21. Observations of the release of non-methane hydrocarbons from fractured shaleRoberto Sommariva, Robert S Blake, Robert J Cuss, Rebecca L Cordell, Jon F Harrington, Iain R White, Paul S Monks, 2014, izvirni znanstveni članek Opis: The organic content of shale has become of commercial interest as a source of hydrocarbons, owing to the development of hydraulic fracturing ("fracking"). While the main focus is on the extraction of methane, shale also contains significant amounts of non-methane hydrocarbons (NMHCs). We describe the first real-time observations of the release of NMHCs from a fractured shale. Samples from the Bowland-Hodder formation (England) were analyzed under different conditions using mass spectrometry, with the objective of understanding the dynamic process of gas release upon fracturing of the shale. A wide range of NMHCs (alkanes, cycloalkanes, aromatics, and bicyclic hydrocarbons) are released at parts per million or parts per billion level with temperature- and humidity-dependent release rates, which can be rationalized in terms of the physicochemical characteristics of different hydrocarbon classes. Our results indicate that higher energy inputs (i.e., temperatures) significantly increase the amount of NMHCs released from shale, while humidity tends to suppress it; additionally, a large fraction of the gas is released within the first hour after the shale has been fractured. These findings suggest that other hydrocarbons of commercial interest may be extracted from shale and open the possibility to optimize the "fracking" process, improving gas yields and reducing environmental impacts.
Najdeno v: ključnih besedah
Ključne besede: Environmental impact, Hydraulic fracturing, Mass spectrometry
Objavljeno: 18.07.2019; Ogledov: 2161; Prenosov: 0
 Polno besedilo (2,47 MB) |
22. TD/GC–MS analysis of volatile markers emitted from mono- and co-cultures of Enterobacter cloacae and Pseudomonas aeruginosa in artificial sputumCraig Portsmouth, Pedro Póvoa, Jan H Leopold, Pouline M P van Oort, Emili Diaz, Gemma Goma, Timothy Felton, Paul Dark, Alan Davie, Luis Coelho, Lieuwe D Bos, Marta Camprubi, Antonio Artigas, Jonathan Barnard-Smith, Waqar M Ahmed, Stephen J Fowler, Tamara M E Nijsen, Royston Goodacre, Weda Hans, Hugo Knobel, Oluwasola Lawal, Iain R White, 2018, izvirni znanstveni članek Opis: Introduction: Infections such as ventilator-associated pneumonia (VAP) can be caused by one or more pathogens. Current methods for identifying these pathogenic microbes often require invasive sampling, and can be time consuming, due to the requirement for prolonged cultural enrichment along with selective and differential plating steps. This results in delays in diagnosis which in such critically ill patients can have potentially life-threatening consequences. Therefore, a non-invasive and timely diagnostic method is required. Detection of microbial volatile organic compounds (VOCs) in exhaled breath is proposed as an alternative method for identifying these pathogens and may distinguish between mono- and poly-microbial infections. Objectives: To investigate volatile metabolites that discriminate between bacterial mono- and co-cultures. Methods: VAP-associated pathogens Enterobacter cloacae and Pseudomonas aeruginosa were cultured individually and together in artificial sputum medium for 24 h and their headspace was analysed for potential discriminatory VOCs by thermal desorption gas chromatography–mass spectrometry. Results: Of the 70 VOCs putatively identified, 23 were found to significantly increase during bacterial culture (i.e. likely to be released during metabolism) and 13 decreased (i.e. likely consumed during metabolism). The other VOCs showed no transformation (similar concentrations observed as in the medium). Bacteria-specific VOCs including 2-methyl-1-propanol, 2-phenylethanol, and 3-methyl-1-butanol were observed in the headspace of axenic cultures of E. cloacae, and methyl 2-ethylhexanoate in the headspace of P. aeruginosa cultures which is novel to this investigation. Previously reported VOCs 1-undecene and pyrrole were also detected. The metabolites 2-methylbutyl acetate and methyl 2-methylbutyrate, which are reported to exhibit antimicrobial activity, were elevated in co-culture only. Conclusion: The observed VOCs were able to differentiate axenic and co-cultures. Validation of these markers in exhaled breath specimens could prove useful for timely pathogen identification and infection type diagnosis.
Najdeno v: ključnih besedah
Ključne besede: Bacteria, Enterobacter cloacae, Gas Chromatography-Mass Spectrometry, Infection, Pseudomonas aeruginosa, Volatile organic compounds
Objavljeno: 18.07.2019; Ogledov: 2341; Prenosov: 99
Polno besedilo (1,29 MB) |
23. Capturing and Storing Exhaled Breath for Offline AnalysisStephen J Fowler, Iain R White, 2019, samostojni znanstveni sestavek ali poglavje v monografski publikaciji Opis: In this chapter we will summarize and discuss methods for the capture and storage of exhaled breath, prior to offline (and indirect online) analysis. We will detail and compare methods currently in use, including their applications, key strengths, and limitations. In synthesizing the best features of each technique, we will propose an ideal standardized breath sampling solution, and give a personal vision on the next steps to be taken in this exciting area of breath research.
