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Abstract Hypoxic-ischemic encephalopathy (HIE) is a diffuse brain tissue injury caused by acute ischemia and hypoxia, and it is most commonly found in newborn infants but can also occur in adults. Mesenchymal stem cell (MSC) therapies have showed improved outcomes for treating HIE-induced neuronal defects. However, many key issues associated with poor cell viability and tolerance of grafted MSCs after HIE remain to be resolved. Genetic engineering could endow MSCs with more robust regenerative capacities. Our research, along with that of other scientists, has found that the expression of intracellular erythropoietin (EPO) in human umbilical cord MSCs (hUC-MSCs) increases proportionally with the duration of hypoxia exposure. Furthermore, we observed that EPO, when introduced into the EPO gene-modified hUC-MSCs, can be secreted into the extracellular space. However, the underlying mechanisms that support the neuroprotective effects of EPO-MSCs remain unclear. EPO-MSCs, hUC-MSCs, and NC-MSCs were identified by flow cytometry, osteogenic, and adipogenic differentiation assays. The oxygen-glucose deprivation (OGD)-induced SH-SY5Y cell-line was established, and five groups were set up: control, 24-h ischemia-hypoxia, co-cultured with hUC-MSCs, NC-MSCs, and EPO-MSCs after hypoxia. LEGENDplex™ multi-factor flow cytometry was used to detect the secretion of inflammatory factors in cell supernatants and cerebrospinal fluid. Chromosome-targeted excision and tagging (CUT&Tag) sequencing was applied to detect genomic H3K4me2 modifications, and conjoint analysis with transcriptome sequencing (RNA-seq) was performed. Lentiviral vector infection was used to construct SH-SY5Y cells with stable knockdown of RE1-silencing transcription factor (REST), and flow cytometry was used to detect alterations in apoptosis. Finally, the molecular mechanism underlying the neuroprotective and anti-apoptotic effects of EPO-MSCs was investigated using RNA sequencing, qRT-PCR, and western blot assays. Our results suggest that EPO-MSCs are genetically engineered to secrete significantly more EPO. EPO-MSCs treatment has anti-apoptotic properties and offers neuronal protection during ischemic-hypoxic injury. Furthermore, RNA-seq results suggest that multiple inflammation-related genes were down-regulated after EPO-MSCs treatment. Application of RNA-seq and CUT&Tag combined analysis found that the expressions of REST were significantly up-regulated. Lentiviral vector infection to construct REST knockdown SH-SY5Y failed to rescue apoptosis after hypoxia and co-culture with EPO-MSCs, and SETD2-mediated H3K36me3 protein level expression was reduced. EPO-MSCs may promote neuronal survival by affecting H3K4me2 and thus activating the expression of REST and TET3. EPO-MSCs also upregulated the modification level of SETD2-mediated H3K36me3 and regulated the expression of inflammation-related genes such as PLCG2, as well as apoptosis genes BCL2A1. To investigate the neuroprotective effects of EPO-modified hUC-MSCs and the underlying epigenetic regulatory mechanisms, this study aims to provide a theoretical foundation for the potential application of EPO gene-modified hUC-MSCs in the treatment of HIE.

To reveal the mechanism for high brake thermal efficiency (BTE) of diesel methanol dual fuel (DMDF) engine meeting China VI emission regulations without urea, experimental and computational methods were used to study the exergy distribution with different regulatory strategies. As the methanol energy ratio (MER) increased, the incomplete combustion exergy loss increased from 0.3 % to 5.5 %, while the exhaust exergy loss and heat transfer exergy loss decreased slightly. As the HP-EGR increased from 3 % to 23 %, exergy losses of incomplete combustion and exhaust decreased, resulting in a reduction in the engine exergy losses. As the LP-EGR increased from 3 % to 21 %, the exergy losses of heat transfer and incomplete combustion slightly decreased. By advancing the main injection timing, the decrease in exhaust flow rate and temperature led to a decrease in exhaust exergy loss and the combustion efficiency was improved from 95.0 % to 96.5 %. Both of them resulted in the highest exergy efficiency of 35.2 % at 12°CA BTDC. Finally, the exergy distributions of DMDF and diesel modes were compared at high and low loads. The research results can provide theoretical basis and engineering practical value for the development and optimization of DMDF engines from the perspective of exergy.

