Sunlight-driven photosynthesis by covalent organic frameworks (COFs) from water and air without using sacrificial reagents is a promising H2O2 fabrication approach, but is still restricted by the insufficient charge separation and sluggish 2e- water oxidation process. Herein, we provide a facile strategy to simultaneously improve charge separation and water oxidation in COFs via confining the charge transfer pathways from two diversion ones to a confluence one through regulating the site of nitrogen in bipyridine. Combining in-situ characterization with computational calculations, we reveal that compared to COF-BD1 containing two diversion charge transfer pathways, the charge transfer pathway in COF-BD2 is confined to a confluence one due to the electron-deficiency effect of nitrogen, which greatly accelerates the intermolecular and out-of-plane charge transfer. Via effectively reducing the energy barrier of rate-determining water oxidation reaction, the subsequent water oxidation process to produce key *OH intermediate in COF-BD2 is also greatly facilitated, boosting the yield of H2O2 (5211 μmol g-1 h-1) from water, oxygen, and light without sacrificial agents or additional energy consumption. We further demonstrate that H2O2 can be efficiently produced by COF-BD2 in broad pH range, in real water, and in enlarged reactor with using natural sunlight for water decontamination.
Using data from the China Family Panel Studies (CFPS), this study examines the impact of art education on Chinese citizens’ trust in Americans. We find that participation in art tutorials correlates with increased trust towards Americans, with the level of trust rising with time spent in art education. Further analysis indicates that this effect is more pronounced in males and individuals whose parents already hold positive views of Americans. These results highlight the role of art education in fostering intercultural understanding. The study contributes to the literature on trust formation and the effects of art education, underscoring the significance of cultural engagement in promoting cross-cultural trust in global relations.
Addressing poverty is paramount, aligning with the first Sustainable Development Goal focused on eradicating poverty in all its forms. While the effects of high-speed rail (HSR) on absolute poverty have been documented, its impact on relative poverty remains understudied. This paper examines the influence of HSR on household relative poverty in China through a quasi-experimental design. The main results are as follows: (1) The opening of HSR significantly reduced the household relative poverty by approximately 1.8 %. (2) This alleviation effect primarily transpires through the expansion of economic activities and employment opportunities. (3) Notably, the impact of HSR is more pronounced in lower-ranked, smaller cities and in the western regions of China. Moreover, households with migrant workers or those engaged in non-agricultural sectors derive greater benefits from HSR developments. Our results suggest that HSR opening could have contributed to China’s relative poverty alleviation. Policymakers can consider the role of transportation infrastructure in mitigating household relative poverty, especially for low rank cities, small cities and periphery regions in other developing countries.
The advantage of Chinese-as-a-heritage-language (CHL) learners in acquiring Chinese has been widely recognized. However, it is still unclear whether the effect of CHL background on Chinese receptive vocabulary breadth varies across different countries. To address this gap, the present study recruited 232 Chinese language learners (half were CHL learners) from Indonesia and Thailand and administered a Chinese vocabulary proficiency test. The results of regression analysis revealed an interaction effect between country and CHL background on vocabulary breadth, with the contribution of CHL background to vocabulary breadth more robust in the Indonesian group than that in the Thai group. Interviews were then conducted to explore the factors that might influence such an interaction effect. Analysis of the interview data found that the influencing factors could be categorized into four themes, including individual differences, family background, Chinese language education and socio-cultural factors. The overall results were discussed within the framework of ecological system theory, and pedagogical implications for CHL learners were proposed.
Worldwide, humanities and social sciences (HSS) scholars produce and disseminate knowledge in an unequal global knowledge space, which can be caused by various structural, epistemological, and individual-level factors. Although global epistemic injustice receives much attention, the factors contributing to it, including the extraverted mindsets and practices of non-Euro-American scholars, remain less discussed. This article draws on semibiographical interviews with 30 high-achieving ethnic Chinese HSS scholars in mainland China, in Hong Kong, and overseas. It explores how these scholars display intellectual extraversion and why and how they are reflexive about and confronting it. The findings reveal three manifestations of intellectual extraversion, four sources of reflexivity regarding such extraversion, and three ways to confront it. The research uncovers the continuous reflexivity and efforts of ethnic Chinese HSS scholars in dealing with lingering epistemic discontinuities and exclusions and sheds light on new possible approaches to challenging global epistemic injustice in HSS research.
Insufficient charge separation and sluggish two-electron water-oxidation reaction are two critical factors restricting the photosynthesis performance of metal-free covalent organic frameworks (COFs) for hydrogen peroxide (H2O2) generation from naturally abundant water and air. Herein, we develop a facile strategy to simultaneously boost the charge-separation efficiency and water-oxidation capability through constructing short and rapid charge-transfer tunnels within highly charge-confined COFs via replacing the phenyl with pyrimidine. Compared with a single charge-transfer tunnel within a lowly charge-confined COF-5-(4-aminophenyl)pyrimidin-2-amine (APM) with pyrimidine, dual charge-transfer tunnels are constructed within a highly charge-confined COF-5,5′-bipyrimidine-2,2′-diamine (BPM) with bipyrimidine due to the ground-state charge transfer between para-carbon and meta-nitrogen, which significantly accelerates the intermolecular charge-transfer process and prevents charge recombination. This strategy also decreases the energy barrier of rate-determining water oxidation in H2O2 photosynthesis and thus promotes the effective generation of the key *OH intermediates, facilitating the generation of H2O2 at a production rate of 5521 μmol g−1 h−1 from water, oxygen and light without sacrificial reagents or additional energy consumption by COF-BPM. Furthermore, COF-BPM can also efficiently produce H2O2 under broad pH conditions, in widely available real water, on a floatable foam sheet, in a continuous-flow reactor and in a scaled-up reactor by using natural solar light for water decontamination.
