Cohomological finiteness conditions for a class of metabelian groups

We consider a class of metabelian groups first studied by Baumslag and Stammbach and we show that these groups are consistent with the Bieri-Groves conjecture which relates cohomological finiteness conditions to the Bieri-Neumann-Strebel sigma invariant.Comment: 10 pages Accepted for publication in the Bulletin of the London Mathematical Societ

Operation of Complex Hydropower Schemes and its Impact on the Flow Regime in the Downstream River System under Changing Scenarios

Hydropower is the world’s most important renewable electricity source. More than 40% of European hydroelectric energy is produced in Alpine countries. High-head storage hydropower plants (HPP) contribute significantly to peak energy production as well as electricity grid regulation. Future plant management is faced with several challenges concerning modified availability of water resources due to climate change as well as new economic constraints associated with legal, political and electricity market issues. HPP operation results in unsteady water release to the downstream river system. Hydropeaking is the primary factor of flow regime alteration, impacting the river ecosystem. Even when the biological response to hydropeaking is not fully understood, the recently adapted law on water protection prescribes its mitigation in Switzerland. In this research project, a novel integrative approach to model and assess the impact of the operation of a complex hydropower scheme on the downstream river system is developed. It contains (1) a precipitation-runoff model extended for long-term simulations of glacierized Alpine catchment areas, (2) an operation tool for high-head storage HPP, (3) flow regime generation with cost estimation of hydropeaking mitigation measures and (4) a habitat model of reference river morphologies for a target species. The upper Aare River (Hasliaare) in Switzerland is an Alpine stream, affected by hydropeaking from a complex hydropower scheme with several storage volumes and power houses. Since the 1930s, seasonal water transfer from summer to winter and the amplitude and frequency of daily peak discharge have been continuously increased. Furthermore, the dynamic braided river network with various mesohabitats gave way to a mainly monotonous channel. Although diversity of species and biomass of aquatic biota have drastically decreased, the potential of redevelopment remains. Investigations to improve the river morphology and the flow regime are under discussion. The upper Aare River catchment is therefore an appropriate case study for analysis of the interactions between climatic, hydrological, hydraulic, economic as well as ecological parameters. The simulation of runoff in Alpine catchment areas is essential for optimal hydropower exploitation under normal flow conditions, but also for the analysis of flood events. The semi-distributed conceptual modeling approach Routing System contains a reservoir-based precipitation-runoff transformation model (GSM-SOCONT), extended by dynamic glacier simulation tool. Spatial precipitation and temperature distributions are taken into account for simulating the relevant hydrological processes, such as glacier melt, snowpack constitution and melt, soil infiltration and runoff. The model development, calibration and validation are illustrated for the 2005 flood event, where the flood reduction capacity of the HPP is discussed, as well as future long-term runoff estimations. Climate change scenarios, based on a reference climate period, take into account intra-annual temperature and precipitation variations as well as their long-term tendencies. Runoff series of daily resolution are produced by hourly updating of the meteorological, glaciological and hydrological parameters. An almost complete deglacierization of the upper Aare River basin is simulated for the late 21st century. The resulting reduction of glacier melt in summer and earlier snowmelt in spring change the runoff regime from glacio-nival to nival. The implemented heuristic hydropower modeling tool in Routing System allows simulation of the operating mode of complex HPP. Within the case study of the upper Aare River catchment and despite the complexity of the HPP network, the influence of climate change, electricity market issues, plant enhancements as well as hydropeaking constraints is simulated and assessed. Despite the reduction of future runoff, increased flexibility due to new turbine and pumped-storage capacities allows compensation, especially in the case of volatile electricity prices, and could even partially restore the natural flow regime. Several operational and construction measures to reduce hydropeaking are implemented in the model. Resulting flow regimes as well as the related costs are defined. Operational constraints, such as limitation of turbine discharge, increase of residual flow or limited drawdown range, generate relatively high costs compared to their environmental effectiveness. Better ecological and economic response is achieved by construction measures, such as flow deviation systems or compensation basins installed downstream of the power house outflow where the water is temporarily stored and then released to the river by a guided system. The simulated flow regimes are rated by a river specific habitat model for representative morphologies and three life stages of the target species brown trout (Salmo trutta fario). This is based on results from a 2D hydrodynamic model and in situ investigations undertaken in the framework of a joint project of EAWAG. Steady and dynamic indicators quantify fish habitat suitability and allow comparison through economic indices of the implemented mitigation measures. For the Hasliaare River, investments for mitigation of hydropeaking are only justified by morphological improvements. The developed approach is useful for the enhancement of complex storage hydropower schemes regarding mitigation of altered flow regimes. Despite several uncertainties, it allows operators, authorities and researchers to define and rate the impact of HPP operation on the river network, to ecologically and economically assess mitigation measures and thus to address hydropeaking in a straightforward manner

