Search

By installing on-board diagnostics (OBD) on tested vehicles, the after-treatment exhaust emissions can be monitored in real time to construct driving cycle-based emission models, which can provide data support for the construction of dynamic emission inventories of mobile source emission. However, in actual vehicle emission detection systems, due to the equipment installation costs and differences in vehicle driving conditions, engine operating conditions, and driving behavior patterns, it is impossible to ensure that the emission monitoring data of different vehicles always follow the same distribution. The traditional machine learning emission model usually assumes that the training set and test set of emission test data are derived from the same data distribution, and a unified emission model is used for estimation of different types of vehicles, ignoring the difference in monitoring data distribution. In this study, we attempt to build a diesel vehicle NOx emission prediction model based on the deep transfer learning framework with a few emission monitoring data. The proposed model firstly uses Spearman correlation analysis and Lasso feature selection to accomplish the selection of factors with high correlation with NOx emission from multiple sources of external factors. Then, the stacked sparse AutoEncoder is used to map different vehicle working condition emission data into the same feature space, and then, the distribution alignment of different vehicle working condition emission data features is achieved by minimizing maximum mean discrepancy (MMD) in the feature space. Finally, we validated the proposed method with the diesel vehicle OBD data that were collected by the Hefei Environmental Protection Bureau. The comprehensive experiment results show that our method can achieve the feature distribution alignment of emission data under different vehicle working conditions and improve the prediction performance of the NOx inversion model given a little amount of NOx emission monitoring data., Author(s): Zhenyi Xu (corresponding author) [1,2]; Ruibin Wang [1,3]; Yu Kang (corresponding author) [1,4,5,6]; Yujun Zhang [7]; Xiushan Xia [8]; Renjun Wang [1,3] 1. Introduction With the rapid development of [...]

Background/Aims: Tempol is a protective antioxidant against ischemic injury in many animal models. The molecular mechanisms are not well understood. Nuclear factor erythroid 2-related factor (Nrf2) is a master transcription factor during oxidative stress, which is enhanced by activation of protein kinase C (PKC) pathway. Another factor, tubular epithelial apoptosis, is mediated by activation of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, Akt) signaling pathway during renal ischemic injury. We tested the hypothesis that tempol activates PKC or PI3K/Akt/Nrf2 pathways to transcribe many genes that coordinate endogenous antioxidant defense. Methods: The right renal pedicle was clamped for 45 minutes and the left kidney was removed to study renal ischemia/reperfusion (I/R) injury in C57BL/6 mice. The response was assessed from serum parameters, renal morphology and renal expression of PKC, phosphorylated-PKC (p-PKC), Nrf2, heme oxygenase-1 (HO-1), Akt, phosphorylated-Akt (p-Akt), pro-caspase-3 and cleaved caspase-3 in groups of sham and I/R mice given vehicle, or tempol (50 or 100 mg/kg, intraperitoneal injection). Results: The serum malondialdehyde (MDA, marker of reactive oxygen species) doubled and the BUN and creatinine increased 5- to 10-fold after I/R injury. Tempol (50 or 100 mg/kg) prevented the increases in MDA but only tempol (50 mg/kg) lessened the increases in BUN and creatinine and moderated the acute tubular necrosis. I/R did not change expression of PKC or p-PKC but reduced renal expression of Nrf2, p-Akt, HO-1 and pro-caspase-3 and increased cleaved caspase-3. Tempol (50 mg/kg) prevented these changes produced by I/R whereas tempol (100 mg/kg) had lesser or inconsistent effects. Conclusion: Tempol (50 mg/kg) prevents lipid peroxidation and attenuates renal damage after I/R injury. The beneficial pathway apparently is not dependent on upregulation or phosphorylation of PKC, at lower tempol doses, does implicate upregulation of Akt with expression of Nrf2 that could account for the increase in the antioxidant gene HO-1 and a reduction in the cleavage of the cellular damage marker pro-caspase-3. [ABSTRACT FROM AUTHOR]

The reaction mechanisms of vinyl acetate with OH radicals in the atmosphere have been studied using the density functional theory method. The geometry parameters and frequencies of all of the stationary points are calculated at the MPWB1K level with the 6-31G(d,p) basis sets. The single-point energy calculations are carried out at the MPWB1K/6311+G(3df,2pd)level. The detailed profiles of the potential energy surfaces for the reactions are constructed. Two OH addition and three H abstraction reaction pathways are considered for the reaction of vinyl acetate with OH radicals. The theoretical study shows that the most energetically favorable isomer is that of OH addition to the terminal carbon positions (C1 atom). The Å-ester rearrangement, which is characteristic of ester oxidation processes, is confirmed to be thermodynamically and kinetically favorable. The main products of the OH-initiated atmospheric oxidation of vinyl acetate are formaldehyde, formic acetic anhydride, and acetic acid. Key words: vinyl acetate, OH radicals, reaction mechanism, quantum chemical calculation. On a etudie les mecanismes reactionnels de l'acetate de vinyle avec les radicaux OH de l'atmosphere en faisant appel a la theorie de la fonctionnelle de la densite. On a calcule les parametres geometriques et les frequences des points stationnaires au niveau MPWBK1K de la theorie avec des ensembles de base 6-31G(d,p). Les calculs d'energie ponctuelle ont ete faits au niveau MPWB1K/6-311+G(3df,pd). On a construit les profils detailles des surfaces d'energie potentielle des reactions. On a considere l'addition de deux OH et l'enlevement de trois H comme voies reactionnelles pour la reaction de l'acetate de vinyle avec les radicaux OH. L'etude theorique montre que l'isomere le plus favorable d'un point de vue energetique est celui correspondant a l'addition d'un OH sur les positions carbonees terminales (C1). On a pu confirmer que le rearrangement de l'[alfa]-ester, qui est caracteristique des processus d'oxydation d'ester, est le plus favorable tant d'un point de vue thermodynamique que cinetique. Les produits principaux qui resultent d'une oxydation atmospherique de l'acetate de vinyle, initiee par un radical OH, sont le formaldehyde, l'anhydride mixte de l'acide formique et acetique et l'acide acetique. Mots-cles: acetate de vinyle, radicaux OH, mecanisme reactionnel, calculs de chimie quantique., Introduction Vinyl acetate (VA) ([C[H3.sub.]C(O)OCH=C[H.sub.2]]) is a synthetic unsaturated ester and has a wide variety of industrial applications. The major use of VA is to produce polyvinyl alcohol, polyvinyl acetate, [...]