Designing a highly active electrocatalyst with optimal stability at low cost is must and non‐negotiable if large‐scale implementations of fuel cells are to be fully realized. Zeolitic‐imidazolate ...frameworks (ZIFs) offer rich platforms to design multifunctional materials due to their flexibility and ultrahigh surface area. Herein, an advanced Co–Nx/C nanorod array derived from 3D ZIF nanocrystals with superior electrocatalytic activity and stability toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) compared to commercial Pt/C and IrO2, respectively, is synthesized. Remarkably, as a bifunctional catalyst (Ej = 10 (OER) − E1/2 (ORR) ≈ 0.65 V), it further displays high performance of Zn–air batteries with high cycling stability even at a high current density. Such supercatalytic properties are largely attributed to the synergistic effect of the chemical composition, high surface area, and abundant active sites of the nanorods. The activity origin is clarified through post oxygen reduction X‐ray photoelectron spectroscopy analysis and density functional theory studies. Undoubtedly, this approach opens a new avenue to strategically design highly active and performance‐oriented electrocatalytic materials for wider electrochemical energy applications.
A highly active bifunctional electrocatalyst is designed via a structural transformation of 3D ZIF nanocrystals into an array of 1D metal/N functionalized carbon nanorod frameworks. The obtained catalyst exhibits superior bifunctional activity and stability toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), leading to high Zn‐air battery performances compared to the state‐of‐the‐art counterparts.
There were two similar series of burst waiting time experiments carried out on Godiva-II and Caliban respectively and analyzed for neutron initiation study, unfortunately both the strength of ...spontaneous fission neutron source given in the published papers are not consistent with the spontaneous fission data of U-235 and U-238.
In this paper, the discrepancies of spontaneous fission data of U-235 and U-238 from different references are reviewed and clarified and the correct strength of spontaneous fission neutron source for Godiva-II and Caliban are calculated respectively, then the multiplication equivalence method of arbitrary source is introduced and the equivalent fundamental-mode(EFM) co-efficiencies of spontaneous fission neutron source for Godiva-II and Caliban are calculated with MC software, lastly the strength of neutron source for these two HEU metal burst reactor in EFM are deduced. The EFM neutron strength of this two burst reactors are much less than proposed values used for burst waiting investigation in published papers respectively, and with the new data, the inconsistency of burst waiting time to the published results is presented and discussed.
Replacement of noble‐metal platinum catalysts with cheaper, operationally stable, and highly efficient electrocatalysts holds huge potential for large‐scale implementation of clean energy devices. ...Metal–organic frameworks (MOFs) and metal dichalcogenides (MDs) offer rich platforms for design of highly active electrocatalysts owing to their flexibility, ultrahigh surface area, hierarchical pore structures, and high catalytic activity. Herein, an advanced electrocatalyst based on a vertically aligned MoS2 nanosheet encapsulated Mo–N/C framework with interfacial Mo–N coupling centers is reported. The hybrid structure exhibits robust multifunctional electrocatalytic activity and stability toward the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction. Interestingly, it further displays high‐performance of Zn–air batteries as a cathode electrocatalyst with a high power density of ≈196.4 mW cm−2 and a voltaic efficiency of ≈63 % at 5 mA cm−2, as well as excellent cycling stability even after 48 h at 25 mA cm−2. Such outstanding electrocatalytic properties stem from the synergistic effect of the distinct chemical composition, the unique three‐phase active sites, and the hierarchical pore framework for fast mass transport. This work is expected to inspire the design of advanced and performance‐oriented MOF/MD hybrid‐based electrocatalysts for wider application in electrochemical energy devices.
An advanced electrocatalyst is designed based on a vertically‐aligned MoS2 nanosheet encapsulated Mo–N/C framework with Mo–N coupling centers at the interface. The hybrid electrocatalyst exhibits high multifunctional activity and stability toward the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction, as well as high Zn–air battery performance.