Beurteilung von Massnahmen zur Reduktion von Schwall und Sunk

Das revidierte Gewässerschutzgesetz schreibt für Schwall-und Sunk-beeingträchtigte Gewässer eine Sanierung des Abflussregimes vor. Um Massnahmen in komplexen Kraftwerkssystemen wirtschaftlich und ökologisch zu beurteilen, ist ein interdisziplinärer Ansatz sinnvoll. Der Betrieb des Kraftwerks wird mit dem Softwaretool Routing System simuliert. Daraus resultiert die Ganglinie im Fluss sowie die durch die zu testende Sanierungsmassnahme entstandenen Kosten. Die Beurteilung der Bachforellenhabitate berücksichtigt nebst den kritischen Entwichlungsstadien der Forelle auch den Einfluss der Gerinnmorphologie

Influence of lamination parameters on LTCC shrinkage under unconstrained sintering

LTCC (Low-Temperature Cofired Ceramic) has attracted considerable interest as a material for sensors and microfluidic circuits, for which dimensional accuracy is essential. The irregular shrinkage behaviour of LTCC tapes must be taken into account when designing devices. Furthermore the shrinkage observed in practice can be different than that given by the manufacturers. This study analyses and models with Design of Experiments the shrinkage of DuPont GreenTapeTM 951AX LTCC foils. Unlike most past studies, which concentrated on firing conditions or paste compositions, only the influence of the most obvious lamination parameters is characterised in this paper. A linear model is proposed and the relative importance of the parameters discussed. The most important (lamination pressure and temperature) play a non-negligible role (up to 1% of linear dimension) on shrinkage for a given firing profile. As expected, the more pre-densification the LTCC receives during lamination, the less it shrinks during firing

Herausforderungen des heutigen wasserbaulichen Versuchswesens mit drei Beispielen

Die meisten technischen Universitäten oder Hochschulen, welche Bauingenieure ausbilden, verfügen seit annähernd 100 Jahren über wasserbauliche Laboratorien. Darin werden mittels physikalischer Modellierung Elemente von Talsperren, Wasserkraftwerken oder Hochwasserschutz-Maßnahmen überprüft und optimiert. Mehrmals wurde dieser klassischen Methode bereits das Ende vorausgesagt, trotzdem sind die Versuchsanstalten ausgebucht. Die Autorenumreißen den Wandel der Branche und geben drei Beispiele dazu

Upstream and downstream sequence elements determine the specificity of the rice tungro bacilliform virus promoter and influence RNA production after transcription initiation

The contribution of sequences upstream and downstream of the transcription start site to the strength and specificity of the promoter of rice tungro bacilliform virus was analysed in transgenic rice plants. The promoter is strongly stimulated by downstream sequences which include an intron and is active in all vascular and epidermal cells. Expression in the vascular tissue requires a promoter element located between −100 and −164 to which protein(s) from rice nuclear extracts bind. Elimination of this region leads to specificity for the epidermis. Due to the presence of a polyadenylation signal in the intron, short-stop RNA is produced from the promoter in addition to full-length primary transcript and its spliced derivatives. The ratio between short-stop RNA and full-length or spliced RNA is determined by upstream promoter sequences, suggesting the assembly of RNA polymerase complexes with different processivity on this promote

FATE: Feminisation, Agricultural Transition and rural Employment

Project summary and description of the FATE project (Feminisation, agricultural transition and rural employment) - social and political conditions of asset building in the context of export-led agricultur