科研成果

Fine particulate matter (PM2.5) pollution poses significant health risks worldwide, including metabolic syndrome-related diseases with the characteristic feature of insulin resistance. However, the mechanism and influencing factors of this effect are poorly understood. In this serial in vitro study, we aimed at testing the hypothesis that macrophage-mediated effects of PM2.5 on hepatic insulin resistance depend on its chemical composition. Mouse macrophages were exposed to PM2.5 that had been collected during summer or winter in Beijing, which represented different compositions of PM2.5. Thereafter, hepatocytes were treated with macrophage-conditioned medium (CM). PM2.5 induced interleukin-6, tumor necrosis factor-alpha, and monocyte chemoattractant protein-1 expression and secretion in macrophages, particularly after winter PM2.5 exposure. Correspondingly, winter CM weakened hepatocellular insulin-stimulated glucose consumption. Further investigation revealed that the normal insulin pathway was suppressed in winter CM-treated hepatocytes, with increased phosphorylation of insulin receptor substrate 1 at serine residue 307 (Ser307) and decreased phosphorylation of protein kinase B (PKB/AKT) and forkhead box transcription factor O1 (FoxO1). Moreover, c-Jun N-terminal kinase, a key moderator of the sensitivity response to insulin stimulation, was activated in hepatocytes treated with winter CM. Although further studies are warranted, this preliminary study suggested an association between PM composition and insulin resistance, thus contributing to our understanding of the systemic toxicity of PM2.5.

We establish a variational principle for properly mapping a fractional quantum Hall state to a fractional Chern insulator (FCI). We find that the mapping has a gauge freedom which could generate a class of FCI ground-state wave functions appropriate for different forms of interactions. Therefore, the gauge should be fixed by a variational principle that minimizes the interaction energy of the FCI model. For a soft and isotropic electron-electron interaction, the principle leads to a gauge coinciding with that for maximally localized two-dimensional projected Wannier functions of a Landau level.

Black carbon (BC) exerts profound impacts on air quality and climate because of its high absorption cross-section over a broad range of electromagnetic spectra, but the current results on absorption enhancement of BC particles during atmospheric aging remain conflicting. Here, we quantified the aging and variation in the optical properties of BC particles under ambient conditions in Beijing, China, and Houston, United States, using a novel environmental chamber approach. BC aging exhibits two distinct stages, i.e., initial transformation from a fractal to spherical morphology with little absorption variation and subsequent growth of fully compact particles with a large absorption enhancement. The timescales to achieve complete morphology modification and an absorption amplification factor of 2.4 for BC particles are estimated to be 2.3 h and 4.6 h, respectively, in Beijing, compared with 9 h and 18 h, respectively, in Houston. Our findings indicate that BC under polluted urban environments could play an essential role in pollution development and contribute importantly to large positive radiative forcing. The variation in direct radiative forcing is dependent on the rate and timescale of BC aging, with a clear distinction between urban cities in developed and developing countries, i.e., a higher climatic impact inmore polluted environments. We suggest that mediation in BC emissions achieves a cobenefit in simultaneously controlling air pollution and protecting climate, especially for developing countries.

Black carbon (BC) exerts profound impacts on air quality and climate because of its high absorption cross-section over a broad range of electromagnetic spectra, but the current results on absorption enhancement of BC particles during atmospheric aging remain conflicting. Here, we quantified the aging and variation in the optical properties of BC particles under ambient conditions in Beijing, China, and Houston, United States, using a novel environmental chamber approach. BC aging exhibits two distinct stages, i.e., initial transformation from a fractal to spherical morphology with little absorption variation and subsequent growth of fully compact particles with a large absorption enhancement. The timescales to achieve complete morphology modification and an absorption amplification factor of 2.4 for BC particles are estimated to be 2.3 h and 4.6 h, respectively, in Beijing, compared with 9 h and 18 h, respectively, in Houston. Our findings indicate that BC under polluted urban environments could play an essential role in pollution development and contribute importantly to large positive radiative forcing. The variation in direct radiative forcing is dependent on the rate and timescale of BC aging, with a clear distinction between urban cities in developed and developing countries, i.e., a higher climatic impact inmore polluted environments. We suggest that mediation in BC emissions achieves a cobenefit in simultaneously controlling air pollution and protecting climate, especially for developing countries.

