Isotopenuntersuchungen zur Wechselwirkung von Grund- und Oberflächenwasser in der Entstehungsphase von Bergbauseen

Environmental isotopes such as ³ H, ² H, ¹⁸ O, ³⁴ S and ²²² Rn were applied to characterize relationships within and between ground and surface waters in two developing mining lakes. Using a two-component-model the portion of saline waters ascending through the lake bottom into the lakes was estimated. Similarly the contribution of pyritic sulphur participating in the lake sulfate has been assessed. Locally, the lakes are hydrochemically stratified. Mixing processes are reflected by all isotopes mentioned above. δ ¹³ C _DIC values of the most mineralized lake water did not correspond with those of deep groundwater from Zechstein strata revailing additional effects such as CO ₂ production. ²²² Rn was checked for assessing groundwater fluxes through the lake bottom. ²²² Rn was found in lake water regions with elevated salt contens but being always in an equilibrium with radium (excepting the sediment-lake water interface). Thus, radium must be taken in consideration in order to interprete radon values in saline groundwaters.     

Morphological and elemental integrity of freeze-fractured,freeze-dried cultured cells during ion microscopic analysis

The effects of progressive ion beam bombardment on freeze-fractured, freeze-dried cultured cells during ion microscopic (SIMS) analysis were studied with scanning electron microscopy (SEM) and ion microscopy. The freeze-fracture, freeze-dry sample preparation method was generally found to preserve cell morphology to a level far exceeding the spatial resolution of the ion microscope, with splitting at the nuclear envelope being the most commonly observed artefact. SEM monitoring of surface topography of an NRK-49F fibroblast after various ion bombardment doses showed relatively uniform erosion of cellular material, with some apparent selective retention of small cytoplasmic granules. Prolonged bombardment produced no detectable lateral elemental translocation. ⁴¹K+/²⁴Mg+ signal ratios from Swiss 3T3 fibroblasts and RBL rat basophilic leukaemia cells were shown to vary generally by less than 10% during the course of extended ion bombardment. GM0415 human skin fibroblasts containing engorged lysosomes characteristic of Hurler's Syndrome were used to evaluate the effects of ion bombardment during a typical analysis session, where ion images of ³⁹K+, ²³Na+, ⁴⁰Ca+ and ²⁴Mg+ are sequentially recorded. This cell line was chosen as a worst-case system, because these cells are often thinly spread and possess extreme surface topography. Thin cell edges were shown sometimes to sputter away during analysis, giving misleadingly low ion signals from these regions in some ²⁴Mg+ micrographs. Various nonuniform sputtering phenomena occurring in the submicrometre spatial domain had little or no measurable impact on local intensities in ion micrographs, indicating that freeze-dried, freeze-fractured cells are sampled in a sufficiently uniform fashion that quantitative ion microscopic evaluations of intracellular elemental levels in the general cytoplasmic or nuclear regions are feasible.     

The role of social sustainability in building assessment

ABSTRACT

Can social sustainability be built? What are the challenges and potential for incorporating the concept of social sustainability into the assessment of building projects? Theoretical approaches to social sustainability are examined for the ways it is applied in practice by building industry stakeholders. A fundamental question is whether and how social sustainability can be measured, assessed and certified in the construction or renewal of housing and neighbourhoods. In addition to physical and functional indicators, it is suggested that certification systems (e.g. the Deutsche Gesellschaft für Nachhaltiges Bauen – DGNB) should also reward social initiatives. A framework was developed involving 12 indicators grouped three overarching themes: social cohesion; participatory processes; and accessibility to living opportunities. A collaborative case study project involving two Danish social housing neighbourhoods examines how social sustainability indicators could be integrated into the application of certification systems such as the DGNB and whether the certification system can be improved by integrating social and organizational aspects with the existing criteria for physical and functional layout. It is found that certifications must take the housing complex or neighbourhood's relationship with the surrounding city into account, as well as its development over time and flexibility towards future needs.     

Review of the hydrolysis of iron(III) and the crystallization of amorphous iron(III) hydroxide hydrate

Hydrolysis of ferric solutions leads initially to mono- and dinuclear species which interact to produce further species of higher nuclearity. These polynuclear species age eventually to either crystalline compounds or to an amorphous precipitate (amorphous iron(III) hydroxide hydrate). Amorphous iron(III) hydroxide hydrate is thermodynamically unstable and gradually transforms to α-FeO(OH) and α-Fe₂O₃. These crystalline products form by competing mechanisms and the proportion of each in the final product depends on the relative rates of formation. The master variable governing the rates at which these compounds form is pH. Other important factors are temperature and the presence of additives. Most additives retard the transformation and by suppressing formation of α-FeO(OH) lead to an increase in the amount of α-Fe₂O₃ in the product; some additives also directly promote formation of the latter compound. Metal ions can oftxen replace a proportion of Fe in the α-FeO(OH) and α-Fe₂O₃ lattices. At high enough concentrations they can induce formation of additional phases. Additives may also modify the morphology of the crystalline products.     

Yielding and deformation behavior of the single crystal superalloy PWA 1480

Interrupted tensile tests were conducted to fixed plastic strain levels on (001) oriented single crystals of the nickel-base superalloy PWA 1480. Testing was done in the range from 20 to 1093 °C, at strain rates of 0.5 and 50 pct/min. The yield strength was constant from 20 to 760 °C, above which the strength dropped rapidly and became a strong function of strain rate. The data could be represented very well by an Arrhenius-type equation, which resulted in three distinct temperature regimes. The deformation substructures could also be grouped in the same three regimes, indicating that there was a fundamental relationship between the deformation mechanisms and the activation energies. At low temperatures, the activation energy for yielding was zero, and the deformation was dominated by γ′ shearing by pairs of 111a/2(110) dislocations. At high temperatures, the true activation energy for yielding was calculated to be 500 kJ/mol, which is indicative of a diffusion-controlled process, and deformation was dominated by γ′ by-pass. Intermediate temperatures exhibited transitional behavior. No currently available precipitation hardening model could adequately describe the behavior observed in the low temperature regime, due to the observation that penetration into the precipitate was not rate-limiting at all temperatures. In the high temperature regime, the functional form of the Brown-Ham by-pass model fit the data fairly well. The results of this study also demonstrated that the initial deformation mechanism was frequently different from that which would be inferred by examination of specimens which had been tested to failure.