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To explore the influence of the working face excavation rate on the rock deformation mechanism and seepage characteristics, deformation and seepage tests of sandstone under different loading and unloading stress paths, such as constant axial pressure unloading confining pressure and loading axial pressure unloading confining pressure, were carried out. Particle Flow Code in 3 Dimensions (PFC3D) and Python were used to realize fluid-solid coupling, and numerical simulation calculations were performed along the test path to analyze the influence of the unloading rate on the fine-scale deformation mechanism and permeability characteristics of sandstone, and the relationship between crack type and permeability was obtained. A sandstone fracture mechanics model is established to analyze the stress concentration degree at the end of the branch crack of the test path. The results show that the rate of confining pressure unloading is inversely proportional to the strain. Additionally, permeability correlates with the principal stress difference in an exponential manner. Interestingly, the sensitivity of permeability to stress shows an inverse trend with the unloading rate of confining pressure. Furthermore, there exists a linear relationship between permeability and the number of cracks. During the unloading process, tensile cracks predominate, and the propagation of shear cracks lags behind that of tensile cracks. The proportion of tensile cracks decreases with the increase of the unloading rate when the axial pressure is unchanged but increases when axial pressure is added, resulting in axial compression deformation and expansion deformation along the unloading direction. These research outcomes offer theoretical insights for the prudent selection of mining rates, and they hold significant implications for mitigating water inrush disasters in deep mining operations. [ABSTRACT FROM AUTHOR]

Coral reef limestone is a biogenic limestone with a hyperdeveloped pore structure. The complex structural features of coral reef limestone can directly affect its mechanical and seepage characteristics, which are not yet well-understood. The pore structure information of two coral reef limestone specimens, including one with coarse pores (CR-C) and one with fine pores (CR-F), was obtained by combining CT scanning technology, 3D visualization reconstruction, and pore identification algorithms. The pore structure characteristics were interpreted considering the porosity's spatial variability, fractal dimension, and tensorial anisotropy. A seepage tensor derived from the geometry component of Hagen-Poiseuille's law was proposed to assess the seepage anisotropy, which was then verified through seepage simulations along different directions. It was found that the spatial distribution of the porosity of CR-C was less uniform than that of CR-F. Both testing specimens had distinct pore structures with obvious directionality that varied with sampling size. Seepage simulations on a representative elementary volume (REV) of CR-C revealed that the permeability along the identified dominant seepage direction was indeed the largest. Some empirical correlations between the permeability and the deviation angle from the dominant seepage direction were established. This study highlights the importance of considering structural anisotropy when interpreting the properties of coral reef limestone. [ABSTRACT FROM AUTHOR]

In this study, the bond-slip behavior between textile reinforced concrete (TRC)-confined concrete and rebars both at ambient temperature and after ISO 834 standard fire was investigated experimentally through pull-out tests. The failure modes, ultimate load, average ultimate bonding stress and energy consumption were obtained and discussed. Effects of rebar diameters (12 mm, 14 mm and 16 mm), bonding lengths (2.5d, 5d and 7.5d) and high-temperature exposure durations (30 min and 60 min) on the bonding behavior between TRC-confined concrete and rebars were examined emphatically. It was observed that the damage modes of specimens changed from pull-out failure at ambient temperature into splitting failure for both TRC-confined specimens and companion unconfined specimens exposed to high temperatures. The results obtained demonstrated that both the ultimate load and the average ultimate bonding stress can be significantly improved by the utilization of TRC jackets after 30 min exposure, and the increment of the average ultimate bonding stress can reach up to 90% as compared to those unconfined specimens. However, the enhancement of TRC jackets became unobvious after 60 min. Finally, based on test results and Prigogine's dissipative structure theory, the energy analysis of bond-slip curves was evaluated to verify the enhancement of TRC jackets quantitatively. [ABSTRACT FROM AUTHOR]

Due to the complexity of the talus-like rock mass with different values of volumetric block proportion (VPB), it is thus crucial to explore the VBP effect on the excavation-induced ground responses. We conduct a series of 2D DEM (discrete element method) simulations on a common circular tunnel excavation in the talus-like rock mass with different VBPs (0%, 15%, 50%, 85% and 100%). For each VBP, two support scenarios, i.e., unsupported and supported by a rigid lining, are considered. The micro characteristics of the excavation-induced ground responses, including the contact force, force chain, coordination number and shear-slip contact, and the stress distribution and ground settlement are elaborated in detail. Accordingly, three types of talus-like rock masses are identified as soil-, hybrid- and rock-types, corresponding to VBP = 0–15%, 50%, and 85–100%, respectively. It is found that the lining support is essential for maintaining the ground stability of a tunnel excavation in the soil- and hybrid-type talus-like rock masses while the backbones formed by rock blocks in the rock-type talus-like rock mass can provide a certain support for the surrounding ground. Our findings have important implications for optimizing the construction scheme of tunnel excavation in different types of talus-like rock masses. [ABSTRACT FROM AUTHOR]

