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Das schnelle Schalten elektrischer Strome ist die Grundlage der modernen Elektronik und Computertechnologie. Der mit dem Schaltprozess verbundene Energieverbrauch und die daraus resultierende Warmeentwicklung ist zugleich der limitierende Faktor fur die Erhohung der Schaltfrequenzen. Experimente mit einer Zeitauflosung im Attosekundenbereich zeigen einen moglichen Ausweg. Mit dem starken elektrischen Feld ultrakurzer Laserimpulse lassen sich elektrische Strome mit Lichtfrequenz bei gleichzeitig verschwindendem Energieverlust schalten. Diese physikalischen Prozesse erfordern noch ein tiefergehendes Verstandnis. Davon konnte eine zukunftige “Lichtelektronik” profitieren, die wesentlich schnellere und leistungsfahigere Informationstechnologien hervorbringen konnte.

As the world's population increasingly relies on the use of modern technology, cyberbullying becomes an omnipresent risk for children and adolescents and demands counteraction to prevent negative (online) experiences. The classroom-based German preventive intervention "Medienhelden" (engl.: "Media Heroes") builds on previous knowledge about links between cognitive empathy, affective empathy, and cyberbullying, among others. For an evaluation study, longitudinal data were available from 722 high school students aged 11-17 years (M = 13.36, SD = 1.00, 51.8% female) before and six months after the implementation of the program. A 10-week version and a 1-day version were conducted and compared with a control group (controlled pre-long-term-follow-up study). Schools were asked to randomly assign their participating classes to the intervention conditions. Multi-group structural equation modeling (SEM) showed a significant effect of the short intervention on cognitive empathy and significant effects of the long intervention on affective empathy and cyberbullying reduction. The results suggest the long-term intervention to be more effective in reducing cyberbullying and promoting affective empathy. Without any intervention, cyberbullying increased and affective empathy decreased across the study period. Empathy change was not generally directly linked to change in cyberbullying behavior. "Media Heroes" provides effective teaching materials and empowers schools to address the important topic of cyberbullying in classroom settings without costly support from the outside.

Two morphologically similar pre-dams (Hassel and Rappbode pre-dams, Harz Mountains, Germany) of a large reservoir with different land use in their catchments were compared with respect to their physical, chemical, and biological properties in order to test if differences can be attributed to the different land use. In addition, local geology, soil types, and topography were evaluated in detail to distinguish its influence from that of present-day land use. Despite a remarkable similarity in physical variables and stratification, the annual development of hydrochemistry and biology differed between Rappbode and Hassel pre-dam. While the Hassel pre-dam received much higher nitrogen and phosphorus inputs from the catchment, the Rappbode pre-dam received more dissolved organic carbon. The quality of dissolved organic carbon also differed between the two catchments, indicating different sources. The higher residence time of Hassel pre-dam amplified the effects of these inputs on the trophic state of both pre-dams. The phytoplankton communities in summer were dominated by diatoms in the Rappbode pre-dam and by cyanobacteria in the Hassel pre-dam. In conclusion, land use appeared to be an important driver for the observed lake characteristics. However, it was itself strongly related to soil types and topography, which on the other hand influences the residence time of water within the catchments.

Anaerobic microbial processes in reservoirs have a strong influence on water quality, and these processes are influenced by inputs from the catchment. Two morphologically similar pre-dams of the large Rappbode reservoir system in Germany were studied for oxygen consumption, carbon dioxide production, nitrate reduction, manganese and iron reduction, sulfate reduction, and methanogenesis. Rates were obtained by calculations from hypolimnion size and hypolimnetic water chemistry and from incubation of sediment samples (manganese and iron reduction, sulfate reduction, and methanogenesis only). Length of anoxic conditions (anoxic factor) and anaerobic process rates were generally higher for Hassel pre-dam, a water body with 58% grasslands and agriculture in its catchment. Rappbode pre-dam had higher iron reduction rates. Oxygen consumption and sulfate reduction (and nitrate reduction for Hassel pre-dam) were the most important respiratory processes. While hypolimnion chemistry was similar and showed mainly temporal differences in seasonal development, the pre-dam sediments differed considerably with roughly twofold higher microbial biomass and 102–104 fold higher counts of sulfate-reducing prokaryotes in Hassel pre-dam compared to Rappbode pre-dam. These differences can be explained by the higher nutrient input, longer water retention time, and consequently higher biomass production in Hassel pre-dam. The view of microbial activities against known loads of solutes also implies that the quality of allochthonous organic matter and particulate fluxes likely governs respiratory processes in the pre-dams by providing electron donors and acceptors.

