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  • 1
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (142 Seiten = 31MB) , Illustrationen, Graphen
    Edition: Online-Ausgabe 2023
    Language: German
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The chemokine receptors that mediate HIV-1 entry in cultured cells vary in their tissue distribution. CCR5 is expressed in primary monocyte/macrophages, primary T cells, and granulocyte precursors2'4. CXCR4 is expressed in a broader range of tissues and cell types, including the brain and T cells1. ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 116 (1985), S. 569-580 
    ISSN: 1434-4475
    Keywords: Ternary alkaline earth and rare earth metal palladium arsenides, antimonides, and bismuthides ; Crystal structure ; Band structure ; Intermediate valency of Eu compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Fifteen compounds of compositionMPd2 Pn 2 (M = alkaline earth or rare earth metal,Pn = As, Sb, Bi) were prepared. TheirGuinier powder patterns show that the arsenides crystallize with the ThCr2Si2 type structure, the bismuthides with the closely related CaBe2Ge2 type structure. The antimonides most likely also have the CaBe2Ge2 structure as is demonstrated by a structure refinement of EuPd2Sb2 from single crystal X ray data (R = 0.039 for 366 independent structure factors and 15 variable parameters). The structure of SrPd2As2 (ThCr2Si2 type) was refined to a residual ofR = 0.020 for 182F values and 9 variables. EuPd2Sb2 is paramagnetic and a metallic conductor. A comparison of the cell volumes suggests intermediate valency for Eu in EuPd2As2. Chemical bonding and especially the reasons for the adoption of the ThCr2Si2 or CaBe2Ge2 type structures by these compounds are discussed. It is suggested that in going from the phosphides to the bismuthides the ThCr2Si2 structure is loosing and the CaBe2Ge2 structure is gaining stability due to decreasing Pd-Pd bonding and increasing Pd-pnictogen bonding. This trend is caused by the increasing size of the pnictogen component.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of paleolimnology 19 (1998), S. 55-62 
    ISSN: 1573-0417
    Keywords: Cladocera ; Chironomidae ; subfossil remains ; lake level ; inshore/offshore sediments ; planktonic/littoral ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Water level fluctuations affect the size of the pelagic zone relative to the size of littoral habitats, and thus may influence the relative abundance of remains from planktonic and littoral cladocerans in sediment. The application of this planktonic/littoral ratio for the reconstruction of past water level changes is discussed using examples of: (1) surficial profundal sediments from lakes of different water depths; (2) Holocene variation in a profundal sediment core; (3) horizontal variation in surficial sediments within a lake; and (4) long term variation in an inshore sediment core. The latter seemed to be the most promising application of this ratio. Maximum effects of water depth changes on the lake fauna are expected in the littoral zone. It is, however, difficult to read this effect directly from subfossil cladoceran and chironomid assemblages from inshore sediments as shown by a sediment profile from a site exposed to a long term decrease of water depth.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-0417
    Keywords: transfer functions ; WA-PLS ; total phosphorus ; trophic state ; eutrophication ; surface sediments ; Switzerland ; diatoms ; cladocera ; chironomids ; chrysophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Surface sediments from 68 small lakes in the Alps and 9 well-dated sediment core samples that cover a gradient of total phosphorus (TP) concentrations of 6 to 520 μg TP l-1 were studied for diatom, chrysophyte cyst, cladocera, and chironomid assemblages. Inference models for mean circulation log10 TP were developed for diatoms, chironomids, and benthic cladocera using weighted-averaging partial least squares. After screening for outliers, the final transfer functions have coefficients of determination (r2, as assessed by cross-validation, of 0.79 (diatoms), 0.68 (chironomids), and 0.49 (benthic cladocera). Planktonic cladocera and chrysophytes show very weak relationships to TP and no TP inference models were developed for these biota. Diatoms showed the best relationship with TP, whereas the other biota all have large secondary gradients, suggesting that variables other than TP have a strong influence on their composition and abundance. Comparison with other diatom – TP inference models shows that our model has high predictive power and a low root mean squared error of prediction, as assessed by cross-validation.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-0417