Oblique photography 3D models are increasingly used in 3D modeling and visualization, urban planning and design, smart cities, smart mines, and other fields. To ensure that 3D models can be replaced and updated, it is necessary to deal with the model holes and incomplete areas caused by the incorrect matching of feature points in the modeling process. Moreover, in 3D models of the planning and management of certain mining areas or urban areas to be developed, regions can also be delineated for replacements and updates. Due to the unsatisfactory display effect of the manually modeled models used to replace and update, the authenticity of the model texture and the detail characteristics of the model triangle meshes cannot be guaranteed during integration. Therefore, this paper proposes a 3D model triangle mesh integration method for oblique photography data which integrates the real and complete 3D models used for replacement with the incomplete part or the part of the original model that needs to be replaced. The experimental results show that this method can integrate the original terrain model and the replacement model efficiently and quickly, the integrated model has no gap, and the display effect is good, effectively achieving model repair or model update and replacement.

Trauma-induced osteonecrosis of the femoral head (TI-ONFH) is a pathological process in which the destruction of blood vessels supplying blood to the femoral head causes the death of bone tissue cells. Vascular cell adhesion molecule 1 (VCAM-1) has been shown to have potent proangiogenic activity, but the role in angiogenesis of TI-ONFH is unclear. In this work, we discovered that VCAM-1 was significantly downregulated in the bone marrow mesenchymal stem cells (BMSCs) derived from patients with TI-ONFH. Subsequently, we constructed BMSCs overexpressing VCAM-1 using a lentiviral vector. VCAM-1 enhances the migration and angiogenesis of BMSCs. We further performed mRNA transcriptome sequencing to explore the mechanisms by which VCAM-1 promotes angiogenesis. Gene ontology biological process enrichment analysis demonstrated that upregulated differentially expressed genes (DEGs) were related to blood vessel development. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that upregulated DEGs were engaged in the Apelin signaling pathway. Apelin-13 is the endogenous ligand of the APJ receptor and activates this G protein-coupled receptor. Treatment with Apelin-13 activated the Apelin signaling pathway and suppressed the expression of cellular communication network factor 2 in BMSCs. Furthermore, Apelin-13 also inhibits the migration and angiogenesis of VCAM-1-BMSCs. In summary, VCAM-1 plays an important role in vascular microcirculation disorders of TI-ONFH, which provides a new direction for the molecular mechanism and treatment of TI-ONFH.

Prediction of the rate of penetration (ROP) is integral to drilling optimization. Many scholars have established intelligent prediction models of the ROP. However, these models face challenges in adapting to different formation properties across well sections or regions, limiting their applicability. In this paper, we explore a novel prediction framework combining feature construction and incremental updating. The framework fine-tunes the model using a pre-trained ROP representation. Our method adopts genetic programming to construct interpretable features, which fuse bit properties with engineering and hydraulic parameters. The model is incrementally updated with constant data streams, enabling it to learn the static and dynamic data. We conduct ablation experiments to analyze the impact of interpretable features’ construction and incremental updating. The results on field drilling datasets demonstrate that the proposed model achieves robustness against forgetting while maintaining high accuracy in ROP prediction. The model effectively extracts information from data streams and constructs interpretable representational features, which influence the current ROP, with a mean absolute percentage error of 7.5% on the new dataset, 40% lower than the static-trained model. This work provides a theoretical reference for the interpretability and transferability of ROP intelligent prediction models.

Existing approaches for the 3D modeling of tunnels suffer from several problems, such as highly difficult data acquisition, redundancy of model data, large computational burden, and the inability of the resulting models to be monolithic. Therefore, solutions to the tunnel network modeling problem for complex structures need to be proposed and elaborated in detail. In this paper, a construction method for a three-dimensional tunnel general monomer model based on parallel pathfinding is proposed. Widely used tunnel CAD drawings are analyzed and read, a disordered arc ensemble intersection trend decision method is developed, and an automatic path extraction solution algorithm for unidirectional modeling of tunnel centerlines is constructed. By constructing and splicing the surface elements of the 3D model, a monomeric 3D tunnel model representing the complex network structure is finally obtained. Moreover, the modeling of shafts is realized based on the monomer model, allowing for the three-dimensional topological relationships between different sub-levels of the tunnel and the ground to be established. The automatic modeling method proposed in this paper is applied to the digital twin platform of a filling project in a mining area in Gansu province, China. The experimental results demonstrate that the 3D tunnel models constructed in this way have a smaller data volume, higher modeling accuracy, and more stable growth of modeling speed.

