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Because anthropogenic sulfur dioxide (SO2) emissions have decreased considerably in the last decade, PM2.5 pollution in China has been alleviated to some extent. However, the effects of reduced SO2 on the particle number concentrations and subsequent contributions of grown new particles to cloud condensation nuclei (CCN) populations, particularly at high altitudes with low aerosol number loadings, are poorly understood. In contrast, the increase in provincial forest areas in China with rapid afforestation over the last few decades expectedly increases the biogenic emissions of volatile organic compounds and their oxidized products as nucleating precursors therein. In this study, we evaluated the campaign-based measurements made at the summit of Mt. Tai (1534 m a.s.l.) from 2007 to 2018. With the decrease in SO2 mixing ratios from 15 ± 13 ppb in 2007 to 1.6 ± 1.6 ppb in 2018, the apparent formation rate (FR) of new particles and the net maximum increase in the nucleation-mode particle number concentration (NMINP) in the spring campaign of 2018 was 2- to 3-fold higher than those in the spring campaign of 2007 with almost the same occurrence frequency of new particle formation (NPF) events. In contrast, the campaign-based comparison showed that the occurrence frequency, in which the maximum geometric median diameter of the grown new particles (Dpgmax) was > 50 nm, decreased considerably from 43 %–78 % of the NPF events before 2015 to < 12 % in 2017–2018. Assuming > 50 nm as a CCN threshold size at high supersaturations, the observed net CCN production decreased from 3.7 × 103 cm−3 (on average) in the five campaigns before 2015 to 1.0 × 103 cm−3 (on average) in the two campaigns in 2017–2018. We argue that the increases in the apparent FR and NMINP are mainly determined by the availability of organic precursors that participate in nucleation and initial growth, whereas the decrease in the growth probability is caused by the reduced emissions of anthropogenic precursors. However, large uncertainties still exist because of a lack of data on the chemical composition of these smaller particles.

In this work, Ni-rich layered micron-sized LiNi0.8Co0.1Mn0.1O2 (SC-NCM) single crystals were prepared by wet ball-milling and molten-salt methods. Through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectrometry (XPS), the differences between SC-NCM and a commercial polycrystalline micron-sized NCM material (M-NCM) were compared. An extended sintering process for SC-NCM plays a role in decreasing cationic mixing accompanied by the ordered growth of single crystals. The SC-NCM sample presents homogeneous micron-sized crystals. The Ni3+ content in SC-NCM constitutes 90.45% of the total Ni content, while the Ni3+ in M-NCM constitutes only 68.49%. The existence of Ni2+ in ternary cathode materials is harmful to electrochemical stability and cyclic stability. The initial specific discharge capacity of SC-NCM (168 mAh g−1) is lower than that of M-NCM (187 mAh g−1); however, M-NCM shows a rapid decline in capacities and voltage plateaus from the 1st to 180th cycle. After 300 cycles at a 5 C rate, M-NCM remains only 42 mAh g−1 with a capacity retention rate of only 25.6% in comparison with SC-NCM with a remaining capacity of 80.7 mAh g−1 and a capacity retention of 62.0%. The effect of micron-sized single crystals on electrochemical properties during redox reactions is negative in terms of conductivity but positive in terms of structural stability.

A low-cost separable PCR chip, consisting of a reusable electrode part and a disposable PDMS-glass bonded chamber part, is presented. To achieve spatial uniformity of temperature over the whole reactive chamber, the heater of the electrode part with optimized electrode patterns based on traditional serpentine meanders was designed and simulated by using COMSOL Multiphysics. The separable PCR chip was fabricated using MEMS fabrication method. A temperature control thermal cycler system based on ARM microcontroller employing fuzzy-PID algorithm was constructed to provide the PCR required temperatures of denaturation, annealing and extension of each cycle. A thermal infrared imager was used to test the temperature distribution of the fabricated PCR chip. The temperature field simulation and infrared imager test verified that the heater with optimized electrode pattern can provide uniform temperature distribution in the area of the chamber where horizontal temperature fluctuation was within 1 °C. The performances of the microchip and the temperature control system were verified by β-actin gene PCR experiment. The 239 bp DNA segment of 6 μL sample in the micro-PCR chip was successfully amplified similarly to that in the conventional PCR instrument. The experiment proves that the fabricated PCR chip employing reusable heater of optimized electrode can provide efficient DNA amplification product while with less total time than the conventional PCR device. Multiple separable PCR chips with its reusable electrodes part employing the multi-channel thermal cycler system will be feasible for multiple DNA amplification.