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- Kumar, Varun, et al.
(author)
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Highly time-resolved chemical speciation and source apportionment of organic aerosol components in Delhi, India, using extractive electrospray ionization mass spectrometry
- 2022
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 22:11, s. 7739-7761
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Journal article (peer-reviewed)abstract
- In recent years, the Indian capital city of Delhi has been impacted by very high levels of air pollution, especially during winter. Comprehensive knowledge of the composition and sources of the organic aerosol (OA), which constitutes a substantial fraction of total particulate mass (PM) in Delhi, is central to formulating effective public health policies. Previous source apportionment studies in Delhi identified key sources of primary OA (POA) and showed that secondary OA (SOA) played a major role but were unable to resolve specific SOA sources. We address the latter through the first field deployment of an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) in Delhi, together with a high-resolution aerosol mass spectrometer (AMS). Measurements were conducted during the winter of 2018/19, and positive matrix factorization (PMF) was used separately on AMS and EESI-TOF datasets to apportion the sources of OA. AMS PMF analysis yielded three primary and two secondary factors which were attributed to hydrocarbon-like OA (HOA), biomass burning OA (BBOA-1 and BBOA-2), more oxidized oxygenated OA (MO-OOA), and less oxidized oxygenated OA (LO-OOA). On average, 40 % of the total OA mass was apportioned to the secondary factors. The SOA contribution to total OA mass varied greatly between the daytime (76.8 %, 10:00–16:00 local time (LT)) and nighttime (31.0 %, 21:00–04:00 LT). The higher chemical resolution of EESI-TOF data allowed identification of individual SOA sources. The EESI-TOF PMF analysis in total yielded six factors, two of which were primary factors (primary biomass burning and cooking-related OA). The remaining four factors were predominantly of secondary origin: aromatic SOA, biogenic SOA, aged biomass burning SOA, and mixed urban SOA. Due to the uncertainties in the EESI-TOF ion sensitivities, mass concentrations of EESI-TOF SOA-dominated factors were related to the total AMS SOA (i.e. MO-OOA + LO-OOA) by multiple linear regression (MLR). Aromatic SOA was the major SOA component during the daytime, with a 55.2 % contribution to total SOA mass (42.4 % contribution to total OA). Its contribution to total SOA, however, decreased to 25.4 % (7.9 % of total OA) during the nighttime. This factor was attributed to the oxidation of light aromatic compounds emitted mostly from traffic. Biogenic SOA accounted for 18.4 % of total SOA mass (14.2 % of total OA) during the daytime and 36.1 % of total SOA mass (11.2 % of total OA) during the nighttime. Aged biomass burning and mixed urban SOA accounted for 15.2 % and 11.0 % of total SOA mass (11.7 % and 8.5 % of total OA mass), respectively, during the daytime and 15.4 % and 22.9 % of total SOA mass (4.8 % and 7.1 % of total OA mass), respectively, during the nighttime. A simple dilution–partitioning model was applied on all EESI-TOF factors to estimate the fraction of observed daytime concentrations resulting from local photochemical production (SOA) or emissions (POA). Aromatic SOA, aged biomass burning, and mixed urban SOA were all found to be dominated by local photochemical production, likely from the oxidation of locally emitted volatile organic compounds (VOCs). In contrast, biogenic SOA was related to the oxidation of diffuse regional emissions of isoprene and monoterpenes. The findings of this study show that in Delhi, the nighttime high concentrations are caused by POA emissions led by traffic and biomass burning and the daytime OA is dominated by SOA, with aromatic SOA accounting for the largest fraction. Because aromatic SOA is possibly more toxic than biogenic SOA and primary OA, its dominance during the daytime suggests an increased OA toxicity and health-related consequences for the general public.
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- Coyne, Karin S, et al.
(author)
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The prevalence of chronic constipation and faecal incontinence among men and women with symptoms of overactive bladder.
- 2011
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In: BJU International. - 1464-410X. ; 107:2, s. 254-261
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Journal article (peer-reviewed)abstract
- Study Type - Symptom prevalence (non-consecutive cohort) Level of Evidence 4 OBJECTIVE To estimate the prevalence and overlap of overactive bladder (OAB), chronic constipation (CC) and faecal incontinence (FI) among a general population sample of adults in the USA. MATERIALS AND METHODS A cross-sectional internet-based survey of randomly selected panel members who were >/=40 years of age was conducted. Participants reported how often they experienced symptoms of OAB, CC and FI using Likert scales and modified Rome III criteria. Analyses were conducted to examine the overall prevalence of OAB, CC and FI in men and women separately and to characterize the extent of overlap between these conditions in participants with OAB vs those without OAB, and those participants with continent vs incontinent OAB. RESULTS The response rate for the survey was 62.2% and the final sample (N= 2000) included 927 men and 1073 women. The overall prevalence of OAB [defined as a response of >/='sometimes' to urinary urgency (i.e. 'sometimes' or more often) or 'yes' to urinary urgency incontinence (UUI)] was 26.1% in men and 41.2% in women. The overall prevalence of CC was significantly lower in men than in women (15.3 vs 26.3%), but both men and women with OAB were significantly more likely to report CC (22.3 and 35.9% vs 5.7 and 6.7%, respectively, P < 0.0001). The overall prevalence of FI reported 'rarely' or more was 16.7% of men and 21.9% of women. Men and women with OAB were significantly more likely to report FI than those without OAB. FI was also more common in participants with incontinent OAB than in those with continent OAB. Logistic regressions controlling for demographic factors and comorbid conditions suggest that OAB status is a very strong predictor of CC, FI and overlapping CC and FI (odds ratios, range 3.55-7.96). CONCLUSIONS Chronic constipation, FI and overlapping CC and faecal incontinence occur more frequently in patients with OAB and should be considered when evaluating and treating patients with OAB. These findings suggest a shared pathophysiology among these conditions. Additional study is needed to determine if successful treatment of one or more of these conditions is accompanied by commensurate improvement in symptoms referable to the other organ system.
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- Vats, Nilesh, et al.
(author)
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Catalyzing Bond-Dissociation in Graphene via Alkali-Iodide Molecules
- 2021
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In: Small. - : John Wiley & Sons. - 1613-6810 .- 1613-6829. ; 17:42
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Journal article (peer-reviewed)abstract
- Atomic design of a 2D-material such as graphene can be substantially influenced by etching, deliberately induced in a transmission electron microscope. It is achieved primarily by overcoming the threshold energy for defect formation by controlling the kinetic energy and current density of the fast electrons. Recent studies have demonstrated that the presence of certain species of atoms can catalyze atomic bond dissociation processes under the electron beam by reducing their threshold energy. Most of the reported catalytic atom species are single atoms, which have strong interaction with single-layer graphene (SLG). Yet, no such behavior has been reported for molecular species. This work shows by experimentally comparing the interaction of alkali and halide species separately and conjointly with SLG, that in the presence of electron irradiation, etching of SLG is drastically enhanced by the simultaneous presence of alkali and iodine atoms. Density functional theory and first principles molecular dynamics calculations reveal that due to charge-transfer phenomena the C-C bonds weaken close to the alkali-iodide species, which increases the carbon displacement cross-section. This study ascribes pronounced etching activity observed in SLG to the catalytic behavior of the alkali-iodide species in the presence of electron irradiation.
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