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Designing an effective and stable composite photocatalyst is of significance for the further realization of practical applications. In this study, a series of CoP/CoO composites are ...successfully prepared by a straight one-step phosphating method. The reasonable design and controllable preparation of CoP/CoO composite make it exhibit improved photocatalytic performance for overall water splitting and excellent stability under visible light irradiation in comparison with pure CoO, which is derived from the CoP nanoparticles well dispersed on the (111) facets of CoO octahedrons, intimate interface between them and efficiently accelerated of photo-induced electrons from CoO to CoP. This study presents a simple method to design highly-effective composite photocatalysts for overall water splitting to meet the energy demand.
•Numerical simulations with linear stability analysis are conducted to study density-driven flow with dissolution in porous media.•A multiscale approach that combines Darcy-scale linear stability ...analysis and pore-scale simulations are performed.•The transport processes are largely dominated by the interplay among density contrast, reaction rate and porosity evolution.
In the present work, a suite of numerical experiments with linear stability analysis are conducted to study density-driven flow with chemical dissolution of two reactive fluids in synthetic porous media. Linear stability analysis at the Darcy scale is first performed to predict the interfacial phenomena and instability at the initial time. Pore-scale simulations using the lattice Boltzmann method (LBM) are further conducted to capture more mechanistic information and advance the understanding of the transport processes. Under different scenarios, it is demonstrated that the transport processes exhibit distinct behaviors, which are largely dominated by the interplay among density contrast, chemical reaction rate and evolution of the porosity/permeability. All the results indicate that the interfacial instability can be triggered by the density contrast between two miscible fluids, leading to the Rayleigh-Taylor (R-T) instability. The R-T instability can be suppressed by the heterogeneous surface reaction between the fluid and solid phases, which prevents the transport of the denser fluid. Over the long term, it is found that the interfacial instability is influenced by the evolution of the porosity/permeability due to dissolution, which potentially restarts the transport of the denser fluid.
The spatial heterogeneity and temporal variability of hillslope subsurface flow (SSF) generation are poorly understood in the alpine critical zone (CZ). Owing to the limitations of observation ...technology bottlenecks and harsh environments, existing studies lack a holistic and process‐based understanding of SSF generation, particularly for the deep CZ and annual freeze‐thaw (FT) cycle. This study improves the conventional trenching observation scheme and is the first to have successfully monitored SSF processes from the soil to the bedrock layer with high‐resolution from 2017 to 2020 in a headwater catchment of the Qinghai‐Tibetan Plateau. The results show that hillslope runoff generation exhibited similar trends over the years while exhibiting distinct patterns across seasons. Spatially, slope aspects significantly affect the runoff amount and ratio. The south‐facing slope is dominated by overland flow (OF, 84.2%–97.0%), while the north‐facing slope is dominated by SSF (88.9%–97.3%). The runoff depth of the north‐facing slope is 11.0 times that of the south‐facing slope. The SSF in the deep CZ accounts for 20.8%–37.8% of the total runoff along the north‐facing slope. Temporally, runoff generation exhibits distinct patterns across seasons. OF exhibits two different patterns, while SSF exhibits five across seasons. Our results indicate that runoff generation in different FT stages should be studied by the time phase. Therefore, we propose seasonal or FT period‐based classification criteria and divide OF and SSF into two and three consecutive periods throughout the calendar year. We suggest that these inferences and observations should be considered in the framework of hydrological models in cold regions.
Key Points
Overland and subsurface flow (SSF) exhibit distinguished patterns across seasons in a small headwater catchment on the Qinghai‐Tibetan Plateau
SSF in the deep critical zone composed of saprolite and weathered bedrock accounts for 20.8%–37.8% of the hillslope runoff
Slope aspect has significant impacts on the dominant flow regime, while freeze‐thaw cycles control the seasonal variation in SSF
Marcus theory states that the rate of charge transfer is directly proportional to the amount of intermolecular orbital overlap. Theoretically optimizing the electronic coupling through the ...orientation and distance which both can increase the frontier orbital overlap between molecules is an attractive route to potentially provide theoretical insight for discovering new high performance semiconductor materials. To investigate how these parameters qualitatively affect charge transfer of model systems, unconstrained dimer optimizations with MP2 and dispersion-corrected DFT methods were used to probe the π–π interactions of methylated, fluorinated, and trifluoromethylated benzene, pyridine, and bipyridine dimers. These systems can serve as simplified models representing weak noncovalent interactions in organic semiconductor materials. Enhanced intermolecular interaction energies, reduced π–π distances, and more favorable cofacial orientations were found with the trifluoromethylated dimers compared to fluorinated and methylated dimers studied. Similar effects were found with donor–acceptor pairs that represent organic p-n heterojunction systems. These enhanced π–π interactions are likely caused by increased molecular quadrupole moment and dispersion interaction associated with trifluoromethylation. This computational study illustrates the strong potential of trifluoromethylation and, possibly perfluoroalkylation of acenes and heteroacenes, leading qualitatively to enhanced electron transfer through better π–π stacked structures, making them viable candidates for use as n-type organic semiconductor materials. The findings also provide insight for fundamental interactions between drug molecules that include fluorinated and trimethylfluorinated aromatics binding to protein receptors.