Abstract Beginning in the early 1990’s, grazing lands once held in common were contracted to individual households in the rangeland regions of China. The resulting fragmentation of rangelands has led to ecological and social problems. As China seeks to address intractable poverty and rangeland degradation, attention has turned to rental, or transfer, of contracted grazing land as a market-based approach to re-aggregating grazing land into larger units that support economies of scale. However, given that many pastoral regions still maintain community customary institutions, what the relationship between market mechanisms and local customary institutions should be in rangeland management needs further analysis. This paper applies comparative case studies of two types of relationships between market mechanisms and customary institutions: (1) market mechanisms that replace customary institutions in the case of Axi village, and (2) market mechanisms that are embedded within customary institutions in Xiareer village. This allows contrast of the impacts of differing approaches on livelihoods, livestock production, and wealth differentiation among pastoral households. We found that there is a higher level of livestock mortality, lower livestock productivity, and higher livestock production cost in Axi Village compared to Xiareer Village. In addition, household asset levels are higher and there is less income differentiation in Xiareer Village. It is concluded that embedding market mechanisms within customary institutions has had notable benefits for the herders of Xiareer Village, because it is a better fit to the coupled pastoral social-ecological system. Based on these findings, we argue that in pastoral communities where the rangeland transfer system for contracted grazing land has not yet been implemented, it is critical to reconsider China’s current policy approach to pay greater attention to the innovative management systems being developed in local regions. Instead of considering market-based approaches as oppositional to traditional institutions, options that derive from the interaction of market-based and customary institutions should be considered.

New particle formation (NPF) and its subsequent growth plays a key role in air quality and climate change at regional and global scales. Especially under complex air pollution in China, nucleation and growth can be highly efficient, claimed to be a main source of cloud condensation nuclei (CCN) and an important cause of secondary aerosol pollution. Currently, the mechanism of particle formation and growth as well as its environmental effects are still poorly understood. Thereby, fully understanding of the atmospheric nucleation and subsequent growth still presents a big challenge to atmospheric chemistry researches. This study reviews the current results from studies on mechanisms and environmental effects of atmospheric nucleation and growth. We summarize that traditional nucleation theories such as binary nucleation of H2SO4-H2O, ternary nucleation of H2SO4-NH3-H2O, ion-induced nucleation are not capable in explaining new particle formation under complex air pollution, while newly proposed mechanisms such as organic acids and amine induced nucleation were not verified because of technique limitation. We propose that the future researches should focus on identifying the key chemical precursor response for driving nucleation and initial and subsequent growth, and understand the physical and chemical processing of new particle formation and growth. In particularly, application and development of novel techniques, such as APi-TOF-CIMS, PSM, Nano-HTDMA in new particle formation study is very important. Also, future researches should establish whole process tracking on new particle formation, from precursor, nucleation, growth till the environmental effects, by integrating field observation, chamber simulation, and modelling. Currently, the mechanism of highly efficient nucleation and rapid growth taking place under complex air pollution in China is urgently needed to be in-depth studied in order to improve our understanding of regional haze formation. This could be helpful to understand the similarity and difference in the nucleation mechanism between clean and polluted atmospheric environments.

New particle formation (NPF) and its subsequent growth plays a key role in air quality and climate change at regional and global scales. Especially under complex air pollution in China, nucleation and growth can be highly efficient, claimed to be a main source of cloud condensation nuclei (CCN) and an important cause of secondary aerosol pollution. Currently, the mechanism of particle formation and growth as well as its environmental effects are still poorly understood. Thereby, fully understanding of the atmospheric nucleation and subsequent growth still presents a big challenge to atmospheric chemistry researches. This study reviews the current results from studies on mechanisms and environmental effects of atmospheric nucleation and growth. We summarize that traditional nucleation theories such as binary nucleation of H2SO4-H2O, ternary nucleation of H2SO4-NH3-H2O, ion-induced nucleation are not capable in explaining new particle formation under complex air pollution, while newly proposed mechanisms such as organic acids and amine induced nucleation were not verified because of technique limitation. We propose that the future researches should focus on identifying the key chemical precursor response for driving nucleation and initial and subsequent growth, and understand the physical and chemical processing of new particle formation and growth. In particularly, application and development of novel techniques, such as APi-TOF-CIMS, PSM, Nano-HTDMA in new particle formation study is very important. Also, future researches should establish whole process tracking on new particle formation, from precursor, nucleation, growth till the environmental effects, by integrating field observation, chamber simulation, and modelling. Currently, the mechanism of highly efficient nucleation and rapid growth taking place under complex air pollution in China is urgently needed to be in-depth studied in order to improve our understanding of regional haze formation. This could be helpful to understand the similarity and difference in the nucleation mechanism between clean and polluted atmospheric environments.

