant differences in the intramolecular distance between the termini of alpha(1C), but significantly affects the distance between the termini of neighbor alpha(1C) subunits, which varies from 67 A with beta(1b) to 79 A with beta(3).ConclusionsThus, our results show that the structural organization of Ca(v)1.2 channels in the plasma membrane depends on the type of Ca(v)beta subunits present.