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We report the design and fabrication of a vertical structure using a distributed Bragg reflector and dielectric material layer to achieve optimized optical absorption enhancement for a stack of monolayer WS2 and MoS2, namely, a tenfold increase in absorption over a 100 nm spectral range. Our research indicates that we can approach over 50% absorption by finely tuning the thickness of the spacer layer. Our theoretical model shows that the dependence of the absorption coefficient on the spacer thickness can be understood as a solution of a non-Hermitian Schrödinger equation. These results advance the development of broadband optical devices, including solar energy conversion and sensitive optical sensors, by using two-dimensional excitonic materials. [ABSTRACT FROM AUTHOR]

Concrete is subject to the combined erosive effects of physical and chemical activities in cold, salty soil regions. In this work, durability tests of recycled concrete (RC) subjected to sulfate freeze-thaw cycles were conducted. The macroscopic performance deterioration law of RC under the influence of the replacement rate (0%, 50%, 100%) and the moisture content of coarse recycled concrete aggregate (CRCA) (0%, 50%, 100%) was investigated by analyzing the change characteristics of apparent damage, mass loss rate, and Relative dynamic modulus of elasticity (RDME) of RC during the erosion process. At the same time, nuclear magnetic resonance (NMR) and microhardness testing equipment were used to examine the multi-parameter evolution features such as porosity, pore distribution, interfacial transition zone (ITZ) width, and strength. The findings indicate that the main cause of the variation in the degree of damage to the RC surface layer is the variance in the effective water-cement (w/c) ratio of the mortar due to replacement rate and moisture content. The strength and area of erosion damage increase when the CRCA replacement rate rises due to the easier inward penetration of the sulfate solution. CRCA with a 50% moisture content could increase the strength of the mortar by decreasing the mortar's effective w/c ratio. The rate and effectiveness of salt solution replenishment inward were simultaneously slowed down by the improved ITZ performance. In erosive situations, the fractal dimension of RC reduces to varying degrees. This is due to the expansion of the pore structure. The porosity/fractal dimension is employed as the comprehensive pore parameter η in this research so as to take into account the integrity of the pore structure and the specificity of the pore distribution. The improved microstructure damage variables can reflect the erosive microstructure deterioration process of RC. • The effect of recycled aggregate moisture content on the properties of the interfacial transition zone was analyzed. • The changes of pore distribution of recycled concrete under sulfate freeze-thaw cycle are investigated • An improved microstructure damage variable is proposed to describe the process of microstructure deterioration of recycled concrete under corrosive environment. [ABSTRACT FROM AUTHOR]

Bismuth ferrite (BiFeO 3), a perovskite-type oxide, possesses unique morphology and multiferroicity, rendering it highly versatile for various applications. Recent investigations have demonstrated that BiFeO 3 exhibits enhanced Fenton-like and photocatalytic behaviors, coupled with its piezoelectric/ferroelectric properties. BiFeO 3 can catalytically generate highly oxidative reactive oxygen species (ROS) when exposed to hydrogen peroxide or light irradiation. Consequently, bismuth ferrite-based nanomaterials have emerged as promising candidates for various biomedical applications. However, the precise fabrication of BiFeO 3 -based materials with controllable features and applications in diverse biomedical scenarios remains a formidable challenge. In this review, we initially summarize the Fenton reaction property, ferroelectric, and piezoelectric properties of BiFeO 3. We further survey the current methodologies for synthesizing BiFeO 3 nanomaterials with diverse morphologies. Subsequently, we explore the effects of element doping and heterojunction formation on enhancing the photocatalytic activity of BiFeO 3 , focusing on microstructural, electronic band structure, and modification approaches. Additionally, we provide an overview of the recent advancements of BiFeO 3 -based nanomaterials in biomedicine. Finally, we discuss the prevailing obstacles and prospects of BiFeO 3 for biomedical applications, offering valuable insights and recommendations for forthcoming research endeavors. [Display omitted] • Summary of the Fenton reaction, ferroelectricity, and piezoelectricity in BiFeO 3. • Summary of the shape and photocatalytic performance in BiFeO 3. • Summary of the applications of BiFeO 3 in bioimaging, antibacterial and anticancer. [ABSTRACT FROM AUTHOR]