Due to the sensitivity of sandy soil's mechanical behavior to the particle shape, it is thus of importance for interpreting the effect of particle shape on the ground response induced by tunnel excavation in sandy formations. We conducted a series of 2D DEM (discrete element method) simulations on a common circular tunnel excavation in sandy soil with variable-shaped particles, which are characterized as two descriptors, i.e., aspect ratio (AR) and convexity (C). The macroscopic responses and the microscopic characteristics of the sandy ground are elaborated in detail. The simulation results show obvious asymmetrical features of the excavated ground, which results from the ground heterogeneity caused by the irregular particle shape. In addition, we investigate the roles of AR and C on the ground response and find that reducing AR or increasing C will enlarge the ground settlement, i.e., the sandy ground deformation is more sensitive to the particles with more irregular shapes. However, elongated particles are beneficial for the generation of soil arching with stronger bearing capacity and thus reduce the soil pressure on the tunnel lining. Our findings have important implications for the safety assessment of the tunnel excavation, as well as other underground structure construction in sandy formations. [ABSTRACT FROM AUTHOR]

The talus-like rock mass is a special kind of geomaterial widely distributed in southwestern China, which has induced serious engineering disasters for tunneling engineering. However, the mechanical behavior of the talus-like rock mass remains unclear as the previous studies mainly focused on similar geomaterials such as the soil–rock mixtures. In this paper, we have carried out both experimental and discrete element method (DEM)-based numerical analyses to investigate the shearing characteristics of the talus-like rock mass collected from a real project site. Large-scale direct shear tests reveal that the strength parameters increase with the block content, which is different from the traditional soil–rock mixture. A dependence has been discovered in that the specimen dilation becomes more obvious under lower normal stress and larger block content. It is also observed that higher normal stress is beneficial for crushing blocks. The force chains obtained in the DEM simulations show that distinct internal structures are generated in the rock samples with different block contents. The distribution of coordination number establishes the dependence of fabric stability on block content during shearing. Bond-break evolution reveals the tendencies of crushed particles were consistent with those of experimental tests. The findings provide a more in-depth understanding about the mechanical behavior of the talus-like rock mass, which helps to uncover the cause of the collapse of the real tunnel project. [ABSTRACT FROM AUTHOR]

Tayi tunnel is one of the component tunnels in the Jian-Ge-Yuan Highway Project located in Yunnan Province, southeast of China. It mainly passes through talus-like formations comprised of rock blocks of diverse sizes and weak interlayers with clayey soils with different fractions. Such a special composition leads to the loose and fractured structure of talus-like formations, which is highly sensitive to the excavation perturbation. Therefore, Tayi tunnel has become the controlled pot of the whole highway project as the construction speed has to be slowed down to reduce the deformation of surrounding talus-like rock mass. To better understand the tunnel-induced ground response and the interaction between the surrounding rock mass and tunnel lining, a comprehensive in situ monitoring program was set up. The in situ monitoring contents included the surrounding rock pressure on the primary lining, the primary lining deformation, and the stress of steel arches. Based on the monitoring data, the temporal and the long-term spatial characteristics of mechanical behavior of surrounding rock mass and lining structure due to the excavation process were analyzed and discussed. It is found that the excavation of lower benches released the surrounding rock pressure around upper benches, resulting in the decrease of the surrounding rock pressure on the primary lining and the stress of steel arches. In addition, the monitoring data revealed that the primary lining sustained bias pressure from the surrounding rock mass, which thereby caused unsymmetrical deformation of the primary lining, in accordance with the monitored displacement data. A dynamically adaptive support system was implemented to strengthen the bearing capacity of the lining system especially in the region of an extremely weak rock mass. After such treatment, the deformation of the primary lining has been well controlled and the construction speed has been considerably enhanced. [ABSTRACT FROM AUTHOR]

