Überlichtgeschwindigkeit in extragalaktischen Radioquellen?

After a discussion of the observed phenomena a short account of the very-long-baseline radio interferometry and the redshift controversy is given. The issue of superluminal velocities in the theory of relativity is clarified and a variety of physical models that have been proposed to account for the observed phenomena are discussed. Finally the data of some superluminal sources and their implications are reviewed.     

Pestizide im Tabakrauch II. Pyrolyseverhalten von ausgewählten pestiziden beim Tabakrauchen

The fate of Lindan, DDT, Malathion, Monolinuron, Captan and Maneb during smoking process was studied and it was observed that the amount of unchanged pesticides in the mainstream smoke depends on steam volatility of the substances, while the vapor pressures have no significant influence.     

Dechlorination of PCE in the presence of Fe0 enhanced by a mixed culture containing two Dehalococcoides strains

A mixed culture capable of supplying its energy requirements by the oxidation of zero-valent iron (Fe0) and concomitant reduction of chlorinated ethenes was established. The culture contained Dehalococcoides species as determined by polymerase chain reaction (PCR) with genus specific primers. The use of a newly designed ARDRA procedure and subsequent sequencing revealed the presence of two Dehalococcoides strains, one closely related to Dehalococcoides ethenogenes strain 195, a bacterium respiring with chlorinated ethenes, and one closely related to strain CBDB1 a chlorobenzene and dioxin dehalogenating anaerobe. The mixed culture was used to study dechlorination of tetrachloroethene (PCE) to ethene in the presence of Fe0. Whereas abiotic transformation of PCE by Fe0 led to incomplete dechlorination, the mixed culture mediated fast and complete dechlorination of PCE to ethene with Fe0 as electron donor. Compared to cultures with hydrogen added as electron donor, cultures with Fe0 as electron donor showed the same or higher rates of PCE dechlorination. Growth of the Dehalococcoides strains in the mixed culture is linked to the presence of Fe0 as electron donor and PCE as electron acceptor demonstrating that Dehalococcoides spp. play a pivotal role in the dechlorination of chlorinated ethenes in Fe0 systems.     

Über die Bildung des Instinktbegriffes

The Science of Nature -     

Development of an integrative passive sampler for the monitoring of organic water pollutants

The development of convenient and competitive devices and methods for monitoring of organic pollutants in the aquatic environment is of increasing interest. An integrative passive sampling system has been developed which consists of a solid poly(dimethylsiloxane) (PDMS) material (tube or rod), acting as hydrophobic organic receiving phase, enclosed in a water-filled or an air-filled low-density polyethylene (LDPE) membrane tubing. These samplers enable the direct analysis of the pollutants accumulated during exposure in the receiving phase by thermodesorption-GC/MS, avoiding expensive sample preparation and cleanups. The capabilities of these sampling devices were studied for the sampling of 20 persistent organic pollutants (chlorobenzenes, hexachlorocyclohexanes, p,p'-DDE, PAHs, and PCBs) in laboratory exposure experiments. For the three sampler designs investigated the uptake of all target analytes was integrative over exposure periods up to 9 days (except PCB 101). The determined sampling rates range from 4 to 1340 microl h(-1) for the water-filled samplers and from 20 to 6360 microl h(-1) for the air-filled ones, respectively. The sampling rate of the analytes is dependent on their molecular weight, partition between water and sampler media (PDMS, polyethylene, water, air) and also of the sampler design. The passive samplers enable the estimation of time-weighted average (TWA) concentration of water pollutants in the lower ng l(-1) to pg l(-1) range.     

Die räumliche Orientierung vonParamecium aurelia

The Science of Nature -     

Pestizide im tabakrauch I. Methode zur bestimmung des überganges von pestiziden und deren pyrolyseprodukten in Haupt- und Nebenstromrauch

A modified apparatus for the adsorption of pyrolysis products both in mainstream smoke and sidestream smoke has been developed. The efficiency of the assembly has been checked with the pyrolysis of 4.4′-DDT in spiked cigarettes and the results were compared with the literature.     

Simulating forest succession after blowdown events: The crucial role of space for a realistic management

Ecological patterns vary in space and time. Therefore, when using dynamic models in ecology, the spatial aspect should not be neglected prematurely since it could possibly change the model outcomes to a considerable extent. In view of this problem, we describe here a method how to construct a non-spatial version from a spatially explicit simulation model. The principle idea is to suppress the spatial correlations of cells in a grid in time by continuously re-assigning a random neighbourhood for each cell on the grid. Since this procedure actually eliminates the spatial dimensions, it allows to quantify the unadulterated impact of spatial processes on the model results. To illustrate an important application of this approach in the context of forest management we use a grid-based model that simulates succession of Norway spruce (Picea abies (L.) Karst.) at mountainous sites after blowdown events. The output of this model is compared with the results of the deduced non-spatial version of this model regarding the predicted amount of re-growing trees. The non-spatial version dramatically overestimates the number of spruce trees on different microsites. Thus, the uncritical use of the non-spatial model might give reason to wrong management decisions that are based on too optimistic predictions. In practice, this may lead to dangerous situations, especially in mountain forests serving as protection against avalanches and landslides. This example demonstrates the successful applicability of our approach. Our method can be interpreted as a contribution to an extended sensitivity analysis: it analyses the sensitivity of the results due to structural changes of the model. This sensitivity allows one to estimate the redundancy or the necessity of spatially explicit processes in a model with regard to the parsimony principle of modelling. Since our approach is not dependent on special features of the simulation model used here, it is assumed to be applicable for other spatial models, too, and can thus be considered of general interest for a diligent model analysis.     

The constitutively active Ah receptor (CA-AhR) mouse as a model for dioxin exposure - effects in reproductive organs

The dioxin/aryl hydrocarbon receptor (AhR) mediates most toxic effects of dioxins. In utero/lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) impairs fetal/neonatal development and the developing male reproductive tract are among the most sensitive tissues. TCDD causes antiestrogenic responses in rodent mammary gland and uterus and in human breast cancer cell lines in the presence of estrogen. Also, more recently an estrogen-like effect of TCDD/AhR has been suggested in the absence of estrogen. A transgenic mouse expressing a constitutively active AhR (CA-AhR) was developed as a model mimicking a situation of constant exposure to AhR agonists. Male and female reproductive tissues of CA-AhR mice were characterized for some of the effects commonly seen after dioxin exposure. Sexually mature CA-AhR female mice showed decreased uterus weight, while an uterotrophic assay in immature CA-AhR mice resulted in increased uterus weight. In immature mice, both TCDD-exposure and CA-AhR increased the expression of the estrogen receptor target gene Cathepsin D. When co-treated with 17β-estradiol no increase in Cathepsin D levels occurred in either TCDD-exposed or CA-AhR mice. In sexually mature male CA-AhR mice the weights of testis and ventral prostate were decreased and the epididymal sperm reserve was reduced. The results of the present study are in accordance with previous studies on dioxin-exposed rodents in that an activated AhR (here CA-AhR) leads to antiestrogenic effects in the presence of estrogen, but to estrogenic effects in the absence of estrogen. These results suggest the CA-AhR mouse model as a useful tool for studies of continuous low activity of the AhR from early development, resembling the human exposure situation.