A Model Chain Application to Estimate Mixing Layer Height Related to PM10 Dispersion Processes.

The mixing layer height (MLH) is a crucial parameter in order to investigate the near surface concentrations of air pollutants. The MLH can be estimated by measurements of some atmospheric variables, by indirect estimates based on trace gases concentration or aerosol, or by numerical models. Here, a modelling approach is proposed. The developed modelling system is based on the models WRF-ARW and CALMET. This system is applied on Firenze-Prato-Pistoia area (Central Italy), during 2010, and it is compared with in situ measurements. The aim of this work is to evaluate the use of MLH model estimates to characterize the critical episodes for PM10 in a limited area. In order to find out the meteorological conditions predisposing accumulation of PM10 in the atmosphere's lower level, some indicators are used: daily mean wind speed, cumulated rainfall, and mean MLH estimates from CALMET model. This indicator is linked to orography, which has important consequences on local weather dynamics. However, during critical events the local emission sources are crucial to the determination of threshold exceeding of PM10. Results show that the modelled MLH, together with cumulative rainfall and wind speed, can identify the meteorological conditions predisposing accumulation of air pollutant at ground level.

Ultrastructural and histochemical features of the ground substance in cyclosporin A-induced gingival overgrowth.

The overgrowth-affected gingiva of patients treated with cyclosporin A after kidney transplant was examined with ultrastructural and histochemical methods to evaluate the involvement of connective tissue. Gingival overgrowth has the same clinical signs as local edema. The ultrastructural study showed that the dimensional increase was largely due to increased production of amorphous ground substance by fibroblasts, possibly resulting from an increased release of histamine by mast cells. The histochemical data revealed that the affected tissues contained higher levels of glycosaminoglycans and that cyclosporin A induced comparably high levels of glycosaminoglycans in in vitro cultures of fibroblasts obtained from normal gingiva. The combination of ultrastructural and histochemical data, therefore, strongly suggests that the response of the connective tissue in gingival overgrowth cannot be ignored and may be the main cause of the observed pathological condition.