Search

Open biomass burning (OBB) emits significant amounts of non-methane hydrocarbons (NMHCs), and the mixing of OBB with urban plumes could exacerbate regional ozone (O3) pollution. In the present study, an observational field campaign was performed in a rural area at the northern edge of the Yangtze River Delta region (YRDR) from 15 May to 24 June 2010, during intensive open burning of wheat residues. The net photochemical production rate of oxidant (Ox = O3 + NO2) at the site was evaluated based on a box model (Regional Atmospheric Chemical Mechanism, Version 2) constrained by real-time ambient measurements (e.g., O3, volatile organic compounds (VOCs), NOx (NO2 + NO), J values). Our results showed that both in situ photochemistry and direct transport from urban areas in the YRDR were responsible for the high Ox concentration at the site. During an OBB-impact case, net photochemical production of Ox in the daytime was pronounced, with a 6 h averaged Ox production rate of 13 ± 4 ppbv h-1 (maximum value of 21 ppbv h-1 at 12:00 CST). Photochemical Oxproduction changed from VOC-limited in the morning to NOx-limited in the afternoon due to the rapid photochemical consumption of NOx during the day. A combined analysis with positive matrix factorization demonstrated that O3 pollution in the rural area of the YRDR was largely affected by urban emission, and OBB-related emissions also contributed to in situ photochemical production, particularly in the afternoon. Our study suggested that a joint effort in reducing both NMHCs (e.g., aromatics) and NOx emissions in the urban area, as well as local OBB activities, may be effective in eliminating high-O3 pollution risk in the rural areas of the YRDR. [ABSTRACT FROM AUTHOR]

Open biomass burning (OBB) has been reported to emit substantial amounts of non-methane hydrocarbons (NMHCs), and the mixing of OBB with urban plumes could exacerbate regional ozone (O3) pollution. In the present study, an observational field campaign was performed in a rural area at the edge of Yangtze River Delta region (YRDR) during harvest season when intensive open burning of wheat residues was observed. The O3 production rate at the site was calculated using a photochemical box model (Regional Atmospheric Chemical Mechanism, Version 2) constrained by realtime ambient measurements (e.g., O3, volatile organic compounds (VOCs), the sum of NO2 +NO (NOx), J values). During the period impacted by OBB, the O3 concentration frequently exceeded 100 ppbv. Analysis showed that the net O3 production was pronounced, in particular when the site was characterized by a prevailing southerly wind that also brought substantial amounts of NOx emitted from urban areas. At these times, the maximum rate of O3 production was 20 ppbv h-1 with potential production rate of 102 ppbv on a daily basis. The O3 production at the site was typically VOC-sensitive in the morning because NO3 dominated the plumes. However, in the afternoon, conditions became NOx-sensitive due to the rapid photochemical consumption of NOx in the production of O3. A positive matrix factorization analysis indicated that solvent usage and OBB were the primary contributors to the mass fraction of ambient NMHCs observed at the study site, and were responsible for 35 and 23% of the total O3 production, respectively. The preferential presence of NOx in the morning inhibited net O3 production; meanwhile O3 built up in the afternoon due to a decrease in NOx concentrations. These results indicated that a joint effort in the regulation of solvent (aromatics) usage and OBB, as well as NOx from on-road vehicle exhaust may be effective in eliminating high-O3 pollution risk in the rural areas of the YRDR. [ABSTRACT FROM AUTHOR]

We conducted an intensive field campaign at the summit of Mt. Tai (36.26℃ N, 117.11℃ E, 1534m above sea level), Shandong Province, located at the center of central East China, during the period 28 May to 30 June 2006, to study seasonal maxima of regional air pollution with respect to ozone (O3) and aerosols. The specific objectives, campaign design, and major findings are summarized. High concentrations of O3 and its precursors, and aerosols, were detected and studied in the context of annual variations. Most importantly, we identified that emissions from regionalscale open crop residue burning after the harvesting of winter wheat, together with photochemical aging, strongly increased the concentrations of O3, aerosols, and primary pollutants in this month of year. Studies of in situ photochemical activity, regional source attribution of O3, O3-aerosol interactions, validation of satellite observations of tropospheric NO2, behaviors of volatile organic compounds and organic/inorganic aerosol species, loss rates of black carbon (BC), and instrument inter-comparisons are also summarized. The observed BC levels must have a strong impact on the regional climate. [ABSTRACT FROM AUTHOR]