• Effect of unloading and temperature on properties of unlined tunnel surrounding rock. • Considering the state of unlined tunnel rock undergoing excavation and then fire. • High temperature tests and reloading tests were performed on unloaded samples. • Tunnel excavation caused different stress release levels. Recently, the frequency of highway tunnel fire has been increasing annually, which necessitates attention toward the stability and safety of surrounding rocks in the unlined tunnels exposed to fires. This study aimed to investigate the influence of the high temperature of excavation unloading on the physical and mechanical properties of unlined tunnel surrounding rock that has been exposed to fire erosion and tunnel ventilation. To this end, granite specimens that had undergone hierarchical unloading tests were selected as the research object, and high temperature and triaxial reloading tests were carried out on unloading-damaged specimens. The variation of mechanical properties and failure characteristics of unloading-damaged specimens with temperature was analyzed, and the differences in their mass, wave velocity, magnetic properties and apparent characteristics under the influence of high temperatures were compared. The results are as follows: (1) The mechanical properties of the unloading-damaged specimens deteriorate obviously under high temperatures, and the greater the temperature, the higher is the reduction in the sample peak strength; there is an obvious nonlinear relationship between them when the unloading-damaged specimens are reloaded after being exposed to a high temperature, and there is a certain threshold for the reduction of mechanical strength of the specimens due to temperature. (2) During triaxial reloading, the pre-peak strain is not related to the confining pressure, but the post-peak strain is closely related to the unloading confining pressure. The higher the temperature, the greater the post-peak accelerated strain. (3) The unloading effect provides a channel for the high temperature to change the physical and mechanical characteristics of the parent rock. The unloading-damaged specimens are gray white at 25 ℃, gray brown at 300 ℃, and reddish brown at 600 ℃. The results show that the wave velocity of the unloading damage specimen decreases slightly at 300 ℃, but significantly at 600 ℃, with an average decrease of 64.73%. (4) The thermal load intensifies the crack evolution, expansion, and structural relaxation of the unloading-damaged specimens, and the unloading magnitude and temperature change the distribution of the dominant fracture surface of the specimens. The confining pressure plays a dominant role in the deformation and failure of the specimens at low temperatures, while thermal load dominates at high temperatures. The research results can provide a theoretical reference for the engineering design of unlined tunnels with surrounding rocks. [ABSTRACT FROM AUTHOR]

The existing research data show that, after reservoir impoundment, due to the repeated rise and fall of water level and water-rock interaction, the mechanical parameters of landslide are reduced, which will have an adverse effect on the stability of landslide. Therefore, sufficient attention must be paid to the stability of slope after reservoir impoundment. Hejia landslide is the largest landslide near the bank of Miaojiaba hydropower station, and its stability plays an important role in the normal operation of the hydropower station. Through field investigation and analysis of regional geological conditions, it is concluded that Hejia landslide is a large-scale landslide, through long-term sliding-bending deformation; it is generated from the external hard rock with thick layers and sliding zone for layered soft rock; the formation mechanism of landslide is as follows: (1) high-steep and hard-soft layered slope is the slope structure condition that caused the large landslide; (2) the existence of thick soft rock belt provides material conditions for the formation of slip surface; (3) certain air conditions provide displacement space for the separation and disintegration of the sliding body, and the landslide is stable at present. Numerical analysis results show that reservoir impoundment will adversely affect the stability of landslide. In order to ensure the normal operation of power station, certain engineering measures must be taken to treat Hejia landslide. After taking measures, years of monitoring data show that the deformation of Hejia landslide tends to be stable, and the current operation is normal, indicating that the engineering treatment measures are reasonable and feasible. [ABSTRACT FROM AUTHOR]