Najdeno v: ključnih besedah
Ključne besede: Breath analysis, Breath sampling, Offline analysis, Thermal desorption, Gas chromatography-mass spectrometry
Objavljeno: 22.07.2019; Ogledov: 2530; Prenosov: 0
Polno besedilo (36,24 MB) |
24. Hypoxia influences the cellular cross-talk of human dermal fibroblasts. A proteomic approach.Naldini Antonella, Tiozzo Roberta, Sommer Pascal, Carraro Fabio, Annovi Giulia, Boraldi Federica, Quaglino Daniela, 2007, izvirni znanstveni članek Opis: The ability of cells to respond to changes in oxygen availability is critical for many physiological and pathological processes (i.e. development,
aging, wound healing, hypertension, cancer). Changes in the protein profile of normal human dermal fibroblasts were investigated in vitro after
96 h in 5% CO2 and 21% O2 (pO2=140 mm Hg) or 2% O2 (pO2=14 mm Hg), these parameters representing a mild chronic hypoxic exposure
which fibroblasts may undergo in vivo. The proliferation rate and the protein content were not significantly modified by hypoxia, whereas
proteome analysis demonstrated changes in the expression of 56 proteins. Protein identification was performed by mass spectrometry. Data
demonstrate that human fibroblasts respond to mild hypoxia increasing the expression of hypoxia inducible factor (HIF1a) and of the 150-kDa
oxygen-regulated protein. Other differentially expressed proteins appeared to be related to stress response, transcriptional control, metabolism,
cytoskeleton, matrix remodelling and angiogenesis. Furthermore, some of them, like galectin 1, 40S ribosomal protein SA, N-myc-downstream
regulated gene-1 protein, that have been described in the literature as possible cancer markers, significantly changed their expression also in
normal hypoxic fibroblasts. Interestingly, a bovine fetuin was also identified that appeared significantly less internalised by hypoxic fibroblasts. In
conclusion, results indicate that human dermal fibroblasts respond to an in vitro mild chronic hypoxic exposure by modifying a number of
multifunctional proteins. Furthermore, data highlight the importance of stromal cells in modulating the intercellular cross-talk occurring in
physiological and in pathologic conditions.
Najdeno v: ključnih besedah
Ključne besede: Human fibroblast, Primary cell culture, Hypoxia, Connective tissue, Proteome, 2D gel electrophoresis, Mass-spectrometry
Objavljeno: 22.07.2019; Ogledov: 2524; Prenosov: 0
Polno besedilo (919,07 KB) |
25. Uranium bearing dissolved organic matter in the porewaters of uranium contaminated lake sedimentsBreda Novotnik, Wei Chen, R. Douglas Evans, 2018, izvirni znanstveni članek Opis: Uranium (U) mobility in the environment strongly depends on its oxidation state and the presence of complexing
agents such as inorganic carbon, phosphates, and dissolved organic matter (DOM). Despite the importance of
DOM in U mobility, the exact mechanism is still poorly understood. Therefore, the aim of our investigation was
to characterise sediment porewater DOM in two lakes in Ontario, Canada (Bow and Bentley Lakes) that were
historically contaminated with U and propose possible composition of UO2-bearing DOM. Depth profiles of U
concentrations in porewaters and total sediment digests reveal U levels of up to 1.3 mg L−1 in porewater and up
to 0.8 mg−1 g in sediment. Depth profiles of U did not correlate with Fe, Mn, SO4
2−, or Eh profiles. Therefore,
porewater DOM was analysed and taken into consideration as the primary source of U mobility. Porewater DOM
in each sediment section (1 cm sections, 20 cm core length) was analysed by high-resolution electrospray ionisation
mass spectrometry. PCA analyses of porewater DOM mass spectra showed grouping and clear separation
of DOM in sediment sections with elevated U concentrations in comparison to sections with background U
concentrations. Several criteria were set to characterise UO2-bearing DOM and more than 70 different molecules
were found. The vast majority of these UO2-DOM compounds fell in the category of carboxyl-containing aliphatic
molecules (H/C between 0.85 and 1.2 and O/C≤0.4) and had a mean value of m/z about 720.
Najdeno v: ključnih besedah
Ključne besede: Uranium
Lake sediments
Porewater
Disolved organic matter
High resolution mass spectrometry
Objavljeno: 09.10.2019; Ogledov: 2348; Prenosov: 0
Polno besedilo (1,48 MB) |
26. Substantial brown carbon emissions from wintertime residential wood burning over FranceJean-Luc Jaffrezo, Valérie Gros, Griša Močnik, Gilles Levigoureux, Marta Dominik-Sègue, Eve Chrétien, Sabrina Pontet, Gregory Gille, Florie Chevrier, Véronique Jacob, Jean-Eudes Petit, Alexandre Albinet, Yunjiang Zhang, Olivier Favez, 2020, izvirni znanstveni članek Opis: Brown carbon (BrC) is known to absorb light at subvisible wavelengths but its optical properties and sources are still poorly documented, leading to large uncertainties in climate studies. Here, we show its major wintertime contribution to total aerosol absorption at 370 nm (18–42%) at 9 different French sites. Moreover, an excellent correlation with levoglucosan (r2 = 0.9 and slope = 22.2 at 370 nm), suggesting important contribution of wood burning emissions to ambient BrC aerosols in France. At all sites, BrC peaks were mainly observed during late evening, linking to local intense residential wood burning during this time period. Furthermore, the geographic origin analysis also highlighted the high potential contribution of local and/or small-regional emissions to BrC. Focusing on the Paris region, twice higher BrC mass absorption efficiency value was obtained for less oxidized biomass burning organic aerosols (BBOA) compared to more oxidized BBOA (e.g., about 4.9 ± 0.2 vs. 2.0 ± 0.1 m2 g−1, respectively, at 370 nm). Finally, the BBOA direct radiative effect was found to be 40% higher when these two BBOA fractions are treated as light-absorbing species, compared to the non-absorbing BBOA scenario.
