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  • Springer  (52)
  • American Physical Society (APS)
  • American Meteorological Society (AMS)
  • 1995-1999  (52)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 52 (1996), S. 757-761 
    ISSN: 1420-9071
    Keywords: Vasculogenesis ; angiogenesis ; muscle ; embryonic ; metabolites ; fibroblast growth factor (FGF) ; chorioallantoic membrane (CAM)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Normal and pathological formation of blood vessels is of considerable interest both in terms of basic scientific processes and clinical applications. Angiogenic events in the adult are likely to represent persistence of developmental mechanisms, and embryos are therefore a suitable experimental model for these processes. Among embryonic tissues, muscle is particularly appropriate for investigation, since it is highly vascularised from early stages. There are a number of competing explanations of how this process is controlled. Bioassays offer advantages over conventional molecular localisation techniques, in that they reveal the presence of active processed forms of the molecules under study, rather than non-processed forms, or non-translated meassages. Using these techniques, we report here that embryonic chick muscle, taken from the stages at which blood vessels are forming, produces an angiogenic activity on the chick chorioallantoic membrane (CAM), and transforms NR6 cells in soft agar. Basic fibroblast growth factor (bFGF) is shown to be angiogenic on the CAM in the same way, and also transforms NR6 cells (NR6 cells lack functional epidermal growth factor/transforming growth factor-a receptors, and are believed to respond only to bFGF in this way). Anti-bFGF removes the transforming activity of the embryonic muscle. We conclude that this represents evidence that embryonic chick muscle is producing an FGF-like molecule which is capable of acting as an angiogenic agent at the appropriate times in development.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Artificial intelligence review 9 (1995), S. 129-146 
    ISSN: 1573-7462
    Keywords: natural language ; multimedia ; human-computer interaction ; communication modalities ; dialogue ; generation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In the late Eighties the Natural Language Processing community began appreciating the role of multimodality in interactive systems. Intelligent multimodal systems are systems that integrate natural language (generally so far keyboard-based input, shortly also voice) with other media such as gestures in input or graphics in output. The perspective of what can be called visible interactive communication is discussed and considered as a possible new modality of natural language, after the spoken and the written ones. This should not be confused with the type of hypermedia that are now being developed. There, basically, the interface space is finite, even if one dimension may be added. Here the infinite creativity of human language is potentially preserved as the fundamental communication instrument.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 361 (1998), S. 645-646 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A cold working steel was coated both with high temperature CVD (TiN) and moderate temperature CVD (Ti[C,N]). AES depth profiles show a significant difference at the interface, where a thin oxide layer remains detectable at deposition temperatures of 750 °C. It could be shown that an impedance signal at a frequency of 13 MHz is well suited to detect the early stages of the growth of a CVD coating.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 42 (1996), S. 352-353 
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 41 (1995), S. 612-615 
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1939
    Keywords: Nitrogen isotope discrimination ; Cape floristic region ; Fynbos ; Strandveld ; Acacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examines the impacts of woody, N2-fixing invasive Acacia spp. on the patterns of nutrient cycling in two invaded ecosystems of differing nutrient status in the Cape floristic region. Patterns of soil nutrient mineralization were measured by a field incubation method while the significance of the fixation process in altering nutrient cycling was assessed by the δ15N natural abundance technique. The results confirm earlier reports that invasion by woody shrubs results in organic matter and nutrient enrichment of surface soils of both ecosystems. However, patterns of nutrient availability (phosphorus and nitrogen) were not necessarily enhanced. In the more fertile strandveld both phosphorus and nitrogen (significant at P〈0.10) showed trends towards enhanced annual mineralization rates upon invasion, while in the low nutrient fynbos system only phosphorus followed this trend. It is unclear whether this differential response is a consequence of plant- or soil-derived feedbacks on the decomposition processes in each system. The δ15N values of the soils from the invaded sites of both ecosystems indicated a strong influence of the alien species on the soil nitrogen component. However, as with other studies of natural ecosystems, the contribution of nitrogen from fixation could not be readily quantified with the δ15N natural abundance method because of problems in selecting suitable non-N2-fixing reference plants. A technique of disrupting nodule structure and function, by fumigation with O2, to obtain the δ15N value of a non-N2-fixing speciment of the study species was tried and found to overcome some of the problems associated with the lack of suitable reference plants. With this technique it was possible to detect the almost total dependence of A. saligna on N2-fixation in the fynbos soils with their low nitrogen mineralization rates. In the strandveld ecosystem with much higher soil nitrogen release rates A. cyclops was only partly dependent on fixation (about half) for its nitrogen. The nutrient enrichment of both ecosystems and trends towards enhanced rates of nutrient mineralization could have profound implications on the long-term success of alien invader clearing operations and the restoration of the indigenous flora at these sites.