The mechanism of health effects caused by organohalogen pollutants, e.g., toxins from electronic waste (e-waste), is poorly understood. We supposed that microRNAs (miRNAs), an important post-transcriptional regulator, could play a role in this process. In this study, fasting peripheral blood samples were collected from residents living at an e-waste site in northern China and a nearby reference population. Concentrations of e-waste related organohalogen pollutants in plasma from the exposure group were higher than the corresponding measurement in the reference group. Correspondingly, sixty miRNAs in plasma showed > 2-fold change between the two groups in microarray analysis. Among them, miR-125a-5p was confirmed to be upregulated by qRT-PCR and its validated targets were enriched in responses to xenobiotics and cancer related pathways. Furthermore, significant positive conelations were found between levels of miR-125a-5p in plasma and reactive oxygen species (ROS) in polymorphonuclear neutrophil leukocytes (P < 0.05). These evidences suggested oxidative stress might be an intermediate between e-waste related POPs exposure and alteration of plasma miRNA.

This study aims to simulate depositions of size-segregated particles in human airway in Beijing, China during seasons when fine particulate matter concentrations are high (December 2011 and April 2012). Particle size distributions (5.6-560 nm, electrical mobility diameter) near a major road in Beijing were measured by the TSI Fast Mobility Particle Sizer (FMPS). The information of size distributions provided by FMPS was applied in the Multiple-Path Particle Dosimetry model (MPPD) to quantify number and mass depositions of particles in human airway including extrathoracic (ET), tracheobronchial (TB), and pulmonary (PUL) regions of exposed Chinese in Beijing. Our results show that under ambient conditions, particle number concentration (NC) deposition in PUL is the highest in the three major regions of human airway. The total particle NC deposition in human airway in winter is higher than that in spring, especially for ultrafine particles (1.8 times higher) while particle mass concentration (MC) deposition is higher in spring. Although particle MC in clean days are much lower than that in heavily polluted days, total particle NC deposition in human airway in clean days is comparable to that in heavily polluted days. NC deposition for nucleation mode particles (10-20 nm, aerodynamic diameter) in clean days is higher than that in heavily polluted days. MC deposition for accumulation mode particles (100-641 nm, aerodynamic diameter) in heavily polluted days is much higher than that in clean days, while that of nucleation mode is negligible. The temporal variation shows that the arithmetic mean and the median values of particle NC and MC depositions in the evening are both the highest, followed by morning and noon, and it is most likely due to increased contribution from traffic emissions. (C) 2015 Elsevier Ltd. All rights reserved.

The structural and electronic properties of monolayer graphene synthesized on a periodically reconstructed substrate can be widely modulated by the generation of superstructure patterns, thereby producing interesting physical properties, such as magnetism and superconductivity. Herein, using a facile chemical vapor deposition method, we successfully synthesized high-quality monolayer graphene with a uniform thickness on Au foils. The hex-reconstruction of Au(001), which is characterized by striped patterns with a periodicity of 1.44 nm, promoted the formation of a quasi-one-dimensional (1D) graphene superlattice, which served as a periodic quasi-1D modulator for the graphene overlayer, as evidenced by scanning tunneling microscopy/spectroscopy. Intriguingly, two new Dirac points were generated for the quasi-1D graphene superlattice located at −1.73 ± 0.02 and 1.12 ± 0.12 eV. Briefly, this work demonstrates that the periodic modulation effect of reconstructed metal substrates can dramatically alter the ele...

Biogenic secondary organic aerosols (SOA) are generally considered to be more abundant in summer than in winter. Here, polar organic marker compounds in urban background aerosols from Mumbai were measured using gas chromatography-mass spectrometry. Surprisingly, we found that concentrations of biogenic SOA tracers at Mumbai were several times lower in summer (8-14 June 2006; wet season; n = 14) than in winter (13-18 February 2007; dry season; n = 10). Although samples from less than 10% of the season are extrapolated to the full season, such seasonality may be explained, by the predominance of the southwest summer monsoon, which brings clean marine air masses to Mumbai. While heavy rains are an important contributor to aerosol removal during the monsoon season, meteorological data (relative humidity and T) suggest no heavy rains occurred during our sampling period. However, in winter, high levels of SOA and their day/night differences suggest significant contributions of continental aerosols through long-range transport together with local sources. The winter/summer pattern of SOA loadings was further supported by results from chemical transport models (NAQPMS and GEOS-Chem). Furthermore, our study suggests that monoterpene- and sesquiterpene-derived secondary organic carbon. (SOC) were more significant than those of isoprene- and toluene-SOC at Mumbai.