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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8529-8536 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study theoretically the angular relaxation and translational diffusion of stiff rodlike micelles that can undergo reversible scission reactions, in both the dilute and the entangled regime. The very strong dependence of the angular diffusion constant on rod length leads to an anomalous superdiffusive behavior of the typical angular deflection of a subunit at short times. Despite this, angular correlation functions such as 〈u(t)⋅u(0)〉 (also the linear birefringence and entropic stress response) decay exponentially with a relaxation time that is a power law combination of the time scales for reversible scission and for angular rotation of a (hypothetical) unbreakable rod. This relaxation time corresponds to the waiting time for a subunit to find itself on a rod that is short enough to rotate through an angle of order π before recombining with another rod. The translational diffusion of rodlike micelles shows no anomaly in contrast to the angular case. However, the collective diffusion and self-diffusion constants differ by a factor of 2 at all concentration ranges for which rod micelles exist. The diffusion equation for collective motion is nonlinear (even below the overlap threshold) since the mobility of the rods depends on their local concentration. The dynamic structure factor S(q,t) is calculated to order q4, the quartic terms providing, in principle, a probe of the micellar scission time.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7260-7266 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study theoretically the process of "end-evaporation'' in living polymer systems, such as wormlike surfactant micelles. End-evaporation occurs when single monomers either break away from, or join onto, a chain end, the rates being described by the (mean-field) rate constants k and k', respectively. Thus the chains can exchange material with one-another via a bath of free monomers. The relaxation of a system of living polymers after a small temperature jump (T-jump) is studied theoretically. The effect of a T-jump is to prepare the system with the wrong mean chain length, which relaxes to its equilibrium value L¯ by end-evaporation. It is found that the number of free monomers in the system relaxes almost completely in a time of order 1/kL¯, while the weight-average chain length, which is the quantity measured in light scattering experiments, relaxes on a time scale τD=4L¯2/k, which is three powers of L¯ longer. We also predict that the stress relaxation after a step strain is dominated by end-evaporation whenever τD(approximately-less-than)τrep, where τrep is the reptation (disengagement) time for a chain of length L¯. In this case the stress relaxation is found to be "stretched exponential'' for times smaller than τD and single exponential for longer times.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 8142-8153 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structure of grafted polymer "brushes'' may be profoundly modified by the action of "external fields''—local shifts in chemical potential due to, e.g., interfacial effects at the grafting surface. We discuss the strong-stretching limit of the self-consistent mean-field theory for a brush exposed to an arbitrary external potential, a simple scaling law for the brush height arises in the case where the external field pushes monomers towards the surface. In contrast, repulsive interactions can lead to "exclusion zones'' or regions from which polymer ends are repelled, leading to a breakdown of the simple scaling formula. We exactly solve the self-consistent theory of the brush in a repulsive square well where an exclusion zone always appears. Our results describe a brush in the case where a thin layer of one component of a binary solvent that is a worse solvent for the polymer than is the bulk mixture wets the grafting surface. We also discuss the effects of thermal fluctuations and chain polydispersity on our results, and estimate the effects of various interfacial phenomena on the brush structure.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 23 (1990), S. 268-276 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 27 (1994), S. 3812-3820 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 136-142 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 22 (1989), S. 1454-1458 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 26 (1993), S. 7189-7194 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2242
    Keywords: Key words AFLP ; Pseudo-testcross ; Eucalyptus ; QTL ; Vegetative propagation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We have detected quantitative trait loci (QTLs) affecting vegetative propagation traits in Eucalyptus tereticornis and Eucalyptus globulus. Using amplified fragment length polymorphism (AFLP) genetic linkage maps, the inheritance of 199 markers was assessed in 94 F1 individuals with extreme adventitious rooting response, and in 221 randomly chosen F1 individuals. Phenotypes were scored in 1995 and 1996. QTL analyses were performed using chi-square tests (χ2), single-marker analysis (SMA), interval mapping (IM) and composite interval mapping (CIM). All approaches yielded similar QTL detection results. Three QTLs are hypothesized for mortality (MORT=% dead cuttings), nine for adventitious rooting (ROOT, RCT=% rooted cuttings relative to the surviving or total cuttings, respectively), four for petrification (PETR=% surviving unrooted cuttings), one for sprouting ability (SPR=number of stump sprout cuttings harvested in 1995) and four for the stability of adventitious rooting (STAB=absolute value of the difference ROOT95-ROOT96). All putative QTLs for MORT and PETR were located on the E. tereticornis map, and for SPR and STAB on the E. globulus map. We found different QTLs for MORT, ROOT, RCT, SPR and STAB. Putative QTLs accounted for 2.6–17.0% of the phenotypic variance of a trait (R2). Estimated standardized gene substitution effects varied between 0.13 and 0.49 phenotypic standard deviations (σp). These results indicate that the phenotypic variation in these traits has a meaningful genetic component and that stable QTLs can be found in a family of reasonable size where no previous knowledge of the trait was available.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 96 (1998), S. 727-737 
    ISSN: 1432-2242
    Keywords: Key words Genetic map ; Linkage ; Eucalyptus ; AFLP marker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Amplified fragment length polymorphism (AFLP) analysis is a rapid and efficient technique for detecting large numbers of DNA markers in eucalypts. We have used AFLP markers in a two-way pseudo-testcross strategy to generate genetic maps of two clones of different Eucalyptus species (E. tereticornis and E. globulus). Of 606 polymorphic fragments scored, 487 segregated in a 1 : 1 ratio, corresponding to DNA polymorphisms heterozygous in one parent and null in the other. In the maternal E. tereticornis map, 268 markers were ordered in 14 linkage groups (919 cM); the paternal E. globulus map had 200 markers in 16 linkage groups (967 cM). Results from PGRI software were compared with MAPMAKER. The average density of markers was approximately 1 per 3.9 cM. Framework markers were ordered with an average confidence level of 90%, covering 80–100% of the estimated Eucalyptus genome size. In order to investigate the homologies between the E. tereticornis and the E. globulus genetic linkage maps, we included 19 markers segregating 3 : 1 in the analysis. Some homeologous linkage groups were recognized. The linkage data developed in these maps will be used to detect loci controlling commercially important traits.
    Type of Medium: Electronic Resource
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