Samples of airborne PM2.5 particles were collected during Fall 2011 from Guangzhou urban area. The morphology and size distribution of individual particles were analyzed by a Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectrometer(SEM-EDX) and Image Analysis System. Based on the morphology, three typical particles(soot aggregates, minerals, and coal fly ash) and other unknown particles in PM2.5 were identified. Results showed that the number-size distribution of PM2.5, peaking in the range of 0.1~0.2 μm, was dominated by the condensing sub-mode within the accumulation mode where gas phase reaction products were distributed. Both number and volume contribution of three typical particles were on the order of mineral soot aggregate fly ash. Minerals were mainly distributed in range of 0.1~0.3 μm with 41.97% in number percentage. The percentage of minerals in range of 0.1~0.2 μm was as high as 26.42%, which was the major factor influencing the overall size distribution of PM2.5. Size distributions of PM2.5particles were fairly similar during different sampling period(morning, afternoon, evening) as well as before and after raining, but the proportions of particles having sizes less than 0.1 μm were significantly decreased in the evening and after raining.
Nitrous oxide (N2O) emission from wastewater treatment plants (WWTPs) has received increasing attention. This paper presented how N2O emission was significantly reduced in a pilot-scale Carrousel oxidation ditch under reasonable nitrification and denitrification. N2O emission from the reactor was found as low as 0.027% of influent nitrogen, which was much less than that from other processes. Further measurements on spatial variation of N2O emission in the alternative aerobic/anoxic zones with help of a series of batch experiments demonstrated that about 90% of the emission was contributed by nitrifier denitrification (ND). Moreover, the taxonomic analysis based on high through-put 16S rRNA gene sequencing revealed that the high abundance of denitrifying bacteria and nitrite-oxidizing bacteria (NOB) was responsible for low nitrite accumulations and consequent low N2O emissions. However, N2O generation would be greatly increased upon the normal operation being shocked by either ammonia overload or aeration failure of the oxidation ditch system. (C) 2014 Elsevier Ltd. All rights reserved.
In the past two years, the power conversion efficiency (PCE) of organic-inorganic hybrid perovskite solar cells has significantly increased up to 20.1%. These state-of-the-art new devices surpass other third-generation solar cells to become the most promising rival to the silicon-based solar cells. Since the morphology of the perovskite film is one of the most crucial factors to affect the performance of the device, many approaches have been developed for its improvement. This review provides a systematical summary of the methods for morphology control. Introductions and discussions on the mechanisms and relevant hotspots are also given. Understanding the growth process of perovskite crystallites has great benefits for further efficiency improvement and enlightens us to exploit new technologies for large-scale, low-cost and high-performance perovskite solar cells.
Trifluoromethane (CHF3, HFC-23), with a 100-year global warming potential (GWP) of 12400, is regulated under the Kyoto Protocol. HFC-23 emissions in East Asia, especially in China, are currently thought to represent the majority of global HFC-23 emissions. This study provides both a bottom-up emission inventory and the multiannual top-down estimate of HFC-23 emissions in East Asia during 2007-2012. The new bottom-up inventory yields improved simulated HFC-23 mixing ratios compared to previous bottom-up inventories. The top-down estimate uses inverse modeling to further improve the model-measurement agreement. Results show that China contributed 94-98% of all HFC-23 emissions in East Asia. Annual a posteriori emissions from China were around 6.3 Gg/yr during the period 2007-2010 after which they increased to 7.1 +/- 0.7 Gg/yr in 2011 and 8.8 +/- 0.8 Gg/yr in 2012. For the first time, this study also provides a top-down estimate of HFC-23/HCFC-22 (chlorodifluoromethane, CHClF2) coproduction ratios in non-CDM (Clean Development Mechanism) HCFC-22 production plants as well as in all HCFC-22 production plants in China.
This paper concentrates on a (1+1)-dimensional nonlinear Dirac (NLD) equation with a general self-interaction, being a linear combination of the scalar, pseudoscalar, vector and axial vector self-interactions to the power of the integer $k+1$. The solitary wave solutions to the NLD equation are analytically derived, and the upper bounds of the hump number in the charge, energy and momentum densities for the solitary waves are proved analytically in theory. The results show that: (1) for a given integer $k$, the hump number in the charge density is not bigger than $4$, while that in the energy density is not bigger than $3$; (2) those upper bounds can only be achieved in the situation of higher nonlinearity, namely, $k\in\{5,6,7,\cdots \}$ for the charge density and $k\in\{3,5,7,\cdots\}$ for the energy density; (3) the momentum density has the same multi-hump structure as the energy density; (4) more than two humps (resp. one hump) in the charge (resp. energy) density can only happen under the linear combination of the pseudoscalar self-interaction and at least one of the scalar and vector (or axial vector) self-interactions. Our results on the multi-hump structure will be interesting in the interaction dynamics for the NLD solitary waves.
