Compared to the severe winter haze episodes in the North China Plain (NCP),
haze pollution during summertime has drawn little public attention. In this
study, we present the highly time-resolved ...chemical composition of submicron
particles (PM1) measured in Beijing and Xinxiang in the NCP region
during summertime to evaluate the driving factors of aerosol pollution.
During the campaign periods (30 June to 27 July 2015, for Beijing and 8 to
25 June 2017, for Xinxiang), the average PM1 concentrations were 35.0
and 64.2 µg m−3 in Beijing and Xinxiang. Pollution episodes
characterized with largely enhanced nitrate concentrations were observed at
both sites. In contrast to the slightly decreased mass fractions of sulfate,
semivolatile oxygenated organic aerosol (SV-OOA), and low-volatility
oxygenated organic aerosol (LV-OOA) in PM1, nitrate displayed a
significantly enhanced contribution with the aggravation of aerosol
pollution, highlighting the importance of nitrate formation as the driving
force of haze evolution in summer. Rapid nitrate production mainly occurred
after midnight, with a higher formation rate than that of sulfate, SV-OOA, or
LV-OOA. Based on observation measurements and thermodynamic modeling, high
ammonia emissions in the NCP region favored the high nitrate production in
summer. Nighttime nitrate formation through heterogeneous hydrolysis of
dinitrogen pentoxide (N2O5) enhanced with the development of haze
pollution. In addition, air masses from surrounding polluted areas during
haze episodes led to more nitrate production. Finally, atmospheric
particulate nitrate data acquired by mass spectrometric techniques from
various field campaigns in Asia, Europe, and North America uncovered a higher
concentration and higher fraction of nitrate present in China. Although
measurements in Beijing during different years demonstrate a decline in the
nitrate concentration in recent years, the nitrate contribution in PM1
still remains high. To effectively alleviate particulate matter pollution in
summer, our results suggest an urgent need to initiate ammonia emission
control measures and further reduce nitrogen oxide emissions over the NCP
region.
The North China Plain (NCP) frequently experiences heavy haze pollution, particularly during wintertime. In winter 2015–2016, the NCP region suffered several extremely severe haze episodes with air ...pollution red alerts issued in many cities. We have investigated the sources and aerosol evolution processes of the severe pollution episodes in Handan, a typical industrialized city in the NCP region, using real-time measurements from an intensive field campaign during the winter of 2015–2016. The average (±1σ) concentration of submicron aerosol (PM1) during 3 December 2015–5 February 2016 was 187.6 (±137.5) µg m−3, with the hourly maximum reaching 700.8 µg m−3. Organic was the most abundant component, on average accounting for 45 % of total PM1 mass, followed by sulfate (15 %), nitrate (14 %), ammonium (12 %), chloride (9 %) and black carbon (BC, 5 %). Positive matrix factorization (PMF) with the multilinear engine (ME-2) algorithm identified four major organic aerosol (OA) sources, including traffic emissions represented by a hydrocarbon-like OA (HOA, 7 % of total OA), industrial and residential burning of coal represented by a coal combustion OA (CCOA, 29 % of total OA), open and domestic combustion of wood and crop residuals represented by a biomass burning OA (BBOA, 25 % of total OA), and formation of secondary OA (SOA) in the atmosphere represented by an oxygenated OA (OOA, 39 % of total OA). Emissions of primary OA (POA), which together accounted for 61 % of total OA and 27 % of PM1, are a major cause of air pollution during the winter. Our analysis further uncovered that primary emissions from coal combustion and biomass burning together with secondary formation of sulfate (mainly from SO2 emitted by coal combustion) are important driving factors for haze evolution. However, the bulk composition of PM1 showed comparatively small variations between less polluted periods (daily PM2. 5 ≤ 75 µg m−3) and severely polluted periods (daily PM2. 5 > 75 µg m−3), indicating relatively synchronous increases of all aerosol species during haze formation. The case study of a severe haze episode, which lasted 8 days starting with a steady buildup of aerosol pollution followed by a persistently high level of PM1 (326.7–700.8 µg m−3), revealed the significant influence of stagnant meteorological conditions which acerbate air pollution in the Handan region. The haze episode ended with a shift of wind which brought in cleaner air masses from the northwest of Handan and gradually reduced PM1 concentration to < 50 µg m−3 after 12 h. Aqueous-phase reactions under higher relative humidity (RH) were found to significantly promote the production of secondary inorganic species (especially sulfate) but showed little influence on SOA.
is an important medicinal plant that has long been used in Chinese traditional medicine. Acteoside, one of the bioactive components from
, possessed various pharmacological activities for human ...health; however, the molecular mechanism of acteoside formation is not fully understood. In the current study, a novel tyrosine decarboxylase (designated as RgTyDC2) was identified from the
transcriptome. Biochemical analysis of RgTyDC2 showed RgTyDC2 uses tyrosine and dopa as the substrate to produce tyramine and dopamine, respectively, and it displays higher catalytic efficiency toward tyrosine than dopa. Moreover, the transcript level of
was consistent with the accumulation pattern of acteoside in
, supporting its possible role in the biosynthesis of acteoside in vivo.