The Hapke two-layer medium model is an efficient way of simulating the spectra of dusty leaves. However, the simulation accuracy is low when the amount of dustfall is small. To solve this problem, we introduced the dust coverage factor and the linear spectral mixing model, to improve the accuracy of the Hapke two-layer medium model. Firstly, based on the assumption of spherical dust particles, the arrangement and accumulation mode of the particles were set, and the coverage factor and accumulation thickness of particles in the leaf area were calculated. Then, the coverage factor was used as an abundance. Endmembers were the spectra of dust-free leaves (measured) and dust-covered leaves (simulated by model), and the final simulated spectra were calculated using linear spectral mixing theory. This study presents the following findings: (1) When the coverage factor was calculated using the exponential model, the maximum difference between the corrected simulated spectra and the measured spectra was 3.4%, and the maximum difference between the original simulated spectra and the measured spectra was 15.2%. The accuracy of the corrected spectra is much higher than that of the original simulated spectra. (2) In this study, the physical thickness and optical thickness calculated by the Hapke two-layer medium model are equivalent, which is quite different from the actual dust accumulation. When the linear spectral mixing model is introduced, to modify the simulation value when the number of dust particles accumulated is less than one layer, the spectral endmember value of the simulated dust leaf is replaced by the simulation spectrum when the number of dust particles accumulated is exactly one layer. The calculated cor-rection spectrum has high rationality and credibility. This finding may be beneficial for monitoring amounts of dustfall accurately using remote sensing in mining areas.

Path planning is widely used in many domains, and it is crucial for the advancement of map navigation, autonomous driving, and robot path planning. However, existing path planning methods have certain limitations for complex field scenes with undulating terrain and diverse landcover types. This paper presents an energy-efficient 3D path planning algorithm based on an improved A* algorithm and the particle swarm algorithm in complex field scenes. The evaluation function of the A* algorithm was improved to be suitable for complex field scenes. The slope parameter and friction coefficient were respectively used in the evaluation function to represent different terrain features and landcover types. The selection of expanding nodes in the algorithm depends not only on the minimum distance but also on the minimum consumption cost. Furthermore, the turning radius factor and slope threshold factor of vehicles were added to the definition of impassable points in the improved A* algorithm, so that the accessibility of path planning could be guaranteed by excluding some bends and steep slopes. To meet the requirements for multi-target path planning, the improved A* algorithm was used as the fitness function of the particle swarm algorithm to solve the traveling salesman problem. The experimental results showed that the proposed algorithm is capable of multi-target path planning in complex field scenes. Furthermore, the path planned by this algorithm is more passable and more energy efficient. In this experimental environment model, the average energy-saving efficiency of the path planned by the improved algorithm is 14.7% compared to the traditional A* algorithm. This would be beneficial to the development of ecotourism and geological exploration.

Unmanned aerial vehicle (UAV) oblique photography technology is widely used in a variety of fields because of its excellent efficiency, realism, and low cost of manufacturing. However, due to the influence of lighting, occlusion, weak textures, and other factors in aerial images, the modeling results can have the problem of an incorrect structure that is inconsistent with the real scene. The edge line of a building is the main external expression of its structure. Whether the edge line is straight or not will directly affect the realism of the building, so the restoration of the edge line can improve the realism of the building. In this study, we proposed and developed a method for the restoration of the edge line of a 3D building model based on triangular mesh cutting. Firstly, the feature line of the edge line was drawn using human–computer interaction, and axis-aligned bounding box (AABB) collision detection was carried out around the feature line to determine the triangular patches to be cut. Then, the triangular cutting algorithm was used to cut the triangular patches projected onto the plane. Finally, the structure and texture of the 3D building model were reconstructed. This method allowed us to actualize the physical separation of continuous triangulation; the triangulation around the edge line was cut, and the plane was fitted. This method was able to improve cutting accuracy and edge flatness and enhance the edge features of buildings and the rendering quality of models. The experimental results showed that the edge restoration method proposed in this paper is reliable and that it can effectively improve the building rendering effect of a 3D building model based on UAV oblique photography and can also enhance the realism of the model.

The Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) satellite uses a synchronized multi-beam photon-counting method to collect data from three pairs of synchronous ground tracks. The sampling rate along the ground tracks is designed to be ∼0.7 m, much smaller than that used in conventional radar altimeters. Hence, it is reasonable to expect an improvement in marine gravity recovery over coastal zones using ICESat-2 data. ICESat-2 provides valid sea surface height (SSH) measurements and a standard data product (ATL12) over ocean areas. This led us to consider the possibility of investigating its ability to calculate the deflection of vertical (DOV) and marine gravity anomalies. We processed ATL12 data about 22 months over the South China Sea (0°–23°N, 103°–120°E) and verified the ability of ICESat-2 SSH measurements to be used in calculating directional components of DOV. The results show that the ICESat-2 SSH data have a similar centimeter-magnitude accuracy level as data from the Jason-2 satellite. Furthermore, the accuracy of cross-track deflection of vertical (CTDOV) calculations between non-identical side beams is lower. For along-track points, the difference in accuracy between the solution of the prime component and the meridional component is significantly reduced, the prime component accuracy is significantly better than the directional components of the gridded deflection of vertical (GDOV), although the enhancement is weak for the meridional component. We also implemented the inversion of the ICESat-2 single mission based on the inverse Vening Meinesz formula, and verified the capability of ICESat-2 gravity field detection using shipborne gravity measurements and XGM2019 gravity field model, and found that the accuracy is 1.35 mGal and 2.47 mGal, respectively. ICESat-2 deserves the attention of the altimetry community, and its advantages are expected to make it an alternative data source for multi-mission fusion inversion of the ocean gravity field in the future.

Plants frequently suffer from different types of stress and their combination. Timely and effective monitoring of plant stresses is necessary for the precision management of crops and environmental protection. Hyperspectral remote sensing may help monitoring demand based on spectral feature analysis. However, existing studies are still insufficient for the spectral identification of plant stress types, including the combined stress type. In this paper, drought, copper, and their combined stresses on maize seedlings were designed to analyze differences of plant parameters and spectral indices by comparing with a control group. The experimental results indicate that: 1) chlorophyll content, leaf area, and relative water content could be used as key parameters to express the inter-type stress differences, and in particular, chlorophyll content was the most important bio-parameter due to its unique characteristic to distinguish a combined stress from drought stress; 2) red-edge position, the first derivative at the red edge and shortwave infrared water stress index was found to be effective for characterizing the three plant parameters under plant stresses because they could minimize the effect of variations of stress types on the prediction of these parameters; and 3) the three spectral indices might be used to identify the three stress types of maize seedlings by a decision tree analysis. The results may be useful for the precision management of crops and for environmental protection and monitoring as well.

Mining can provide necessary mineral resources for humans. However, mining activities may cause damage to the surrounding ecology and environment. Vegetation change analysis is a key tool for evaluating damage to ecology and the environment. Liaoning is one of the major mining provinces in China, with rich mineral resources and long-term, high-intensity mining activities. Taking Liaoning Province as an example, vegetation change in six mining areas was investigated using multisource remote sensing data to evaluate ecological and environmental changes. Based on MODIS NDVI series data from 2000 to 2019, change trends of vegetation were evaluated using linear regression. According to the results, there are large highly degraded vegetation areas in the Anshan, Benxi, and Yingkou mining areas, which indicates that mining activities have seriously damaged the vegetation in these areas. In contrast, there are considerable areas with improved vegetation in the Anshan, Fushun, and Fuxin mining areas, which indicates that ecological reclamation has played a positive role in these areas. Based on Sentinel-2A data, leaf chlorophyll content was inferred by using the vegetation index MERIS Terrestrial Chlorophyll Index (MTCI) after measurement of leaf spectra and chlorophyll content were carried out on the ground to validate the performance of MTCI. According to the results, the leaf chlorophyll content in the mines is generally lower than in adjacent areas in these mining areas with individual differences. In the Yingkou mining area, the chlorophyll content in adjacent areas is close to the magnesite mines, which means the spillover effect of environmental pollution in mines should be considerable. In the Anshan, Benxi, and Diaobingshan mining areas, the environmental stress on adjacent areas is slight. All in all, iron and magnesite open-pit mines should be monitored closely for vegetation destruction and stress due to the high intensity of mining activities and serious pollution. In contrast, the disturbance to vegetation is limited in resource-exhausted open-pit coal mines and underground coal mines. It is suggested that land reclamation should be enhanced to improve the vegetation in active open-pit mining areas, such as the Anshan, Benxi, and Yingkou mining areas. Additionally, environmental protection measures should be enhanced to relieve vegetation stress in the Yingkou mining area.