Najdeno v: ključnih besedah
Ključne besede: Brown carbon, Multi sites, Residential wood burning, Mass absorption efficiency, France
Objavljeno: 20.07.2020; Ogledov: 2100; Prenosov: 0
Polno besedilo (2,94 MB) |
27. Mass Composition of Cosmic Rays with Energies above 10[sup]17.2 eV from the Hybrid Data of the Pierre Auger ObservatoryLukas Zehrer, Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, Alexey Yushkov, 2019, objavljeni znanstveni prispevek na konferenci Najdeno v: ključnih besedah
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays (UHECR), UHECR hybrid detection, UHECR mass composition
Objavljeno: 21.12.2020; Ogledov: 1472; Prenosov: 56
Polno besedilo (749,44 KB) |
28. |
29. Evaluation of recently-proposed secondary organic aerosol models for a case study in Mexico CityKatja Džepina, R. M. Volkamer, Sasha Madronich, P. Tulet, I. M. Ulbrich, Q. Zhang, C. D. Cappa, P. J. Ziemann, Jose L. Jimenez, 2009, izvirni znanstveni članek Opis: Recent field studies have found large discrepancies in the measured vs. modeled SOA mass loadings in both urban and regional polluted atmospheres. The reasons for these large differences are unclear. Here we revisit a case study of SOA formation in Mexico City described by Volkamer et al. (2006), during a photochemically active period when the impact of regional biomass burning is minor or negligible, and show that the observed increase in OA/Delta CO is consistent with results from several groups during MILAGRO 2006. Then we use the case study to evaluate three new SOA models: 1) the update of aromatic SOA yields from recent chamber experiments (Ng et al., 2007); 2) the formation of SOA from glyoxal (Volkamer et al., 2007a); and 3) the formation of SOA from primary semivolatile and intermediate volatility species (P-S/IVOC) (Robinson et al., 2007). We also evaluate the effect of reduced partitioning of SOA into POA (Song et al., 2007). Traditional SOA precursors (mainly aromatics) by themselves still fail to produce enough SOA to match the observations by a factor of similar to similar to 7. The new low-NOx aromatic pathways with very high SOA yields make a very small contribution in this high-NOx urban environment as the RO2 center dot+NO reaction dominates the fate of the RO2 center dot radicals. Glyoxal contributes several mu g m(-3) to SOA formation, with similar timing as the measurements. P-S/IVOC are estimated from equilibrium with emitted POA, and introduce a large amount of gas-phase oxidizable carbon that was not in models before. With the formulation in Robinson et al. (2007) these species have a high SOA yield, and this mechanism can close the gap in SOA mass between measurements and models in our case study. However the volatility of SOA produced in the model is too high and the O/C ratio is somewhat lower than observations. Glyoxal SOA helps to bring the O/C ratio of predicted and observed SOA into better agreement. The sensitivities of the model to some key uncertain parameters are evaluated.
Najdeno v: ključnih besedah
Ključne besede: polycyclic aromatic-hydrocarbons, positive matrix factorization, mass-spectrometry, volatility measurements
Objavljeno: 11.04.2021; Ogledov: 1270; Prenosov: 0
Polno besedilo (1,18 MB) |
30. Evolution of organic aerosols in the atmosphereJ. H. Kroll, P. F. DeCarlo, J. David Allan, H. Coe, Katja Džepina, Jose L. Jimenez, M. R. Canagaratna, N. M. Donahue, A. S. H. Prevot, Q. Zhang, 2009, izvirni znanstveni članek Opis: Organic aerosol (OA) particles affect climate forcing and human health, but their sources and evolution remain poorly characterized. We present a unifying model framework describing the atmospheric evolution of OA that is constrained by high–time-resolution measurements of its composition, volatility, and oxidation state. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated organic aerosol (OOA), with concentrations comparable to those of sulfate aerosol throughout the Northern Hemisphere. Our model framework captures the dynamic aging behavior observed in both the atmosphere and laboratory: It can serve as a basis for improving parameterizations in regional and global models.
Najdeno v: ključnih besedah
Ključne besede: secondary organic aerosol, source apportionment, aerodyne aerosol mass spectrometer, global field measurements, laboratory experiments
Objavljeno: 11.04.2021; Ogledov: 1315; Prenosov: 0
Polno besedilo (721,30 KB) |
