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The frequent haze episodes in the Yangtze River Delta (YRD) of China have been of great public concern due to the high risks to human health. Therefore, a better understanding of the sources and characteristics of particulate matters (PM) and associated elements is crucial and urgent for haze controlling. In this study, air particulates were collected from six different functional areas in a megacity of the YRD, China in early winter of 2012. Highly time- and size-resolved analysis of PM-elements was conducted to trace their sources. Our results showed that the main donors to particulate elements were crustal dust, followed by traffic and industrial influences due to the mixed residential, commercial and industrial zones at most sites. Anthropogenesis contributed more to the sources of finer particles and associated elements than those of coarser ones. Besides the local emission sources, meteorological conditions also affected the distribution patterns of ambient elements. Furthermore, the risks of hazard metals in PM 2.5 and PM 1.0 to human health were estimated. The highest non-carcinogenic and carcinogenic risks were observed at urban living quarter (ULQ) and eco-industrial park (EIP), respectively. In addition, the general risks at rural living quarters (RLQ) were the lowest. Results from this study may provide valuable information for air pollution control and management in the YRD, China. [ABSTRACT FROM AUTHOR]

This paper proposes a bias-corrected expression for maximum likelihood estimators using the sequential number-theoretic method for optimization (SNTO) to improve the efficiency and accuracy of the estimators in three extreme value distributions (EVDs). It is well known that the widely used maximum likelihood estimation (MLE) could be often biased for small-size samples in EVDs. Meanwhile, numerical simulation results reveal that maximum likelihood estimators are suffered from high variance when the sample size is small and the impact is non-negligible. A comprehensive comparison study which includes classical bias-corrected methods and more recent ones is presented. Based on the simulation studies, the bias-correction estimator via SNTO is highly recommended to reduce the bias and variance of estimators. In addition, a real data set is illustrated to employ different techniques. [ABSTRACT FROM AUTHOR]

AbstractHypothesis testing for the Weibull distribution always raises attention in the literature. It is challenging especially in small-sample scenarios. In this paper, we propose a new Kolmogorov-Smirnov type test based on the distance between two empirical functions, one from the data and another from the representative points of the underlying distribution. A bias correction technique is used to estimate unknown parameters in the Weibull distribution. We also discuss how to choose a suitable number of representative points based on the proposed loss function, which is recommended for constructing the empirical function from the Weibull distribution. To compare with tailor-made tests in the literature, a simulation study of the empirical type I error and testing power is conducted. It shows that our proposed test statistic is more powerful in most alternative scenarios, and it significantly improves the power of testing in small-sample scenarios. Finally, two real-world datasets are conducted to further demonstrate the efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

This paper discusses new approaches to parameter estimation of gamma distribution based on representative points. In the first part, the existence and uniqueness of gamma mean squared error representative points (MSE-RPs) are discussed theoretically. In the second part, by comparing three types of representative points, we show that gamma MSE-RPs perform well in parameter estimation and simulation. The last part proposes a new Harrel–Davis sample standardization technique. Simulation studies reveal that the standardized samples can be used to improve estimation performance or generate MSE-RPs. In addition, a real data analysis illustrates that the proposed technique yields efficient estimates for gamma parameters. [ABSTRACT FROM AUTHOR]

The multivariate normal is a common assumption in many statistical models and methodologies for high-dimensional data analysis. The exploration of approaches to testing multivariate normality never stops. Due to the characteristics of the multivariate normal distribution, most approaches to testing multivariate normality show more or less advantages in their power performance. These approaches can be classified into two types: multivariate and univariate. Using the multivariate normal characteristic by the Mahalanobis distance, we propose an approach to testing multivariate normality based on representative points of the simple univariate F-distribution and the traditional chi-square statistic. This approach provides a new way of improving the traditional chi-square test for goodness-of-fit. A limited Monte Carlo study shows a considerable power improvement of the representative-point-based chi-square test over the traditional one. An illustration of testing goodness-of-fit for three well-known datasets gives consistent results with those from classical methods. [ABSTRACT FROM AUTHOR]

The NCTU micro-orifice cascade impactor (NMCI) was redesigned and tested to enable the measurement and adjustment of the jet-to-plate distance (S) of the impactors by using a micrometer. Each stage of the NMCI contains an impaction plate and a nozzle plate which are separated. The bottom casing for impaction plate assembly and the nozzle plate holder of each stage are separated. Calibration results show that the cutoff aerodynamic diameter (dpa50) of the three lower stages (dpa50= 180, 100, and 56 nm) are close to the nominal values given in Marple et al. (1991). In addition, theS/W(W: nozzle diameter) effects on thedpa50for the three lower stages were investigated and an empirical equation was developed to facilitate the prediction ofdpa50when the nozzle diameters may change slightly from one batch to another. The relationship between the nozzle diameter and pressure drop of the micro-orifice impactors at the fixed operational flow rate of 30 L/min was also established so that the nozzle diameters can be predicted from the pressure drop measurement. An empirical equation was proposed to express the correlation between the dimensionless cutoff size and theS/Wratio when considering isentropic flow to facilitate the design of micro-orifice impactors forS/W> 4. It is expected that the present NMCI could improve the accuracy of size classification of submicron particles below 180 nm, especially for nanoparticles. Copyright 2015 American Association for Aerosol Research [ABSTRACT FROM PUBLISHER]

Background/Aims: Epithelial cells line the intestinal mucosa and form an important barrier for maintaining host health. This study aimed to explore the mechanism of the Sphingosine-1-phosphate (S1P)/Sphingosine-1-phosphate receptor 2 (S1PR2) pathway in intestinal epithelial cells (IECs) that participate in the intestinal barrier function. Methods: In this study, we constructed a knockout of the S1PR2 gene in mice, and Dextra sulfate sodium (DSS) was used to induce colitis. We isolated IECs from wild type (WT) and S1PR2–/– mice, and the endogenous expression of S1PR2 and Zonula occludens 1 (ZO-1) in IEC were detected by Western blot. Next, the major histocompatibility complex II (MHC-II) expression was analyzed by reverse transcription quantitative real-time (RT-qPCR) and flow cytometry. The in vivo and in vitro intestinal permeability were evaluated by serum fluorescein isothiocyanate (FITC) concentration. The tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interferon-γ (IFN-γ) levels in cell suspension were analyzed by enzyme-linked immuno sorbent assay (ELISA). A carboxyfluorescein diacetate succinimidyl ester (CFSE) assay was used to detect the T-cell proliferation in a co-culture system. Results: The intestinal mucosal barrier damage in S1PR2–/– mice was more severe than in the WT mice, and there were more CD4+T-cells in the colon tissue of DSS-treated S1PR2–/– mice. Either the mouse colon carcinoma cell line (CT26. WT) or the IECs upregulated MHC-II expression, which then promoted CD4+T-cell proliferation. The S1P/S1PR2 pathway controlled MHC-II expression to regulate CD4+T-cell proliferation via the extracellular signal-regulated kinase (ERK) pathway. In addition, the IFN-γ that was secreted by CD4+T-cells increased DSS-induced damage of intestinal epithelial cell barrier function. ZO-1 expression was increased by S1P in CT26.WT cells, while S1PR2 antagonist JTE-013 expression was downregulated. However, in CT26.WTsi-S1PR2 cells, S1P had no effect on ZO-1 expression. Conclusions: The S1P/S1PR2 axis in IECs mediated CD4+T-cell activation via the ERK pathway and MHC-II expression to regulate intestinal barrier function. [ABSTRACT FROM AUTHOR]