A supply of minerals is critical to socioeconomic development. However, such a supply also induces negative impacts on environment and ecology, e.g., leading to dust emission and deposition. An ultra-low-grade magnetite has been exploited as a new iron type since 2001 in China. In this paper, two Landsat images were used for monitoring foliar dust in Changhe River Mining Area, China. First, models were established to estimate foliar dust using vegetation indices (VIs) differences according to laboratory spectral measurements; normalized differenced VI was selected as an optimal VI for estimating foliar dust amount based on both field and laboratory spectral measurements (RMSE = 6.58 g/m2), and finally, the spatial patterns of foliar dust were analyzed by using ancillary high-resolution data. The result showed that most foliar dust distributed near ore transportation roads and around mining sites and tailings ponds, which was related to ultra-low-grade characteristics of the iron ore due to large-area extraction and tailings occupation, and large-amount dust emission released from ore transportation. The remote sensing method for estimating foliar dust may be beneficial for environmental management in mining areas.

Dust pollution is severe in some mining areas in China due to rapid industrial development. Dust deposited on the vegetation canopy may change its spectra. However, a relationship between canopy spectra and dust amount has not been quantitatively studied, and a pixel-scale condition for remote sensing application has not been considered yet. In this study, the dust dispersion characteristics in an iron mining area were investigated using the American Meteorological Society (AMS) and the U.S. Environmental Protection Agency (EPA) regulatory model (AERMOD). Further, based on the three-dimensional discrete anisotropic radiative transfer (DART) model, the spectral characteristics of vegetation canopy under the dusty condition were simulated, and the influence of dustfall on vegetation canopy spectra was studied. Finally, the dust effect on vegetation spectra at the canopy scale was extended to a pixel scale, and the response of dust effect on vegetation spectra at the pixel scale was determined under different fractional vegetation covers (FVCs). The experimental results show that the dust pollution along a haul road was more severe and extensive than that in a stope. Taking dust dispersion along the road as an example, the variation of vegetation canopy spectra increased with the height of dust deposited on the vegetation canopy. At the pixel scale, a lower vegetation FVC would weaken the influence of dust on the spectra. The results derived from simulation spectral data were tested using satellite remote sensing images. The tested result indicates that the influence of dust retention on the pixel spectra with different FVCs was consistent with that created with the simulated data. The finding could be beneficial for those making decisions on monitoring vegetation under dusty conditions and reducing dust pollution in mining areas using remote sensing technology.

Two years after the Zhanghewan Pumped-Storage Power Station was put into operation, more than 500 blisters appeared in the asphalt concrete facing of the upper reservoir, and nearly half of them ruptured at the surface. The blistering mechanism of the asphalt concrete facing was studied in this paper. Through on-site inspection and coring inspection, it was found that the blistering was caused by the vapor pressure formed by the water enclosed in the middle of the impervious layer during high temperatures. Numerical analysis showed that the temperature 5 cm below the surface could reach 50−60 °C. Through numerical analysis and model tests, the internal water at this temperature may form a vapor pressure of 20 kPa. Finally, the blister size of the asphalt concrete facing at this temperature and pressure was studied with a model test. The possible sources of moisture inside the impervious layer were also analyzed through a core test, which found that moisture was most likely to be introduced by water spraying during rolling.

Iron tailings ponds are engineered dam and dyke systems used to capture iron tailings. They are high-risk hazards with high potential energy. If the tailings dam broke, it would pose a serious threat to the surrounding ecological environment, residents’ lives, and property. Rainfall is one of the most important influencing factors causing the tailings dam break. This paper took Chengde Area, a typical iron-producing area, as the study area, and proposed a remote sensing method to evaluate the safety risk of tailings ponds under rainfall condition by using runoff coefficient and catchment area. Firstly, the vegetation coverage in the study area was estimated using the pixel dichotomy model, and the vegetation type was classified by the support vector machine (SVM) method from Landsat 8 OLI image. Based on DEM, the slope of the study area was extracted, and the catchment area of the tailings pond was plotted. Then, taking slope, vegetation coverage, and vegetation type as three influencing factors, the runoff coefficient was constructed by weight assignment of each factor using analytic hierarchy process (AHP) model in both quantitative and qualitative way. Finally, the safety risk of tailings ponds was assessed according to average runoff coefficient and catchment area in the study area. The results showed that there were 124 low-risk tailings ponds, 16 moderate-risk tailings ponds, and 4 high-risk tailings ponds in the study area. This method could be useful for selecting targeted tailings ponds for focused safety monitoring. Necessary monitoring measurements should be carried out for the high-risk and moderate-risk tailings ponds in rainy season.