Voting Advice Applications (VAAs) have experienced a rising demand in recent years, being an efficient and reliable way for voters to gain political information prior to elections. This article uses an online survey to examine the impact of the German VAA (the “Wahl-O-Mat”) on the political knowledge of its users concerning party positions during the 2009 German Federal Election. The article first assesses empirically the extent to which Wahl-O-Mat users are able to correctly identify party positions on relevant issues, and the extent to which they are misinformed. Multivariate analyses with a path model for categorical data are then undertaken to establish whether Wahl-O-Mat usage enhances political knowledge about party positions. It is shown that Wahl-O-Mat use has a positive effect on political knowledge, indicating that electoral effects can be partially explained by this change in the information level of users. However, it is also shown that political knowledge is very heterogeneous, and the level of confusion about party positions is high.

To model chemically stratified lakes numerically, chemical transformations must be reflected in the density function. In this contribution, partial molal volumes are used to calculate density from the chemical composition of lake water. Such values have been evaluated for cations and anions separately, to facilitate an easy implementation into geochemical stratification models for lakes. Coefficients for temperature dependence and variation for higher ionic strengths were evaluated from previously published data. An algorithm RHOMV to calculate density with a second order approximation for temperature dependence and ionic strength dependence is proposed. The accuracy is tested for seawater composition. We conclude that this approach delivers a representation of density based on the actual chemical composition of the lake water, which is accurate enough for most limnological purposes. The implementation of RHOMV into geochemical stratification models facilitates the numerical tackling of pressing questions, such as meromixis or double diffusive features or altered circulation patterns of lakes due to changing climate or change of use.

Analyses of water, suspended particulate matter, and sediment for the area drained by the river Mulde (Germany) for the early 90's show a high level of pollution in several sections of the river system. This was caused primarily by mining, and industrial and urban activity. The influence of the extreme “100-year-flood” into the Mulde and Elbe river systems as a result of the extremely high precipitation in the ore mountains (Erzgebirge) in August 2002 was studied. During the flood, large amounts of strongly polluted sediments were transported into the Freiberger Mulde and Zwickauer Mulde, and deposited on the flooded areas and along river banks in the Vereinigte Mulde. Concentrations of As and heavy metals in the flood sediments of the Freiberger Mulde were found to be very high. This is due primarily to waste dump leaching into the polluted part of the river near Freiberg. Studies in such strongly polluted area show that there is a permanent supply of pollutants from point and diffuse sources, and new sediments with the same level of pollution are formed in the river system. The study of the Bitterfelder Mulde river reservoir documents its function as a sink for suspended matter and heavy metals in the lower Mulde and Elbe system, even at extremely high flow rates. As a result of the flooding of the Lake Goitsche, large amounts of sediment were observed, particularly in the first subbasin Dobern. The deposited sediments contained large concentrations of As and heavy metals. Die Arsen- und Schwermetallverteilung in der Mulde Untersuchungen der Wasser, der suspendierten partikularen Substanz und der Sedimente im Einzugsgebiet der Mulde (Deutschland) Anfang der neunziger Jahre zeigten, dass eine hohe Arsen- und Schwermetallbelastung durch geogene (Mineralisationen und Lagerstatten) und anthropogene (Bergbau, Industrie und Besiedelung) Quellen in definierten Abschnitten des Flusssystems vorliegt. An dieser Ausgangssituation wurde der Einfluss eines extremen „Jahrhundert”-Hochwassers in den Flussen Mulde und Elbe als ein Ergebnis der extrem hohen Niederschlage im Erzgebirge studiert. Es wurde nachgewiesen, dass wahrend des Hochwassers grose Mengen hoch belasteter Sedimente in der Freiberger und Zwickauer Mulde transportiert und in den Uberflutungsflachen und Auenbereichen der Vereinigten Mulde abgelagert wurden. Besonders fur Arsen und Schwermetalle waren die Konzentrationen in den Flutsedimenten der Freiberger Mulde sehr hoch, was insbesondere auf die Abtragung von Haldenmaterial aus der Verhuttung im Hauptbelastungsgebiet Freiberg (Bereich Muldenhutten) zuruckzufuhren ist. Die Untersuchung der zeitlichen Entwicklung der Belastung in hoch belasteten Flussabschnitten wie z. B. der Freiberger Mulde bei Freiberg oder der Zwickauer Mulde bei Aue-Schlema nach dem Hochwasser zeigten, dass eine permanente Nachlieferung aus punktuellen und diffusen Quellen stattfindet und neue ahnlich belastete Sedimente im Flusssystem gebildet werden. Die Untersuchungen des Bitterfelder Muldestausees unterstrichen seine Funktion als Senke fur suspendierte partikulare Substanz, Arsen und Schwermetalle in der unteren Mulde, besonders bei extremen Durchflussraten. Die Flutung des Goitschesees fuhrte ebenfalls zur Ablagerung groser Sedimentmengen mit hohen Konzentrationen an Arsen und Schwermetallen, besonders im ersten Teilbecken Dobern.

