Omineca Herald, February, 02, 1966

Item does not contain fulltext19 oktober 200

Omineca Herald, April, 19, 1933

Item does not contain fulltext12 oktober 201

Cold war in the classroom

https://stars.library.ucf.edu/prism/1105/thumbnail.jp

α-Toxin permeabilized rat pheochromocytoma cells

The channel forming α-toxin of Staphylococcus aureus (about 50 μg/ml) markedly reduces the Ca2+ requirement for dopamine release by the rat pheochromocytoma cell line (PC 12). Maximal secretion by intact cells requires approximately 1 mM Ca2+, whereas release by α-toxin-permeabilized cells can already be triggered with μM concentrations of Ca2+. The latter process reaches a plateau at about 1 μM free Ca2+ and increases again with 10–20 μM free Ca2+. The sensitivity to low concentrations of Ca2+ indicates that the toxin, as a selective cell membrane permeabilizing agent, can be used as a powerful instrument to study stimulus-secretion coupling

Effects of elevated CO₂ and N fertilization on plant and soil carbon pools of managed grasslands: a meta-analysis

Elevated atmospheric CO₂ levels and increasing nitrogen deposition both stimulate plant production in terrestrial ecosystems. Moreover, nitrogen deposition could alleviate an increasing nitrogen limitation experienced by plants exposed to elevated CO₂ concentrations. However, an increased rate of C flux through the soil compartment as a consequence of elevated CO₂ concentrations has been suggested to limit C sequestration in terrestrial ecosystems, questioning the potential for terrestrial C uptake to mitigate the increasing atmospheric CO₂ concentrations. Our study used data from 69 published studies to investigate whether CO₂ elevation and/or nitrogen fertilization could induce an increased carbon storage in grasslands, and considered the influence of management practices involving biomass removal or irrigation on the elevated CO₂ effects. Our results confirmed a positive effect of elevated CO₂ levels and nitrogen fertilization on plant growth, but revealed that N availability is essential for the increased C influx under elevated CO₂ to propagate into belowground C pools. However, moderate nutrient additions also promoted decomposition processes in elevated CO₂, reducing the potential for increased soil C storage. An important role in the soil carbon response to elevated CO₂ was attributed to the root response, since there was a lower potential for increases in soil C content when root biomass was more responsive to CO₂ elevation. Future elevated CO₂ concentrations and increasing N deposition might thus increase C storage in plant biomass, but the potential for increased soil C storage is limited

Studying the thermal conductivity of a deep Eocene clay formation: direct measurements vs back-analysis results

An experimental study on Ypresian clays–one of the potential deep and sedimentary clay formations in Belgium for the geological disposal of heat-emitting radioactive waste–has been undertaken to systematically study its thermal conductivity using different experimental techniques. As a first step, a new experimental setup with heat flux measurement has been used and careful pre-conditioning protocols have been followed to directly measure this thermal property. The aim of these pre-conditioning tests has been ensuring a very high degree of saturation and the closure of fissures / gaps along bedding planes before the thermal tests are run under low stress conditions. Thermal tests have shown to be particularly sensitive when the thermal conductivity is determined along a direction orthogonal to these bedding planes. The study is then complemented by using a constant volume heating cell, in which heating pulse tests have been carried out under fully saturated conditions that have been ensured with a high water back-pressure. Numerical models have been used to interpret this pulse test, to exploit all the information provided by temperature measurements and to back-analyse the thermal conductivity. Direct thermal conductivity data with the improved pre-conditioning protocol allowed obtaining results consistent with the values reported when using back-analysis in the constant volume cell. The article discusses the importance of restoring full saturation conditions, particularly on retrieval of deep sedimentary clays, which may undergo opening of fissures along bedding planes that may affect the correct determination of the thermal conductivity.Peer ReviewedPostprint (author's final draft

Hydro-chemical modelling of in situ behaviour of bituminized radioactive waste in Boom Clay

The hydro-chemical (CH) interaction between swelling Eurobitum bituminized radioactive waste (BW) and Boom Clay was investigated to assess the feasibility of geological disposal for the long-term management of this waste. First, the long-term behaviour of BW in contact with water was studied. A CH formulation of chemically and hydraulically coupled flow processes in porous materials containing salt crystals is discussed. The formulation incorporates the strong dependence of the osmotic efficiency of the bitumen membrane on porosity and assumes the existence of high salt concentration gradients that are maintained for a long time and that influence the density and motion of the fluid. The impacts of temporal and spatial variations of key transport parameters (i.e. osmotic efficiency (s), intrinsic permeability (k), diffusion, etc.) were investigated. Porosity was considered the basic variable. For BW porosity varies in time because of the water uptake and subsequent processes (i.e. dissolution of salt crystals, swelling of hydrating layers, compression of highly leached layers). New expressions of s and k describing the dependence of these parameters on porosity are proposed. Several cases were analysed. The numerical analysis was proven to be able to furnish a satisfactory representation of the main observed patterns of the behaviour in terms of osmotic-induced swelling, leached mass of NaNO3 and progression of the hydration front when heterogeneous porosity and crystal distributions have been assumed. Second, the long-term behaviour of real Eurobitum drums in disposal conditions, and in particular its interaction with the surrounding clay, was investigated. Results of a CH analysis are presented.Peer ReviewedPostprint (published version