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  • 1
    ISSN: 1432-1009
    Keywords: Sulfate ; Nitrate ; Critical loads ; Modeling ; Deposition standards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The critical loads approach is emerging as an attractive means for evaluating the effects of atmospheric deposition on sensitive terrestrial and aquatic ecosystems. Various approaches are available for modeling ecosystem responses to deposition and for estimating critical load values. These approaches include empirical and statistical relationships, steady-state and simple process models, and integrated-effects models. For any given ecosystem, the most technically sophisticated approach will not necessarily be the most appropriate for all applications; identification of the most useful approach depends upon the degree of accuracy needed and upon data and computational requirements, biogeochemical processes being modeled, approaches used for representing model results on regional bases, and desired degree of spatial and temporal resolution. Different approaches are characterized by different levels of uncertainty. If the limitations of individual approaches are known, the user can determine whether an approach provides a reasonable basis for decision making. Several options, including point maps, grid maps, and ecoregional maps, are available for presenting model results in a regional context. These are discussed using hypothetical examples for choosing populations and damage limits.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 57 (1989), S. 1069-1098 
    ISSN: 1572-9613
    Keywords: Block copolymers ; generating function ; Polya's theorem ; gelation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We determine the statistical properties of block copolymer complexes in solution. These complexes are assumed to have the topological structure of (i) a tree or of (ii) a line-dressed tree. In case the structure is that of a tree, the system is shown to undergo a gelation transition at sufficiently high polymer concentration. However, if the structure is that of a line-dressed tree, this transition is absent. Hence, we show the assumption about the topological structure to be relevant for the statistical properties of the system. We determine the average size of the complexes and calculate the viscosity of the system under the assumption that the complexes geometrically can be treated as porous spheres.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 57 (1989), S. 1099-1122 
    ISSN: 1572-9613
    Keywords: Block copolymers ; generating function method ; Polya's theorem ; gelation ; nonnested structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We determine the statistical properties of block copolymers in solution. These complexes are assumed to have the topological structure of connected graphs with “nonnested” loops and cycles. The generating function method is used to determine the number of topologically different complexes containing a given number of block copolymers. It is shown that at sufficiently high concentration the system undergoes a transition to a gel phase. Furthermore, the average number of polymers per complex is calculated. Finally, the relative increase in viscosity is found under the assumption that the complexes can be treated as porous spheres.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0736-0266
    Keywords: Sulfate ; Cartilage ; Glycosaminoglycans ; Mouse ; Articular ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have studied the effect of environmental sulfate concentration on the glycosaminoglycan synthesis of anatomically intact patellar cartilage of the mouse in vitro. Incubation of mouse patellae in medium with sulfate concentrations below 0.5 mM resulted in a diminished incorporation of sulfate but in unaltered incorporation of glucosamine. This suggested the synthesis of undersulfated glycosaminoglycans under these conditions. We characterized glycosaminoglycans synthesized at three different sulfate concentrations: a sulfate concentration physiological for the mouse (1.0 mM), a sulfate concentration in the range where sulfate incorporation was strongly diminished (0.1 mM), and an extremely low sulfate concentration (10 nM). Analysis of glycosaminoglycan disaccharides and DEAE anion chromatography of the glycosaminoglycans could not confirm the synthesis of undersulfated glycosaminoglycans at 0.1 mM. The chromatogram of glycosaminoglycans synthesized in medium containing 10 nM showed the presence of a very low sulfated glycosaminoglycan pool not observed at higher medium sulfate concentrations. Intermediately sulfated glycosaminoglycans were also synthesized during incubation with 10 nM sulfate. So, our data indicate that only very low sulfate concentrations in the medium lead to the synthesis of undersulfated glycosaminoglycans and that the sulfation mechanism of murine patellar cartilage chondrocytes does not seem to fit completely in an “all-or-nothing” pattern.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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