Abstract: Various alloys are interconnected with W using a Ni intermediate layer by the diffusion bonding (DB) technique. During solid-state heating in the DB technique, however, reactive diffusion occurs at the interconnection between Ni and W. In order to examine the kinetics of the reactive diffusion, sandwich Ni/W/Ni diffusion couples were isothermally annealed at temperatures of T =1023–1173K for various times up to t =366h. Owing to annealing, Ni4W is produced as a layer at the Ni/W interface in the diffusion couple and grows predominantly towards Ni. The thickness of the Ni4W layer increases in proportion to a power function of the annealing time. The exponent of the power function is close to 0.5 at T =1173K and gradually decreases with decreasing annealing temperature. Furthermore, grain growth takes place in Ni4W due to annealing. Therefore, volume diffusion is the rate-controlling process for the growth of Ni4W at T =1173K. At T <1173K, however, boundary diffusion contributes to the rate-controlling process, and the contribution of boundary diffusion increases with decreasing annealing temperature. On the other hand, a region alloyed with W is formed in Ni from the Ni4W/Ni interface by diffusion-induced recrystallization (DIR). The growth rate of the DIR region is much greater than the penetration rate of W into Ni by volume diffusion, and the concentration of W in the DIR region at the Ni4W/Ni interface is equal to the solubility of W in Ni. Such growth behavior of the DIR region was numerically analyzed using a mathematical model. The analysis indicates that the growth of the DIR region is controlled by the interface reaction at the moving boundary of the DIR region as well as the boundary diffusion along the grain boundaries across the DIR region under the present annealing conditions. [Copyright &y& Elsevier]

Owing to recent industrialization, Central East China has become a significant source of air pollutants. To examine the processes controlling the chemistry and transport of tropospheric ozone, we performed on-line measurements of non-methane volatile organic compounds (NMVOCs) as part of an intensive field campaign at Mount Tai, China, in June 2006 (MTX2006), using proton transfer reaction mass spectrometry (PTR-MS). Temporal variations of NMVOCs were recorded in mass-scan mode from m/z 17 to m/z 300 during 12-30 June 2006. More than thirty kinds ofNMVOCs were detected up to m/z 160, including alkenes, aromatics, alcohols, aldehydes, and ketones. In combination with non-methane hydrocarbon data obtained by a gas chromatography with flame ionization detection, it was found that oxygenated VOCs were the predominant NMVOCs. Diurnal variations depending mainly on local photochemistry were observed during 24-28 June. During the night of 12 June, we observed an episode of high NMVOCs concentrations attributed to the burning of agricultural biomass. The ΔNMVOCs/ΔCO ratios derived by PTR-MS measurements for this episode (with biomass burning (BB) plume) and during 16-23 June (without BB plume) are compared to emission ratios from various types of biomass burning as reviewed by Andreae and Merlet (2001) and to ratios recently measured by PTR-MS in tropical forests (Karl et al., 2007) and at urban sites (Warneke et al., 2007). [ABSTRACT FROM AUTHOR]

Owing to recent industrialization, Central East China has become a significant source of air pollutants. To examine the processes controlling the chemistry and transport of tropospheric ozone, we continuously measured non-methane volatile organic compounds (NMVOCs) as part of an intensive field campaign at Mount Tai, China, in June 2006 (MTX2006), using proton transfer reaction mass spectrometry (PTR-MS). Temporal variations of NMVOCs were recorded in mass-scan mode from m/z 17 to m/z 300 during 12-30 June 2006. More than thirty kinds of NMVOCs were detected up to m/z 160, including alkenes, aromatics, alcohols, aldehydes, and ketones. Oxygenated VOCs were the predominant NMVOCs. During the night of 12 June, we observed an episode of high NMVOCs concentrations attributed to the burning of agricultural biomass. The ΔNMVOCs/ΔCO ratios derived by PTR-MS measurements for this episode are compared to emission ratios from various types of biomass burning as reviewed by Andreae and Merlet (2001) and to ratios recently measured by PTR-MS in tropical forests (Karl et al., 2007) and at urban sites (Warneke et al., 2007). [ABSTRACT FROM AUTHOR]

An observation-based box model approach was undertaken to estimate concentrations of OH, HO2, and RO2 radicals and the net photochemical production rate of ozone at the top of Mount Tai, located in the middle of Central East China, in June 2006. The model calculation was constrained by the measurements of O3, H2O, CO, NO, NO2, hydrocarbon, HCHO, and CH3CHO concentrations, and temperature and J values. The net production rate of ozone was estimated to be 6.4 ppb h-1 as a 6-h average (09:00-15:00 CST), suggesting 58±37 ppb of ozone is produced in one day. Thus the daytime buildup of ozone recorded at the mountain top as ~23 ppb on average is likely affected by in situ photochemistry as well as by the upward transport of polluted air mass in the daytime. On days with high ozone concentrations (hourly values exceeding 100 ppb at least once), in situ photochemistry was more active than it was on low ozone days, suggesting that in situ photochemistry is an important factor controlling ozone concentrations. Sensitivity model runs for which different NOx and hydrocarbon concentrations were assumed suggested that the ozone production occurred normally under NOx-limited conditions, with some exceptional periods (under volatile-organic-compound-limited conditions) in which there was fresh pollution. We also examined the possible influence of the heterogeneous loss of gaseous HO2 radicals in contact with aerosol particle surfaces on the rate and regimes of ozone production. [ABSTRACT FROM AUTHOR]