Maternal separation (MS) causes long-lasting epigenetic changes in the brain and increases vulnerability to traumatic events in adulthood. Of interest, there may be sex-specific differences in these ...epigenetic changes. In this study, the extent of histone acetylation in the hippocampus (HIP) and the expression of BDNF were measured to determine whether BDNF influences risk of PTSD following MS in early life. Rat offspring were separated from their dams (3 h/day or 6 h/day from PND2~PND14). Then, pups were treated with a single prolonged stress (SPS) procedure when they reached adulthood (PND80). In animals stressed with the SPS procedure in adulthood, those that had increased MS intensity in childhood demonstrated more significant changes in performance on tests of anxiety, depression, and contextual fear memory. Reduced levels of total BDNF mRNA and protein were observed after SPS treatment and further declined in groups with greater MS time in childhood. Interestingly, these changes were correlated with decreased H3K9ac levels and increased HDAC2 levels. Additional MS also led to more severe ultrastructural synaptic damage in rats that experienced the SPS procedure, particularly in the CA1 and CA3 region of the HIP, reflecting impaired synaptic plasticity in these regions. Interestingly, male rats in the MS3h-PTSD group showed decreased anxiety, but no similar changes were found in female rats, suggesting a degree of gender specificity in coping with stress after mild MS. In summary, this study suggests that the epigenetic signatures of the BDNF genes can be linked to HIP responses to stress, providing insights that may be relevant for people at risk of stress-related psychopathologies.
To improve the adaptability of the robot pan–tilt to the high-temperature environment, a design scheme for a composite thermal protection structure composed of aerogel felt, hollow glass, and skin is ...proposed. The effects of aerogel felt thickness, glass type, and ambient temperature on the thermal protection performance of the structure are studied, using a fluid–solid–thermal coupling model. Numerical results show that the structure exhibits good protection performance, and that the thermal resistance distribution changes the main path of heat transmission. The optimal thickness of the aerogel felt is approximately 8 mm. Compared to 3 mm, 5 mm, and 10 mm thicknesses, 8 mm reduces the maximum temperature by 15.90%, 8.37%, and 6.22%, and reduces the total entropy by 79.23%, 52.44%, and 12.5%. Lower thermal conductivity of the gas inside the hollow glass results in decreased maximum temperatures and total entropy. Using argon-filled hollow glass at 573.15 K decreases maximum temperature by 33.52% and 8.40%, with a total entropy reduction of 33.46% and 6.04%, compared to the single-layer and air-filled glass. Higher ambient temperatures correlate with increased maximum temperature, total entropy, and average surface-heat-transfer coefficient, indicating that the adaptability of the structure to high-temperature environments is limited.
Single-phase converters are commonly used in small and medium power supply systems, but their inherent 2ω-ripple power has a significant impact on system performance, including maximum power point ...fluctuations in photovoltaic systems, low-frequency light flicker in light-emitting diode lighting systems, and the efficiency and lifetime of fuel cell systems. In this paper, we review the single-phase converter topologies with 2ω-ripple suppress and provide a comprehensive summary and comparison of power decoupling topologies. Power decoupling topology can be divided into passive power decoupling topology (PPDT) and active power decoupling topology (APDT). Among them, the PPDT does not need to add switching devices and has simple structure and convenient control. However, due to the volume and life of the energy storage element, the application place is also limited. The APDT needs to add an active power buffer to suppress the 2ω-ripple power. According to the different working modes of the active power buffer switch, the APDT can be divided into independent APDT and dependent APDT. The former operates independently in the original converter, while the latter needs to share switching devices or energy storage elements with the original converter. This paper systematically summarizes the existing single-phase converter circuit topologies for suppressing 2ω-ripple and their development process, aiming to provide classification and comparison for researchers and engineers to select the circuit topologies suitable for their specific applications.
Text classification is an important topic in natural language processing, with the development of social network, many question-and-answer pairs regarding health-care and medicine flood social ...platforms. It is of great social value to mine and classify medical text and provide targeted medical services for patients. The existing algorithms of text classification can deal with simple semantic text, especially in the field of Chinese medical text, the text structure is complex and includes a large number of medical nomenclature and professional terms, which are difficult for patients to understand. We propose a Chinese medical text classification model using a BERT-based Chinese text encoder by
N
-gram representations (ZEN) and capsule network, which represent feature uses the ZEN model and extract the features by capsule network, we also design a
N
-gram medical dictionary to enhance medical text representation and feature extraction. The experimental results show that the precision, recall and
F
1-score of our model are improved by 10.25%, 11.13% and 12.29%, respectively, compared with the baseline models in average, which proves that our model has better performance.
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