The mechanisms leading to secondary aerosol pollution in the Yangtze Delta region (such as Nanjing) are still poorly constrained. Here we conducted a field campaign to elucidate the chemical characteristics of fine aerosols, with a focus on variations and formation mechanisms of secondary components in summer Nanjing. The average PM 1 mass concentration was 18.88 μg m−3 and was dominated by the secondary species (78%). Secondary inorganic species accounted for 30% of PM 1 mass and high PM 1 loading was closely relevant with nitrate rather than sulfate. Nitrate was mainly produced from nighttime heterogeneous/aqueous process (production rate of 0.38 g/g H 2 O) and its variation was driven by thermodynamic equilibrium. On the other hand, sulfate was governed by daytime photochemical production (production rate of 0.013 g/g O x)(O x =NO 2 + O 3) while contribution of aqueous process was minor. Positive matrix factorization identified and quantified a traffic-related hydrocarbon OA (HOA), a cooking OA (COA), and four SOA factors including a local secondary OA (LSOA), a less oxygenated OA (LO-OOA), a moderately oxygenated OA (MD-OOA), and a more-oxidized oxygenated OA (MO-OOA). LSOA was likely from local photochemical conversion of HOA and COA; LO-OOA was semi-volatile thus evaporation/diffusion would offset its weak photochemical production. MO-OOA was very clearly linked with photochemistry, based on its afternoon enhancement and tight positive correlations with O x (0.029 g/g O x , occupying ∼60% of photochemical SOA production) and sulfate. MD-OOA was a minor contributor of SOA (∼6%) but it was clearly from aqueous process given the strong positive correlation with aerosol liquid water content (ALWC) and nitrate. Both nitrate and MD-OOA concentrations increased against pH while those of sulfate and MO-OOA decreased. We further investigated the organic nitrate (ON) characteristics, and found that ON was a very minor component of OA in summer Nanjing (0.08–0.14 μg m−3, 0.6–1.1% of OA) and it was predominantly associated with aqueous process. Overall, this work reveals in details formation processes of different secondary species, and therefore is insightful for future air pollution modelling and efficient control in similar regions. • Organics and sulfate dominated PM 1 , yet high PM 1 loading was mainly caused by nitrate. • Nitrate was mainly produced from nighttime heterogeneous/aqueous process. • Sulfate was governed by daytime photochemical processes. • MO-OOA was clearly from photochemistry and MD-OOA from aqueous process. • Organic nitrate was very minor (0.6–1.1% of OA) and associated with aqueous process. [ABSTRACT FROM AUTHOR]

Rock mechanics tests are essential for advancing theoretical and practical knowledge in the field. The rock failure mechanism can be studied by analyzing the failure characteristics of rock samples through mechanical tests. However, despite their usefulness, quantitative rock classification systems still possess certain limitations that need to be addressed. The main objective of this paper was to develop a comprehensive quantitative rock classification system based on rock failure characteristics. The rock classification indices, including crack density and crack saturation, were systematically introduced based on rigorous statistical analyses conducted on a diverse set of 200 rock samples. In particular, the crack saturation index serves as a crucial metric that primarily captures and quantifies the extent of actual crack propagation within the rock samples. Moreover, it is important to note that the two evaluation indices, crack density and crack saturation, work in harmony and complement each other, enhancing the overall understanding of rock fragmentation and failure characteristics. By taking into account both crack density and crack saturation, the proposed method effectively categorizes rock fragmentation into five distinct classes, namely "relatively intact", "slightly fragmented", "fragmented", "very fragmented" and "extremely fragmented." The validation process confirmed the efficacy of the proposed classification method in accurately capturing the crack-propagation characteristics of rocks. This outcome is highly significant as it significantly advances ones understanding of rock failure mechanisms and provides valuable insights into the overall characteristics of rocks. [ABSTRACT FROM AUTHOR]

In this paper, the strength and deformation failure characteristics of bearing coal rock mass are related to the confining pressure, and the SAS-2000 experimental system is used to carry out uniaxial and 3, 6, and 9 MPa triaxial tests on coal rock to assess the strength and deformation failure characteristics of coal rock under different confining pressure conditions. The results show that the stress–strain curve of coal rock undergoes four evolutionary stages after fracture: compaction, elasticity, plasticity, and rupture. With confining pressure, the peak strength of coal rock increases, and the elastic modulus increases nonlinearly. The coal sample changes more with confining pressure, and the elastic modulus is generally smaller than that of fine sandstone. The stage of evolution under confining pressure constitutes the failure process of coal rock, with the stress of different evolution stages causing various degrees of damage to coal rock. In the initial compaction stage, the unique pore structure of the coal sample makes the confining pressure effect more apparent; the confining pressure makes the bearing capacity of the coal rock plastic stage stronger, the residual strength of the coal sample has a linear relationship with the confining pressure, and the residual strength of the fine sandstone has a nonlinear relationship with the confining pressure. Changing the confining pressure state will cause the two kinds of coal rock samples to change from brittle failure to plastic failure. Different coal rocks under uniaxial compression experience more brittle failure, and the overall degree of crushing is higher. The coal sample in the triaxial state experiences predominantly ductile fracture. The whole is relatively complete after failure as a shear failure occurs. The fine sandstone specimen experiences brittle failure. The degree of failure is low, and the confining pressure's effect on the coal sample is obvious. [ABSTRACT FROM AUTHOR]

