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Opis: We present optical and near-infrared observations of two Type Ibn supernovae (SNe), SN\,2018jmt and SN\,2019cj. Their light curves have rise times of about ten days, reaching an absolute peak magnitude of $M_g$(SN\,2018jmt) = $-$19.07 pm 0.37 and $M_V$(SN\,2019cj) = $-$18.94 pm 0.19 mag, respectively. The early-time spectra of SN\,2018jmt are dominated by a blue continuum, accompanied by narrow (600$-$1000 km $) He i lines with the P-Cygni profile. At later epochs, the spectra become more similar to those of the prototypical SN Ibn 2006jc. At early phases, the spectra of SN\,2019cj show flash ionisation emission lines of C iii N iii and He ii superposed on a blue continuum. These features disappear after a few days, and then the spectra of SN\,2019cj evolve similarly to those of SN\,2018jmt. The spectra indicate that the two SNe exploded within a He-rich circumstellar medium (CSM) lost by the progenitors a short time before the explosion. We modelled the light curves of the two SNe Ibn to constrain the progenitor and the explosion parameters. The ejecta masses are consistent with either what is expected for a canonical SN Ib (sim 2 odot $) or for a massive Wolf Rayet star ($>$ sim 4 M$_ odot $), with the kinetic energy on the order of $10^ $ erg. The lower limit on the ejecta mass ($>$ sim 2 M odot $) argues against a scenario involving a relatively low-mass progenitor (e.g. $M_ ZAMS $ sim 10 M$_ odot $). We set a conservative upper limit of sim 0.1 M$_ odot $ for the 56Ni masses in both SNe. From the light curve modelling, we determined a two-zone CSM distribution, with an inner, flat CSM component and an outer CSM with a steeper density profile. The physical properties of SN\,2018jmt and SN\,2019cj are consistent with those expected from the core collapse of relatively massive envelope-stripped stars.
Ključne besede: supernovae
Objavljeno v RUNG: 06.11.2024; Ogledov: 1186; Prenosov: 7
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Opis: Background Inhaled mannitol provokes bronchoconstriction via mediators released during osmotic degranulation of inflammatory cells, and, hence represents a useful diagnostic test for asthma and model for acute attacks. We hypothesised that the mannitol challenge would trigger changes in exhaled volatile organic compounds (VOCs), generating both candidate biomarkers and novel insights into their origin. Methods Participants with a clinical diagnosis of asthma, or undergoing investigation for suspected asthma, were recruited. Inhaled mannitol challenges were performed, followed by a sham challenge after 2 weeks in participants with bronchial hyper-responsiveness (BHR). VOCs were collected before and after challenges and analysed using gas chromatography–mass spectrometry. Results Forty-six patients (mean (SD) age 52 (16) years) completed a mannitol challenge, of which 16 (35%) were positive, and 15 of these completed a sham challenge. Quantities of 16 of 51 identified VOCs changed following mannitol challenge (p<0.05), of which 11 contributed to a multivariate sparse partial least square discriminative analysis model, with a classification error rate of 13.8%. Five of these 16 VOCs also changed (p<0.05) in quantity following the sham challenge, along with four further VOCs. In patients with BHR to mannitol distinct postchallenge VOC signatures were observed compared with post-sham challenge. Conclusion Inhalation of mannitol was associated with changes in breath VOCs, and in people with BHR resulted in a distinct exhaled breath profile when compared with a sham challenge. These differentially expressed VOCs are likely associated with acute airway inflammation and/or bronchoconstriction and merit further investigation as potential biomarkers in asthma.
