322 research outputs found
Chapter 5:Atmospheric Chemistry of Halogenated Organic Compounds
No full textHalogenated organic compounds play an important role in atmospheric chemistry. We provide an overview of the atmospheric chemistry of halogenated organic compounds starting with a discussion of sources, emissions, and atmospheric concentrations. The chemistry associated with formation and loss of stratospheric ozone and processes related to halogenated organics is described. A discussion of the atmospheric chemistry of halogenated alkanes, alkenes, oxygenates, sulfur-, nitrogen-, and phosphorus-containing organics is provided. The contribution of halogenated organics to radiative forcing of climate change and the environmental impact of halogenated organic compounds is described.</p
Steroid-induced deficiency of mucosal-associated invariant T cells in the chronic Obstructive Pulmonary Disease lung: Implications for Nontypeable <i>Haemophilus influenzae</i> Infection
No full textRationale: Mucosal associated invariant T (MAIT) cells are a recently-described, abundant, pro-inflammatory T cell subset with unknown roles in pulmonary immunity. Non-typeable Haemophilus influenzae (NTHi) is the leading bacterial pathogen during COPD exacerbations and a plausible target for MAIT cells.Objectives: To investigate whether MAIT cells respond to NTHi and the effects of inhaled corticosteroids on their frequency and function in COPD. Methods: 11 participants with COPD receiving inhaled corticosteroids (ICS), 8 with steroid-naïve COPD and 21 healthy controls underwent phlebotomy, sputum induction, bronchoalveolar-lavage and endobronchial biopsy. Pulmonary and monocyte-derived macrophages were cultured in vitro with NTHi. Measurements: Frequencies of Va7.2+CD161+ MAIT cells, surface expression of MHC-related protein 1 (MR1) and intracellular IFN-y expression were measured by flow cytometry.Main Results: MAIT cell frequencies were reduced in peripheral blood in ICS-treated COPD (median 0.38% (IQR, 0.25-0.96) compared with health (1.8% (IQR, 1.4-2.5), P=0.001)) or steroid-naïve COPD (1.8% (1.2-2.3), P=0.04). MAIT cells were reduced in bronchial biopsies in steroid-treated COPD (0.73% (0.46-1.3)) compared with health (4.0% (1.6-5.0), P=0.02). Co-culture of live NTHi increased macrophage surface expression of MR1 and induced IFN-? from CD4 cells and CD8 cells, but most potently from MAIT cells (median IFN-y positive frequencies 2.9%, 8.6% and 27.6% respectively). In vitro fluticasone and budesonide reduced MR1 surface expression 2-fold and decreased NTHi-induced IFN-y secretion 8-fold.Conclusions: MAIT cells are deficient in blood and bronchial tissue in steroid-treated, but not steroid-naïve COPD. NTHi constitutes a target for pulmonary MAIT cell immune responses, which are significantly impaired by corticosteroids.<br/
Atmospheric Chemistry of n-C6F13CH2CHO: Formation from n-C6F13CH2CH2OH, Kinetics, and Mechanisms of Reactions with Chlorine Atoms and OH Radicals
No full textSmog chamber FTIR techniques were used to measure k(Cl + n-C 6F13CH2CHO) = (1.84 ± 0.22) -10 -11, k(Cl + n-C6F13CHO) = (1.75 ± 0.70) - 10-12, and k(OH + n-C6F13CH2CHO) = (2.15 ± 0.26) - 10-12 cm3 molecule-1 s-1 in 700 Torr of N2 or air diluent at 296 ± 2K. The chlorine-atom-initiated oxidation of n-C6F13CH 2CH2OH in air gives n-C6F13CH 2CHO in a molar yield of 99 ± 8%. The atmospheric fate of n-C6F13CH2C(O) radicals is reaction with O 2, while the fate of n-C6F13C(O) radicals is decomposition to give n-C6F13 radicals and CO. The results are discussed with respect to the atmospheric chemistry of fluorinated alcohols and the formation of perfluorocarboxylic acids.Fil: Chiappero, Malisa Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Argüello, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Hurley, Michael D.. Ford Motor Company; Estados UnidosFil: Wallington, Timothy J.. Ford Motor Company; Estados Unido
