RESUMO
Light-absorbing aerosols heat the atmosphere; an accurate quantification of their absorption coefficient is mandatory. However, standard reference instruments (CAPS, MAAP, PAX, PTAAM) are not always available at each measuring site around the world. By integrating all previous published studies concerning the Aethalometers, the AE33 filter loading parameter, provided by the dual-spot algorithm, were used to determine the multiple scattering enhancement factor from the Aethalometer itself (hereinafter CAE) on an yearly and a monthly basis. The method was developed in Milan, where Aethalometer measurements were compared with MAAP data; the comparison showed a good agreement in terms of equivalent black carbon (R2 = 0.93; slope = 1.02 and a negligible intercept = 0.12 µg m-3) leading to a yearly experimental multiple scattering enhancement factor of 2.51 ± 0.04 (hereinafter CMAAP). On a yearly time base the CAE values obtained using the new approach was 2.52 ± 0.01, corresponding to the experimental one (CMAAP). Considering the seasonal behavior, higher experimental CMAAP and computed CAE values were found in summer (2.83 ± 0.12) whereas, the lower ones in winter/early-spring (2.37 ± 0.03), in agreement with the single scattering albedo behavior in the Po Valley. Overall, the agreement between the experimental CMAAP and CAE showed a root mean squared error (RMSE) of just 0.038 on the CMAAP prediction, characterized by a slope close to 1 (1.001 ± 0.178), a negligible intercept (-0.002 ± 0.455) and a high degree of correlation (R2 = 0.955). From an environmental point of view, the application of a dynamic (space/time) determination of CAE increases the accuracy of the aerosol heating rate (compared to applying a fixed C value) up to 16 % solely in Milan, and to 114 % when applied in the Arctic at 80°N.
RESUMO
PURPOSE: Management of perianal Crohn's disease is still controversial, and reports on large series are very few in the literature. The aim of this multicenter study was to investigate the outcome of both medical and surgical treatment in 225 patients. METHODS: Patients cared for at different institutions were followed up for a median of six years. Most of them had either anal fistula or an abscess (86 percent and 43 percent, respectively), but fissures were also present in 26 percent of the cases. Diarrhea and anal pain were the most common symptoms. Anal lesions preceded the onset of intestinal symptoms in 19 percent of cases. RESULTS: Medical treatment was curative only in 21 of 123 patients. Overall, medical and surgical treatment either cured or improved 62 percent of the cases. Fifty percent had an intestinal resection. Abscess drainage and fistulotomy were the most common anal surgeries. Rectovaginal fistulas (n = 30) required intestinal surgery in 36 percent and anal surgery in 20 percent of the cases, 50 percent with good results. Of 166 patients who had anal surgery, 97 (58 percent) had a positive outcome. Recurrence of anal disease requiring further surgery occurred in 24.5 percent of the cases. CONCLUSIONS: Limited surgeries seem to achieve satisfactory results in more than one-half of the patients affected by perianal Crohn's lesions, whereas medical treatment alone is curative in a small portion of them.
