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  • Articles  (2)
  • Articles: DFG German National Licenses  (2)
  • Diet  (1)
  • Physics  (1)
  • 1995-1999  (2)
  • 1980-1984
  • Physics  (1)
  • Biology  (1)
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  • Articles  (2)
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  • Articles: DFG German National Licenses  (2)
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  • 1995-1999  (2)
  • 1980-1984
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  • 1
    ISSN: 0887-6266
    Keywords: polyethylene ; poly(butylene terephthalate) ; blend ; rheology ; Palierne's model ; morphology ; differential scanning calorimetry ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystallization at high supercooling of polybutylene terephthalate (PBT) droplets dispersed in a molten polyethylene (PE) matrix was investigated through rheological and DSC experiments. The Palierne's emulsion model was used as a theoretical framework for studying the viscoelastic behavior of the blends in different ranges of temperature: on the one hand, when the two polymers are molten (T 〉 225°C) and on the other hand, when PBT droplets are at high supercooling in the molten PE matrix (130°C 〈 T 〈 205°C). From rheological experimental evidences it was shown that molten and solidified droplets coexist at high supercooling. The Palierne's model was then successfully adapted to take into account the three phases (molten PE, molten PBT droplets, and solidified PBT droplets). The evolution of the behavior with the temperature is consistent with the growing amount of crystallized droplets. Moreover, a calculation taking into account the droplets size distribution and the number of nuclei is introduced to explain the crystallization behavior of three different blend ratios.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2573-2585, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-1561
    Keywords: Diet ; calcium ; carnivore ; herbivore ; omnivore ; oral homeostasis ; proline-rich proteins ; saliva ; secretion ; tannin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We review information on the structure of proline-rich proteins (PRPs), their various functions related to oral homeostasis and dietary tannin, and the structural basis of these functions. Consideration of the multifunctional nature of these salivary proteins helps explain both the subtle and large variations found in structure and secretion rates both within individuals and between species. We propose that the ancestral function of PRPs is in maintaining oral homeostasis and that counteracting dietary tannins by binding with them is a derived function. PRPs are effective in oral homeostasis at low secretion levels, whereas counteracting tannin depends on high secretion levels. In the dietary habits ranging from carnivores through omnivores to exclusively planteaters, the dietary nitrogen level is progressively reduced, and plant allelochemical intake, including tannins, increases. We suggest that during this evolution from meat-eater to plant-eater, there was some point in omnivory at which selective pressure from nitrogen limitations, arising from a low nitrogen/high tannin diet, became sufficiently great for the evolution of increased secretion level and diversification of PRPs for dealing with tannin. If this hypothesis is correct, carnivorous mammals should secrete low levels of PRPs for oral homeostasis, but should never secrete high levels, unless they are secondarily carnivorous. Omnivores consuming a diet of very little animal tissue but higher levels of tannin-containing foliage or fruit should generally have the capacity to produce high levels of salivary PRPs. Browsers and frugivores should also produce high levels of PRPs, but grazers may have reduced secretion rates depending on the antiquity of the dietary habit. This hypothesis is consistent with the limited information available on the abundance, type, and distribution of PRPs in mammals. Studies are suggested which would test the functional and evolutionary arguments presented.
    Type of Medium: Electronic Resource
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