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  • 1
    Publication Date: 2018-02-10
    Description: A thorough analysis of the photophysical properties involved in electronic transitions in excitation–emission spectra of xylene isomers has been carried out using the time-dependent density functional theory (PBEPBE/6-31 + G(d,p)) method. For the first time a structural and spectroscopic investigation to distinguish isomers of xylene, a widespread priority pollutant, was conducted experimentally and theoretically. The fluorescence properties of xylene isomers (sole and mixture (binary and ternary)) in water were studied. The fluorescence peak intensities of xylenes were linearly correlated to concentration, in the order of p -xylene 〉 o -xylene 〉 m -xylene at an excitation/emission wavelength (ex/em) of 260 nm/285 nm for o -, m -xylene and ex/em 265 nm/290 nm for p -xylene at the same concentration. The theoretical excitation/emission wavelengths were at ex/em 247 nm/267 nm, 248 nm/269 nm and 251 nm/307 nm for o -, m - and p -xylene, respectively. The vertical excitation and emission state energies of p -xylene (ex/em 4.94 eV/4.03 eV) were lower and the internal conversion energy difference (0.90 eV) was higher than those of m -xylene (ex/em 5.00 eV/4.60 eV) (0.4 eV) and o -xylene (ex/em 5.02 eV/4.64 eV) (0.377 eV). The order of theoretical emission and oscillator strength (0.0187 〉 0.0175 〉 0.0339) for p -xylene 〉 o -xylene 〉 m -xylene was observed to be in agreement with the experimental fluorescence intensities. These findings provide a novel fast method to distinguish isomers based on their photophysical properties.
    Keywords: computational chemistry, environmental chemistry, environmental science
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 2
    Publication Date: 2018-01-28
    Description: Objectives This study aimed to assess the relationship between infection with multiple human papillomavirus (HPV) types and abnormal anal cytology in HIV-infected men. Design An observational, cross-sectional study. Setting A regional referral hospital in Taiwan. Participants In total, 714 HIV-infected men were enrolled between March 2011 and June 2016. Thin preparation anal Pap smears were interpreted according to the 2001 Bethesda System. Thirty-seven types of HPV were detected by reverse line blotting, including 13 oncogenic types and 24 non-oncogenic types. Outcome measures The relationship between anal HPV infection and abnormal anal cytology in people of Asian ethnicity and the coverage efficacy in HPV-vaccinated HIV-infected men. Results On anal cytology, 175 (24.5%) subjects had atypical squamous cells of undetermined significance (ASCUS) or higher grades of dysplasia, including 87 (49.7%) with ASCUS, 73 (41.7%) with low-grade squamous intraepithelial lesions (LSILs) and 15 (8.6%) with high-grade squamous intraepithelial lesions (HSILs). A higher proportion of subjects with those without LSIL/HSIL (93.1% vs 67.3%, P〈0.0001) had multiple HPV types. The odds of having LSIL/HSIL increased with an increasing number of HPV types: the ORs ranged from 1 for no HPV types to 6.96 (95% CI 2.38 to 20.37) for more than five types (P trend 〈0.0001). Multivariate logistic regression analysis showed a significant association between LSIL/HSIL and the number of HPV genotypes present (OR 1.20; 95% CI 1.02 to 1.42, P〈0.05). HPV types covered by the nonavalent HPV vaccine (types 6/11/16/18/31/33/45/52/58) were detected in 70.1% of the patients in this study. Conclusions The odds of having anal LSIL/HSIL are approximately seventimes greater in HIV-infected men with than withoutsix or more types of HPV. Multiple HPV types in HIV-infected patients deserves aggressive follow-up, and HPV vaccination programme require scaling up.
    Keywords: Oncology, Open access
    Electronic ISSN: 2044-6055
    Topics: Medicine
    Published by BMJ Publishing
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