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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 90 (1995), S. 584-594 
    ISSN: 1432-2242
    Keywords: Multiple-population breeding (MPBS) Hierarchical open-ended breeding (HOPE) Genetic conservation ; Conifers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Advanced-generation domestication programs for forest-tree species has raised some concerns about the maintenance of genetic diversity in forest-tree breeding programs. Genetic diversity in natural stands was compared with two genetic conservation options for a third-generation elite Pinus taeda breeding population. The breeding population was subdivided either on the basis of geographic origin and selection goals (multiple-population or MPBS option) or stratified according to genetic value (hierarchical or HOPE option). Most allelic diversity in the natural stands of loblolly pine is present in the domesticated breeding populations. This was true at the aggregate level for both multiple-population (MPBS) and the hierarchical (HOPE) populations. Individual subpopulations within each option had less genetic diversity but it did not decline as generations of improvement increased. Genetic differentiation within the subdivided breeding populations ranged from 1 to 5%, genetic variability is within each subpopulation rather than among subpopulations for both MPBS (〉95%) and the HOPE approaches (〉98%). Nei's Gst estimates for amongpopulation differentiation were biased upwards relative to estimates of θ from Weir and Cockerham (1984).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2242
    Keywords: Key words Age-age genetic correlations ; Phenotypic correlations ; Conifers ; Tree breeding ; Woody perennials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A meta-analysis of 520 parents and 51,439 individuals was used to develop two equations for predicting age-age genetic correlations in Pinus taeda L. Genetic and phenotypic family mean correlations and heritabilities were estimated for ages ranging from 2 to 25 years on 31 sites in the southern U.S. and Zimbabwe. Equations for predicting age-age correlations based on P. taeda populations from west and east of the Mississippi River proved statistically different. Both predictive equations proved conservative for validation datasets consisting of younger tests in the U.S. and Zimbabwe. Age-dependent log-linear predictive equations were favored over growth-dependent equations. All P. taeda predictive equations based on genetic correlations favored earlier selection when compared to a generalized conifer predictive equation based on phenotypic correlations. The age-age correlations structure showed stability independent of planting density and across a wide range of family sizes.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 5 (1994), S. 79-89 
    ISSN: 1042-7147
    Keywords: Copolymers bropylene-7 methyl 1-6 octadiene ; Sulfonation ; Ionomers aggregation state ; Mechanical properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Polypropylene ionomers have been prepared by sulfonation of copolymers of propene and 7 methyl, 1-6 octadiene, followed by neutralization to cesium salts. Both WAXS and SAXS were used to study the morphology of the samples, while their thermal properties were studied by DSC and their mechanical properties by DMTA. The sulfonation process is shown to cause a further drop in crystallinity in addition to the effect of comonomer incorporation. Ion clustering is observed when the extent of sulfonation is high enough, the limit being dependent on the copolymer composition. The ion pairs which are not incorporated into the cluster cause a small-angle upturn in the WAXS pattern. The mechanical properties are strongly affected by the drop in crystallinity, but may be partly recovered due to ion clustering. No disruption of the ion clusters is observed before thermal decomposition of the polymer.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1979-1986 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Block copolymers consisting of long styrene midblocks and much shorter 4-vinyl pyridine end-blocks were quaternized with n-iodo alkanes (2 ≤ n ≤ 10) to give block ionomers of a novel architecture. The name “bottlebrush” seems appropriate for these materials. A preliminary investigation of the morphology of these systems, prepared by in situ quaternization, is reported here. The morphology is dependent on both the length of the iodo alkane and the relative sizes of the blocks. Even with identical sample histories, two distinct morphologies are seen. One of these is characterized by a single broad SAXS peak, while the other shows a much narrower peak and higher-order features. The latter morphology is associated with the higher ionic to nonionic ratios and long side chains.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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