Abstract The coupled green energy and chemical production by photocatalysis represents a promising sustainable pathway, which poses great challenges for the multifunction integration of catalytic systems. Here we show a promising green photocatalyst design using Cu-ZnIn2S4 nanosheets and carbon dots as building units, which enables the integration of reaction, mass transfer, and separation functions in the nano-space, mimicking a nanoreactor. This function integration results in great activity promotion for benzyl alcohol oxidation coupled H2 production, with H2/benzaldehyde production rates of 45.95/46.47 mmol g−1 h−1, 36.87 and 36.73 times to pure ZnIn2S4, respectively, owning to the enhanced charge accumulation and mass transfer according to in-situ spectroscopies and computational simulations of the built-in electrical field. Near-unity selectivity of benzaldehyde is achieved via the effective separation enabled by the Cu(II)-mediated conformation flipping of the intermediates and subsequent π-π conjugation. This work demonstrates an inspiring proof-of-concept nanoreactor design of photocatalysts for coupled sustainable systems.

Steroid-induced osteonecrosis of the femoral head (SONFH) is a refractory, progressive disease. However, the underlying mechanisms that aggravate femoral head necrosis remain unclear. Extracellular vesicles (EVs) act as molecular carriers in intercellular communication. We hypothesize that EVs derived from human (h) bone marrow stromal cells (BMSC) resident in SONFH lesion areas promote the pathogenesis of SONFH. In the present study, we determined the modulatory effects of SONFH-hBMSCs-derived EVs on the pathogenesis of SONFH in vitro and in vivo. We found that the expression of hsa-miR-182-5p was downregulated in SONFH-hBMSCs and EVs isolated from those hBMSCs. After tail vein injection, EVs isolated from hBMSCs transfected with hsa-miR-182-5p inhibitor aggravated femoral head necrosis in the SONFH mouse model. We conclude that miR-182-5p regulates bone turnover in the SONFH mouse model via targeting MYD88 and subsequent upregulation of RUNX2 expression. We further assume that EVs derived from hBMSCs resident in SONFH lesion areas aggravate femoral head necrosis by downregulating miR-182-5p secreted from hBMSC located outside these lesions. We suggest that miR-182-5p could provide a novel target for future therapeutic approaches to treat or prevent SONFH. [ABSTRACT FROM AUTHOR]

Abstract Owing to the specific electronic-redistribution and spatial proximity, diatomic catalysts (DACs) have been identified as principal interest for efficient photoconversion of CO2 into C2H4. However, the predominant bottom-up strategy for DACs synthesis has critically constrained the development of highly ordered DACs due to the random distribution of heteronuclear atoms, which hinders the optimization of catalytic performance and the exploration of actual reaction mechanism. Here, an up-bottom ion-cutting architecture is proposed to fabricate the well-defined DACs, and the superior spatial proximity of CuAu diatomics (DAs) decorated TiO2 (CuAu-DAs-TiO2) is successfully constructed due to the compact heteroatomic spacing (2-3 Å). Owing to the profoundly low C-C coupling energy barrier of CuAu-DAs-TiO2, a considerable C2H4 production with superior sustainability is achieved. Our discovery inspires a novel up-bottom strategy for the fabrication of well-defined DACs to motivate optimization of catalytic performance and distinct deduction of heteroatom synergistically catalytic mechanism.

The manipulation of trap states plays a crucial role in the development of efficient photocatalysts. An ultrathin-shelled Zn-AgIn5S8/ZnS quantum dots (QDs) photocatalyst was synthesized via in situ growth using a low-temperature hydrothermal method. The optical properties of the samples coated with ZnS shell were studied vis UV-vis absorption and fluorescence spectra. The ultrathin ZnS shell plays an important role in the Zn-AgIn5S8/ZnS core–shell heterostructure photocatalytic water splitting system, which could reduce surface defects, prolong the carrier lifetime and improve the photo-generated electron–hole pair separation effectively, resulting in the improved photocatalytic efficiency and enhanced stability of the catalyst. The results provide an effective guideline for shell thickness design in future constructions of the core–shell heterostructure photocatalyst.

