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Cross-project defect prediction （CPDP） uses the labeled data from external source software projects to com- pensate the shortage of useful data in the target project, in order to build a meaningful classification model. However, the distribution gap between software features extracted from the source and the target projects may be too large to make the mixed data useful for training. In this paper, we propose a cluster-based novel method FeSCH （Feature Selection Using Clusters of Hybrid-Data） to alleviate the distribution differences by feature selection. FeSCH includes two phases. Tile feature clustering phase clusters features using a density-based clustering method, and the feature selection phase selects features from each cluster using a ranking strategy. For CPDP, we design three different heuristic ranking strategies in the second phase. To investigate the prediction performance of FeSCH, we design experiments based on real-world software projects, and study the effects of design options in FeSCH （such as ranking strategy, feature selection ratio, and classifiers）. The experimental results prove the effectiveness of FeSCH. Firstly, compared with the state-of-the-art baseline methods, FeSCH achieves better performance and its performance is less affected by the classifiers used. Secondly, FeSCH enhances the performance by effectively selecting features across feature categories, and provides guidelines for selecting useful features for defect prediction.

High concentrations of organic aerosol (OA) occur in Asian countries, leading to great health burdens. Clean air actions have resulted in significant emission reductions of air pollutants in China. However, long-term nation-wide trends in OA and their causes remain unknown. Here, we present both observational and model evidence demonstrating widespread decreases with a greater reduction in primary OA than in secondary OA (SOA) in China during the period of 2013 to 2020. Most of the decline is attributed to reduced residential fuel burning while the interannual variability in SOA may have been driven by meteorological variations. We find contrasting effects of reducing NO x and SO 2 on SOA production which may have led to slight overall increases in SOA. Our findings highlight the importance of clean energy replacements in multiple sectors on achieving air-quality targets because of high OA precursor emissions and fluctuating chemical and meteorological conditions. Clean air actions affect air quality greatly. Here, the authors report widespread decreases in organic aerosol (OA) in China from 2013 to 2020 with primary OA decreasing more than secondary OA. However, further reductions are challenging.

PM2.5 and PM10 samples were collected simultaneously in each season in Beijing, Tianjin and Shijiazhuang to identify the characteristics of water-soluble ion compositions in the North China Plain. The water-soluble ions displayed significant seasonal variation. The dominant ions were NO3(-), SO4(2-), NH4(+) and Cl(-), accounting for more than 90% and 86% to the mass of total water-soluble ions in PM2.5 and PM10, respectively. The anion/cation ratio indicated that the ion acidity of each city varied both between sites and seasonally. Over 50% of the ion species were enriched in small particles ≤1 µm in diameter. The [NO3(-)]/[SO4(2-)] ratio indicated that vehicles accounted for the majority of the particulate pollution in Beijing. Shijiazhuang, a city highly reliant on coal combustion, had a higher SO4(2-) concentration.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and typically fatal lung disease with a very low survival rate. Excess accumulation of fibroblasts, myofibroblasts and extracellular matrix creates hypoxic conditions within the lungs, causing asphyxiation. Hypoxia is, therefore, one of the prominent features of IPF. However, there have been few studies concerning the effects of hypoxia on pulmonary fibroblasts. In this study, we investigated the molecular mechanisms of hypoxia-induced lung fibroblast proliferation. Hypoxia increased the proliferation of normal human pulmonary fibroblasts and IPF fibroblasts after exposure for 3–6 days. Cell cycle analysis demonstrated that hypoxia promoted the G1/S phase transition. Hypoxia downregulated cyclin D1 and A2 levels, while it upregulated cyclin E1 protein levels. However, hypoxia had no effect on the protein expression levels of cyclin-dependent kinase 2, 4, and 6. Chemical inhibition of hypoxia-inducible factor (HIF)-2 reduced hypoxia-induced fibroblast proliferation. Moreover, silencing of Nuclear Factor Activated T cell (NFAT) c2 attenuated the hypoxia-mediated fibroblasts proliferation. Hypoxia also induced the nuclear translocation of NFATc2, as determined by immunofluorescence staining. NFAT reporter assays showed that hypoxia-induced NFAT signaling activation is dependent on HIF-2, but not HIF-1. Furthermore, the inhibition or silencing of HIF-2, but not HIF-1, reduced the hypoxia-mediated NFATc2 nuclear translocation. Our studies suggest that hypoxia induces the proliferation of human pulmonary fibroblasts through NFAT signaling and HIF-2.

