Does national air quality monitoring reduce local air pollution? The case of PM2.5 for China.

Fine particulate matter (PM2.5) has become a major pressing challenge for China and remains a concern of its central government. This paper draws on a natural experiment generated by the National Ambient Air Quality Monitoring Network (NAAQMN) program in China to explore whether national air quality monitoring reduces local air pollution. In this study, we use a city-level dataset for 4200 Chinese cities covering 2001-2015 and a difference-in-differences (DID) assessment design to assess the impact of the NAAQMN program on local PM2.5 emissions in China. The results suggest that the NAAQMN program significantly reduces the local PM2.5 concentrations by 1.325 mg/m3, and each additional NAAQMN program will cause a decrease of 0.154 mg/m3 in the local PM2.5 concentrations. Furthermore, we determine the heterogeneous impacts of the NAAQMN program on local PM2.5 emission levels through the local government leaders' characteristics, PM2.5 emission levels, and economic development levels. In addition, a mediation effect is found between the NAAQMN program and local PM2.5 emissions through the efficiency of environmental governance. The Chinese government should continue to promote the implementation of the NAAQMN program by promoting the NAAQMN program to the county and rural areas as well as adding the sites of the NAAQMN program in the existing cities. Also, during the process of promoting the NAAQMN program, sufficient differentiation in policies should be developed for different cities.

Effect of Ball Milling Time on the Microstructure and Properties of High-Silicon-Aluminum Composite.

The duration of ball milling greatly influences the characteristics of high-silicon-aluminum composite during the ball milling process. This study examines how the microstructure, thermal conductivity, and hardness of a high-silicon-aluminum composite are affected by different ball milling times. We exposed the powder to various durations of ball milling and employed different pellet ratios. Following this treatment, the powder underwent consolidation via discharge plasma sintering. Our findings show that with a pellet ratio of 10:1 and a milling duration of 8 h, the powder particles were refined, resulting in a more uniform and dense material composition. This refined material boasted a thermal conductivity of 111.6 W/m·K, a Brinell hardness of 136.8 HBW, and a density of 2.304 g/cm3. This method facilitates the creation of a uniform composite powder composition. It encourages the development of a fine-grain structure, which enables the production of particle-reinforced composites with superior properties.

A Wearable Electrochemical Sensor Based on Anti-Fouling and Self-Healing Polypeptide Complex Hydrogels for Sweat Monitoring.

Although continuous monitoring of constituents in complex sweat is crucial for noninvasive physiological evaluation, biofouling on the sweat sensor surface and inadequate flexible self-healing materials restrict its applications. Herein, a fully self-healing and strong anti-biofouling polypeptide complex hydrogel (AuNPs/MoS2/Pep hydrogel) with excellent electrochemical performances was created. The anti-fouling electrochemical sweat sensor was fabricated based on the AuNPs/MoS2/Pep hydrogel to address these issues. It was found that the polypeptide hydrogel was designed to form a network structure and carried abundant hydrophilic groups, resulting in a AuNPs/MoS2/Pep hydrogel with superior anti-biofouling properties in sweat for 30 min and even long-term stability in undiluted human sweat. In addition, SEM, TEM, UV, XPS, and infrared spectrogram demonstrated that the binding force of π-π stacking force between MoS2 and naphthalene groups in the designed peptide endowed the polypeptide complex hydrogel with an excellent self-healing property. Furthermore, the polypeptide complex hydrogel preserved wearable device function of continuously monitoring uric acid (UA) and ascorbic acid (AA) in sweat in situ. This novel fabricated sweat sensor with high anti-biofouling ability, excellent self-healing property, and sensitive and selective analytical capability describes a new opportunity for health monitoring in situ.

Theoretical Studies of the Spin-Dependent Electronic Transport Properties in Ethynyl-Terminated Ferrocene Molecular Junctions.

The spin-dependent electron transport in the ferrocene-based molecular junctions, in which the molecules are 1,3-substituted and 1,3'-substituted ethynyl ferrocenes, respectively, is studied by the theoretical simulation with nonequilibrium Green's function and density functional theory. The calculated results suggest that the substitution position of the terminal ethynyl groups has a great effect on the spin-dependent current-voltage properties and the spin filtering efficiency of the molecular junctions. At the lower bias, high spin filtering efficiency is found in 1,3'-substituted ethynyl ferrocene junction, which suggests that the spin filtering efficiency is also dependent on the bias voltage. The different spin-dependent transport properties for the two molecular junctions originate from their different evolutions of spin-up and spin-down energy levels.