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Field experiments on the fate of lead and chromium in an intertidal benthic mesocosm, the Bremerhaven Caisson (1983)

Schulz-Baldes, M. ; Rehm, E. ; Farke, H.

Springer

Marine biology 75 (1983), S. 307-318

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ISSN: 1432-1793

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The Bremerhaven Caisson, a benthic mesocosm enclosing a 13 m2 sediment area and 13 m3 trapped water column at high tide, was used for field experiments on the fate of lead and chromium at the isle of Norderney, Southern German Bight. The caisson, made from seawater resistant aluminium, settled on fine sand (mean grain size: 0.2 mm) at an experimental site with about 0.9-m tidal height and 4.5 h of water coverage. During 38 consecutive tides a constant amount of lead was administered to the inflowing water, resulting in a nominal concentration of 0.1 mg l-1 at high tide. A second caisson was taken for chromium using the same procedure. The compartments analysed (water, seston, sediment, and infauna) showed distinct differences for lead and chromium. The particle-reactive element Pb adsorbed by 50–70% onto seston particles, the soluble element Cr-VI by less than 2%. Only a moderate enrichment was measured in the sediment, about 3–4% of the total Pb and Cr added accumulated in the top 3 cm. The fauna attained much higher accumulation factors than the sediment. The lead uptake rates of 15 species and 2 taxa can be placed in order according to the feeding type: filter feeder 〉 deposit feeder (surface) 〉 opportunistic feeder (deposit feeder or predator) 〉 deposit feeder (depth). Chromium was accumulated about 10 times lower than lead, the uptake seems to be more related to the systematic position of the animal (calcareous shell versus chitinous cuticle). In the total mass balance only 0.2% of the lead added and 0.02% of the chromium added were fixed by the fauna.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00406017

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Modeling of real 20-component protein chains: Determination of the electronic density of states of aperiodic seven-component polypeptide chains containing strongly different amino acid residues (1990)

Bakhshi, A. K. ; Otto, P. ; Liegener, C.-M. ; [et al.]

New York, NY : Wiley-Blackwell

International Journal of Quantum Chemistry 38 (1990), S. 573-583

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ISSN: 0020-7608

Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: To model a real 20-component protein chain, the results of the electronic density of states (DOS) of seven-component periodic and aperiodic polypeptide chains calculated on the basis of ab initio matrix block negative factor counting method are presented. The seven amino acid residues taken into account are rather different: glycine, serine, cysteine, asparagine, histidine, aspartic acid, and tryptophane. In the case of aperiodic chains, the energy states are found to be distributed over a much wider range of energy than in the corresponding periodic chains. In the intrinsic state, both periodic and aperiodic polypeptide chains are predicted to be insulators. The effect of the block copolymerization on the DOS distribution and the band gap values of both periodic and aperiodic polypeptide chains has been also investigated. Finally, the methods to calculate from the DOS curves hopping conductivities and the possibilities to compare them with experiment are outlined.

Additional Material: 8 Ill.