Multitissue transcriptomics delineates the diversity of airway T cell functions in asthma
No full textAsthma arises from the complex interplay of inflammatory pathways in diverse cell types and tissues. We sought to undertake a comprehensive transcriptomic assessment of the epithelium and airway T cells that remain understudied in asthma, and investigate interactions between multiple cells and tissues. Epithelial brushings and flow-sorted CD3+ T cells from sputum and bronchoalveolar lavage were obtained from healthy subjects (N=19) and asthmatic patients (mild, moderate and severe asthma; N=46). Gene expression was assessed using Affymetrix HT HG-U133+ PM GeneChips and results were validated by real-time quantitative PCR. In the epithelium, IL-13 response genes (POSTN, SERPINB2, CLCA1), mast cell mediators (CPA3, TPSAB1), inducible nitric oxide synthase and cystatins (CST1, CST2, CST4) were upregulated in mild asthma but, except for cystatins, were suppressed by corticosteroids in moderate asthma. In severe asthma – with predominantly neutrophilic phenotype – several distinct processes were upregulated including neutrophilia (TCN1, MMP9), mucins and oxidative stress responses. The majority of the disease signature was evident in sputum T cells in severe asthma, where 267 genes were differentially regulated compared to health, highlighting compartmentalisation of inflammation. This signature included IL-17-inducible chemokines (CXCL1, CXCL2, CXCL3, IL8, CSF3) and chemoattractants for neutrophils (IL8, CCL3, LGALS3), T cells and monocytes. A protein interaction network in severe asthma highlighted signatures of responses to bacterial infections across tissues (CEACAM5, CD14, TLR2) including toll-like receptor signalling. In conclusion, the82 activation of innate immune pathways in the airways suggests that activated T cells may be driving neutrophilic inflammation and steroid-insensitive IL-17 response in severe asthma
Carbon implications of marginal oils from market-derived demand shocks
No full textExpanded use of novel oil extraction technologies has increased the variability of petroleum resources and diversified the carbon footprint of the global oil supply1. Past life-cycle assessment (LCA) studies overlooked upstream emission heterogeneity by assuming that a decline in oil demand will displace average crude oil2. We explore the
life-cycle greenhouse gas emissions impacts of marginal crude sources, identifying the upstream carbon intensity (CI) of the producers most sensitive to an oil demand decline (for example, due to a shift to alternative vehicles). We link econometric models
of production profitability of 1,933 oilfields (~90% of the 2015 world supply) with their production CI. Then, we examine their response to a decline in demand under three oil market structures. According to our estimates, small demand shocks have different upstream CI implications than large shocks. Irrespective of the market structure, small shocks (−2.5% demand) displace mostly heavy crudes with ~25–54% higher CI than that of the global average. However, this imbalance diminishes as the shocks become bigger and if producers with market power coordinate their response to a demand decline.
