Severe regional haze pollution events occurred in eastern and central China in January 2013, which had adverse effects on the environment and public health. Extremely high levels of particulate ...matter with aerodynamic diameter of 2.5 μm or less (PM2.5) with dominant components of sulfate and nitrate are responsible for the haze pollution. Although heterogeneous chemistry is thought to play an important role in the production of sulfate and nitrate during haze episodes, few studies have comprehensively evaluated the effect of heterogeneous chemistry on haze formation in China by using the 3-D models due to of a lack of treatments for heterogeneous reactions in most climate and chemical transport models. In this work, the WRF-CMAQ model with newly added heterogeneous reactions is applied to East Asia to evaluate the impacts of heterogeneous chemistry and the meteorological anomaly during January 2013 on regional haze formation. As the parameterization of heterogeneous reactions on different types of particles is not well established yet, we arbitrarily selected the uptake coefficients from reactions on dust particles and then conducted several sensitivity runs to find the value that can best match observations. The revised CMAQ with heterogeneous chemistry not only captures the magnitude and temporal variation of sulfate and nitrate, but also reproduces the enhancement of relative contribution of sulfate and nitrate to PM2.5 mass from clean days to polluted haze days. These results indicate the significant role of heterogeneous chemistry in regional haze formation and improve the understanding of the haze formation mechanisms during the January 2013 episode.
Extreme haze episodes repeatedly shrouded Beijing during the winter of 2012-2013, causing major environmental and health problems. To better understand these extreme events, we performed a ...model-assisted analysis of the hourly observation data of PM2.5 and its major chemical compositions. The synthetic analysis shows that (1) the severe winter haze was driven by stable synoptic meteorological conditions over northeastern China, and not by an abrupt increase in anthropogenic emissions. (2) Secondary species, including organics, sulfate, nitrate, and ammonium, were the major constituents of PM2.5 during this period. (3) Due to the dimming effect of high loading of aerosol particles, gaseous oxidant concentrations decreased significantly, suggesting a reduced production of secondary aerosols through gas-phase reactions. Surprisingly, the observational data reveals an enhanced production rate of secondary aerosols, suggesting an important contribution from other formation pathways, most likely heterogeneous reactions. These reactions appeared to be more efficient in producing secondary inorganics aerosols than organic aerosols resulting in a strongly elevated fraction of inorganics during heavily polluted periods. (4) Moreover, we found that high aerosol concentration was a regional phenomenon. The accumulation process of aerosol particles occurred successively from cities southeast of Beijing. The apparent sharp increase in PM2.5 concentration of up to several hundred mu g m-3 per hour recorded in Beijing represented rapid recovery from an interruption to the continuous pollution accumulation over the region, rather than purely local chemical production. This suggests that regional transport of pollutants played an important role during these severe pollution events.
While some DNA base modifications such as 5-methylcytosine have been known and studied for decades, recent discoveries of a number of other modified bases have stimulated research to understand their ...origin and function. Chemistry-based methods for their detection and analysis have proven to be important for advancing the field. Here, we feature a selection of methods that have helped advance the field, along with some key advances in the understanding of how the chemistry of modified bases affects biological functions. We also discuss fundamental questions in the field that remain unanswered.
A lithium-ion capacitor was developed using a mixture of stabilized lithium metal powder and hard carbon as the anode electrode, while activated carbon was used as the cathode. A specific energy of ...approximately 82 Wh kg−1 was obtained based on the weight of electrode materials; however, when the electrolyte, separator, and current collectors were included, the specific energy of an assembled Li-ion capacitor was about 25 Wh kg−1. The capacitor was able to deliver over 60% of the maximum energy at a discharge C-rate of 44C. Through continuous galvanostatic charge/discharge cycling, the capacitance of the Li-ion capacitor degraded less than 3% over 600 cycles.
► Demonstrated a novel Li-ion capacitor structure and electrode composition. ► Achieved a specific energy of 82 Wh kg−1 based on the weight of electrode materials. ► Studied specific power, rate, cycle life, and electrochemical impedance spectra.
