PM2.5 pollution is substantially affected by ammonia emissions in China

Urban air quality in China has been declining substantially in recent years due to severe haze episodes. The reduction of sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions since 2013 does not yet appear to yield substantial benefits for haze mitigation. As the reductions of those key precursors to secondary aerosol formation appears not to sufficient, other crucial factors need to be considered for the design of effective air pollution control strategies. Here we argue that ammonia (NH3) plays a - so far - underestimated role in the formation of secondary inorganic aerosols, a main component of urban fine particulate matter (PM2.5) concentrations in China. By analyzing in situ concentration data observed in major cities alongside gridded emission data obtained from remote sensing and inventories, we find that emissions of NH3 have a more robust association with the spatiotemporal variation of PM2.5 levels than emissions of SO2 and NOx. As a consequence, we argue that urban PM2.5 pollution in China in many locations is substantially affected by NH3 emissions. We highlight that more efforts should be directed to the reduction of NH3 emissions that help mitigate PM2.5 pollution more efficiently than other PM2.5 precursors. Such efforts will yield substantial co-benefits by improving nitrogen use efficiency in farming systems. As a consequence, such integrated strategies would not only improve urban air quality, but also contribute to China's food-security goals, prevent further biodiversity loss, reduce greenhouse gas emissions and lead to economic savings

Cleaning up nitrogen pollution may reduce future carbon sinks

Biosphere carbon sinks are crucial for reducing atmospheric carbon dioxide (CO2) concentration to mitigate global warming, but are substantially affected by the input of reactive nitrogen (Nr). Although the effects of anthropogenic CO2 emission and nitrogen deposition (indicated by Nr emission to atmosphere) on carbon sink have been studied, it is unclear how their ratio (C/N) changes with economic development and how such change alters biosphere carbon sinks. Here, by compiling datasets for 132 countries we find that the C/N ratio continued to increase despite anthropogenic CO2 and Nr emissions to atmosphere both showing an asymmetric para-curve with economic growth. The inflection points of CO2 and Nr emissions are found at around $15,000 gross domestic product per capita worldwide. Economic growth promotes the use of Nr and energy, while at the same time increases their use efficiencies, together resulting in occurrences of inflection points of CO2 and Nr emissions. Nr emissions increase slower but decrease faster than that of CO2 emissions before and after the inflection point, respectively. It implies that there will be relatively more anthropogenic CO2 emission but less N deposition with economic growth. This may limit biosphere carbon sink because of relative shortage of Nr. This finding should be integrated/included in global climate change modelling. Efforts, such as matching N deposition with carbon sequestration on regional scale, to manage CO2 and Nr emissions comprehensively to maintain a balance are critical

Virus-Like Particles of SARS-Like Coronavirus Formed by Membrane Proteins from Different Origins Demonstrate Stimulating Activity in Human Dendritic Cells

The pathogenesis of SARS coronavirus (CoV) remains poorly understood. In the current study, two recombinant baculovirus were generated to express the spike (S) protein of SARS-like coronavirus (SL-CoV) isolated from bats (vAcBS) and the envelope (E) and membrane (M) proteins of SARS-CoV, respectively. Co-infection of insect cells with these two recombinant baculoviruses led to self-assembly of virus-like particles (BVLPs) as demonstrated by electron microscopy. Incorporation of S protein of vAcBS (BS) into VLPs was confirmed by western blot and immunogold labeling. Such BVLPs up-regulated the level of CD40, CD80, CD86, CD83, and enhanced the secretion of IL-6, IL-10 and TNF-α in immature dendritic cells (DCs). Immune responses were compared in immature DCs inoculated with BVLPs or with VLPs formed by S, E and M proteins of human SARS-CoV. BVLPs showed a stronger ability to stimulate DCs in terms of cytokine induction as evidenced by 2 to 6 fold higher production of IL-6 and TNF-α. Further study indicated that IFN-γ+ and IL-4+ populations in CD4+ T cells increased upon co-cultivation with DCs pre-exposed with BVLPs or SARS-CoV VLPs. The observed difference in DC-stimulating activity between BVLPs and SARS CoV VLPs was very likely due to the S protein. In agreement, SL-CoV S DNA vaccine evoked a more vigorous antibody response and a stronger T cell response than SARS-CoV S DNA in mice. Our data have demonstrated for the first time that SL-CoV VLPs formed by membrane proteins of different origins, one from SL-CoV isolated from bats (BS) and the other two from human SARS-CoV (E and M), activated immature DCs and enhanced the expression of co-stimulatory molecules and the secretion of cytokines. Finding in this study may provide important information for vaccine development as well as for understanding the pathogenesis of SARS-like CoV

