Reconstruction of Current Flow and Imaging of Current-Limiting Defects in Polycrystalline Superconducting Films

Magneto-optical imaging was used to visualize the inhomogeneous penetration of magnetic flux into polycrystalline TlBa2Ca2Cu3Ox films with high critical current densities, to reconstruct the local two-dimensional supercurrent flow patterns and to correlate inhomogeneities in this flow with the local crystallographic misorientation. The films have almost perfect c-axis alignment and considerable local a- and b-axis texture because the grains tend to form colonies with only slightly misaligned a and b axes. Current flows freely over these low-angle grain boundaries but is strongly reduced at intermittent colony boundaries of high misorientation. The local (<10-micrometer scale) critical current density Jc varies widely, being up to 10 times as great as the transport Jc (scale of approximately 1 millimeter), which itself varies by a factor of about 5 in different sections of the film. The combined experiments show that the magnitude of the transport Jc is largely determined by a few high-angle boundaries.     

Soil education: A public need Developments in Germany since the mid 1990s

Soil is a public good that has important public functions. However, public knowledge about soils was rather scanty in Germany up until the mid 1990s. This article summarizes and comments on the developments that have taken place in Germany since then with regard to the four major dimensions of soil education—time, target groups, actors, and media. In summary, a wealth of initiatives was started (and has since vanished), leaving behind a number of remarkable results like internet and e‐learning sites, exhibitions, and science trails. Meanwhile, intellectual results have also become visible, with most citizens now being able to respond to questions on what soil and its functions are and how they are endangered. Progress is still lacking, however, in education—a minimum of soil science knowledge is still not sufficiently anchored in official school curricula, and institutions for this task are not in place. Finally, it is strongly urged to use the opportunity that soil protection has recently been on the agenda of the European Union in order to develop international perspectives for soil education, especially in the field of e‐learning.     

Dune whitening and inter-dune freshwater ponds in NE Brazil

The changes in color of sand dunes from white to yellow or red is often interpreted to signify their age or their source materials. In this study we demonstrate the effect seasonal inter-dune freshwater ponds have on the bleaching of the color of sand dunes by iron reduction in the anaerobic conditions they create. By combining spectral measurements of field samples of dune sand together with the analysis of satellite images covering three dune fields in NE Brazil (Lençóis Maranhenses, Jericoacoara and Canoa Quebrada) we demonstrate its existence in the field. In areas where ponds cover 41% of the dune field (as in Lençóis Maranhenses) an almost total bleaching in the color of the sand occurs after which the dunes remain white with no relation to distance from the coastline. In areas with less ponds (e.g. Jericoacoara or Canoa Quebrada) dune whitening is less active, and there are areas where dune rubification occurs. As this process may have occurred in other dune fields during past climate conditions that may have been different from current ones, interpretations of dunes age based on their color should be handled with care.     

Resilience of macroinvertebrate communities in acidified and limed streams

Benthic macroinvertebrate communities in 13 acidified South Swedish streams were sampled in 1981. The same localities were revisited in 1994 when most of the streams had been limed. Untreated streams were used as references. Species richness and proportion of predators increased between the two years. The differences are probably due to the warm and dry summer in 1994. However, the proportions of acid-sensitive species in various groups of streams were about the same the two years, indicating that liming had an insignificant effect on the return of these species. The resilience of the bottom fauna may be attributable to biotic conditions or the failure of the practiced liming methods to maintain healthy chemical conditions.     

Do stream invertebrates accumulate aluminium at low pH conditions?

Acidified surface waters often show elevated aluminium (Al) levels, detrimental to fish and some invertebrates. Whether Al can accumulate in benthic invertebrates, with time and/or along the food chain, is not clear. To test this, benthic invertebrates, representing different functional feeding groups, were collected in spring from streams, with different acidity and Al concentrations. Weight-specific Al content was determined with an AAS. At localities with pH ≈ 4, high Al contents (≈ 1 mg inorg-Al g^?1 af dw) were found in shredders and/or deposit feeders (Asellus aquaticus, Nemoura sp., and limnephilids), while the predator Isoperla grammatica contained only ≈ 0.3 mg Al g^?1, and the “filtering predator” Plectrocnemia conspersa almost no Al. Also at pH ≈ 6 Nemoura sp. and limnephilids showed significantly higher Al contents than did the predators Isoperla grammatica and Rhyacophila nubila, Al concentrations of the animals were often higher at pH 4 than at pH 6. Thus, no evidence of any food chain accumulation (or biomagnification) of Al could be validated. Accordingly, this study gives no support that the high concentrations of Al in fish and birds are due to their feeding on benthic invertebrates at low pH conditions. It was also found that animals that inhabit and/or consume benthic detritus as food contain highest Al levels.     

Characterisation of new oat germplasm for resistance to powdery mildew

Summary Wild oat accessions from the Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben were selected as potential sources of resistance to powdery mildew (Erysiphe graminis f.sp. avenae). The Avena strigosa accessions AVE 128, AVE 488 and AVE 264, along with A. occidentalis accession CAV 3889 showed high levels of mildew resistance in tests at early and late growth stages over two years; the latter is a particularly useful source because it is a hexaploid species. Moderate levels of resistance were also found in A. fatua accession AVE 1981, AVE 2032 and A.sterilis accession AVE 1373 but this could be due to the later maturity of these genotypes.