Open-cast lignite mining has exposed formerly anaerobic layers to the air. Pyrite and marcasite are oxidized to sulfuric acid and iron sulfate, which later hydrolyses to iron hydroxide. When the pit is refilled with groundwater, its pH is 2–3. These geogenically acidified mining lakes are brown, with high iron content. Biological conditions differ greatly from those in most natural lakes and resemble those in sulfur-acidic lakes impaired by acid rain. The usability of these fish-free lakes is also restricted for recreational purposes. Neutralization with lime is expensive. The iron-buffered water has a high base buffering capacity stabilizing at pH 2–4. The complex of potential measures for neutralization comprises: the revegetation of the waste heaps, the hydrological regime and coupled transport processes, the selection of suitable filling water and in-lake technologies. Desulfurication takes place with sulfidic binding of iron and natural neutralization under locally anaerobic conditions in the reclaimed overburden heaps, in the deep water of mining lakes, in macrophyte stands and in the sediments. Anaerobic conditions should be established within the lakes during stratification periods: in the hypolimnion of eutrophic or the monimolimnion of meromictic lakes. Acidic lakes often are not sufficiently productive to achieve deep-water oxygen depletion. Measures to increase the stability of stratification may be necessary, for example by installation of barriers to establish an environment suitable for biological neutralization. Carbon sources for microbial desulfurication may be added artificially or autochthonically produced by primary producers. Therefore, a controlled eutrophication may be useful in the initial filling stages of acidic mining lakes.

Pyrite and marcasite oxidation in the consequence of lignite surface mining creates lakes with pH as low as 2 to 3, buffered by high contents of iron and aluminium. Living conditions in this extreme habitat for plants and animals are described as well as the characteristics of the pioneer settlement. The utilization of these fish-free lakes is very limited. As possibilities for a water quality improvement special recultivation methods of overburden, chemical neutralization and biological ecotechnologies are recommended.

The prediction presented is based on the application of the GDR standard TGL 27885/01 for the classification of the stagnant waters. The expected trophic state of the worked-out open cut filling with water is estimated by means of the phosphorus surface load. The oxygen balance of the hypolimnion proceeds from the saturation of air at a water temperature of 10°C during the spring full overturn and the theoretically possible oxygen consumption of the biomass formed at complete conversion of the inflowing orthophosphate. As an example, the prediction of a worked-out open cut for 50 years at filling with groundwater and varying proportions of river water and bank-filtered water is graphically represented.