The Research Data Centre of the Centre for European Economic Research (ZEW-FDZ)

Das Zentrum für Europäische Wirtschaftsforschung (ZEW) in Mannheim stellt eine Reihe seiner Forschungsdatensätze externen Wissenschaftlern zur Verfügung. Das ZEW folgt damit den Empfehlungen der „Kommission zur Verbesserung der informationellen Infrastruktur zwischen Wissenschaft und Statistik“ und unterstützt so die Weiterentwicklung der empirischen Wirtschafts- und Sozialforschung. Im November 2012 ist das ZEW-FDZ vom Rat für Sozial und Wirtschaftsdaten (RatSWD) akkreditiert worden. Bei den im ZEW-FDZ angebotenen ZEW Forschungsdaten handelt es sich um Mikrodaten von ZEW Unternehmensbefragungen, ZEW Expertenbefragungen oder ZEW Personenbefragungen. Die Daten einiger ZEW-Befragungen werden externen Wissenschaftlern in einer faktisch anonymisierten Form als Scientific-Use-Files zur Verfügung gestellt. Neben der Nutzung der Scientific-Use-Files können externe Forscher einen Antrag auf Nutzung von formal anonymisierten ZEW-Daten stellen, mit denen sie in den FDZ-Räumen des ZEW arbeiten dürfen. Formal anonymisiert bedeutet, dass die Datensätze weder Namen noch Adressen, aber ansonsten alle Originalangaben der Befragten enthalten. Die formal anonymisierten Daten befinden sich dazu auf einem Stand-alone-Rechner ohne Netzwerkanbindung, von dem keine Daten heruntergeladen werden können. Für das Mannheimer Innovationspanel (MIP) wurden zudem absolut anonymisierte Education-Use-Files für die Nutzung in der Lehre erstellt. Das ZEW-FDZ schließt an die bisherige Praxis des ZEW an, eigene Erhebungsdaten an externe Wissenschaftler weiterzugeben. Vor dem Start des ZEW-FDZ im Januar 2013, stellte das ZEW etwa 280 Wissenschaftlern vom ZEW erhobene Forschungsdaten zur Verfügung; die meisten sind Nutzer des Mannheimer Innovationspanels (250). Das ZEW wird sein Datenangebot für externe Wissenschaftler laufend erweitern. Dies gilt auch für Daten zukünftiger Erhebunge

Vapor Pressure of Ionic Liquids

We argue that the extremely low vapor pressures of room temperature ionic liquids near their triple points are due to the combination of strong ionic characters and of low melting temperatures.Comment: Initially submitted manuscript of article M. Bier and S. Dietrich, Mol. Phys. 108, 211 (2010) [Corrigendum: Mol. Phys. 108, 1413 (2010)

Why Are Alkali Halide Solid Surfaces Not Wetted By Their Own Melt?

Alkali halide (100) crystal surfaces are anomalous, being very poorly wetted by their own melt at the triple point. We present extensive simulations for NaCl, followed by calculations of the solid-vapor, solid-liquid, and liquid-vapor free energies showing that solid NaCl(100) is a nonmelting surface, and that its full behavior can quantitatively be accounted for within a simple Born-Meyer-Huggins-Fumi-Tosi model potential. The incomplete wetting is traced to the conspiracy of three factors: surface anharmonicities stabilizing the solid surface; a large density jump causing bad liquid-solid adhesion; incipient NaCl molecular correlations destabilizing the liquid surface. The latter is pursued in detail, and it is shown that surface short-range charge order acts to raise the surface tension because incipient NaCl molecular formation anomalously reduces the surface entropy of liquid NaCl much below that of solid NaCl(100).Comment: 4 pages, 3 figure

Stellar Kinematics and Structural Properties of Virgo Cluster Dwarf Early-Type Galaxies from the SMAKCED Project. I. Kinematically Decoupled Cores and Implications for Infallen Groups in Clusters

We present evidence for kinematically decoupled cores (KDCs) in two dwarf early-type (dE) galaxies in the Virgo cluster, VCC 1183 and VCC 1453, studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. These KDCs have radii of 1.8'' (0.14 kpc) and 4.2'' (0.33 kpc), respectively. Each of these KDCs is distinct from the main body of its host galaxy in two ways: (1) inverted sense of rotation; and (2) younger (and possibly more metal-rich) stellar population. The observed stellar population differences are probably associated with the KDC, although we cannot rule out the possibility of intrinsic radial gradients in the host galaxy. We describe a statistical analysis method to detect, quantify the significance of, and characterize KDCs in long-slit rotation curve data. We apply this method to the two dE galaxies presented in this paper and to five other dEs for which KDCs have been reported in the literature. Among these seven dEs, there are four significant KDC detections, two marginal KDC detections, and one dE with an unusual central kinematic anomaly that may be an asymmetric KDC.The frequency of occurence of KDCs and their properties provide important constraints on the formation history of their host galaxies. We discuss different formation scenarios for these KDCs in cluster environments and find that dwarf-dwarf wet mergers or gas accretion can explain the properties of these KDCs. Both of these mechanisms require that the progenitor had a close companion with a low relative velocity. This suggests that KDCs were formed in galaxy pairs residing in a poor group environment or in isolation whose subsequent infall into the cluster quenched star formation.Comment: 14 pages, accepted for publication in Ap

Selenium interactions with algae: Chemical processes at biological uptake sites, bioaccumulation, and intracellular metabolism

Selenium (Se) uptake by primary producers is the most variable and important step in determining Se concentrations at higher trophic levels in aquatic food webs. We gathered data available about the Se bioaccumulation at the base of aquatic food webs and analyzed its relationship with Se concentrations in water. This important dataset was separated into lotic and lentic systems to provide a reliable model to estimate Se in primary producers from aqueous exposure. We observed that lentic systems had higher organic selenium and selenite concentrations than in lotic systems and selenate concentrations were higher in lotic environments. Selenium uptake by algae is mostly driven by Se concentrations, speciation and competition with other anions, and is as well influenced by pH. Based on Se species uptake by algae in the laboratory, we proposed an accurate mechanistic model of competition between sulfate and inorganic Se species at algal uptake sites. Intracellular Se transformations and incorporation into selenoproteins as well as the mechanisms through which Se can induce toxicity in algae has also been reviewed. We provided a new tool for risk assessment strategies to better predict accumulation in primary consumers and consequently to higher trophic levels, and we identified some research needs that could fill knowledge gaps

A continuum of structure and stellar content from Virgo cluster early-type dwarfs to giants?

Based on the wealth of multiwavelength imaging data from the SDSS, we investigate whether dwarf and giant early-type galaxies in the Virgo cluster follow a continuum in their structural parameters and their stellar population characteristics. More specifically we study the relation between size and brightness for the galaxies and their color magnitude relation. In both cases, we find noticeable deviations from a simple joint behavior of dwarfs and giants. We discuss these findings in the light of the different formation mechanisms commonly assumed for dwarf and giant early types, thereby taking into account the existence of several distinct early-type dwarf subclasses. By comparing our results to a semianalytic model of galaxy formation, we argue that the analyzed relations might be reproduced by processes that form dwarfs and giants altogether. The work presented here is based on Janz & Lisker 2008, 2009.Comment: 7 pages, 3 figures, to be published in Astronomische Nachrichten (proceedings of Symposium 6 of the JENAM 2008, Vienna