The aim of this study is to explore the association between the aspartate amino transferase (AST)/alanine aminotransferase (ALT) ratio and all-cause mortality (ACM) in stable coronary artery disease ...(CAD) patients treated by percutaneous coronary intervention (PCI). The study is a secondary analysis of a retrospective cohort study involving 203 stable CAD patients. Patients were divided into two groups, based on the optimal AST/ALT ratio threshold calculated by the ROC curve (low group: AST/ALT ratio < 1.40; high group: AST/ALT ratio ≥ 1.40). Results were compared using hazard ratio (HR) and a 95% confidence interval (CI). ACM occurred in 18 patients after an average follow-up time of 749 (435-1122) days. Among them, ACM occurred in 6 patients in the low group and 12 patients in the high group, with significant differences between the groups (4.65% versus 16.22%, P value = 0.005). In the Kaplan-Meier analysis, an elevated AST/ALT ratio was associated with increased ACM in stable ACD patients (HR 3.78, 95% CI 1.44-9.93, P value < 0.001). An elevated AST/ALT ratio was still found to be an independent prognostic factor for ACM (HR 2.93, 95% CI 1.08-7.91, P value = 0.034) after adjusting for potential confounders. Therefore, an elevated AST/ALT ratio is an independent prognostic factor for ACM in stable ACD patients.
The technology of fault diagnosis is helpful to improve the reliability of wind turbines, and further reduce the operation and maintenance cost at wind farms. However, in reality, wind turbines are ...not allowed to operate with faults, so few fault samples could be obtained. With a small amount of training data, traditional fault diagnosis models that need huge samples under a deep learning framework are difficult to maintain with high accuracy and effectiveness. Few-shot learning can effectively solve the problem of overfitting caused by fewer fault samples in model training. In view of model-agnostic meta-learning (MAML), this paper proposes a model for few-shot fault diagnosis of the wind turbines drivetrain, which is named model-agnostic meta-baseline (MAMB). The training data is input to the base classification model for pre-training, then, some data is randomly selected from the training set to form multiple meta-learning tasks that are utilized to train the MAML to finally fine-tune the later layers of the model at a smaller learning rate. The proposed model was analyzed by the small samples of the bearing data from Case Western Reserve University (CWRU) data, the generator bearings, and gearboxes vibration data in wind turbines under randomly changing operating conditions. The results verified that the proposed method was superior in one-shot, five-shot, and ten-shot tasks of wind turbines.
Benthic oxygen flux with complex spatiotemporal variations is essential for the global budget of carbon dioxide and the regional security of water quality and ecology, but its dominant driver under ...different circumstances has yet to be identified. In this study, a parametric scheme of oxygen flux was proposed and validated with aquatic eddy correlation measurements and then coupled with a diagenesis model and a water environment model. The coupled model was applied to a river‐reservoir with significant environmental gradients in hydrodynamics, diagenesis, and hypoxia, which are three factors that competitively drive the variation in benthic oxygen flux. The results indicate that hydrodynamics dominate the flux in the riverine and thalweg areas, diagenesis is the dominant driver of the lacustrine and bank areas, and hypoxia shows dominance only in the hypolimnetic anoxic area. In general, diagenesis is the dominant driver of oxygen flux in river‐reservoirs, followed by hydrodynamics, both of which are more prominent than hypoxia. If the operated reservoir experiences a wet year, the dominance of hydrodynamics tends to increase, while that of diagenesis and hypoxia decreases. The three divers exhibit similar but more stable dominance in riverine systems than in reservoirs, while diagenesis becomes the exclusive driver of oxygen fluxes in lacustrine systems.
Plain Language Summary
The consumption of dissolved oxygen in sediments regulates the types of substances released from them. When the oxygen supply to the sediments is insufficient, they release substances with a stronger greenhouse effect (such as methane) and a more significant threat to water quality (such as heavy metals). Flow conditions, sediment features, and water properties collectively drive the variation in sediment oxygen consumption, but their relative importance within complex aquatic environments remains to be investigated. This study quantifies the dominance of these three drivers on sediment oxygen consumption in a river‐reservoir system and then establishes their relationship with spatiotemporal variations in the aquatic environment. Sediment features are the primary drivers of sediment oxygen consumption in the studied river‐reservoir, followed by flow conditions and water properties represented by oxygen concentrations. The results also suggest that the relative dominance of these three drivers in river‐type systems is similar to that in reservoirs, but the dominance of sediment features could further increase in lake‐type systems. This study highlights the variable role of factors driving sediment oxygen consumption, which is critical for quantifying the release of deoxygenation products in complex aquatic ecosystems.
