Wie in Wolken der Regen entsteht : Kristallisationskeime als Schlüssel

Wolken haben einen maßgeblichen Einfluss auf den Wasserhaushalt der Erde, das Wettergeschehen und das Klima. Sie wissenschaftlich zu beschreiben, ist schwierig – und das erschwert die Niederschlagsvorhersage ebenso wie die Klimamodellierung. Wichtig für die Entstehung von Regen in unseren Breiten sind Eispartikel. Sie machen einen großen Teil der Wolken aus. Doch wie bilden sie sich, und warum sind sie für viele physikalische Prozesse in den Wolken unentbehrlich? Und schließlich: Wirkt sich menschliches Handeln auf die Wolken aus

Effects of fluctuations on the initial eccentricity from the Color Glass Condensate in heavy ion collisions

We introduce a modified form of the Kharzeev-Levin-Nardi (KLN) approach for nuclear collisions. The new ansatz for the unintegrated gluon distribution function preserves factorization, and the saturation scale is bound from below by that for a single nucleon. It also reproduces the correct scaling with the number of collisions at high transverse momentum. The corresponding Monte Carlo implementation allows us to account for fluctuations of the hard sources (nucleons) in the transverse plane. We compute various definitions of the eccentricity within the new approach, which are relevant for the interpretation of the elliptic flow. Our approach predicts breaking of the scaling of the eccentricity with the Glauber eccentricity at the level of about 30%.Comment: 9 pages, 10 figures, Updated version as accepted by Phys.Rev.

Temporal Changes in Total Serum Immunoglobulin E Levels in East German Children and the Effect of Potential Predictors

Background: Elevated total serum immunoglobulin E (IgE) levels are a prominent feature of allergic and parasitic diseases. An epidemiologic study was conducted in East German children to describe trends in the development of total serum IgE levels and analyze the impact of potential determinants. Methods: The study consisted of three cross-sectional surveys in 1992-1993, 1995-1996 and 1998-1999 and was conducted in three areas of the former German Democratic Republic. In total, 8,051 questionnaires were completed by the parents of children aged 5-14 years, supplying information on allergic symptoms and potential risk factors. A total of 5,918 measurements of total serum IgE and specific IgE to 5 common aeroallergens were available from 4,353 schoolchildren. Generalized estimating equations were applied to data from all children and stratified for atopic and nonatopic children to identify trends and estimate the effect of potential determinants on total IgE. Results: Total serum IgE levels decreased significantly with a linear trend in East German schoolchildren between 1992 and 1999, the effect being stronger in nonatopic children. The following factors were associated with lower total serum IgE levels: female gender, living in a household with fewer than 4 people, no history of helminth infestation, younger age group (5-7 years), no parental allergy and high socioeconomic status. No association was seen for `smoking at home' and close contact to pets. Conclusion: Total serum IgE declined parallel to helminth infestation; however, the latter explained the decrease only in part. Furthermore, total IgE developed in an opposite direction to specific IgE, indicating that it has determinants other than allergic sensitization. Copyright (C) 2011 S. Karger AG, Base