| 1. |
- Mehra, Archit, et al.
(författare)
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Evaluation of the chemical composition of gas- and particle-phase products of aromatic oxidation
- 2020
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Ingår i: ATMOSPHERIC CHEMISTRY AND PHYSICS. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 20:16, s. 9783-9803
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Tidskriftsartikel (refereegranskat)abstract
- Aromatic volatile organic compounds (VOCs) are key anthropogenic pollutants emitted to the atmosphere and are important for both ozone and secondary organic aerosol (SOA) formation in urban areas. Recent studies have indicated that aromatic hydrocarbons may follow previously unknown oxidation chemistry pathways, including autoxidation that can lead to the formation of highly oxidised products. In this study we evaluate the gas- and particle-phase ions measured by online mass spectrometry during the hydroxyl radical oxidation of substituted C-9-aromatic isomers (1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, propylbenzene and isopropylbenzene) and a substituted polyaromatic hydrocarbon (1-methylnaphthalene) under low- and medium-NO x conditions. A time-of-flight chemical ionisation mass spectrometer (ToF-CIMS) with iodide-anion ionisation was used with a filter inlet for gases and aerosols (FIGAERO) for the detection of products in the particle phase, while a Vocus protontransfer-reaction mass spectrometer (Vocus-PTR-MS) was used for the detection of products in the gas phase. The signal of product ions observed in the mass spectra were compared for the different precursors and experimental conditions. The majority of mass spectral product signal in both the gas and particle phases comes from ions which are common to all precursors, though signal distributions are distinct for different VOCs. Gas- and particle-phase composition are distinct from one another. Ions corresponding to products contained in the near-explicit gas phase Master Chemical Mechanism (MCM version 3.3.1) are utilised as a benchmark of current scientific understanding, and a comparison of these with observations shows that the MCM is missing a range of highly oxidised products from its mechanism. In the particle phase, the bulk of the product signal from all precursors comes from ring scission ions, a large proportion of which are more oxidised than previously reported and have undergone further oxidation to form highly oxygenated organic molecules (HOMs). Under the perturbation of OH oxidation with increased NOx, the contribution of HOM-ion signals to the particle-phase signal remains elevated for more substituted aromatic precursors. Up to 43% of product signal comes from ring-retaining ions including HOMs; this is most important for the more substituted aromatics. Unique products are a minor component in these systems, and many of the dominant ions have ion formulae concurrent with other systems, highlighting the challenges in utilising marker ions for SOA.
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| 2. |
- Buchholz, Angela, et al.
(författare)
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Insights into the O : C-dependent mechanisms controlling the evaporation of alpha-pinene secondary organic aerosol particles
- 2019
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:6, s. 4061-4073
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Tidskriftsartikel (refereegranskat)abstract
- The volatility of oxidation products of volatile organic compounds (VOCs) in the atmosphere is a key factor to determine if they partition into the particle phase contributing to secondary organic aerosol (SOA) mass. Thus, linking volatility and measured particle composition will provide insights into SOA formation and its fate in the atmosphere. We produced alpha-pinene SOA with three different oxidation levels (characterized by average oxygen-to-carbon ratio; (O:C) over bar = 0.53, 0.69, and 0.96) in an oxidation flow reactor. We investigated the particle volatility by isothermal evaporation in clean air as a function of relative humidity (RH < 2 %, 40 %, and 80 %) and used a filter-based thermal desorption method to gain volatility and chemical composition information. We observed reduced particle evaporation for particles with increasing <(O:C )over bar> ratio, indicating that particles become more resilient to evaporation with oxidative aging. Particle evaporation was increased in the presence of water vapour and presumably particulate water; at the same time the resistance of the residual particles to thermal desorption was increased as well. For SOA with (O:C ) over bar = 0.96, the unexpectedly large increase in mean thermal desorption temperature and changes in the thermogram shapes under wet conditions (80 % RH) were an indication of aqueous phase chemistry. For the lower (O:C ) over bar cases, some water-induced composition changes were observed. However, the enhanced evaporation under wet conditions could be explained by the reduction in particle viscosity from the semi-solid to liquid-like range, and the observed higher desorption temperature of the residual particles is a direct consequence of the increased removal of high-volatility and the continued presence of low-volatility compounds.
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| 3. |
- Graeffe, Frans, et al.
