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  • crystallization mechanism  (1)
  • open-water aquaculture  (1)
  • Springer  (2)
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  • Springer  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 13 (1998), S. 119-124 
    ISSN: 1573-4846
    Keywords: hydrothermal synthesis ; zircon ; crystallization mechanism ; fluoride medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrothermal synthesis of zircon in a fluoride medium leads principally to two kinds of zircons, differentiated by their morphology, chemical composition, thermal stability and solubility. Differences in the thermodynamic parameters of solution (pH, temperature, [F−]) could explain the formation of these two kinds of zircons. The main hypothesis involves two crystallization mechanisms. Both include a step of gel dissolution with formation of soluble species that are responsible for the crystallization. In each case, the silicon species seem to be monomeric without fluorine. However, the nature of soluble zirconium species depends on the thermodynamic parameters of the solution. At acid pH and with fluoride ions, the reactive species for the crystallization seem to be fluoride rich zirconium complexes. In this case, the zircon obtained contains a large amount of fluoride presumably located in silicon sites (Zircon A). At basic pH, and whatever the concentration of fluoride, the reactive species for crystallization seems to be linear polymeric entities. In this case, the zircon obtained shows a typical morphology in the form of layered agglomerates and a high specific surface area (Zircon B).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5117
    Keywords: Chondrus crispus ; open-water aquaculture ; cold-water aquaculture ; daily growth rate ; carrageenans ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The red alga Chondrus crispus (Irish moss) has been commercially harvested in Eastern Canada for almost 60 years. Its land-based tank aquaculture was initiated in the 1970s. In the 1990s, it became clear that production costs of these capital intensive systems were still too high for the carrageenan market but not for the production of edible seaweeds. Open-water aquaculture of cold-temperate species of carrageenophytes, and in particular of C. crispus, has rarely been attempted. This study re-examined the potential of the unique unattached and mostly vegetative population of C. crispus at Basin Head, in eastern Prince Edward Island (P.E.I.), and at 5 transplant sites in western P.E.I. Basin Head plants were successfully transplanted to other sites, providing similar or different environmental conditions, and yielding comparable, or even higher, productivity. During the peak growth periods (May to end of June and autumn), daily growth rates (DGRs) between 3 and 4% d−1 were recorded at Basin Head and Freeland, with some plants exceeding 6% d−1. Over the whole study period (May to October), DGRs between 2 and 4% d−1 were lower than those reported for different species of Eucheuma and Kappaphycus alvarezii; they were, however, compensated for by extremely high carrageenan yields (between 58.1 and 71.0% DW) during the summer months when nutrients (phosphorus and nitrogen) levels in seawater and algal tissue were low. The DGRs could be increased by developing culture structures retaining fragmenting, but otherwise healthy, large distal clumps, lost with the present simple tying of plants on screens. Preliminary results demonstrated that transplantation and grow-out techniques are biologically successful, and that the Basin Head population of C. crispus has significant potential for open-water aquaculture in estuaries and basins of Atlantic Canada.
    Type of Medium: Electronic Resource
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