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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 5 (1990), S. 309-314 
    ISSN: 1572-879X
    Keywords: Fischer-Tropsch ; cobalt single crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Fischer-Tropsch reaction is studied on a cobalt (0001) single crystal. Under the reaction conditions (1 bar synthesis gas; H2∶CO = 2∶1;T=250 °C) methane is the major product, with lesser amounts of heavier hydrocarbons. It is shown that the readsorption and subsequent hydrogenation of initially formed ethene is an important pathway to ethane. The activation energies for methane, ethane and propane formation are equal, which suggests that the rate-determining steps are similar.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic ecology 28 (1994), S. 11-17 
    ISSN: 1573-5125
    Keywords: benthos ; vertical distribution ; water mites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The paper analyses the distribution and seasonal changes in numbers of the water mite fauna of Lake Maarsseveen I. Water mites were collected from 1977 until 1986 by dipnet, underwater light trap, hydraulic lift sampler and by frame net. Fifty-two species belonging to the Hydrachnellae and one to the Halacaridae were sampled. The faunal picture obtained is characteristic of mesotrophic to eutrophic lakes.Arrenurus nobilis. Piona paucipora andP. imminuta can be characterised as lake species. The dominant species in the littoral sand flat areHygrobates nigromaculatus andH. trigonicus, at a depth of 0.5–1 m, andMideopsis orbicularis at depths of 2–7 m.Limnesia maculata is also very common on depths between 2 and 7 m. In early summer, however, they prefer shallow water up to 1 m depth. Some species likeHygrobates nigromaculatus andH. trigonicus were not captured by the underwater light trap. The hydraulic lift sampler gave underestimations of the densisty of certain speciese.g. Hygrobates spp. andLimnesia maculata. Unionicola spp. even can avoid this sampler. Sampling by frame net gave the most realistic data. The highest number of water mites was observed in the littoral sand flat, generally up to 1000 ind. m−2. The genusHygrobates was represented with an average of 800 adult ind. m−2 throughout the year, and appeared to be the main invertebrate predator in this habitat.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 253 (1993), S. 100-100 
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 192 (1990), S. 143-148 
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By means of sequential extractions with Ca-NTA and EDTA, a separation was performed between Fe(OOH) ≈ P and CaC03≈P in a few sediments; the remaining fraction, considered to be organic phosphate, was quantified as well. We found that with the commonly used method of extraction with NaOH and H2S04, less Fe(OOH) ≈ P and much more CaC03 ≈ P was found than with the chelating extractants. The organic phosphate pool in live and dead algal material and in some mud samples was partly hydrolysed and therefore recovered as inorganic phosphates with classical extractions. The difference between chelating extractants and the classical ones is discussed.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 252 (1993), S. 117-126 
    ISSN: 1573-5117
    Keywords: phytate ; organic phosphate ; sediment ; P-fractionation ; Camargue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The organic phosphate pool of some Camargue sediments (South of France) was studied, after removal of inorganic phosphate, with Ca-NTA/dithionite (Fe bound phosphate) and Na-EDTA (Ca bound phosphate). The organic phosphate was divided into an acid soluble organic phosphate fraction (ASOP) and a residual organic phosphate fraction (ROP). The extraction of organic matter with 2.0 M NaOH (90 °C) from ROP yielded considerable quantities of Org-P. In this extract the presence of phytate (inositol hexa phosphate) could be demonstrated using phytase to hydrolyse the phytate. Phytate was shown to account for a considerable part of organic phosphate in sediments of freshwater marsh sediments as well as in the sediment of the brackish/salt water lake ‘Etang de Vaccares’. In laboratory experiments phytate was found to precipitate with all poly-valent cations tested. Furthermore, phytate was found to be strongly adsorbed onto Fe(OOH), which may explain its accumulation and its stability in sediments. Considerable quantities of ASOP were found; the chemical stucture of this pool remains unknown.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 253 (1993), S. 99-100 
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0006-3592
    Keywords: shear ; air-lift loop reactor ; growth rate ; cell size ; hybridoma cell ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To study the effects of the growth rate of the hybridoma cell Mn12 on productivity, cell cycle, cell size, and shear sensitivity, six continuous cultures were run at dilution rate of 0.011, 0.021, 0.023, 0.030, 0.042, and 0.058 h-1. This particular hybridoma cell appeared to be unstable in continuous culture with respect to specific productivity, as a sudden drop occurred after about 30 generations in continuous culture, accompanied by the appearance of two populations with respect to the cytoplasmic lgG content. The specific productivity increased with increasing growth rate. The shear sensitivity of the cell, as measured in a small air-lift loop reactor, increased with increasing growth rate. The mean relative cell size, as determined with a flow cytometer, increased with increasing growth rates. Furthermore, the fraction of cells in the S phase increased, and the fraction of cells in the G1/G0 phase decreased with increasing growth rates. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 465-475 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We investigated the behavior of fetal rat osteoblasts cultured on four bone replacing materials: bioactive glass, hydroxylapatite, a titanium alloy, and stainless steel. The cultures were histologically examined for individual cell morphology and osteoblast expression after several periods of time using scanning electron, fluorescence, and normal light microscopy. Other cultures were used for biochemical determinations of alkaline phosphatase activity (APA) and DNA content. Osteoblasts cultured on bioactive glass showed a better osteoblast-like morphology and a higher proliferation rate, leading to confluent cultures with higher cell density and a generally better expression of the osteoblast phenotype in comparison with the other substrates. The confluent bioactive glass cultures also showed significantly higher DNA content and APA as well as the calculated APA/DNA ratio. Based on the evaluation of histological and biochemical parameters we conclude that osteoblasts cultured on bioactive glass show a generally better osteoblast character than on the other materials. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 9
    Publication Date: 1994-03-01
    Print ISSN: 1380-8427
    Topics: Biology
    Published by Springer
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  • 10
    Publication Date: 1993-03-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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