Lebensmittelhändler im Bergischen Land:Vom Ausgang des 19. Jahrhunderts bis in die 70er Jahre des 20. Jahrhunderts

Die vorliegende Arbeit befasst sich mit der Berufsgruppe der Lebensmitteleinzelhändler und -händlerinnen im Bergischen Land aus volkskundlicher Perspektive. Sie dokumentiert ihren Arbeitsalltag im 20. Jahrhundert auf der Grundlage qualitativer Interviews. Ausgehend von der quantitativen Entwicklung sowie den unterschiedlichen Betriebsformen der einzelnen Lebensmittelläden im 19. und 20. Jahrhundert werden die Veränderungen in diesem Handels- und Dienstleistungsberuf herausgestellt. Für den Alltag der im Lebensmittelhandel Tätigen war seit den 1950er Jahren zunehmend die Konzentration des Einkaufs, die Reduzierung der Arbeitsabläufe und eine generelle Rationalisierung prägend. Die mit dieser Entwicklung einhergehende Anonymisierung an der Schnittstelle zwischen Produzent und Konsument wurde erst spät erkannt und beklagt. Der immer stärker werdende Konkurrenzkampf bedeutet bis Ende der 1980er Jahre für fast alle befragten Ladeninhaber die Schließung ihres Geschäfts

Electrolyte layering at the calcite(104)-water interface indicated by Rb⁺- and Se(VI) K-edge resonant interface diffraction

Calcite-water interface reactions are of major importance in various environmental settings as well as in industrial applications. Here we present resonant interface diffraction results on the calcite(104)-aqueous solution interface{,} measured in solutions containing either 10 mmol L-1 RbCl or 0.5 mmol L-1 Se(vi). Results indicate that Rb+ ions enter the surface adsorbed water layers and adsorb at the calcite(104)-water interface in an inner-sphere fashion. A detailed analysis based on specular and off-specular resonant interface diffraction data reveals three distinct Rb+ adsorption species: one 1.2 A above the surface{,} the second associated with surface adsorbed water molecules 3.2 A above the surface{,} and the third adsorbed in an outer-sphere fashion 5.6 A above the surface. A peak in resonant amplitude between L = 1.5 and L = 3.0 is interpreted as signal from a layered electrolyte structure. The presence of a layered electrolyte structure seems to be confirmed by data measured in the presence of Se(vi)

The influences of cement hydration and temperature on the thixotropy of cement paste

The rheological properties of fresh cement paste are highly influenced by a large number of parameters, among which the most important factors are the applied shear stress, and the shear history, the age of the sample and the temperature. The effects of these parameters on the yield stress (designated as structural limit stress in this work), the viscosity and the structural recovery rate (i.e., the change in dynamic viscosity with time at rest) were studied. In parallel, the changes in ion composition of the carrier liquid, mineral phase content and granulometry were investigated. The results reveal that all investigated rheological parameters exhibit an approximated bi-linear trend with respect to the degree of hydration, with a period of quasi-constant properties until a degree of hydration of approximately 0.07, followed by a non-linear increase. This increase could be attributed to the formation of calcium hydroxide (CH) and calcium-silicate-hydrate (C-S-H) via calorimetry results. With regard to the effect of the shear history of the sample on the rheological properties, the structural limit stress showed a minor dependency on the shear history immediately after the end of shearing, which, however, vanished within the first minute at rest. The same is true for the structural recovery rate. The presented results give detailed insights into the influences of hydration and shear on the rheological properties—especially the thixotropy—of fresh cement pastes

XAS signatures of Am(III) adsorbed onto magnetite and maghemite

Trivalent americium was adsorbed on magnetite and maghemite under similar chemical conditions and the local environment probed by EXAFS spectroscopy. In both samples, partially hydrated Am(III) binds the surface but slightly different surface complexes were identified. On Fe3O4, Am(III) forms monomeric tridentate surface complexes similar to that reported for Pu(III) at the (111) surface. In contrast, the lower number of detected Fe atoms may suggest that Am(III) forms monomeric bidentate surface complexes on γ-Fe2O3. Alternatively, the lower Fe coordination number can also be due to the presence of vacancies in maghemite. XPS data imply very similar binding environments for Am at both Fe oxide surfaces