Die Nervenleitung als Wechselwirkungseffekt

The Science of Nature -     

Eine Bemerkung zu den Quadrupolmomenten der Atomkerne

The Science of Nature -     

Recycling von Straßenkehricht

Waste recycling is provided by law, e.g. the German ‘Kreislaufwirtschafts- und Abfallgesetz’. Even street sweepings can be recycled, e.g. as winter grit. But if street sweepings are repeatedly brought back on street, toxic agents as heavy metals can accumulate. What is the amount of heavy metal load? Regarding this, is it possible to recycle street sweepings? Is it possible to reduce heavy metal load with the smallest size fraction (the highest load being assumed in) is treated as disposal? Are these fractions actually highest loaded? These questions have been the framework of two studies elaborated at Schleswig-Holstein’s State Authority of Nature Protection and Environment (LANU) based on samples from cities in German state Schleswig-Holstein, particularly from its capital city Kiel. Threshold values for that very purpose do not exist in Germany. But a working group of all German states (called LAGA) suggested some approximate values for recycling of waste and other remainder0materials; the values have been fixed in state of law in Schleswig-Holstein. Our evaluation is oriented towards them. The samples taken in autumn 1998 and winter 1999 were devided in three fractions, the amount of heavy metal measured for each fraction with an ICP-AES. Normal disintegration for that purpose is aqua regia. In this case study nitric acid had been used dissolving just a part of heavy metal concentration although it is not a standard method. It is assumed that it better simulates the natural solubility, and additionally, it is less costly. Therefore we insistently recommend to discuss the application of this method. Samples taken in autumn were higher loaded than those taken in winter. It is worth of special remark that there are high values for zinc, copper, and lead in autumn samples. Regarding above mentioned approximate values samples taken in winter can be assessed for recycling, whereas samples taken in autumn were loaded too high. The finest fraction (<0.5 mm) of samples taken in winter were highest loaded as expected. Therefore the heavy metal concentration could be reduced if this fraction would be treated as disposal. The same can not be assumed for samples taken in autumn, probably due to the higher amount of organic matter.     

Impact of host community composition on Lyme disease risk

The drivers of variable disease risk in complex multi-host disease systems have proved very difficult to identify. Here we test a model that explains the entomological risk of Lyme disease (LD) in terms of host community composition. The model was parameterized in a continuous forest tract at the Cary Institute of Ecosystem Studies (formerly the Institute of Ecosystem Studies) in New York State, U.S.A. We report the results of continuing longitudinal observations (10 years) at the Cary Institute, and of a shorter-term study conducted in forest fragments in LD endemic areas of Connecticut, New Jersey, and New York, USA. Model predictions were significantly correlated with the observed nymphal infection prevalence (NIP) in both studies, although the relationship was stronger in the longer-term Cary Institute study. Species richness was negatively, albeit weakly, correlated with NIP (logistic regression), and there was no relationship between the Shannon diversity index (H') and NIP. Although these results suggest that LD risk is in fact dependent on host diversity, the relationship relies explicitly on the identities and frequencies of host species such that conventional uses of the term biodiversity (i.e., richness, evenness, H') are less appropriate than are metrics that include species identity. This underscores the importance of constructing interaction webs for vertebrates and exploring the direct and indirect effects of anthropogenic stressors on host community composition.     

A comparison of simulated and observed ozone mixing ratios for the summer of 1998 in Western Europe

This study describes and evaluates the newly developed European scale Eulerian chemistry transport model CHIMERE-continental. The model is designed for seasonal simulations and real time forecasts without the use of super-computers. For the purpose of model evaluation simulated ozone mixing ratios for the period between 1 May 1998 and 30 September 1998 are compared to observational data from 115 European surface sites. In order to facilitate the interpretation of future forecasts a statistic is established to estimate the reliability of a simulated pollution level. Besides this, the comparison is done by means of time series, scatter plots, a spectral analysis and the calculation of RMS-errors and biases of the model results corresponding to each observation site. It turns out that the mean RMS-error of the simulated daily maximum ozone mixing ratio for the sites considered a priori as well suited for a model comparison is about 10 ppb. For the same period but a reduced number of sites observed concentrations of NO₂ and ethene are compared to simulated values. Difficulties encountered with the representativeness of observations when trying to evaluate a mesoscale air pollution model are discussed.     

From metamorphosis to maturity in complex life cycles: equal performance of different juvenile life history pathways

Performance in one stage of a complex life cycle may affect performance in the subsequent stage. Animals that start a new stage at a smaller size than conspecifics may either always remain smaller or they may be able to "catch up" through plasticity, usually elevated growth rates. We study how size at and date of metamorphosis affected subsequent performance in the terrestrial juvenile stage and lifetime fitness of spadefoot toads (Pelobates fuscus). We analyzed capture-recapture data of > 3000 individuals sampled during nine years with mark-recapture models to estimate first-year juvenile survival probabilities and age-specific first-time breeding probabilities of toads, followed by model selection to assess whether these probabilities were correlated with size at and date of metamorphosis. Males attained maturity after two years, whereas females reached maturity 2-4 years after metamorphosis. Age at maturity was weakly correlated with metamorphic traits. In both sexes, first-year juvenile survival depended positively on date of metamorphosis and, in males, also negatively on size at metamorphosis. In males, toads that metamorphosed early at a small size had the highest probability to reach maturity. However, because very few toadlets metamorphosed early, the vast majority of male metamorphs had a very similar probability to reach maturity. A matrix projection model constructed for females showed that different juvenile life history pathways resulted in similar lifetime fitness. We found that the effects of date of and size at metamorphosis on different juvenile traits cancelled each other out such that toads that were small or large at metamorphosis had equal performance. Because the costs and benefits of juvenile life history pathways may also depend on population fluctuations, ample phenotypic variation in life history traits may be maintained.