RESUMO
The Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud expansion chamber with a volume of 84 m3 was extended for the small cloud expansion chamber AIDA mini (AIDAm) with a volume of 20 L. AIDAm is located in the cold room of AIDA and can perform automated ice-nucleation measurements over longer time periods of hours to days. AIDAm samples from the AIDA chamber, which acts as a reservoir of atmospheric aerosol types, which can slowly be modified by physical or chemical processes similar to those occurring in the atmosphere. AIDAm was validated for accurate ice-nucleation temperature control by measuring homogeneous freezing of pure water droplets at temperatures around -34 °C and for immersion freezing induced by dust aerosol particles in the temperature range between -20 and -30 °C. Further validation experiments at cirrus cloud temperatures of -45 °C revealed that AIDAm can distinguish between heterogeneous ice formation on mineral dust aerosols and homogeneous freezing of sulfuric acid solution particles. The contribution of homogeneous and heterogeneous ice formation processes to the ice-nucleation activity of coated dust particles was investigated in a 7 h long experiment, where solid dust particles were slowly coated with sulfuric acid. The continuous AIDAm measurements with a time resolution of 6 min showed a substantial suppression of the heterogeneous freezing phenomenon and an increasing role of homogeneous freezing while the coating amount was slowly increased. This experiment proved the capability of AIDAm to sensitively detect small changes in the ice-nucleation ability of aerosols, which undergo slow processing like chemical surface coating.
RESUMO
The mass spectral signatures of airborne bacteria were measured and analyzed in cloud simulation experiments at the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) facility. Suspensions of cultured cells in pure water were sprayed into the aerosol and cloud chambers forming an aerosol which consisted of intact cells, cell fragments and residual particles from the agar medium in which the bacteria were cultured. The aerosol particles were analyzed with a high-resolution time-of-flight aerosol mass spectrometer equipped with a newly developed PM2.5 aerodynamic lens. Positive matrix factorization (PMF) using the multilinear engine (ME-2) source apportionment was applied to deconvolve the bacteria and agar mass spectral signatures. The bacteria mass fraction contributed between 75 and 95% depending on the aerosol generation, with the remaining mass attributed to agar. We present mass spectra of Pseudomonas syringae and Pseudomonas fluorescens bacteria typical for ice-nucleation active bacteria in the atmosphere to facilitate the distinction of airborne bacteria from other constituents in ambient aerosol, e.g. by PMF/ME-2 source apportionment analyses. Nitrogen-containing ions were the most salient feature of the bacteria mass spectra, and a combination of C4 H8 N(+) (m/z 70) and C5 H12 N(+) (m/z 86) may be used as marker ions.
Assuntos
Aerossóis/química , Bactérias/química , Espectrometria de Massas/métodos , Proteínas de Bactérias/análise , Proteínas de Bactérias/química , Elétrons , GeloRESUMO
Intraaortic balloon counterpulsation (IABP) was employed between 1977 and 1988 in 132 patients (37 women and 95 men; mean age 60 +/- 9.9 years) with coronary heart disease. Indications for IABP were cardiogenic shock in 93, markedly impaired left ventricular function in 13, and treatment-refractory angina in 26. The hospital mortality rate among those patients in cardiogenic shock was 54%. The mortality rate among the 47 patients who had additional procedures (percutaneous transluminal coronary angioplasty or operation) was 40%, significantly lower than that in 46 patients without further procedure (67%). Complications of IABP occurred in 20% of patients (bleeding, vascular injury, ischaemia in the legs, embolism or infection). The complication rate was, however, reduced to 10% in the last few years by improvements in placement technique and materials. Introduction and placement of the balloon catheter is simple, rapid and reliable. The initially high success rate is particularly valuable for those patients in whom further therapeutic measures can be undertaken.
