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  • 1
    ISSN: 1434-601X
    Keywords: 25.70.Gh ; 25.70.Jj ; 25.85.−w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Scission-related emission of light particles has been studied in the fusion-fission reactions 200, 254 MeV37Cl+124Sn→161Ho*(f) (A, B; E x =100, 140 MeV) and 318 MeV28Si +141Pr→169Ta*(f) (C; E x =207 MeV). Light-particle spectra measured in coincidence with fission fragments at 200 angles in and out of the reaction plane are dominated by sequential emission: (i) from the composite nuclei, prior to scission (α multiplicitiesM α ×100 ≃-1.1, 8.7, 38 forA, B, C) and (ii) from fully accelerated fragments (M α ×100 ≃-0.5, 4.5, 8). At forward angles pre-thermalization emission is observed (M α × 1000≃-0.31, 11.7, 33). While absent in the proton spectra, near-scission emission (NSE) is disclosed in theα spectra by marked deviations from sequential emission: a deficit in direction of (M α ×1000≃-0.14, 10, 16) and a surplus yield perpendicular to the scission axes (M α ×1000≃-0.8, 13, 17) reminiscent of the signature of ternary fission. However, NSE is identified as an evaporative process by the observed scaling of the multiplicities vs.E x with sequential multiplicities thus discarding the ternary fission picture. A new description invokes Coulomb-field induced modulation of the evaporation barriers while fragments are in close contact, and a simple static model is presented that consistently describes the data.
    Type of Medium: Electronic Resource
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  • 2
    Abstract: OBJECTIVE: To longitudinally evaluate effects of smoking cessation on quantitative CT in a lung cancer screening cohort of heavy smokers over 4 years. METHODS: After 4 years, low-dose chest CT was available for 314 long-term ex-smokers (ES), 404 continuous smokers (CS) and 39 recent quitters (RQ) who quitted smoking within 2 years after baseline CT. CT acquired at baseline and after 3 and 4 years was subjected to well-evaluated densitometry software, computing mean lung density (MLD) and 15th percentile of the lung density histogram (15TH). RESULTS: At baseline, active smokers showed significantly higher MLD and 15TH (-822+/-35 and -936+/-25 HU, respectively) compared to ES (-831+/-31 and -947+/-22 HU, p〈0.01-0.001). After 3 years, CS again had significantly higher MLD and 15TH (-801+/-29 and -896+/-23 HU) than ES (-808+/-27 and -906+/-20 HU, p〈0.01-0.001) but also RQ (-813+/-20 and -909+/-15 HU, p〈0.05-0.001). Quantitative CT parameters did not change significantly after 4 years. Importantly, smoking status independently predicted MLD at baseline and year 3 (p〈0.001) in multivariate analysis. CONCLUSION: On quantitative CT, lung density is higher in active smokers than ex-smokers, and sustainably decreases after smoking cessation, reflecting smoking-induced inflammation. Interpretations of quantitative CT data within clinical trials should consider smoking status. KEY POINTS: * Lung density is higher in active smokers than ex-smokers. * Lung density sustainably decreases after smoking cessation. * Impact of smoking cessation on lung density is independent of potentially confounding factors. * Smoke-induced pulmonary inflammation and particle deposition influence lung density on CT.
    Type of Publication: Journal article published
    PubMed ID: 28884215
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