(författare)
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Detecting and Characterizing Particulate Organic Nitrates with an Aerodyne Long-ToF Aerosol Mass Spectrometer
- 2023
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Ingår i: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 7:1, s. 230-242
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Tidskriftsartikel (refereegranskat)abstract
- Particulate organic nitrate (pON) can be a major part of secondary organic aerosol (SOA) and is commonly quantified by indirect means from aerosol mass spectrometer (AMS) data. However, pON quantification remains challenging. Here, we set out to quantify and characterize pON in the boreal forest, through direct field observations at Station for Measuring Ecosystem Atmosphere Relationships (SMEAR) II in Hyytiälä, Finland, and targeted single-precursor laboratory studies. We utilized a long time-of-flight AMS (LToF-AMS) for aerosol chemical characterization, with a particular focus to identify CxHyOzN+ (“CHON+”) fragments. We estimate that during springtime at SMEAR II, pON (including both the organic and nitrate part) accounts for ∼10% of the particle mass concentration (calculated by the NO+/NO2+ method) and originates mainly from the NO3 radical oxidation of biogenic volatile organic compounds. The majority of the background nitrate aerosol measured is organic. The CHON+ fragment analysis was largely unsuccessful at SMEAR II, mainly due to low concentrations of the few detected fragments. However, our findings may be useful at other sites as we identified 80 unique CHON+ fragments from the laboratory measurements of SOA formed from NO3 radical oxidation of three pON precursors (β-pinene, limonene, and guaiacol). Finally, we noted a significant effect on ion identification during the LToF-AMS high-resolution data processing, resulting in too many ions being fit, depending on whether tungsten ions (W+) were used in the peak width determination. Although this phenomenon may be instrument-specific, we encourage all (LTOF-) AMS users to investigate this effect on their instrument to reduce the possibility of incorrect identifications.
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| 4. |
- Göransson, Hanna, et al.
(författare)
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Quantification of normal cell fraction and copy number neutral LOH in clinical lung cancer samples using SNP array data
- 2009
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 4:6, s. e6057-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Technologies based on DNA microarrays have the potential to provide detailed information on genomic aberrations in tumor cells. In practice a major obstacle for quantitative detection of aberrations is the heterogeneity of clinical tumor tissue. Since tumor tissue invariably contains genetically normal stromal cells, this may lead to a failure to detect aberrations in the tumor cells. PRINCIPAL FINDING: Using SNP array data from 44 non-small cell lung cancer samples we have developed a bioinformatic algorithm that accurately models the fractions of normal and tumor cells in clinical tumor samples. The proportion of normal cells in combination with SNP array data can be used to detect and quantify copy number neutral loss-of-heterozygosity (CNNLOH) in the tumor cells both in crude tumor tissue and in samples enriched for tumor cells by laser capture microdissection. CONCLUSION: Genome-wide quantitative analysis of CNNLOH using the CNNLOH Quantifier method can help to identify recurrent aberrations contributing to tumor development in clinical tumor samples. In addition, SNP-array based analysis of CNNLOH may become important for detection of aberrations that can be used for diagnostic and prognostic purposes.
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| 5. |
- Micke, Patrick, et al.
(författare)
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Gene Copy Number Aberrations Are Associated with Survival in Histologic Subgroups of Non-small Cell Lung Cancer
- 2011
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Ingår i: Journal of Thoracic Oncology. - 1556-0864 .- 1556-1380. ; 6:11, s. 1833-1840
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Non-small cell lung cancer (NSCLC) is characterized by a multitude of genetic aberrations with unknown clinical impact. In this study, we aimed to identify gene copy number changes that correlate with clinical outcome in NSCLC. To maximize the chance to identify clinically relevant events, we applied a strategy involving two prognostically extreme patient groups. Methods: Short-term (<20 month; n = 53) and long-term survivors (>58 month; n = 47) were selected from a clinically well-characterized NSCLC patient cohort with available fresh frozen tumor specimens. The samples were analyzed using high-resolution single-nucleotide polymorphism array technology to assess gene copy number variations and array-based gene expression profiling. The molecular data were combined with information on clinical parameters. Results: Genetic aberrations were strongly associated with tumor histology. In adenocarcinoma (n = 50), gene copy number gains on chromosome 8q21-q24.3 (177 genes) were more frequent in long-term than in short-term survivors. In squamous cell carcinoma (n = 28), gains on chromosome 14q23.1-24.3 (133 genes) were associated with shorter survival, whereas losses in a neighboring region, 14q31.1-32.33 (110 genes), correlated with favorable outcome. In accordance with copy number gains and losses, messenger RNA expression levels of corresponding genes were increased or decreased, respectively. Conclusion: Comprehensive tumor profiling permits the integration of genomic, histologic, and clinical data. We identified gene copy number gains and losses, with corresponding changes in messenger RNA levels that were associated with prognosis in adenocarcinoma and squamous cell carcinoma of the lung.
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| 6. |
- Pajunoja, Aki, et al.
