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  • Articles  (8)
  • Articles: DFG German National Licenses  (8)
  • 1995-1999  (8)
  • 1980-1984
  • 1998  (1)
  • 1995  (7)
  • Physics  (6)
  • Biology  (3)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1393-1399 
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: Thermorheological properties of an incompatible polymer blend of polypropylene inclusions dispersed in a ethylene copolymer matrix were discussed from the emulsion model developed by Palierne. Due to the different rheological behaviors with temperature of the two phases, such a system proved to be a judicious blend in order to consider the special cases of the model applications: (1) the two phases are viscoelastic liquids, (2) the dispersed phase is a solid elastic assimilated to rigid spheres in comparison with viscoelastic liquid behavior of the matrix, and (3) the two phases are elastic solids. At low frequencies, the rheological behavior of the blend was not correctly predicted by the model. So interactions other than hydrodynamics can exist in the intrafacial region, and physical entanglements between the chains of the two constituents leading to topological interactions may be assumed at the interphase. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The linear viscoelastic behavior of commercial broad-distribution polypropylenes is studied. The samples underwent different controlled peroxide degradation rates, so they exhibit different molecular distributions. The relaxation spectrum is obtained by assuming that it takes the shape of a Log-Normal distribution. It is in agreement with the linear viscoelasticity theory by providing limiting values, contrary to other models. Moreover, the ratio τw/τn which takes place in this law is very useful to distinguish the synthesis differences of the samples when the Melt Flow Index alone cannot.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Using an integral nonlinear constitutive equation including the Log-Normal relaxation spectrum, the fiber-spinning behavior of commercial polypropylenes is studied. The relaxation spectrum is strongly related to the molecular weight distribution. Moreover, by means of a finite element analysis, simulated stress and velocity profiles are obtained either in isothermal or nonisothermal cases. In the isothermal case, broadening the relaxation spectrum leads to more pronounced curvature of the velocity profile. In the nonisothermal case, the critical draw ratio is sensitive to the mean relaxation time which depends on both average molecular weight and distribution breadth. It is shown that increasing the average relaxation time leads to a less rapid growth of the velocity. Furthermore, this effect is less pronounced when the relaxation spectrum is wider.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 378 (1995), S. 68-70 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Investigation of the genetics, gonads, genitalia or hormone level of transsexuals has not, so far, produced any results that explain their status1'2. In experimental animals, however, the same gonadal hormones that prenatally determine the morphology of the genitalia also influence the morphology ...
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ccd locus of the F plasmid codes for two gene products, CcdA and CcdB, which contribute to the plasmid's high stability by post-segregational killing of plasmid-free bacteria. Like the quinolones, the CcdB protein is a poison of the DNA-topoisomerase II complexes, while CcdA acts as an antidote against CcdB. in addition to these poison-antipoison properties, the CcdA and CcdB proteins act together at transcription level to repress their own synthesis. In this work, we have isolated, in vivo., and characterized several non-killer CcdB mutants. All missense mutations which inactivate CcdB killer activity are located in the region coding for the last three C-terminal residues. However, the resulting mutant CcdB proteins retain their auto-regulatory properties. We conclude that the last three C-terminal residues of CcdB play a key role in poisoning but are not involved in repressor formation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 340-340 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 8
    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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