Water–rock interaction is a common phenomenon in rock mass engineering. Water–rock interaction alters the mineralogical and microstructural properties of a rock mass and leads to engineering problems such as leakage, deformation, and failure of a rock mass. To investigate the local leakage in the limestone reservoir, limestone specimens were taken from the underground chamber. In this study, two test conditions were designed: with and without regular replacement of the reservoir water condition. The results indicated that the porosity increased sharply in the early stages of the soaking. But, the rate of increment dropped after 120 d (regular replacement of reservoir water condition) and 90 d (unchanged reservoir water condition), respectively. The pore in the rock was 4.50 mm deep, while the reservoir water was replaced regularly, which is 1.54 times that of the unchanged reservoir water condition (i.e., 2.50 mm), in 360 soaking days. Relatively, the renewal of reservoir water enhanced the chemical reaction. The water–rock interaction altered the mineralogical composition, spatial structure of the crystal, and pore structure of the rock. The change in the longitudinal wave velocity Vm measures the state of pore development. The porosity evolution model for limestone rock was established by considering the impact of dissolution on the spatial structure of the crystal skeleton. The model accurately predicted the variation trend of porosity in the limestone rock under water–rock interaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ce and S-doped Bi 2 O 3 nanosheets (BOSC) with oxygen defects are designed and synthesized. • Oxygen vacancies enhance the charge transfer and light absorption capacity. • Cascade conversion of reactive oxygen species is realized via band bending. • BOSC exhibits a variety of enzyme-like activities, leading to tumor oxidative stress amplification. • BOSC can initiate inflammatory programmed cell death, known as PANoptosis. Photocatalytic therapy (PCT) is a minimally invasive technique that utilizes reactive oxygen species (ROS) to selectively and optically impair tumor cells. However, the limited efficacy of photocatalysts hinders their more comprehensive application. In this study, we successfully synthesized Ce and S-doped Bi 2 O 3 (BOSC) nanosheets through topological synthesis. BOSC exhibits CAT-like and POD-like enzyme activities and can generate ROS and heat upon near-infrared light irradiation, thereby amplifying tumor oxidative stress. Introducing rare earth Ce element enhances light absorption, introduces oxygen vacancies, reduces bandgap, and facilitates charge separation. This Ce-doping also modifies the band position and Fermi level of BOSC, resulting in increased band bending at the solid–liquid interface, enabling a cascade reaction of ROS and enhancing ROS production. Additionally, BOSC demonstrates multiple enzyme activities by depleting GSH and catalyzing the production of ROS and O 2 from endogenous H 2 O 2 , thereby exacerbating cellular oxidative damage. The synergistic effect of BOSC post-illumination induces panoptosis, thereby improving the therapeutic efficacy against tumors. This strategy, involving the modulation of band structure and band bending through ion doping to introduce oxygen defects into the photosensitizer, provides a viable approach to enhance tumor phototherapy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasound neural regulation is a promising strategy for rational energy excitation of 2D biomaterials. • US-driven rGO shows the best cytocompatibility and PC 12 cell differentiation ability. • 1 MHz frequency and 50 % duty cycle may be the best ultrasound parameter. • 2D biomaterials-based ultrasound therapy mediates the pro/anti-inflammatory microenvironment. Two-dimensional (2D) biomaterials, with unique planar topology and quantum effect, have been widely recognized as a versatile nanoplatform for bioimaging, drug delivery and tissue engineering. However, during the complex application of nerve repair, in which inflammatory microenvironment control is imperative, the gentle manipulation and trigger of 2D biomaterials with inclusion and diversity is still challenging. Herein, inspired by the emerging clinical progress of ultrasound neuromodulation, we systematically studied ultrasound-excited 2D graphene analogues (graphene, graphene oxide, reduced graphene oxide (rGO) and carbon nitride) to explore their feasibility, accessibility, and adjustability for ultrasound-induced nerve repair in vitro. Quantitative observation of cell differentiation morphology demonstrates that PC12 cells added with rGO show the best compatibility and differentiation performance under the general ultrasound mode (0.5 w/cm2, 2 min/day) compared with graphene, graphene oxide and carbon nitride. Furthermore, the general condition can be improved by using a higher intensity of 0.7 w/cm2, but it cannot go up further. Later, ultrasonic frequency and duty cycle conditions were investigated to demonstrate the unique and remarkable inclusion and diversity of ultrasound over conventional electrical and surgical means. The pulse waveform with power of 1 MHz and duty cycle of 50 % may be even better, while the 3 MHz and 100 % duty cycle may not work. Overall, various graphene analog materials can be regarded as biosafe and accessible in both fundamental research and clinical ultrasound therapy, even for radiologists without material backgrounds. The enormous potential of diverse and personalized 2D biomaterials-based therapies can be expected to provide a new mode of ultrasound neuromodulation. [ABSTRACT FROM AUTHOR]