Prediction of mechanical and fracture properties of graphene via peridynamics

Although graphene is believed to be the strongest material, many properties of this material are still worth exploring and discovering, especially the influence of inevitable defects in its preparation on the mechanical and fracture properties which are of high significance. Here a peridynamic (PD) model is 1 established to study the mechanical and fracture properties of polycrystalline graphene in which grains of large size exist. In this study, dependence of the Young s modulus and the fracture strength on the grain size which changes from a few to hundreds of nanometers is obtained, and the inverse pseudo Hall-Petch relation between the fracture strength and the grain size is found. The fracture forms of graphene are consistent with the experimental observations. Based on the Griffith theory, the obtained fracture toughness (i.e. 3.1 - 6.3 ) and (i.e. 10.9 - 45.7 ) is comparable with previously reported theoretical and experimental values, which proves the validity of the proposed PD model and confirms the applicability of the classical Griffith theory in brittle fracture analysis of graphene sheets. Besides, numerical results reveal that the fracture toughness can be greatly enhanced by the blunt pre-crack tip. This work provides insights into mechanical failure of graphene and guidance on fragmentation of graphene for its practical use, which makes a further step on the application of PD theory via presenting a new and feasible way for the study of large-sized graphene

Humoral and Cellular Immune Responses Induced by 3a DNA Vaccines against Severe Acute Respiratory Syndrome (SARS) or SARS-Like Coronavirus in Mice▿

Vaccine development for severe acute respiratory syndrome coronavirus (SARS-CoV) has mainly focused on the spike (S) protein. However, the variation of the S gene between viruses may affect the efficacy of a vaccine, particularly for cross-protection against SARS-like CoV (SL-CoV). Recently, a more conserved group-specific open reading frame (ORF), the 3a gene, was found in both SARS-CoV and SL-CoV. Here, we studied the immunogenicity of human SARS-CoV 3a and bat SL-CoV 3a DNA vaccines in mice through electroporation immunization followed by enzyme-linked immunosorbent, enzyme-linked immunospot, and flow cytometry assays. Our results showed that high levels of specific humoral responses were induced by SARS-CoV 3a and SL-CoV 3a DNA vaccines. Furthermore, a strong Th1-based cellular immune response was stimulated by both DNA vaccines. The vaccines stimulated gamma interferon production mainly by CD8+ T cells and interleukin-2 (IL-2) mainly by CD4+ T cells. Of interest, the frequency of IL-2-positive cells elicited by the SARS-CoV 3a DNA vaccine was significantly higher than that elicited by the SL-CoV 3a DNA vaccine. In summary, our study provides a reference for designing cross-protective DNA vaccines based on the group-specific ORFs of CoVs

Optimizing nitrogen fertilizer use for more grain and less pollution

Optimal nitrogen (N) management is critical for efficient crop production and agricultural pollution control. Approximate 210–220 kg ha−1 N fertilizer was applied in millions of small plots through broadcasting way in China, resulting in over and loss of N fertilizers. However, it is difficult to implement advanced management practices on smallholder farms due to a lack of knowledge. Here, using 35,502 on-farm fertilization experiments, we demonstrated that smallholders in China could actually produce more grain with less N fertilizer use only through optimizing N application rate. The yields of wheat, maize and rice were shown to increase between 10% and 19% while N application rates were reduced by 15–19%. These changes resulted in an increase in N use efficiency (NUE) by 32–46% and a reduction in N surplus by 40% without actually changing farmers’ operational practices. By reducing N application rates in line with official recommendations would not only save fertilizer cost while increasing crop yield, but also at the same time reduce environmental N pollution in China. Beyond of optimizing N application rate, improved management practices were required to produce more grain with less pollution, which would need about 11.8 billion US dollars for the implementation and reducing N loss reduction by 1.75 million tons to the environment