Background Unsaturated fatty acids from sebum affect calcium dynamics in epidermal keratinocytes, disrupt the barrier function and induce abnormal keratinization. However, the mechanisms of these effects have not been clarified. Objectives To investigate the function of unsaturated fatty acids in epidermis. Methods Antagonists of calcium channel receptors were applied to mouse skin together with oleic acid. Measurements were made of transepidermal water loss (TEWL), and hyperproliferation was assessed. The effects of the antagonists on calcium influx into cultured normal human keratinocytes and on cytokine production were also evaluated. Results N-methyl-d-aspartate (NMDA) receptor antagonists such as MK801 and D-AP5 specifically inhibited the increase in TEWL caused by oleic acid, and suppressed keratinocyte hyperproliferation. These compounds also inhibited the increase in the intracellular concentration of calcium ions induced by oleic acid. MK801 suppressed the production of interleukin-1α by keratinocytes induced by oleic acid. Conclusions Unsaturated fatty acids such as oleic acid might function via NMDA receptors. [ABSTRACT FROM AUTHOR]

Formaldehyde (HCHO), the most abundant carbonyl compound in the atmosphere, is generated as an intermediate product in the oxidation of nonmethane hydrocarbons. Proton transfer reaction mass spectrometry (PTR-MS) has the capability to detect HCHO from ion signals at m/z 31 with high time-resolution. However, the detection sensitivity is low compared to other detectable species, and is considerably affected by humidity, due to back reactions between protonated HCHO and water vapor prior to analysis. We performed a laboratory calibration of PTR-MS for HCHO and examined the detection sensitivity and humidity dependence at various field strengths. Subsequently, we deployed the PTR-MS instrument in a field campaign at Mount Tai in China in June 2006 to measure HCHO in various meteorological and photochemical conditions; we also conducted intercomparison measurements by Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS). Correction of interference in the m/z 31 signals by fragments from proton transfer reactions with methyl hydroperoxide, methanol, and ethanol greatly improves agreement between the two methods, giving the correlation [HCHO]MAX-DOAS=(0.99±0.16) [HCHO]PTR-MS+(0.02±0.38), where error limits represent 95% confidence levels. [ABSTRACT FROM AUTHOR]

To investigate potential interactions between lidocaine (lignocaine) metabolism and premedication drugs, i.e. psychotropic and antianxiety agents (diazepam, midazolam), hypnotics (pentobarbital, thiamylal), depolarizing neuromuscular blocking agents (vecuronium, pancuronium and suxamethonium), an antihypertensive agent (clonidine) and an H2-receptor blocking agent (cimetidine) using human liver microsomesin vitro.The interaction effects between lidocaine and premedication were examined using human liver microsomal preparations and monitored for enzyme activity. The lidocaine and its main metabolite (monoethylglycinexylide) were measured by HPLC/UV.Lidocaine metabolism was non-competitively inhibited by midazolam (Ki = 77·6 μm). Thiamylal was a competitive inhibitor of lidocaine metabolism (Ki = 885 μm). Cimethidine, pancuronium and vecuronium weakly inhibited lidocaine metabolism in a concentration-depend manner over the therapeutic range in human liver microsomes. On the contrary, suxamethonium, pentobarbital and clonidine did not inhibit lidocaine metabolism over the therapeutic range in human liver microsomes.These results show that the interactions between lidocaine and midazolam and thiamylal are of potential toxicological and clinical significance. [ABSTRACT FROM AUTHOR]

In this study, we have investigated the relationship between lidocaine metabolism and premedication, i.e., psychotropic and anti-anxiety agents (diazepam, midazolam), hypnotics (pentobarbital, thiamylal), depolarizing muscular relaxants (vecuronium, pancuronium and suxamethonium), an active anti-hypertensive (clonidine) and an H[sub 2] receptor antagonist (cimetidine) using rat hepatic microsomes in vitro. Lidocaine metabolism was noncompetitively inhibited by midazolam (K[sub i]=29.0 μM). Thilamylal was a moderate competitive inhibitor of lidocaine metabolism (K[sub i]=77.8 μM). Pentobarbital, diazepam and cimetidine weakly inhibited lidocaine metabolism formation in a concentration-dependent manner at high substrate concentrations. On the other hand, vecuronium, pancuronium, suxamethonium and clonidine did not inhibit lidocaine metabolism over the therapeutic range. These results show that the interaction between lidocaine and midazolam and thiamylal, catalyzed by a similar cytochrome P450, is of potential importance in toxicological and clinical studies. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Anaesthesia / Journal Canadien d'Anesthésie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)