In this review paper, the research progress on corrosion behavior of hexagonal close-packed (HCP) singular phase, body cubic-centered (BCC) singular phase and (HCP + BCC) duplex-structured Mg–Li alloys has been summarized and reviewed, and the future trend about the studies on corrosion behavior of Mg–Li-based alloys and possible solving methods for the improvement in corrosion resistance are discussed also.

Coal-to-gas (CTG) policies are important energy transformation strategies for addressing air pollution issues, but how well they improve atmospheric lead (Pb) pollution remains poorly understood. By the end of 2018, Beijing had achieved coal-free status in urban and plain areas. The mixing state and atmospheric chemical processes of Pb-rich particles in Beijing were monitored using single-particle aerosol mass spectrometry (SPAMS) in 2019. Based on a large dataset of mass spectra, this study finds that the number fractions of Pb-rich particles, as well as two specific types of Pb-rich particles (K-Na-EC and K-OC, where EC and OC denote elemental and organic carbon, respectively) related to coal combustion during the official Beijing heating period, show lower number fractions than those after the heating period. Based on concentration-weighted trajectory plots, the results indicate that lead aerosols mainly derive from transmission from surrounding provinces. Lead nitrate is one of the important forms of lead in aerosol particles, particularly as a result of photo-chemical reactions in the spring, fall, and winter. Due to nitrate decomposition during high temperatures, the aqueous reaction mechanism contributes more to lead nitrate during the summer. These results improve our understanding of the seasonal distribution, formation mechanisms, and influencing factors of toxic Pb-containing particles after CTG.

The North China Plain (NCP) is becoming one of the most polluted areas characterized by a high frequency of haze pollution. However, the spatial and temporal evolutions of aerosol chemical compositions in such a highly polluted region are not well understood due to the lack of a long-term and comprehensive observation-based network. China’s National Aerosol Composition Monitoring Network (NACMON) has conducted comprehensive offline and online measurements of compositions and optical properties of airborne aerosols in order to systematically investigate the formation process, source apportionments of haze, and interactions between haze pollution and climate change. The objective of the observations is to provide information for policy makers to make strategies for the alleviation of haze occurrence. In this paper, we present instrumentations and methodologies as well as the preliminary results of the offline observations in NACMON stations over the NCP region. The implications and future perspectives of the network are also summarized. Benefiting from simultaneous observations from this network, we found that secondary aerosols were the dominant component in haze pollution. High anthropogenic emissions, low wind speed, and high relative humidity (RH) facilitated gas-to-particle transformation and resulted in high PM 2.5 formation (PM 2.5 is particulate matter that is smaller than 2.5 μ m in diameter). Sulfate-dominant or nitrate-dominant aerosols during the haze period were driven by ambient RH. Moreover, the contributions of coal combustion and biomass burning to PM 2.5 revealed downward trends, whereas secondary aerosols showed upward trends over the last decade. Thus, we highlighted that strict control of anthropogenic emissions of precursor gases, such as NO x , NH 3 , and volatile organic compounds (VOCs), will be an important way to decrease PM 2.5 pollution in the NCP region.

The mixing state and aging characteristics of black carbon (BC) aerosols are the key factors in calculating their optical properties and quantifying their impacts on radiation balance and global climate change. Considerable uncertainty still exists in the absorption properties of BC-containing aerosols and the absorption enhancement (Eabs) due to the lensing effect. It is crucial to reasonably represent the mixing of BC with other aerosol components to reduce this uncertainty. In this study, the absorption properties of PM2.5 were investigated based on the Nested Air Quality Prediction Modeling System (NAQPMS) with different assumptions of the aerosol mixing state. The absorption coefficient (babs) is the highest under the assumption of uniform internal mixing, lower under core–shell mixing, and the lowest under external mixing. The result under core–shell mixing is closest to the observations. The aging process and coating thickness were well reproduced by an advanced particle microphysics (APM) module in NAQPMS. Following this, the fraction of embedded BC and secondary component coating on aerosols was used to constrain the mixing state. Eabs at 880 nm over the Beijing–Tianjin–Hebei region was 2.0–2.5 under core–shell mixing. When the fraction of coated BC and the coating layer are resolved, Eabs_880 – caused by the lensing effect – decreases by 30 %–43 % to 1.2–1.7, which is close to the range reported in previous studies. This study highlights the importance of representing the microphysical processes governing the mixing state and aging of BC and provides a reference for quantifying their radiative effects.