Key Points
A practical parametric scheme for determining benthic oxygen fluxes was proposed and validated
River‐reservoirs have large environmental gradients in hydrodynamics, sedimentation, and stratification
Diagenesis is the primary driver of benthic oxygen fluxes in river‐reservoirs, followed by hydrodynamics and hypoxia
With rapid economic development, China has been plagued by choking air pollution in recent years, and the frequent occurrence of haze episodes has caused widespread public concern. The purpose of ...this study is to describe the sources and formation of haze, summarize the mitigation measures in force, review the relationship between haze pollution and public health, and to discuss the challenges, potential research directions and policy options. Haze pollution has both natural and man-made causes, though it is anthropogenic sources that are the major contributors. Accumulation of air pollutants, secondary formation of aerosols, stagnant meteorological conditions, and trans-boundary transportation of pollutants are the principal causes driving the formation and evolution of haze. In China, haze includes gaseous pollutants and fine particles, of which PM2.5 is the dominant component. Short and long-term exposure to haze pollution are associated with a range of negative health outcomes, including respiratory diseases, cardiovascular and cerebrovascular diseases, mental health problems, lung cancer and premature death. China has paid increasing attention to the improvement of air quality, and has introduced action plans and policies to tackle pollution, but many interventions have only temporary effects. There may be fierce resistance from industry groups and some government agencies, and often it is challenging to enforce relevant control measures and laws. We discuss the potential policy options for prevention, the need for wider public dialogue and the implications for scientific research.
The sources, formation, and health effects of haze pollution in China. Display omitted
•The relationship between haze pollution and public health in China was reviewed for the first time.•The sources and formation of haze episode were described.•The existing mitigation measures and challenges faced China were summarized.•The potential policy options and future research directions were discussed.•Individual prevention measures during haze events from the public aspects were further suggested.
Polymer flooding and polymer/surfactant flooding have achieved good efficiency in the application of conventional reservoir, but the existed chemical flooding technology cannot cannot address the ...issues of the requirements of chemical flooding in high salinity reservoir. Under the condition of high salinity reservoir, due to the increase of calcium and magnesium ions, the increasing viscosity effect of oil displacement system is lost. In order to study the feasibility of applying nanomaterials in the field of enhanced oil recovery under the conditions of high salinity reservoir, develop a low-concentration and high-efficiency oil displacement system. EAPC solution has advantages in reducing interfacial tension, but its viscosity is not good. Therefore, hydrophobically modified silica nanoparticles (SiO2 NPs) were added to the carboxylic acid-type erucic acid amide propyl betaine (EAPC) solution. The interaction between EAPC and hydrophobic carbon chains led to the exposure of carboxyl groups, thus making the system more stable. The interfacial activity and zeta potential were studied, and the interaction mechanism between modified SiO2 Ps and EAPC was obtained. The results show that when the EAPC concentration is 0.3%, the apparent viscosity of the modified silica nanoparticles (SiO2 NPs) composite system can reach 40 mPa3·s, and the oil-water interfacial tension can be reduced to 10-2 mN/m. The micro-visualization model and the simulated oil displacement experiment proved that the modified SiO2 NPs (0.3%)/EAPC (0.3%) composite system has a variety of oil displacement mechanisms. Under the simulated reservoir conditions (total salinity of 25000 mg/L, calcium and magnesium ion concentration of 500 mg/L, 70 °C), it is proved that the modified SiO2 NPs composite system had good viscoelasticity and improved oil washing efficiency. The oil displacement system has guiding significance for effectively enhancing the recovery of high salinity reservoir.
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•The novel amphiphilic polyarylene ether nitrile (amPEN) has been synthesized.•Hydrophobic quantum dot (QD) is transferred into water via self-assembling of amPEN.•Dual emitting ...superparticles (SP) are obtained by encapsulating QD with amPEN.•The obtained SP serve as solid-state effective fluorescence probe for Ag+ detection.•SP doped polydimethylsiloxane can be used as flexible optical strain sensor.
In this work, a novel amphiphilic copolymer named polyarylene ether nitrile (amPEN) was synthesized and further employed to encapsulate oleic acid (OA) capped CdSe@CdS QD via one-step microemulsion self-assembling, which contributed to the facile fabrication of water dispersible QD/amPEN core-shell superparticles (SP) showing dual emissive feature. It was found that the obtained QD/amPEN core-shell SP can be employed as the sensitive and selective fluorescent probe for determination of trace concentration of Ag+ down to 1nM via the photo-induced electron transfer. More interestingly, the obtained QD/amPEN core-shell SP can be integrated with polydimethylsiloxane (PDMS) to fabricate robust luminescent solid state films that still demonstrated sensitive detection of Ag+ even after placing in water for six days. Furthermore, the QD/amPEN core-shell SP doped PDMS film exhibited the stretching dependent luminescent emission, which implied the composite materials could be also developed as flexible optical strain sensors. Given the facile fabrication and competitive sensing performance both in solution phase and solid state, the present work basically provides a universal strategy for the construction of versatile multifunctional luminescent sensors using QD and polyarylene ethers as building blocks.
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