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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Vegetation history and archaeobotany 8 (1999), S. 105-112 
    ISSN: 1617-6278
    Schlagwort(e): Honey ; Pollen analysis ; La Tène ; Iron Age ; Land-use history ; Biodiversity ; Southern Germany
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Klassische Archäologie , Biologie
    Notizen: Abstract Organic contents of bronze vessels from royal burial sites dating to the Iron Age in southern Germany were investigated by pollen analysis. All pollen assemblages observed were dominated by non-arboreal pollen of non-wind pollinated species, a characteristic feature of honey. On the basis of investigations on recent honey, estimates of the original amounts of honey present were made. It is suggested that two of the vessels were filled with a freshly prepared, highly concentrated mead, while a third contained possibly a mead or a beverage sweetened by honey. The high diversity of the pollen assemblages differs from recent honeys and points to a high biodiversity in the Iron Age landscapes, but also to the use of honey mixtures that originate from a large area that included the surrounding uplands. Records for several exotic pollen also support this hypothesis. At the Glauberg site, a honey-source area of more than 50-km radius is probable. This corresponds quite well with the average distance between known Celtic centres in central Europe, which is ca. 100 km.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Vegetation history and archaeobotany 9 (2000), S. 205-218 
    ISSN: 1617-6278
    Schlagwort(e): Human impact ; Prehistory ; Historical period ; Pollen analysis ; Black Forest
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Klassische Archäologie , Biologie
    Notizen: Abstract A detailed,14C-dated, pollen profile from Steerenmoos, a raised bog in the uplands of the southern Black Forest (Schwarzwald) is presented. The Late-glacial and early Holocene vegetation history conforms to the known pattern of forest dynamics for that region. At ca. 6100 cal. B.P.,Abies replaced the mixed oak forest, which is in contrast to adjacent regions whereFagus spread beforeAbies. From the Subboreal onwards,Fagus expanded and slowly largely replacedAbies. The mire developed from a fen to a raised bog. The mountain pine (Pinus mugo ssp.rotundata) on the present-day bog surface is a result of medieval burning. Cereal pollen are first recorded in the Neolithic (7600 cal. B.P.) and there is a closed curve forPlantago Lanceolata — a good indicator of human impact — since the Bronze Age (4000 cal. B.P.). On the basis of the cereal pollen record nine human impact phases (HIP) are described. HIP 1 and 2, which are short, date to ca. 7600 and 6700 cal. B.P., respectively, in a mixed oak forest context and are characterized by declines inCorylus, Tilia, Ulmus and bySalix (but no major deforestation) and peaks in charcoal and loss-on-ignition curves. HIP 3 and 4, which are short and weak, date to ca. 6000 and 5300 cal. B.P., respectively, and occur in the context of anAbies alba forest. The Bronze Age and Iron Age HIPs 5-7 are more intense and of longer duration than the Neolithic phases and result in a decline inAbies and an increase inFagus. The early medieval HIP 8, although rather weak, probably finds expression also in an archaeological artefact, namely a dug-out boat from the near-by Schluchsee. Finally, the late Medieval HIP 9 resulted in a major transformation in the landscape. It is argued that the earlier HIPs are not a reflection of distant events in the lowland valleys of the Rhine, Danube or Neckar but reflect more or less local developments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1745-1749 
    ISSN: 0009-2940
    Schlagwort(e): Density functional calculations ; Tetra(amino)methane ; Tetra(amino)silane ; Transition states ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In all-electron density functional calculations on mono- and tetraaminosubstituted methane and silane the coordination around the nitrogen center is found, in complete agreement with experiment, to be less pyramidal in the silicon compounds. The calculated barrier to inversion at nitrogen is only 0.6 kcal/mol in silylamine, while in methylamine it is 5.5 kcal/mol. The larger flexibility is attributed to the greater ionic character of the Si-N bond compared to that of the C-N bond. In tetra(amino)methane, inversion of one amino group leads to a local minimum (calculated inversion barrier: 6.4 kcal/mol), while a corresponding structure (or barrier) does not exist for the silicon compound. Due to the steric influence of the amino groups, the barrier to rotation around the C-N bond is larger in the tetrasubstituted compound (6.4 kcal/mol compared to 2.3 kcal/mol in methylamine). While the average binding energy of the amino groups is similar in both tetra(amino)compounds, the binding energy of the fourth ligand is about 25% larger in the silicon compound for both homolytic and heterolytic bond cleavage. This difference arises from the relative stabilization of the tri(amino)-methyl species, due to some n contribution to the C-N bond.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2135-2145 
    ISSN: 1434-1948
    Schlagwort(e): Density functional calculations ; Epoxidation ; Peroxo complexes ; Titanium ; Transition states ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Epoxidation of olefins by TiIV peroxo and hydroperoxo (alkylperoxo) complexes was investigated using a hybrid DFT method (B3LYP). Reaction energies and activation barriers for direct oxygen transfer to ethylene as a model olefin were computed for various model complexes to compare the epoxidation activity of Ti(η2-O2) and TiOOR (R = H, CH3) moieties. The activity of complexes with a Ti(O2) peroxo group is shown to be essentially quenched when the coordination sphere of the complex is saturated by strongly basic (σ-donor) ligands. In contrast, the activity of a TiOOH functional group depends only weakly on the saturation of the coordination sphere of the Ti center. Substitution of methyl for hydrogen in a TiOOH group is found to slightly increase the activation barrier of epoxidation. The computational results give preference to reaction paths that involve TiOOR species. The factors governing the activity of Ti(O2) and TiOOR groups, in particular the effects of donor ligands, are discussed on the basis of a molecular orbital analysis.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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