578 research outputs found
Arbeiten und lernen in der Gesundheitsregion Aachen / Hrsg. Martin Frenz, Thomas Mühlbradt Wolfgang Boos
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Mineralisation of amethyst-bearing geodes in Ametista do Sul (Brazil) from low-temperature sedimentary brines: evidence from monophase liquid inclusions and stable isotopes
No full textFluid inclusion studies in combination with hydrogen, oxygen and sulphur isotope data provide novel insights into the genesis of giant amethyst-bearing geodes in Early Cretaceous Parana continental flood basalts at Amestita do Sul, Brazil. Monophase liquid inclusions in colourless quartz, amethyst, calcite, barite and gypsum were analysed by microthermometry after stimulating bubble nucleation using single femtosecond laser pulses. The salinity of the fluid inclusions was determined from ice-melting temperatures and a combination of prograde and retrograde homogenisation temperatures via the density maximum of the aqueous solutions. Four mineralisation stages are distinguished. In stage I, celadonite, chalcedony and pyrite formed under reducing conditions in a thermally stable environment. Low delta S-34(V-CDT) values of pyrite (-25 to -32 aEuro degrees) suggest biogenic sulphate reduction by organotrophic bacteria. During the subsequent stages II (amethyst, goethite and anhydrite), III (early subhedral calcite) and IV (barite, late subhedral calcite and gypsum), the oxidation state of the fluid changed towards more oxidising conditions and microbial sulphate reduction ceased. Three distinct modes of fluid salinities around 5.3, 3.4 and 0.3 wt% NaCl-equivalent characterise the mineralisation stages II, III and IV, respectively. The salinity of the stage I fluid is unknown due to lack of fluid inclusions. Variation in homogenisation temperatures and in delta O-18 values of amethyst show evidence of repeated pulses of ascending hydrothermal fluids of up to 80-90 A degrees C infiltrating a basaltic host rock of less than 45 A degrees C. Colourless quartz and amethyst formed at temperatures between 40 and 80 A degrees C, while the different calcite generations and late gypsum precipitated at temperatures below 45 A degrees C. Calculated oxygen isotope composition of the amethyst-precipitating fluid in combination with delta D values of amethyst-hosted fluid inclusions (-59 to -51 aEuro degrees) show a significant O-18-shift from the meteoric water line. This O-18-shift, high salinities of the fluid inclusions with chloride-sulphate composition, and high delta S-34 values of anhydrite and barite (7.5 to 9.9 aEuro degrees) suggest that sedimentary brines from deeper parts of the Guarani aquifer system must have been responsible for the amethyst mineralisation.Swiss National Science Foundation (SNSF) [200021-119966
Absolute measurement of molecular two-photon absorption cross-sections using a fluorescence saturation technique
No full textVom Chaoten zum Geschäftsführer: biografie- und bildungstheoretische Analyse einer modernen Erwerbsbiografie
No full textDer Beitrag verfolgt das Ziel, die Leitfrage des Sammelbandes aus einer biografie- und bildungstheoretischen Sicht zu beantworten. Im ersten Kapitel des Beitrags werden der Gegenstandsbereich eingegrenzt, die Problemstellung erörtert und der methodische Aufbau der Fallstudie begründet. Kapitel 2 stellt die Ergebnisse der biografischen Fallanalyse des Interviews mit Martin Kranz vor. Hierbei werden insbesondere dessen biografische Gesamtformung und Prozesse strukturaler Bildung rekonstruiert sowie abschließend ein vorläufiges Fazit über den Zusammenhang dieser Biografie und dem Bereich der Energieberatung gezogen. Der Beitrag schließt mit einer theoretischen Verdichtung der gewonnenen Auswertungsergebnisse
Self-organization of self-clearing beating patterns in an array of locally interacting ciliated cells formulated as an adaptive Boolean network
No full textThe observed spatiotemporal ciliary beat patterns leading to proper mucociliary clearance on multiciliated epithelia are suspected to be the result of self-organizing processes on various levels. Here, we present a simplified pluricellular epithelium model, which intends to make the self-organization of ciliary beating patterns as well as of the associated fluid transport across the airway epithelium plausible. The model is based on a two-dimensional array of locally interacting oscillating ciliated cells. Ciliated cells are represented by Boolean actuators, and abstracted hydrodynamic mucociliary interactions are formulated in terms of logical update rules (Boolean functions). In the course of a simulation, initial random conformations of an array of actuators self-organize toward metachronally coordinated states exhibiting efficient transport of mucus. Within the framework of Boolean networks ciliated cells represent the nodes of the network and as the mucus establishes the local interactions among nodes, its distribution (together with the formulated local interactions) determines the topology of the network. Consequently, we propose to consider the dynamics on multiciliated epithelia in the context of adaptive (Boolean) networks. Furthermore, we would like to present insights gained from conducted comprehensive parameter studies. In particular, the dynamical response of the network with respect to variations of the boundary conditions, updating schemes (representing intercellular signaling mechanisms) and the proportion of ciliated cells is presented
Vom Chaoten zum Geschäftsführer: biografie- und bildungstheoretische Analyse einer modernen Erwerbsbiografie
No full textDer Beitrag verfolgt das Ziel, die Leitfrage des Sammelbandes aus einer biografie- und
bildungstheoretischen Sicht zu beantworten. Im ersten Kapitel werden der Gegenstandsbereich eingegrenzt, die Problemstellung erörtert und der methodische Aufbau der Fallstudie begründet. Kapitel 2 stellt die Ergebnisse der biografischen Fallanalyse des Interviews mit Martin Kranz vor. Hierbei werden insbesondere dessen biografische Gesamtformung und Prozesse strukturaler
Bildung rekonstruiert sowie abschließend ein vorläufiges Fazit über den Zusammenhang dieser Biografie und dem Bereich der Energieberatung gezogen. Der Beitrag schließt (in Kapitel 3) mit einer theoretischen Verdichtung der gewonnenen Auswertungsergebnisse
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