Aim
Currently, the optimal treatment strategy for locally advanced esophageal cancer (LAEC) remains controversial. We perform the present study to compare the outcomes of LAEC treated with ...neoadjuvant chemotherapy (neo-CT) or chemoradiotherapy (neo-CRT).
Materials and methods
A population cohort with histologically diagnosed of esophageal cancer was identified from SEER database between 2004 and 2015. The Kaplan–Meier method and Cox-regression proportional hazards model were used to assess the impact of neoadjuvant treatment regimens on the cause-specific survival (CSS) and overall survival (OS) of LAEC. A propensity score model was utilized to balance baseline covariates.
Results
After propensity score matching, a total of 1986 LAEC patients were included for analysis, 1,655 patients treated with neo-CRT and 331 with neo-CT, respectively. The survival outcomes of LAEC treated with neo-CRT were comparable to those treated with neo-CT in terms of 5-year OS (39% vs. 36%,
p
= 0.63) and CSS (51% vs. 51%,
p
= 0.77). In the multivariate Cox analyses, sex, histological grade, ypT stage, ypN( +), and number of LN examined were independent factors for predicting OS and CSS among LAEC treated with neoadjuvant treatment.
Conclusion
The present study based on large cohort demonstrated that no significant survival difference was observed between LAEC patients treated with neo-CRT versus neo-CT. However, the results needed to be confirmed in well-designed prospective trials.
Handan is a heavily polluted city in the northern China. From 6 to December 31, 2015, PM1.0 and PM2.5 samples were synchronously collected for 23.5 h of each day at an urban site in Handan, to study ...the chemical composition and sources of aerosols present during wintertime in North China Plain (NCP). The average mass concentrations of PM1.0 and PM2.5 in Handan were as high as 189.2 μg/m3 and 252.4 μg/m3, while the average PM1.0/PM2.5 ratio was relatively low (74.6%) compared with the results in megacities. Overall, the chemical characteristics of PM1.0 and PM2.5 were quite similar during the campaign. During pollution episodes, SNA (sulphate, nitrate, and ammonium) ions were found dramatically increased, while the fraction of organic carbon (OC) and elemental carbon (EC) decreased in both PM1.0 and PM2.5. As a result of reduced photochemical reactions, the weights of secondary organic carbon (SOC) in PM1.0 and PM2.5 decreased during the pollution episode. Besides, liquid water content (LWC) were found effective for SNA formation. The positive matrix factorization (PMF) model identified similar sources distributions for PM1.0 and PM2.5, and the top three contributors were coal combustion, secondary inorganic aerosols, and industrial emissions. Moreover, the potential source contribution function (PSCF) demonstrated that regional sources in southern Handan might be crucial contributors to haze pollution in Handan.
•The characteristics of PM1.0 and PM2.5 in Handan were investigated and compared.•Aqueous-phase reactions were found to significantly enhance SNA formation.•Coal combustion and SIAs were the main sources of PM1.0 and PM2.5 in winter.•The southern region of Handan had a relatively large potential source contribution.
Urban air pollution has emerged as a prominent public health concern in megacities and highly developed city clusters. Accurate modelling of urban air quality over complex terrain is challenging due ...to heterogeneous urban landscapes and multiscale land-atmosphere interactions. In this study, we investigated the applicability of urban canopy models in the Weather Research and Forecast (WRF) model and assessed the impacts of implementing these models on the urban air quality simulation in the Community Multiscale Air Quality (CMAQ) model over the megacity Chengdu, southwestern China. The land use and land cover of Chengdu were updated in WRF by using the land-use products in 2017 from the Moderate-resolution Imaging Spectroradiometer (MODIS). Sensitivity experiments with various urban canopy models were conducted to investigate the feasibility of different urban canopy models on WRF-CMAQ simulations. We found that the SLAB model significantly underestimates NO2 and PM2.5 concentrations, with mean fractional bias in winter (summer) reaching 52.93% (−50.34%) and −102.82% (−23.12%), respectively. Such large biases are mainly attributed to overpredicted wind speeds resulting from the flat structure in the SLAB model. In contrast, the BEM (a multilayer urban canopy model coupled with air-conditioning systems) model yields the best model performance in both winter and summer, with mean fractional errors of 33.15% (38.96%) and 34.10% (33.15%) for NO2 and PM2.5 in winter (summer), respectively. The UCM (a single-layer urban canopy model) model illustrates good performance in summer, with MFBs of 25.61% for NO2 and 19.03% for PM2.5, while NO2 and PM2.5 concentrations are overestimated in winter, with MFBs of 62.58% and 38.19%, respectively. In contrast, BEP (a multilevel urban canopy model)-modelled NO2 (MFB: 37.18%) and PM2.5 (MFB: 18.72%) correlate well with observations in winter, while significantly overestimated air pollutant concentrations in summer with MFBs of NO2 and PM2.5 of 49.70% and 44.50%, respectively. In general, the BEP model and the BEM model are well suited for air quality simulations over Chengdu in winter, and the BEM model could be considered for air quality simulations in summer. Furthermore, we assessed the effects of extensive usage of air conditioning systems in Chengdu during summertime, and the results suggest that using air conditioning systems facilitates the dispersion of air pollutants over Chengdu. This study pinpoints the limitations of default WRF configurations and tests the applicability of urban canopy models in the WRF-CMAQ model over Chengdu, in addition highlighting the crucial role of urban canopy models in urban meteorological-air quality simulations.
