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Carrier dynamics in methylammonium lead halide (CH3NH3PbI3- xCl x) perovskite thin films, of differing crystal morphology, are examined as functions of temperature and excitation wavelength. At room temperature, long-lived (>nanosecond) transient absorption signals indicate negligible carrier trapping. However, in measurements of ultrafast photoluminescence excited at 400 nm, a heretofore unexplained, large amplitude (50%-60%), 45 ps decay process is observed. This feature persists for temperatures down to the orthorhombic phase transition. Varying pump photon energy reveals that the fast, band-edge photoluminescence (PL) decay only appears for excitation ≥2.38 eV (520 nm), with larger amplitudes for higher pump energies. Lower photon-energy excitation yields slow dynamics consistent with negligible carrier trapping. Further, sub-bandgap two-photon pumping yields identical PL dynamics as direct absorption, signifying sensitivity to the total deposited energy and insensitivity to interfacial effects. Together with first principles electronic structure and ab initio molecular dynamics calculations, the results suggest the fast PL decay stems from excitation of high energy phonon modes associated with the organic sub-lattice that temporarily enhance wavefunction overlap within the inorganic component owing to atomic displacement, thereby transiently changing the PL radiative rate during thermalization. Hence, the fast PL decay relates a characteristic organic-to-inorganic sub-lattice equilibration timescale at optoelectronic-relevant excitation energies. [ABSTRACT FROM AUTHOR]

Background and objective Previous studies have demonstrated that positive blood culture could contribute to poorer outcomes in patients with pneumonia. However, the impact of positive blood culture on the outcomes of patients with sepsis-induced acute respiratory distress syndrome ( ARDS) has not been evaluated. Methods An observational study that prospectively screened 4861 patients admitted to medical or surgical intensive care units ( ICUs) of a tertiary referral centre was performed. Results Among 4861 admitted patients, 146 diagnosed with sepsis-induced ARDS were enrolled (mean age: 66.1 years). Lower PaO2/ FiO2, decreased respiratory system compliance, and higher lung injury scores ( LIS) on the day of ARDS diagnosis were associated with positive blood cultures ( n = 68) rather than negative blood cultures ( n = 78). There was no relationship between positive blood culture and in-hospital mortality. Kaplan-Meier estimates also revealed that positive blood culture was not associated with 60-day mortality but with an increased length of stay in the hospital and in the ICU ( P = 0.007 and P = 0.016, respectively). Using multivariate logistic regression, higher LIS was independently associated with positive blood culture. In addition, chronic pulmonary disease, lower platelet count, higher LIS, and the development of shock on the diagnosis of ARDS, were independent risk factors for in-hospital mortality. Conclusions This study suggests that the presence of positive blood culture is not associated with increased mortality; however, the mean durations of hospital and ICU stays in patients with sepsis-induced ARDS are increased. [ABSTRACT FROM AUTHOR]