Emission characteristics of nonmethane hydrocarbons from private cars and taxis at different driving speeds in Hong Kong

Vehicular emissions are the major sources of a number of air pollutants including nonmethane hydrocarbons (NMHCs) in urban area. The emission composition and emission factors of NMHCs from vehicles are currently lacking in Hong Kong. In this study, speciation and emission factors of NMHCs emitted from gasoline-fuelled private cars and liquefied petroleum gas (LPG)-fuelled taxis at different driving speeds were constructed using a chassis dynamometer. Large variations in the contributions of individual NMHC species to total emission were observed for different private cars at different driving speeds. The variations of individual NMHC emissions were relatively smaller for taxis due to their relatively homogeneous year of manufacture and mileages. Incomplete combustion products like ethane, ethene and propene were the major component of both types of vehicles, while unburned fuel component was also abundant in the exhausts of private cars and taxis (i.e. i-pentane and toluene for private car, and propane and butanes for taxi). Emission factors of major NMHCs emitted from private cars and taxis were estimated. High emission factors of ethane, n-butane, i/n-pentanes, methylpentanes, trimethylpentanes, ethene, propene, i-butene, benzene, toluene and xylenes were found for private cars, whereas propane and i/n-butanes had the highest values for taxis. By evaluating the effect of vehicular emissions on the ozone formation potential (OFP), it was found that the contributions of olefinic and aromatic hydrocarbons to OFP were higher than that from paraffinic hydrocarbons for private car, whereas the contributions of propane and i/n-butanes were the highest for taxis. The total OFP value was higher at lower speeds (≤50 km h-1) for private cars while a minimum value at driving speed of 100 km h-1 was found for taxis. At the steady driving speeds, the total contribution of NMHCs emitted from LPG-fuelled taxis to the OFP was much lower than that from gasoline-fuelled private cars. However, at idling state, the contribution of NMHCs from LPG-fuelled vehicles to OFP was comparable to that from gasoline-fuelled vehicles. The findings obtained in this study can be used to mitigate the air pollution caused by vehicles in highly dense urban areas. © 2011 Elsevier Ltd

Reduced susceptibility to ischaemic brain damage following photochemical stroke in transgenic mice overexpressing the amyloid precursor protein

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Clinical features and risk factors of cognitive impairment after stroke in Hong Kong Chinese

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Characteristics of nonmethane hydrocarbons (NMHCs) in industrial, industrial-urban, and industrial-suburban atmospheres of the Pearl River Delta (PRD) region of south China

In a study conducted in late summer 2000, a wide range of volatile organic compounds (VOCs) were measured throughout five target cities in the Pearl River Delta (PRD) region of south China. Twenty-eight nonmethane hydrocarbons (NMHCs; 13 saturated, 9 unsaturated, and 6 aromatic) are discussed. The effect of rapid industrialization was studied for three categories of landuse in the PRD: Industrial, industrial-urban, and industrial-suburban. The highest VOC mixing ratios were observed in industrial areas. Despite its relatively short atmospheric lifetime (2-3 days), toluene, which is largely emitted from industrial solvent use and vehicular emissions, was the most abundant NMHC quantified. Ethane, ethene, ethyne, propane, n-butane, i-pentane, benzene, and m-xylene were the next most abundant VOCs. Direct emissions from industrial activities were found to greatly impact the air quality in nearby neighborhoods. These emissions lead to large concentration variations for many VOCs in the five PRD study cities. Good correlations between isoprene and several short-lived combustion products were found in industrial areas, suggesting that in addition to biogenic sources, anthropogenic emissions may contribute to urban isoprene levels. This study provides a snapshot of industrial, industrial-urban, and industrial-suburban NMHCs in the five most industrially developed cities of the PRD. Increased impact of industrial activities on PRD air quality due to the rapid spread of industry from urban to suburban and rural areas, and the decrease of farmland, is expected to continue until effective emission standards are implemented. Copyright 2006 by the American Geophysical Union

Ambient halocarbon mixing ratios in 45 Chinese cities

During this study 158 whole air samples were collected in 45 Chinese cities in January and February 2001. The spatial distribution of different classes of halocarbons in the Chinese urban atmosphere, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), Halon-1211, and other chlorinated compounds is presented and discussed. Most of these compounds were enhanced compared to background levels. However, the mean enhancement of CFCs was relatively small, with CFC-12 and CFC-11 increases of 6% (range 1-31%) and 10% (range 2-89%), respectively, with respect to the global background. On the contrary, strongly enhanced levels of CFC replacement compounds and halogenated compounds used as solvents were measured. The average Halon-1211 concentration exceeded the background of 4.3 pptv by 75% and was higher than 10 pptv in several cities. Methyl chloride mixing ratios were also strongly elevated (78% higher than background levels), which is likely related to the widespread use of coal and biofuel in China. © 2006 Elsevier Ltd. All rights reserved

Melatonin reduced volume of cerebral infarct induced by photothrombosis in wild-type mice, not in Cyclooxygenase-1 gene knockout mice

Cyclooxygenase (COX) is crucial in inflammation and plays important role in cerebral ischemia. Anti-inflammatory effects of melatonin have been verified in previous studies. In this study, cerebral blood flow (CBF) was monitored during operation, infarct volume (IFV) was determined with 5-triphenyltetrazolium chloride (TTC) staining and MR image, and neurological functions were evaluated with turn in an alley and fall pole test in both COX-1-gene knockout and wide-type mice with or without melatonin administration 3 days after photothrombosis. CBF reduction, IFV and neurological deficits were not significantly different in COX-1 wild-type and COX-1 knockout mice. Melatonin (15 mg/kg) intraperitoneal injection decreased the CBF reduction, IFV and the latency to turn in an alley in COX-1 wide-type mice, whereas the neuroprotective effect of melatonin was attenuated in COX-1 knockout mice. We concluded that melatonin reduced susceptibility to photothrombotic stroke. COX-1 gene knockout does not alter the susceptibility to cerebral ischemia caused by photothrombosis. COX-1 plays an important role in the pathway of the protection of melatonin.published_or_final_versio

Translation factor eIF5a is essential for IFNγ production and cell cycle regulation in primary CD8 T lymphocytes

Control of mRNA translation adjusts protein production rapidly and facilitates local cellular responses to environmental conditions. Traditionally initiation of translation is considered to be a major translational control point, however, control of peptide elongation is also important. Here we show that the function of the elongation factor, eIF5a, is regulated dynamically in naïve CD8(+) T cells upon activation by post-translational modification, whereupon it facilitates translation of specific subsets of proteins. eIF5a is essential for long-term survival of effector CD8(+) T cells and sequencing of nascent polypeptides indicates that the production of proteins which regulate proliferation and key effector functions, particularly the production of IFNγ and less acutely TNF production and cytotoxicity, is dependent on the presence of functional eIF5a. Control of translation in multiple immune cell lineages is required to co-ordinate immune responses and these data illustrate that translational elongation contributes to post-transcriptional regulons important for the control of inflammation

Characteristics of nonmethane hydrocarbons (NMHCs) in industrial, industrial-urban, and industrial-suburban atmospheres of the Pearl River Delta (PRD) region of south China

Author name used in this publication: Chan, Lo-Yin.Author name used in this publication: Chan, Chuen-Yu.2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Hepatitis C in HIV-infected individuals: a systematic review and meta-analysis of estimated prevalence in Africa

Although hepatitis C virus (HCV) screening is recommended for all HIV-infected patients initiating antiretroviral therapy, data on epidemiologic characteristics of HCV infection in resource-limited settings are scarce