1.The feasibility of different urban canopy models in complex terrain is investigated over the megacity Chengdu.2.Overestimation of wind speed under weak wind fields has been improved by employing urban canopy models.3.The extensive use of air conditioning systems shows improvements in air quality over Chengdu in summer.
This article presents a novel perspective to improve the ride quality of high-speed trains (HSTs), namely, by virtue of the periodicity of lateral dynamics to suppress the lateral vibration of HST. ...To resolve the contradiction between the complex HST model and the effective controller design, a simplified three-degrees-of-freedom (3-DOF) quarter-vehicle model is first employed for controller design, while a 17-DOF full-vehicle model is built for efficiency verification, where periodic and random track irregularities are considered, respectively. An active repetitive learning control (RLC) method is proposed to achieve the periodic tracking control, where the learning convergence is proved rigorously in a Lyapunov way. The configuration of RLC-based lateral suspensions is economical in the sense that only four actuators and six sensors are needed. It is verified by simulation that, compared with the dynamic matrix controller, the proposed RLC controller has greatly reduced the lateral vibration of a vehicle body, especially the lateral acceleration in the frequency range of (0, 3 Hz to which human body is strongly sensitive.
Volatile organic compounds (VOCs) are essential in secondary organic aerosol (SOA) formation due to their dual roles as precursors and oxidant producers. In order to explore the dominant ...contributions of SOA formation from VOCs in central China, 53 VOC species were observed with proton transfer reaction-mass spectrometry (PTR-MS) and canister grab samples in Xinxiang, a mid-sized city located in Henan Province, from November 5th to December 3rd, 2018. The result showed that anthropogenic emissions were intensive compared with many studies in the world. Among the observed VOCs, benzene and toluene had the largest SOA formation potential (SOAFP), and their contributions in SOA formation kept stable with the aggravation of pollution. Among VOCs, formaldehyde was the strongest radical contributor, and the contribution of acetaldehyde was also found significant in this study, especially in polluted periods. Based on the positive matrix factorization (PMF) model, benzenoids (mainly single-ring aromatics) were majorly emitted from chemical process, solvent evaporation, and residential heating, with a total fraction of 75%, and these sources were estimated to have largest SOAFP. However, thermal power generation, chemical process, and solvent evaporation had highest radical contribution rates. According to the backward trajectory analysis, the VOC concentrations were dominated by local emissions. Emissions in the surrounding provinces occupied fractions of 33%–42% in the five sources. Therefore, regional collaborative emission reduction is also important.
Display omitted
•Anthropogenic emissions of VOCs are intensive in autumn in central China.•Benzenoids have the largest SOAFP during the campaign.•Acetaldehyde is also an unignorable VOC to atmospheric oxidation capacity.•Sources of VOCs are resolved and evaluated with chemical properties of VOCs.•Sources from surrounding provinces are also influential to VOC concentrations.
The lateral vibration of high-speed train reduces the ride stability and passenger comfort. Semi-active suspension system is often adopted to suppress the lateral vibration of trains due to its low ...cost and low energy consumption in control, where magnetorheological (MR) damper is the main vibration absorber. In this paper, a full model of the controlled system that consists of the 3-degree of freedom train model and the hysteretic MR damper model is first built. Then, a second-order sliding mode (SOSM) controller is designed for the suppression of lateral vibration of train, where the hysteresis and non-hysteresis nonlinearities are addressed simultaneously and rigorously. Finally, comparative simulations are conducted under the excitation of the German low-interference track spectrum. The results show that the proposed controller can suppress the lateral vibration of high-speed train efficiently in the sense that, compared with the passive control, the internal model-based resonant control and repetitive learning control, the suspension ratio of root-mean-square of lateral acceleration is reduced by 96.98%, 35.70% and 10.54%, respectively.
In the data mining, the analysis of high-dimensional data is a critical but thorny research topic. The LASSO (least absolute shrinkage and selection operator) algorithm avoids the limitations, which ...generally employ stepwise regression with information criteria to choose the optimal model, existing in traditional methods. The improved-LARS (Least Angle Regression) algorithm solves the LASSO effectively. This paper presents an improved-LARS algorithm, which is constructed on the basis of multidimensional weight and intends to solve the problems in LASSO. Specifically, in order to distinguish the impact of each variable in the regression, we have separately introduced part of principal component analysis (Part_PCA), Independent Weight evaluation, and CRITIC, into our proposal. We have explored that these methods supported by our proposal change the regression track by weighted every individual, to optimize the approach direction, as well as the approach variable selection. As a consequence, our proposed algorithm can yield better results in the promise direction. Furthermore, we have illustrated the excellent property of LARS algorithm based on multidimensional weight by the Pima Indians Diabetes. The experiment results show an attractive performance improvement resulting from the proposed method, compared with the improved-LARS, when they are subjected to the same threshold value.
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