The bifunctional oxygen catalysts are crucial to the commercialization of metal-air batteries. In this work, two-dimensional polymerized cobalt phthalocyanine (PPcCo) is combined with three-dimensional graphene (3D-G) through π-π interaction to obtain the PPcCo/3D-G bifunctional oxygen catalysts. The delocalized π-bonds of PPcCo provide greater electron delocalization energy. The π-π interaction between the PPcCo and 3D-G not only solidly anchors PPcCo and fully exposes the Co-N 4 sites but also enhances the performance of the catalyst. The PPcCo/3D-G exhibits excellent electron conduction, a large specific surface area, and a rich pore structure for enhanced mass transfer. In terms of electrochemical performance, the oxygen reduction reaction (ORR) halfwave potential (E 1/2) of PPcCo/3D-G catalytic is 0.860 V vs RHE and the electron transfer number of PPcCo/3D-G is 3.95 (@0.740 V vs RHE). The small overvoltage (ΔE = E j = 10 - E 1/2) of PPcCo/3D-G is 0.780 V. Furthermore, the Zinc-air battery (ZAB) with PPcCo/3D-G as the cathode catalyst has high power density (347 mW cm−2), specific capacity (776 mAh g−1), smaller charge/discharge polarization, and significant long-term stability. The flexible all-solid-state ZAB (FZAB) with PPcCo/3D-G as the cathode catalyst also exhibits excellent performance. These results suggest that the PPcCo/3D-G is available as an efficient cathode bifunctional catalyst for ZAB and FZAB. Poly (cobalt phthalocyanine) (PPcCo) was combined with three-dimensional graphene (3D-G) through π-π interaction to obtain PPcCo/3D-G with mesoporous structure, which exhibited excellent half-wave potential (0.860 V vs. RHE) and small overvoltage value (0.780 V) indicating that PPcCo/3D-G is an excellent bifunctional metal-air battery electrocatalyst. [Display omitted] • The PPcCo has a large conjugated structure and excellent thermal stability. • The π-π interaction between PPcCo and 3D-G enhances catalytic performance. • PPcCo/3D-G has a clearly defined catalytically active site of Co-N 4 structure. • The ZABs with PPcCo/3D-G as cathode exhibit good charge/discharge performance. [ABSTRACT FROM AUTHOR]

The priority pollutant antimony (Sb) exists primarily as Sb(V) and Sb(III) in natural waters, and Sb(III) is generally with greater mobility and toxicity than Sb(V). The bio-reduction of Sb(V) would not become a meaningful Sb-removal process unless the accumulation of produced dissolved Sb(III) could be controlled. Here, we examined the dissimilatory antimonate bio-reduction with or without the coexistence of sulfate using Sb-acclimated biomass. Results demonstrated that 0.8 mM Sb(V) was almost completely bio-reduced within 20 h along with 48.6% Sb(III) recovery. Kinetic parameters q max and K s calculated were 0.54 mg-Sb mg-DW −1 h −1 and 41.96 mg L −1 , respectively. When the concentrations of coexisting sulfate were 0.8 mM, 1.6 mM, and 4 mM, the reduction of 0.8 mM Sb(V) was accomplished within 17, 9, and 5 h, respectively, along with no final Sb(III) recovery. Also, the bio-reduction of sulfate occurred synchronously. The precipitated Sb 2 O 3 and Sb 2 S 3 were characterized by scanning electron microscopy coupled with energy dispersive spectrometer, X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with bacterial compositions of the seed sludge obtained from anaerobic digestion tank in a wastewater treatment plant, new genera of Pseudomonas and Geobacter emerged with large proportions in both Sb-fed and Sb-sulfate-fed sludge, and a small portion of sulfate reduction bacteria emerged only in Sb-sulfate-fed culture. [ABSTRACT FROM AUTHOR]

The sensitivity of perchlorate reduction and microbial composition to varied nitrate and acetate loadings was studied in a biologically activated carbon reactor with perchlorate loading and empty bed contact time fixed at 5 mg/L and 226 min, respectively. In stage 1, the sole electron acceptor ClO 4 − realized complete removal with ≥21.95 mg C/L of acetate supply. As nitrate loading gradually increased to 5 mg/L (stage 2), perchlorate reduction was slightly promoted and both ClO 4 − and NO 3 − were completely removed at an acetate loading of 29.7 mg C/L. When nitrate loading continued increasing to 10–60 mg/L (stage 3), perchlorate reduction converted to be inhibited, along with nondetectable NO 3 − and approximately exhausted DOC in effluent. When acetate loading increased to 43.9 mg C/L in stage 4, both ClO 4 − and NO 3 − were again removed, though lags still existed in perchlorate reduction. β-Proteobacteria accounted for about 60%, 55%, 58%, 61% and 12% in samples from the base and top of the filter in stage 1 and those from the base, middle and top in stage 4, respectively. These findings implied that ratio of NO 3 − to ClO 4 − loadings and acetate loading were two key factors impacting ClO 4 − reduction and microbial structure along the filter. [ABSTRACT FROM AUTHOR]

