972 resultados para Aerosol, Wolken, CCN, klima, Hygroskopizitaet


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In an international perspective cooperation between social services and school has a long tradition. In the German speaking countries we can recognize a historical distance or gap between school and “social pedagogy”, but despite this tradition new forms of cooperation are arising since the last few years. This tendency is part of the development of European societies into “knowledge-based societies” where knowledge and cultural capital are becoming ever stricter criteria for participation in society. This puts particular pressure on those adolescents who threaten to fail in the positional competition for educational qualifications. And it tends to the reproduction and reinforcing of social inequalities due to inequalities in education. For that reason in the article the development of school related social services in different European countries is investigated and it is shown that the increasing pressure to qualification and selection in school creates various problems of integration. Social dimensions of education are pointed out delivering starting points for the cooperation of social services in school and opening opportunities for productive forms of coping with differences between family background, informal social environment and educational milieu in school. Particular attention is paid to differences in socio cultural habits, in socio economical opportunities and in collective practices of interaction. A central focus in the contribution is the orientation towards a participative civil society climate relevant for the interaction between teachers and pupils and between professionals and addressees of social services as well. It is a task of future research in school related social services to analyse their institutional structure and their practices of professional interaction and to find out by European and international comparison in which way social services can contribute to the establishing of a participative civil society climate in school.

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In terms of atmospheric impact, the volcanic eruption of Mt. Pinatubo (1991) is the best characterized large eruption on record. We investigate here the model-derived stratospheric warming following the Pinatubo eruption as derived from SAGE II extinction data including recent improvements in the processing algorithm. This method, termed SAGE_4λ, makes use of the four wavelengths (385, 452, 525 and 1024 nm) of the SAGE II data when available, and uses a data-filling procedure in the opacity-induced "gap" regions. Using SAGE_4λ, we derived aerosol size distributions that properly reproduce extinction coefficients also at much longer wavelengths. This provides a good basis for calculating the absorption of terrestrial infrared radiation and the resulting stratospheric heating. However, we also show that the use of this data set in a global chemistry–climate model (CCM) still leads to stronger aerosol-induced stratospheric heating than observed, with temperatures partly even higher than the already too high values found by many models in recent general circulation model (GCM) and CCM intercomparisons. This suggests that the overestimation of the stratospheric warming after the Pinatubo eruption may not be ascribed to an insufficient observational database but instead to using outdated data sets, to deficiencies in the implementation of the forcing data, or to radiative or dynamical model artifacts. Conversely, the SAGE_4λ approach reduces the infrared absorption in the tropical tropopause region, resulting in a significantly better agreement with the post-volcanic temperature record at these altitudes.

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Abstract Inhalation of ambient air particles or engineered nanoparticles (NP) handled as powders, dispersions or sprays in industrial processes and contained in consumer products pose a potential and largely unknown risk for incidental exposure. For efficient, economical and ethically sound evaluation of health hazards by inhaled nanomaterials, animal-free and realistic in vitro test systems are desirable. The new Nano Aerosol Chamber for in-vitro Toxicity studies (NACIVT) has been developed and fully characterized regarding its performance. NACIVT features a computer-controlled temperature and humidity conditioning, preventing cellular stress during exposure and allowing long-term exposures. Airborne NP are deposited out of a continuous air stream simultaneously on up to 24 cell cultures on Transwell® inserts, allowing high-throughput screening. In NACIVT, polystyrene as well as silver particles were deposited uniformly and efficiently on all 24 Transwell® inserts. Particle-cell interaction studies confirmed that deposited particles reach the cell surface and can be taken up by cells. As demonstrated in control experiments, there was no evidence for any adverse effects on human bronchial epithelial cells (BEAS-2B) due to the exposure treatment in NACIVT. The new, fully integrated and transportable deposition chamber NACIVT provides a promising tool for reliable, acute and sub-acute dose-response studies of (nano)particles in air-exposed tissues cultured at the air-liquid interface.

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