The creation of junctions between 0D and 2D materials can be an efficient strategy to enhance charge separation for solar hydrogen production. In this study, a simple in situ growth method has been used to synthesize a series of 0D/2D Zn-Ag-In-S quantum dots/reduced graphene oxide (ZAIS QDs/RGO) heterojunctions. The developed heterojunctions were characterized for structural characteristics, morphology, and photocatalytic performance, while varying the content of RGO. We observed that photocatalytic hydrogen production reached a maximum at an RGO content of 30 μL (342.34 µmol g−1 h−1), surpassing that of pure ZAIS QDs (110.38 µmol g−1 h−1) by 3.1 times, while maintaining excellent stability. To understand this enhancement, we performed time-resolved fluorescence and electrochemical impedance spectroscopy. The fluorescence lifetime of RGO loaded at 30 μL (417.76 ns) was significantly higher than that of pure ZAIS QDs (294.10 ns) and had the fastest charge transfer, which can be attributed to the charge transfer and storage capacity of RGO to extend the lifetime of photogenerated carriers and improve the charge separation efficiency. This study offers a simple synthesis method for constructing 0D/2D QDs/RGO heterojunction structures and provides a valuable reference for further enhancing the activity and stability of I-III-VI sulfide QDs.

With the rapid development of the steel and iron industry, ultra-low-grade iron ore has been developed extensively since the beginning of this century in China. Due to the high concentration ratio of the iron ore, a large amount of tailings was produced and many tailings ponds were established in the mining area. This poses a great threat to regional safety and the environment because of dam breaks and metal pollution. The spatial distribution is the basic information for monitoring the status of tailings ponds. Taking Changhe Mining Area as an example, tailings ponds were extracted by using Landsat 8 OLI images based on both spectral and texture characteristics. Firstly, ultra-low-grade iron-related objects (i.e., tailings and iron ore) were extracted by the Ultra-low-grade Iron-related Objects Index (ULIOI) with a threshold. Secondly, the tailings pond was distinguished from the stope due to their entropy difference in the panchromatic image at a 7 x 7 window size. This remote sensing method could be beneficial to safety and environmental management in the mining area. [ABSTRACT FROM AUTHOR]

The composite structure of ZnSe-AgZnInS microspheres was synthesized by two-step hydrothermal reaction, in which AgZnInS quantum dots (QDs) attached to the surface of ZnSe microspheres. Compared with pure ZnSe and AgZnInS QDs, the ZnSe-AgZnInS exhibited excellent photocatalytic activity for H2 generation under the illumination of a simulated sunlight. The results also showed that different mass ratios of AgZnInS QDs had a great influence on the photocatalytic performance of ZnSe-AgZnInS microspheres. When the AgZnInS QDs was 0.05 g/mol with the photocatalytic reduction time of 5 h, the H2 formation rate of ZnSe-AgZnInS reached the optimal value (343.108 μmolg−1 h−1), which was ∼20 times and more than 2 times higher than bare ZnSe and AgZnInS QDs, respectively. The related mechanism of photocatalytic hydrogen generation was investigated by suface photovoltage spectroscopy and transisent fluorescence. It was found that the efficient transport of photogenerated carriers at the interface between ZnSe and AgZnInS QDs contributed to the improvement of the photocatalytic performance of ZnSe-AgZnInS. This work provides further insights for the design and preparation of composite photocatalysts. Keywords: Microspheres, Quantum dots, SPV, Charge transport

With the development of economy, global demand for steel has accelerated since 2000, and thus mining activities of iron ore have become intensive accordingly. An ultra-low-grade iron has been extracted by open-pit mining and processed massively since 2001 in Kuancheng County, Hebei Province. There are large-scale stopes and tailings ponds in this area. It is important to extract their spatial distribution information for environmental protection and disaster prevention. A remote sensing method of extracting stopes and tailings ponds is studied based on spectral characteristics by use of Landsat 8 OLI imagery and ground spectral data. The overall accuracy of extraction is 95.06%. In addition, tailings ponds are distinguished from stopes based on thermal characteristics by use of temperature image. The results could provide decision support for environmental protection, disaster prevention, and ecological restoration in the ultra-low-grade iron ore mining area. [ABSTRACT FROM AUTHOR]