    Keywords: transfer functions ; weighted-averagingpartial-least-squares ; summer temperatures ; surfacesediments ; modern training-sets ; Switzerland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatom, chrysophyte cyst, benthic cladocera, planktonic cladocera, and chironomid assemblages were studied in the surface sediments of 68 small lakes along an altitudinal gradient from 300 to 2350 m in Switzerland. In addition, 43 environmental variables relating to the physical limnology, geography, catchment characteristics, climate, and water chemistry were recorded or measured for each lake. The explanatory power of each of these predictor variables for the different biological data-sets was estimated by a series of canonical correspondence analyses (CCA) and the statistical significance of each model was assessed by Monte Carlo permutation tests. A minimal set of environmental variables was found for each biological data-set by a forward-selection procedure within CCA. The unique, independent explanatory power of each set of environmental variables was estimated by a series of CCAs and partial CCAs. Inference models or transfer functions for mean summer (June, July, August) air temperature were developed for each biological data-set using weighted-averaging partial least squares or partial least squares. The final transfer functions, after data screening, have root mean squared errors of prediction, as assessed by leave-one-out cross-validation, of 1.37 °C (chironomids), 1.60 °C (benthic cladocera), 1.62 °C (diatoms), 1.77 °C (planktonic cladocera), and 2.23 °C (chrysophyte cysts).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 214 (1991), S. 207-211 
    ISSN: 1573-5117
    Keywords: Pleniglacial ; maar lakes ; biostratigraphy ; Chironomidae ; Cladocera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sediments from maar lakes in the periglacial area were analysed to obtain information about the limnetic fauna of Pleniglacial lakes. On the basis of abundance and species composition of the subfossil chironomid and cladoceran assemblages, three major zones were biostratigraphically separated: the Upper Pleniglacial, the Middle Pleniglacial, and the Eem Interglacial.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5117
    Keywords: Bosmina (Eubosmina) ; Lake Constance ; sediment analysis ; morphological variation ; introgressive hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Subfossil Bosmina (Eubosmina) remains were analysed in a sediment core from the Untersee of Lake Constance which covered the Late-Glacial/Holocene period. During the Late-Glacial and the early Holocene the lake was inhabited only by Bosmina longispina Leydig. In the Late Holocene a second species, Bosmina coregoni f. kessleri Uljanin, appeared. In the uppermost sediment layers the morphological gap between the two taxa disappeared, apparently from introgressive hybridization.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 255-256 (1993), S. 171-175 
    ISSN: 1573-5117
    Keywords: mesocosm ; rotifers ; bacteria ; nutrients ; population response ; food chain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The impact of organic nutrients and massive addition of bacteria was followed in lake water mesocosms in a eutrophic lake. Increased DOM initiated a sequence of trophic responses indicated by rapid increases in bacterioplankton, protozoa, and algal biomass. The populations of Keratella cochlearis and Keratella quadrata showed a distinct response by rapid increase in birth rate followed by maxima of production and abundance. This succession clearly reflected the trophic position of these rotifer populations in the food chain. A reverse response was observed in Conochilus unicornis.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-5117
    Keywords: cladocera ; sediment analysis ; lake trophy ; bioindication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cladoceran faunas from 13 northern German lakes (the Plön district) of different trophic levels were analysed using the bosminid and chydorid remains in the surficial sediment as an integrated sample of the total lake fauna. In the dimictic lakes, a shift occurred in the composition of planktonic Cladocera from Bosmina coregoni, including morphs with a mucro, to predominance of Chydorus sphaericus and Bosmina c. thersites as trophic state increased. In the benthic Cladocera (Chydoridae), there was a decrease in species diversity, in the percentages of phytophilous species and in the portion of species that are typical of ‘clear water lakes’, but there was an increase both in the number of mud dwellers and species that are typical of ‘polluted lakes’. No positive correlation was found between mean depth of the lakes and the planktonic/littoral ratio.
    Type of Medium: Electronic Resource
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