BACKGROUND: Lower neighborhood-level socioeconomic status (SES) is associated with an increased risk of vascular disease in developed countries. AIMS: This study aims to identify village- and individual-level determinants of stroke and coronary heart disease (CHD) in a rural Chinese population. METHODS: We analyzed data from a population-based survey of 14,424 rural Chinese adults aged over 40 years from 54 villages. Primary outcomes were stroke and coronary heart disease (CHD) prevalence. Village-level SES was determined from the Chinese government's official statistical yearbook. Individual-level characteristics were obtained by in-person interviews. Prevalence rate ratios (RRs) and 95% confidence intervals (95% CIs) were calculated using generalized linear mixed models with log-link function to explore associations of village-level SES and individual social, demographic, and cardiovascular risk factors with stroke or CHD. Variance was expressed using the median rate ratio (MRR) and interval rate ratio (IRR). RESULTS: Village accounted for significant variability in the prevalence of stroke (MRR = 1.70; 95% CI: 1.42-1.94; P < 0.05) and CHD (MRR = 1.59; 95% CI: 1.35-1.78, P < 0.05), with village-level income alone accounting for 10% and 13.5% of between-village variation in stroke and CHD, respectively. High-income villages were at higher risk of both stroke (RR = 1.69, 95% CI: 1.09-2.62) and CHD (RR = 1.63, 95% CI: 1.13-2.34) than lower-income villages. Among individual-level risk factors, hypertension was associated with a higher prevalence of stroke (RR = 2.33, 95% CI: 1.93-2.80) than CHD (RR = 1.58, 95% CI: 1.38-1.82), whereas obesity was only associated with CHD (RR = 1.43, 95% CI: 1.23-1.66). In addition, there was an interaction between age and income; residents of higher-income villages below age 60 had a higher prevalence of CHD (RR = 1.58, 95% CI: 1.15-2.18) but not stroke. CONCLUSIONS: There were differences in vascular risk across rural villages in China, with higher lifetime stroke and CHD prevalence in higher-income villages. For CHD, neighborhood effects were stronger among younger residents of high-income villages. The results may have implications for public health interventions targeting populations at risk.
BACKGROUND: Lower neighborhood-level socioeconomic status (SES) is associated with an increased risk of vascular disease in developed countries.
AIMS: This study aims to identify village- and individual-level determinants of stroke and coronary heart disease (CHD) in a rural Chinese population.
METHODS: We analyzed data from a population-based survey of 14,424 rural Chinese adults aged over 40 years from 54 villages. Primary outcomes were stroke and coronary heart disease (CHD) prevalence. Village-level SES was determined from the Chinese government's official statistical yearbook. Individual-level characteristics were obtained by in-person interviews. Prevalence rate ratios (RRs) and 95% confidence intervals (95% CIs) were calculated using generalized linear mixed models with log-link function to explore associations of village-level SES and individual social, demographic, and cardiovascular risk factors with stroke or CHD. Variance was expressed using the median rate ratio (MRR) and interval rate ratio (IRR).
RESULTS: Village accounted for significant variability in the prevalence of stroke (MRR = 1.70; 95% CI: 1.42-1.94; P < 0.05) and CHD (MRR = 1.59; 95% CI: 1.35-1.78, P < 0.05), with village-level income alone accounting for 10% and 13.5% of between-village variation in stroke and CHD, respectively. High-income villages were at higher risk of both stroke (RR = 1.69, 95% CI: 1.09-2.62) and CHD (RR = 1.63, 95% CI: 1.13-2.34) than lower-income villages. Among individual-level risk factors, hypertension was associated with a higher prevalence of stroke (RR = 2.33, 95% CI: 1.93-2.80) than CHD (RR = 1.58, 95% CI: 1.38-1.82), whereas obesity was only associated with CHD (RR = 1.43, 95% CI: 1.23-1.66). In addition, there was an interaction between age and income; residents of higher-income villages below age 60 had a higher prevalence of CHD (RR = 1.58, 95% CI: 1.15-2.18) but not stroke.
CONCLUSIONS: There were differences in vascular risk across rural villages in China, with higher lifetime stroke and CHD prevalence in higher-income villages. For CHD, neighborhood effects were stronger among younger residents of high-income villages. The results may have implications for public health interventions targeting populations at risk.