Ključne besede: asthma, exhaled volatile organic compounds, pulmonology, breath metabolomics
Objavljeno v RUNG: 31.07.2023; Ogledov: 3375; Prenosov: 5
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Opis: Circadian rhythms control many biological processes in the body in both health and disease. Greater understanding of diurnal variability in disease related biomarkers is crucial for their application in clinical practice and biomarkers of circadian rhythm are required to facilitate further research into disturbed chronicity. To determine if fractional exhaled nitric oxide and breath volatile biomarkers vary rhythmically during the day in healthy and asthmatic individuals. Ten individuals with moderate, atopic asthma (on regular inhaled corticosteroids) and 10 healthy volunteers (all non-smokers) completed an overnight visit where their exhaled breath volatiles and forced exhaled nitric oxide levels were collected every 6 h. Breath volatiles were analysed using gas chromatography mass spectrometry, after trapping these volatiles on sorbent materials for thermal desorption. Nine breath volatiles (including acetone and isoprene) exhibit diurnal variation across all individuals. Furthermore the circadian pattern of several VOCs is altered in individuals with asthma and fractional exhaled nitric oxide is rhythmic in asthma but not in healthy controls. Markers of circadian rhythm can be identified in breath and may offer insight into circadian profiling to help treat disease. Additionally this work suggests that time of day must be controlled when designing future biomarker discovery studies. Further work is required with larger cohorts to validate and extend these findings.
Ključne besede: VOCs, breath, asthma, circadian
Objavljeno v RUNG: 21.10.2019; Ogledov: 5023; Prenosov: 0
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Opis: Real-time profiling of mango ripening based on proton transfer reaction-time of flight-mass spectrometry (PTR–ToF–MS) of small molecular weight volatile organic compounds (VOCs), is demonstrated using headspace measurements of ‘Tommy Atkins’ mangoes. VOC metabolites produced during the ripening process were sampled directly, which enabled simultaneous and rapid detection of a wide range of compounds. Headspace measurements of ‘Keitt’ mangoes were also conducted for comparison. A principle component analysis of the results indicated that several mass channels were not only key to the ripening process but could also be used to distinguish between mango cultivars. The identities of 22 of these channels, tentatively speciated using contemporaneous GC–MS measurements of sorbent tubes, are rationalized through examination of the biochemical pathways that produce volatile flavour components. Results are discussed with relevance to the potential of headspace analysers and electronic noses in future fruit ripening and quality studies.
Ključne besede: Mangifera indica, Tommy Atkins, PTR–ToF–MS, VOCs, Ripening, Mango
Objavljeno v RUNG: 18.07.2019; Ogledov: 4523; Prenosov: 0
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Opis: Secondary Organic Aerosol (SOA) affects atmospheric composition, air quality and radiative transfer, however major difficulties are encountered in the development of reliable models for SOA formation. Constraints on processes involved in SOA formation can be obtained by interpreting the speciation and evolution of organics in the gaseous and condensed phase simultaneously. In this study we investigate SOA formation from dark α-pinene ozonolysis with particular emphasis upon the mass distribution of gaseous and particulate organic species. A detailed model for SOA formation is compared with the results from experiments performed in the EUropean PHOtoREactor (EUPHORE) simulation chamber, including on-line gas-phase composition obtained from Chemical-Ionization-Reaction Time-Of-Flight Mass-Spectrometry measurements, and off-line analysis of SOA samples performed by Ion Trap Mass Spectrometry and Liquid Chromatography. The temporal profile of SOA mass concentration is relatively well reproduced by the model. Sensitivity analysis highlights the importance of the choice of vapour pressure estimation method, and the potential influence of condensed phase chemistry. Comparisons of the simulated gaseous-and condensed-phase mass distributions with those observed show a generally good agreement. The simulated speciation has been used to (i) propose a chemical structure for the principal gaseous semi-volatile organic compounds and condensed monomer organic species, (ii) provide evidence for the occurrence of recently suggested radical isomerisation channels not included in the basic model, and (iii) explore the possible contribution of a range of accretion reactions occurring in the condensed phase. We find that oligomer formation through esterification reactions gives the best agreement between the observed and simulated mass spectra
Ključne besede: Aerosol, Aerosol formation, Smog chamber
Objavljeno v RUNG: 18.07.2019; Ogledov: 4466; Prenosov: 0
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