Assessing carbon footprint (CF) of crop production in a whole crop life-cycle could provide insights into the contribution of crop production to climate change and help to identify possible ...greenhouse gas (GHG) mitigation options. In the current study, data for the major crops of China were collected from the national statistical archive on cultivation area, yield, application rates of fertilizer, pesticide, diesel, plastic film, irrigated water, etc. The CF of direct and indirect carbon emissions associated with or caused by these agricultural inputs was quantified with published emission factors. In general, paddy rice, wheat, maize and soybean of China had mean CFs of 2472, 794, 781 and 222 kg carbon equivalent (CE)/ha, and 0·37, 0·14, 0·12 and 0·10 kg CE/kg product, respectively. For dry crops (i.e. those grown without flooding the fields: wheat, maize and soybean), 0·78 of the total CFs was contributed by nitrogen (N) fertilizer use, including both direct soil nitrous oxide (N2O) emission and indirect emissions from N fertilizer manufacture. Meanwhile, direct methane (CH4) emissions contributed 0·69 on average to the total CFs of flooded paddy rice. Moreover, the difference in N fertilizer application rates explained 0·86–0·93 of the provincial variations of dry crop CFs while that in CH4 emissions could explain 0·85 of the provincial variation of paddy rice CFs. When a 30% reduction in N fertilization was considered, a potential reduction in GHGs of 60 megatonne (Mt) carbon dioxide equivalent from production of these crops was projected. The current work highlights opportunities to gain GHG emission reduction in production of crops associated with good management practices in China.
The asymmetric mechanical response and corresponding statistical grain-scale slip/twinning activity for extruded Mg-(0~5 wt%)Y sheets during room-temperature uniaxial tension and compression along ...the extruded direction were investigated using slip trace analysis and EBSD-based misorientation analysis. The tension-compression asymmetry, in terms of yield strength, ultimate strength and uniform elongation, reduced with the addition of 0.5% Y to Mg. Increasing the Y concentration to 5% resulted in a reversed yield asymmetry (compressive yield strength > tensile yield strength). The non-basal slip activity increased (up to 31%) and the twinning activity decreased with increasing Y content, for both tension and compression. The Y-induced texture change did not significantly affect the pyramidal <c + a> slip, while it promoted basal slip and suppressed prismatic slip. The observed trends of the slip activity suggested that the critical resolved shear stress (CRSS) ratios of CRSSpyramidal <c+a>/CRSSbasal and CRSSpyramidal <c+a>/CRSSprismatic decreased with Y addition. The correlation between macroscopic asymmetric behavior and slip/twinning activity implied that the pronounced pyramidal <c + a> slip, together with the negligible twinning, were responsible for the reversed yield asymmetry. A higher activity of pyramidal <c + a> slip was observed when the slip plane underwent tension compared with that for compression.
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•RT T-C asymmetry of extruded Mg-(0-5)Y sheets was comprehensively and quantitatively investigated.•Statistical grain-scale slip/twinning activity was quantified and correlated to the macroscopic deformation behavior.•Non-basal slip increased, and twinning decreased with increasing Y alloying content.•Enhanced pyramidal slip was observed when the slip plane underwent tension.•The reversed asymmetry was rationalized by the pronounced pyramidal slip and negligible twinning.
Given good safety, low cost, and environmental friendliness, rechargeable aqueous zinc-ion batteries (ZIBs) are considered as a more feasible solution for grid-scale applications than Li-ion ...batteries. The availability of suitable cathode materials to store Zn2+ is a prerequisite to realize high-performance aqueous ZIBs. However, due to the high polarization of bivalent Zn2+, Zn-host cathode materials with excellent electrochemical performances are yet to be discovered. In this review, recent advances in the cathode materials of aqueous ZIBs, including different types of cathode materials, electrode reaction mechanisms, and strategies to enhance their electrochemical performance, are briefed. Finally, current challenges and perspectives on the cathodes of ZIBs are presented.
Abstract Objective In China, elderly make up a large proportion of the society, but their mental health is often overlooked. The aim of this study is to compare mental health and related influencing ...factors among the empty-nest and the non-empty-nest elderly, and attain the purpose of improving their quality of life. Study design Cross-sectional survey. Methods A cross-sectional survey was conducted among 488 elderly people aged 60–92 years in six districts of Taiyuan, China. A demographic questionnaire and SCL-90-R were employed to collect demographic variables and evaluate mental health, respectively. Multiple regression analysis was performed to estimate factors related to mental health of the elderly. Results The empty-nest elderly were mostly male, married, higher education level, higher income and living in urban areas. The scores of SCL-90-R among the empty-nest elderly were lower than those of the non-empty-nest elderly except for psychoticism. Comparing with scores of national norms, some dimension of SCL-90-R had statistically significant differences. Multiple regression analysis showed that the main risk factors of the empty-nest elderly were gender and income, whereas the main risk factor of the non-empty-nest elderly was chronic diseases. Conclusion The mental health status of the empty-nest elderly was better than that of the non-empty-nest elderly. Overall mental health of the study population was at a high level compared with national norms. The elderly who were male, with younger age, having higher income, and without chronic diseases had better mental health status.
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