The carbon emissions benefits of reduction in oil demand are systematically dependent on the magnitude of demand drop and the global oil market structure
Science of the Environmental Chamber
No full textAtmospheric chemistry is simulated in the laboratory using several types of environmental chambers; these include the batch chamber, the continuously mixed flow reactor, and the flow tube reactor. These reactors are used to study gas-phase oxidation of volatile organic compounds (VOCs) as well as the formation of secondary organic aerosol (SOA), the process by which VOCs undergo oxidation to form low-volatility products that condense onto particles. This chapter focuses on the design and characterization of environmental chambers, including: (1) radiation conditions; (2) chamber mixing state; (3) chemical blank experiments; (4) free radical generation (principally the hydroxyl (OH) radical); (5) high-versus-low-NO conditions that govern the nature of VOC oxidation chemistry; (6) deposition of particles onto chamber walls; (7) deposition of organic vapors onto chamber walls; and (8) determination of the yield of SOA. Comparison of the design and behavior of the different types of reactor is addressed in detail. The performance of the differential mobility analyzer (DMA), the prime instrument for measuring aerosol size distributions in chambers, is addressed
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Evaluated kinetic and photochemical data for atmospheric chemistry: Volume VII - Criegee intermediates
No full textThis article, the seventh in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers an extension of the gas-phase and photochemical reactions related to Criegee intermediates previously published in Atmospheric Chemistry and Physics (ACP) in 2006 and implemented on the IUPAC website up to 2020. The article consists of an introduction, description of laboratory measurements, a discussion of rate coefficients for reactions of O3 with alkenes producing Criegee intermediates, rate coefficients of unimolecular and bimolecular reactions and photochemical data for reactions of Criegee intermediates, and an overview of the atmospheric chemistry of Criegee intermediates. Summary tables of the recommended kinetic and mechanistic parameters for the evaluated reactions are provided. Data sheets summarizing information upon which the recommendations are based are given in two files, provided as a Supplement to this article
OBSERVATION OF THE ELECTRONIC TRANSITION OF THE RADICAL
No full textO. J. Neilsen, E. Gamborg, J. Sehested, T. J. Wallington and M. D. Hurley, J. Phys. Chem. 98, 9518(1994) T. J. Wallington, P. Dagaut and M. J. Kurylo, Chem. Rev. 92, 667(1992) E. H. Fink and D. A. Ramsay, J. Mol. Spec. 185, 304(1997) M. B. Pushkarsky, S. J. Zalyubovsky and T. A. Miller, J. Chem. Phys. 112, 10695(2000) S. Sander, H. Pernice and H. Willner, Chem. Eur. J. 6, 3645(2000) N. Vanderkooi and W. B. Fox, J. Chem. Phys. 47, 3634(1967)Author Institution: The Ohio State University; Laser Spectroscopy Facility, Department of Chemistry, The Ohio State UniversityFluorinated peroxy radicals form a class of important intermediates in oxidation and atmospheric of chlorofluorohydrocarbons (CFCs) and hydrofluorocarbons (HFCs). Therefore recently much effort has been devoted to the study of the peroxy kinetics. Detection of peroxy radicals has been largely accomplished via monitoring their broad and structureless absorption . A near IR transition has been observed for the and for the simplest alkyl peroxy . However for the fluorinated analogues there appear to have been no such observations. Their known spectroscopy seems limited to the above mentioned broad UV transition, vibrational in the state using matrix isolation techniques and to EPR of the radicals in solution. We report the first observation of a sharp, structured electronic spectrum for a fluorinated alkyl peroxy radical using the technique of cavity ringdown spectroscopy (CRDS). A value of for the transition of has been determined, as well as values for some state vibrational frequencies. Initial kinetic observations on have been carried out using CRDS to monitor its concentration
Corrigendum to "Evaluated kinetic and photochemical data for atmospheric chemistry: Volume V – heterogeneous reactions on solid substrates" published in Atmos. Chem. Phys. 10, 9059–9223, 2010
No full textNo abstract available
Rate constant of the reaction of chlorine atoms with methanol over the temperature range 291–475 K
No full textThe rate constant of the reaction Cl + CH 3 OH ( k 1 ) has been measured in 500–950 Torr of N 2 over the temperature range 291–475 K. The rate constant determination was carried out using the relative rate technique with C 2 H 6 as the reference compound. Experiments were performed by irradiating mixtures of CH 3 OH, C 2 H 6 , Cl 2 , and N 2 with UV light from a fluorescent lamp whose intensity peaked near 360 nm. The resultant temperature-dependent rate expression is k 1 = 8.6 (±1.3) × 10 −11 exp[−167 (±60)/T] cm 3 molecule −1 s −1 . Error limits represent data scatter (2Σ) in the current experiments and do not include error in the reference rate constant. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 113–116, 2010Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/64549/1/20474_ftp.pd
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