Search

Peroxy acetyl nitrate (PAN) is a key component of photochemical smog and plays an important role in atmospheric chemistry. Though it has been known that PAN is produced via reactions of nitrogen oxides (NOx) with some volatile organic compounds (VOCs), it is difficult to quantify the contributions of individual precursor species. Here we use an explicit photochemical model--Master Chemical Mechanism (MCM) model--to dissect PAN formation and identify principal precursors, by analyzing measurements made in Beijing in summer 2008. PAN production was sensitive to both NOx and VOCs. Isoprene was the predominant VOC precursor at suburb with biogenic impact, whilst anthropogenic hydrocarbons dominated at downtown. PAN production was attributable to a relatively small class of compounds including NOx, xylenes, trimethylbenzenes, trans/cis-2-butenes, toluene, and propene. MCM can advance understanding of PAN photochemistry to a species level, and provide more relevant recommendations for mitigating photochemical pollution in large cities.

Autism Spectrum Disorders (ASD) remain a healthcare challenge and gain considerable attention due to the increasing prevalence rates and insupportable burden on families and society. It is noted that the recognition of children's emotional states plays an important role in the evaluation and intervention process of ASD. In this paper, we aim to address the problem of automatic recognition of the emotional states of ASD children in social interactive scenarios. Since the child can be unconstrained in realistic scenarios, the face occlusion under pose variations and uncertain backgrounds become challenges of this task. To tackle this problem, we employ both facial expressions as well as body poses as cues to recognize the emotional states while most traditional methods only leverage the former. Firstly for the facial information, spatial features are extracted through convolutional neural networks followed by a temporal transformer to extract temporal information. Then for the body pose information, graph convolutional networks combined with the self-attention part are used to represent spatial features and temporal convolutional layers for temporal counterparts. Finally, different multimodal fusion ways are explored to generate final recognition results. We evaluate this method on a challenging database collected by us in real-world child-clinician interactive scenarios and the proposed method achieved significantly better results than baselines using only facial information. Thus it is suggested that there is a potential to assist in clinical practice by providing the recognized emotion as feedback. [ABSTRACT FROM AUTHOR]

Black carbon (BC) in the Tibetan Plateau (TP) region has distinct climate effect, which strongly depends on its mixing state. The aging processes of BC in TP are subject to emissions from various regions, resulting in considerable variability of its mixing state and physicochemical properties. However, the mechanism and magnitude of this effect are not yet clear. In this study, filed observations on physicochemical properties of BC-containing particles (PMBC) were conducted in the northeast (Xihai) and southeast (Lulang) regions of the TP to investigate the impacts of transported emissions from lower-altitude areas on BC characteristics in the TP. Large spatial discrepancies were found in the chemical composition of PMBC. Both sites showed higher concentrations of PMBC when they were affected by transported airmasses outside the TP, but with diverse chemical composition. Source apportionment for organic aerosol (OA) suggested that primary OA in the northeastern TP was attributed to hydrocarbon OA (HOA) from anthropogenic emissions, while it was dominated by biomass burning OA (BBOA) in the southeastern TP. Regarding secondary aerosol, a marked enhancement in nitrate fraction was observed on aged BC coating in Xihai when the airmasses were brought by updrafts and easterly winds from lower-altitude areas. With the development of boundary layer, the enhanced turbulent mixing promoted the elevation of anthropogenic pollutants. In contrast to Xihai, the thickly coated BC in Lulang was mainly caused by self-elevated biomass burning plume from the South Asia, showing a large contribution of secondary organic aerosol (SOA). The distinct transported emissions lead to substantial variations of both chemical composition and light absorption ability of BC across the TP. The thicker coating and higher mass absorption cross-section (MAC) of PMBC in airmasses elevated from lower-altitude regions reveals the promoted BC aging processes and their impacts on the mixing state and light absorption of BC in TP. These findings emphasize the vulnerability of plateau regions to influences of elevated emissions, leading to significant changes in BC concentration, mixing states and light absorption across the TP, which needs to be considered in the evaluation of BC radiative effects for the TP region. [ABSTRACT FROM AUTHOR]