Perchlorate reduction kinetics and effects of various environmental conditions on removal of perchlorate from synthetic water were investigated to seek high-strength perchlorate removal using mixed perchlorate reducing bacteria. Results demonstrated that perchlorate (50–1500 mg L −1 ) could be degraded rapidly within 28 h under the optimal conditions. The maximum specific perchlorate reduction rate ( q max ) and half saturation constant ( K s ) were 0.92 mg-perchlorate (mg-dry weight) −1 h −1 and 157.7 mg L −1 , respectively. In the ClO 4 − – NO 3 − systems obvious but recoverable lags were caused in perchlorate reduction and the lag time increased with the ratio of nitrate to perchlorate concentration increasing from 0.5 to 3. While in the ClO 4 − – SO 4 2 − systems inhibitions didn't occur until the ratio of sulfate to perchlorate concentration exceeded 10. The optimum temperature and pH value were 35 °C and 6.85, respectively. The optimal acetate-to-perchlorate ratio that could consume all perchlorate and acetate simultaneously was about 2. Dechloromonas , one of the most prominent perchlorate reducing bacteria, was identified as the dominant bacterium in the acclimated culture (69.33% of the whole clones). The study demonstrated that the perchlorate-acclimated mixed microorganisms can readily and efficiently realize reduction of highly concentrated perchlorate in wastewater. [ABSTRACT FROM AUTHOR]

Background: Lung is the largest mucosal area of the human body and directly connected to the external environment, facing microbial exposure and environmental stimuli. Therefore, studying the internal microorganisms of the lung is crucial for a deeper understanding of the relationship between microorganisms and the occurrence and progression of lung cancer., Methods: Tumor and adjacent nontumor tissues were collected from 38 lung adenocarcinoma patients and used nanopore sequencing technology to sequence the 16s full-length sequence of bacteria, and combining bioinformatics methods to identify and quantitatively analyze microorganisms in tissues, as well as to enrich the metabolic pathways of microorganisms., Results: the microbial composition in lung adenocarcinoma tissues is highly similar to that in adjacent tissues, but the alpha diversity is significantly lower than that in adjacent tissues. The difference analysis results show that the bacterial communities of Streptococcaceae , Lactobacillaceae , and Neisseriales were significantly enriched in cancer tissues. The results of metabolic pathway analysis indicate that pathways related to cellular communication, transcription, and protein synthesis were significantly enriched in cancer tissue. In addition, clinical staging analysis of nicotine exposure and lung cancer found that Haemophilus , paralinfluenzae , Streptococcus gordonii were significantly enriched in the nicotine exposure group, while the microbiota of Cardiobactereae and Cardiobacterales were significantly enriched in stage II tumors. The microbiota significantly enriched in IA-II stages were Neisseriaeae , Enterobacteriales , and Cardiobacterales , respectively., Conclusion: Nanopore sequencing technology was performed on the full length 16s sequence, which preliminarily depicted the microbial changes and enrichment of microbial metabolic pathways in tumor and adjacent nontumor tissues. The relationship between nicotine exposure, tumor progression, and microorganisms was explored, providing a theoretical basis for the treatment of lung cancer through microbial targets., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yang, Wang, Ding, Zhang, Zhu, Wang, Pan, Li, Wang and Yu.)

An asymmetric approach for the first total synthesis of (-)-rhodomollanol A, a highly oxidized diterpenoid, is described. The efficient synthetic strategy features three key transformations: (1) an oxidative dearomatization-induced (5 + 2) cycloaddition/pinacol-type 1,2-acyl migration cascade to build up the bicyclo[3.2.1]octane skeleton; (2) a retro -Dieckmann fragmentation/vinylogous Dieckmann cyclization cascade to assemble the bicyclo[3.3.0]octane subunit; and (3) a photo-Nazarov cyclization/intramolecular cycloetherification cascade to forge the 7-oxabicyclo[4.2.1]nonane core structure of the natural product.

Alkyl thiocyanates are prevalent in natural products, drugs, and biologically active compounds. We report here a novel, mild, and efficient Pd-catalyzed site-selective sp 3 C-H bond thiocyanation of 2-aminofurans. Using Na 2 S 2 O 8 as the oxidant and readily available NaSCN as the thiocyanation reagent, the kinetically favorable 2-amino-4-thiocyanatomethylfurans are selectively synthesized in promising yields with a broad substrate scope. This reaction represents the first example of transition-metal-catalyzed site-selective sp 3 C-H bond thiocyanation, thus offering a novel strategy for the step- and atom-economic synthesis of alkyl thiocyanates.

The direct access to 2-amino-5-homoallylfurans has been realized by a palladium-catalyzed tandem cycloisomerization/Heck-type coupling between homoallenyl amides and allyltrialkylsilanes, using a novel DDQ/MnO 2 combination as the efficient oxidant. The reaction exclusively affords γ-allylation products in good to excellent yields with broad substrate scope under exceptionally mild reaction conditions. It represents one of the rare examples of the Pd-catalyzed intermolecular Heck-type coupling of allytrialkylsilanes terminated by β-silyl elimination, thus complementing traditional allylation methods because of the excellent γ-selectivity.