Geleitwort

Ohne Zusammenfassung     

Housing Adjustment Costs: Their Impact on Mobility and Housing Demand Elasticities

The role of housing adjustment costs in influencing mobility decisions, and the relationship between these and housing demands is not well understood. Here we try to examine how changes in adjustment costs as well as in such demand factors as income, influence the decision of households to adjust their housing consumption through moving. Empirically, we use a sample of recently moving homeowners from the PSID and provide evidence indicating adjustment costs are more important than other demand factors in influencing mobility decisions. We also argue that sample selection may bias estimates of housing demand elasticities when the sample is restricted to recent movers because the influence of adjustment costs in the mobility decision are not accounted for. Testing for this using the Heckman two-stage procedure, however, showed this was not a significant problem.     

HYDROLOGICAL GRADIENT AND SPECIES TRAITS EXPLAIN GASTROPOD DIVERSITY IN FLOODPLAIN GRASSLANDS

Floodplains are characterized by high spatial and temporal heterogeneity. Despite low active mobility, Central European floodplain gastropod communities show a high species diversity. They are supposed to have developed a large range of resistance and/or resilience strategies to survive in the highly variable and frequently disturbed floodplain habitats. Relating gastropod diversity and species traits to hydrological conditions, we tested how different groundwater and flood regimes affect gastropod diversity and identified the main species traits favouring their survival in highly dynamic floodplain grasslands. Species richness, species diversity and functional diversity peaked at intermediate flood disturbance and moisture levels. Harsher environmental conditions in either dryer or frequently flooded habitats restricted the gastropod communities to a few specialized species. Morphological and life‐history traits showed significant variations along the hydrological gradient. Shell character and mode of reproduction proved to be important functional determinants for gastropod community composition. Species with strongly calcified shells, which limit the risk of injuries in case of dislodgment, were more often found in flood prone sites. Uniparental reproduction dominated in the driest as well as in highly flood‐disturbed habitats, providing reproductive assurance where harsh environmental conditions may reduce the number of potential mates. Intermediate disturbance and moisture levels favoured local gastropod diversity whereas dryer or highly flood‐disturbed habitats sheltered specialized species. Therefore, the maintenance of areas with different disturbance and moisture levels is of major importance in favouring taxonomical and functional mollusc diversity across the whole floodplain. Copyright © 2011 John Wiley & Sons, Ltd.     

Simulation of the wastewater temperature in sewers with TEMPEST.

TEMPEST is a new interactive simulation program for the estimation of the wastewater temperature in sewers. Intuitive graphical user interfaces assist the user in managing data, performing calculations and plotting results. The program calculates the dynamics and longitudinal spatial profiles of the wastewater temperature in sewer lines. Interactions between wastewater, sewer air and surrounding soil are modeled in TEMPEST by mass balance equations, rate expressions found in the literature and a new empirical model of the airflow in the sewer. TEMPEST was developed as a tool which can be applied in practice, i.e., it requires as few input data as possible. These data include the upstream wastewater discharge and temperature, geometric and hydraulic parameters of the sewer, material properties of the sewer pipe and surrounding soil, ambient conditions, and estimates of the capacity of openings for air exchange between sewer and environment. Based on a case study it is shown how TEMPEST can be applied to estimate the decrease of the downstream wastewater temperature caused by heat recovery from the sewer. Because the efficiency of nitrification strongly depends on the wastewater temperature, this application is of practical relevance for situations in which the sewer ends at a nitrifying wastewater treatment plant.     

Spieltheorie: Ein neues Paradigma der Sozialwissenschaft

Ohne ZusammenfassungDeutsche Fassung des Artikels Game Theory: A New Paradigm of Social Science, erschienen in New Methods of Thought and Procedure (Berlin-Heidelberg-New York: Springer, 1967). — Diese Arbeit wurde teilweise über das Econometric Research Program der Princeton University durch das Office of Naval Research unterstützt.     

Development and testing of bioelectrochemical reactors converting wastewater organics into hydrogen peroxide

In a bioelectrochemical system, the energy content in dissolved organic matter can be used to power the production of hydrogen peroxide (H(2)O(2)), which is a potentially useful chemical at wastewater treatment plants. H(2)O(2) can be produced by the cathodic reduction of oxygen. We investigated four types of gas-diffusion electrodes (GDEs) for this purpose. A GDE made of carbon nanoparticles bound with 30% polytetrafluoroethylene (PTFE) (wt./wt.C) to a carbon fiber paper performed best and catalyzed H(2)O(2) production from oxygen in air with a coulombic efficiency of 95.1%. We coupled the GDE to biological anodes in two bioelectrochemical reactors. When the anodes were fed with synthetic wastewater containing acetate they generated a current of up to ～0.4 mA/mL total anode compartment volume. H(2)O(2) concentrations of ～0.2 and ～0.5% could be produced in 5 mL catholyte in 9 and 21 h, respectively. When the anodes were fed with real wastewater, the generated current was ～0.1 mA/mL and only 84 mg/L of H(2)O(2) was produced.     

Altruism, redistribution and social insurance

The paper examines the influence of altruism on voluntary transfers and government redistribution in a simple model: two jobs of different productivity are assigned by chance to two individuals. Ex ante the individuals are identical, ex post they have different incomes. The first part of the paper examines voluntary transfers determined ex post or agreed upon ex ante in the absence of altruism. In the second part, the influence of altruism is examined. Altruism is modelled as a pure public good: the minimum consumption (or income, since there is only one consumption good). Both individuals can contribute to its provision, one person by earning wage income, the other by voluntary transfers. The ex ante solutions generally lead to higher expected welfare but create several incentive problems. Only lump-sum transfers are considered. Received: 28 February 1997 / Accepted: 31 January 2000