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  • 7
    ISSN: 1432-1939
    Keywords: Browsing responses ; Semi-arid shrubs ; Nonstructural carbohydrate accumulation ; Regrowth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nonstructural carbohydrate allocation patterns in response to different frequencies of simulated browsing (leaf and twig removal) were studied in the following semi-arid shrubs: Osteospermum sinuatum, a dwarf deciduous shrub, Pteronia pallens, a dwarf evergreen shrub, and Ruschia spinosa, a dwarf leaf-succulent shrub. Simulated browsing at all frequencies resulted in the elevation, or had no effect, on total nonstructural carbohydrate (TNC) concentrations of O. sinuatum plant parts, and resulted in the decrease in TNC concentrations of R. spinosa plant parts. The responses of P. pallens were intermediate with elevations as well as declines in TNC concentrations of plant parts measured in response to various clipping frequencies. At the low frequency of simulated browsing (every 26 weeks) elevations in plant TNC content were measured in the two non-succulent shrubs O. sinuatum and P. pallens. It was concluded that the overcompensation with respect to TNC accumulation observed in the two non-succulent species represents one of the ways in which excess photosynthate is utilized by browsed shrubs with a limited regiowth potential. Simulated browsing was the least detrimental with respect to biomass production to the non-succulent O. sinuatum and P. pallens, and most injurious to the leaf-succulent shrub, R. spinosa. The observed TNC allocation patterns could not adequately explain the variation among species in the production of new growth and it was concluded that some factor(s) other than the carbon resource was limiting regrowth.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Telomere length, measured by terminal restriction fragments, was examined in tissues from human fetuses of gestational ages estimated as 15–19 weeks. The length of telomeres was similar in most fetal tissues. However, there were significant variations in telomere length among fetuses, with no apparent relationship between gestational age and telomere length. We conclude that synchrony in telomere length exists among tissues of the human fetus. This synchrony is apparently lost during extrauterine life.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Five microhabitat types with varying degrees of bird influence were examined. Soils were collected from open polygons, under mosses and bird nests on a nunatak with breeding snow petrels (Pagodroma nivea) and from open polygons and under mosses on a non-bird nunatak. Nutrient levels (total N and P, nitrate, nitrite and ammonia), moisture levels and δ 15N values were determined and the organic processes of nitrogen fixation (acetylene reduction) and soil respiration (CO2 flux) were examined. Nests represented the most favourable microhabitat type for soil respiration having the highest nutrient levels and most favourable temperature and moisture regimes. The soils under mosses were also favourable and appear to act as a nutrient sink for nutrients originating from the nests. The open polygons were the least favourable for biological activity. There was little nitrogen fixation in any of the soils except for the soils under mosses from the non-bird nunatak. Fixation is possibly limited in favourable microhabitat types on the bird nunatak by high nitrogen levels. These results were confirmed by the δ 15N results, which had high values typical of a seabird signal in the soils from the bird nunatak and values near zero, typical of soils containing fixed nitrogen, on the non-bird nunatak.
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  • 10
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Breeding snow petrels (Pagodroma nivea) may be a major source of nutrients for the ecosystems on the inland nunataks (mountain outcrops) of continental Antarctica. To test this theory, the δ15N and δ13C values of soil and plants (moss, lichen and algae) from 11 nunataks with and without breeding snow petrels in northwestern Dronning Maud Land were compared. High δ15N values in all samples from nunataks with breeding birds provide a strong indication of the presence of breeding birds, as well as the use of bird-derived nitrogen by the plants of these ecosystems. The δ13C values showed little difference between the nunataks and are not a useful indicator of bird effects on ecosystem development.
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