Pressure sensors, especially the typical capacitive sensors that feature low power consumption, have drawn considerable interest in emerging and rapidly growing fields such as flexible electronics and humanoid robots, but often suffer from limited performance. Here, we report a contact-dominated design for capacitive pressure sensors to dramatically improve the sensing response and linearity over a broad pressure range. This design is implemented by utilizing hierarchical microstructured electrodes made of robust conductive composites with metallic coverage and layered dielectrics with high unit-area capacitance to realize localized electric-displacement-field-enhanced capacitance change. We demonstrate a significant improvement in pressure response beyond 3000 and a sensing range exceeding 1 MPa, particularly with a near-linear response (optimized R2 of 0.9998) and high sensitivity of 9.22 kPa−1 in a wide pressure range of 0–100 kPa. Moreover, we present that the integration of the contact-dominated sensor with floating-gate low-dimensional semiconductor transistors can provide a transduced electrical response of \textasciitilde4 × 105 at a low operating voltage of 2.66 V due to the greatly enhanced pressure response. We also demonstrate the potential applications of our sensor in fluid physical property evaluation and precise dynamic control of a robotic arm for manipulation tasks.
As a judicious correspondence to the classical maxcut, the anti-Cheeger cut has more balanced structure, but few numerical results on it have been reported so far. In this paper, we propose a continuous iterative algorithm (CIA) for the anti-Cheeger cut problem through fully using an equivalent continuous formulation. It does not need rounding at all and has advantages that all subproblems have explicit analytic solutions, the objective function values are monotonically updated and the iteration points converge to a local optimum in finite steps via an appropriate subgradient selection. It can also be easily combined with the maxcut iterations for breaking out of local optima and improving the solution quality thanks to the similarity between the anti-Cheeger cut problem and the maxcut problem. The performance of CIAs is fully demonstrated through numerical experiments on G-set from two aspects: one is on the solution quality where we find that the approximate solutions obtained by CIAs are of comparable quality to those by the multiple search operator heuristic method; the other is on the computational cost where we show that CIAs always run faster than the often-used continuous iterative algorithm based on the rank-two relaxation.
Injection of bacteria with petroleum degrading capability into contaminated sites is one of the most cost-effective and environmental friendly strategies for the successful remediation of petroleum-contaminated groundwater. The successful in-situ bioremediation of petroleum contamination in subsurface is greatly impacted by the mobile/retention performance of petroleum-degrading bacteria in porous media, which yet is not well understood. The present study systematically investigated the mobile performance of petroleum-degrading strains in porous media with petroleum contamination under environmentally relevant solution and flow conditions. We found that although the mobile performance of petroleum-degrading bacteria was similar to petroleum non-degrading bacteria in uncontaminated porous media, bacteria containing different petroleum degrading function yet exhibited opposite transport behaviors in petroleum contaminated porous media. Enhanced mobility in porous media with petroleum contamination was achieved for petroleum non-degrading bacteria, while reduced mobility was obtained for petroleum-degrading bacteria. Combining the batch adsorption experiments, capillary chemotaxis assays, in-situ microfluidic chamber experiments together with theoretical calculation, we found that the opposite mobile performance observed for bacteria containing different petroleum degrading functions could be mainly attributed to their different chemotactic responses towards petroleum with negative and positive chemotaxis response respectively for non- and petroleum-degrading bacteria. Clearly, pollutant-degrading bacteria exhibited different mobile performance from non-degrading bacteria in contaminated porous media. The previous findings achieved from the model bacteria without pollutant-degrading capability could not be simply used to predict the mobile performance of pollutant-degrading bacteria. To ensure the successful implementation of in-situ bioremediation, the mobility of pollutant-degrading bacteria in contaminated porous media should be fully understood.
Mineral precipitation is ubiquitous in natural and engineered environments, such as carbon mineralization, contaminant remediation, and oil recovery in unconventional reservoirs. The precipitation process continuously alters the medium permeability, thereby influencing fluid transport and subsequent reaction kinetics. The diversity of preferential precipitation zones controls flow and transport efficiency as well as the capacity of mineral sequestration and immobilization. Taking barite precipitation as an example, previous studies have examined this process in porous and/or fractured media, but pore-scale mechanisms under varying flowing and geochemical conditions remain unexplored. In this study, we conducted real-rock microfluidic experiments to investigate the precipitation dynamics within a fractured porous system. Direct observations of the evolution of the porous structure and flow channel and quantifications of barite precipitation dynamics using X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), revealed two distinct precipitation regimes: precipitation on the fracture surface (regime I) and precipitation in the alteration zone (regime II). Through theoretical analysis of the rate of advection and nucleation, we defined a dimensionless number Da above which regime I occurs and regime II prevails otherwise. At the large Da number, when the precipitation rate is large compared with the flow rate, precipitation on the fracture surface is favored. As the precipitation regimes are expected to impact differently the permeability of the fractured porous media, the mass transfer across matrix and fractures, and the spatial distributions of coprecipitated contaminants, our work sheds light on accurately modeling reactive transport in fractured porous media across diverse applications.