(författare)
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Adsorptive uptake of water by semisolid secondary organic aerosols
- 2015
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 42:8, s. 3063-3068
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Tidskriftsartikel (refereegranskat)abstract
- Aerosol climate effects are intimately tied to interactions with water. Here we combine hygroscopicity measurements with direct observations about the phase of secondary organic aerosol (SOA) particles to show that water uptake by slightly oxygenated SOA is an adsorption-dominated process under subsaturated conditions, where low solubility inhibits water uptake until the humidity is high enough for dissolution to occur. This reconciles reported discrepancies in previous hygroscopicity closure studies. We demonstrate that the difference in SOA hygroscopic behavior in subsaturated and supersaturated conditions can lead to an effect up to about 30% in the direct aerosol forcinghighlighting the need to implement correct descriptions of these processes in atmospheric models. Obtaining closure across the water saturation point is therefore a critical issue for accurate climate modeling.
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| 7. |
- Yiu, Andrew, et al.
(författare)
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Circulating uric acid levels and subsequent development of cancer in 493,281 individuals : findings from the AMORIS Study
- 2017
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Ingår i: Oncotarget. - : Impact Journals, LLC. - 1949-2553. ; 8:26, s. 42332-42342
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Serum uric acid has been suggested to be associated with cancer risk. We aimed to study the association between serum uric acid and cancer incidence in a large Swedish cohort.Results: A positive association was found between uric acid levels and overall cancer risk, and results were similar with adjustment for glucose, triglycerides and BMI. Hazard ratio (HR) for overall cancer for the 4th quartile of uric acid compared to the 1st was 1.08 (95% CI: 1.05-1.11) in men and 1.12 (1.09 - 1.16) in women. Site-specific analysis showed a positive association between uric acid and risk of colorectal, hepatobiliary, kidney, non-melanoma skin, and other cancers in men and of head and neck and other cancers in women. An inverse association was observed for pulmonary and central nervous system (CNS) cancers in men and breast, lymphatic and haematological, and CNS malignancies in women.Materials and Methods: We included 493,281 persons aged 20 years and older who had a measurement of serum uric acid and were cancer-free at baseline in the AMORIS study. Multivariable Cox proportional hazards regression was used to investigate sex-specific quartiles of serum uric acid in relation to cancer risk in men and women. Analysis was further adjusted for serum glucose, triglycerides and, where available, BMI. Site-specific analysis was performed for major cancers.Conclusions: Altered uric acid levels were associated with risk of overall and some specific cancers, further indicating the potential role of uric acid metabolism in carcinogenesis.
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| 8. |
- Ylisirniö, Arttu, et al.
(författare)
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Composition and volatility of secondary organic aerosol (SOA) formed from oxidation of real tree emissions compared to simplified volatile organic compound (VOC) systems
- 2020
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 20:9, s. 5629-5644
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Tidskriftsartikel (refereegranskat)abstract
- Secondary organic aerosol (SOA) is an important constituent of the atmosphere where SOA particles are formed chiefly by the condensation or reactive uptake of oxidation products of volatile organic compounds (VOCs). The mass yield in SOA particle formation, as well as the chemical composition and volatility of the particles, is determined by the identity of the VOC precursor(s) and the oxidation conditions they experience. In this study, we used an oxidation flow reactor to generate biogenic SOA from the oxidation of Scots pine emissions. Mass yields, chemical composition and volatility of the SOA particles were characterized and compared with SOA particles formed from oxidation of alpha-pinene and from a mixture of acyclic-monocyclic sesquiterpenes (farnesenes and bisabolenes), which are significant components of the Scots pine emissions. SOA mass yields for Scots pine emissions dominated by farnesenes were lower than for a-pinene but higher than for the artificial mixture of farne-senes and bisabolenes. The reduction in the SOA yield in the farnesene- and bisabolene-dominated mixtures is due to exocyclic C =C bond scission in these acyclic-monocyclic sesquiterpenes during ozonolysis leading to smaller and generally more volatile products. SOA particles from the oxi- dation of Scots pine emissions had similar or lower volatility than SOA particles formed from either a single precursor or a simple mixture of VOCs. Applying physical stress to the Scots pine plants increased their monoterpene, especially monocyclic beta-phellandrene, emissions, which further decreased SOA particle volatility and increased SOA mass yield. Our results highlight the need to account for the chemical complexity and structure of real-world biogenic VOC emissions and stress-induced changes to plant emissions when modelling SOA production and properties in the atmosphere. These results emphasize that a simple increase or decrease in relative monoterpene and sesquiterpene emissions should not be used as an indicator of SOA particle volatility.
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