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  • Core-fibrils  (2)
  • exchange effects  (2)
  • 1,3,2,4-Diazadiphosphetidinylium salts  (1)
  • 1
    Electronic Resource
    Electronic Resource
    X-ray investigations of the formation of core-fibrils crystallized out of the oriented melt (1988)
    Springer
    Colloid & polymer science 266 (1988), S. 411-418 
    Details
    ISSN: 1435-1536
    Keywords: Core-fibrils ; crystallization models ; fiber morphology ; X-ray analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Crystallization models for the formation of core-fibrils crystallized from the oriented melt are discussed by comparing results from X-ray experiments with theoretical predictions. Two sets of polymer blends, the systems iPP/PB-1 and iPP/aPP have been measured. From wide angle X-ray scattering, the thicknesses of the core-fibrils, lattice distortions, and unit-cell parameters have been determined. Interface distribution functions have been used to evaluate the axial morphology of the fibers from meridional small angle X-ray scattering curves. It appears that the morphological predictions made by the crystallization models of Pennings and of Hoffman cannot be confirmed by the experimental findings. The diffusion model proposed by Petermann partially describes the morphological properties of the core-fibrils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01457257
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Investigation of axial density modulations of core fibrils by interface distribution functions (1986)
    Springer
    Colloid & polymer science 264 (1986), S. 1017-1023 
    Details
    ISSN: 1435-1536
    Keywords: Core-fibrils ; axial density — modulation ; interface distribution functions ; defect clustering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The axial density modulation of core-fibrils in polypropylene and poly (1butene) crystallized from the oriented melt has been investigated by calculating interface distribution functions of the small angle x-ray scattering. The density modulation along the fiber axis originates from the migration of chain defects in the early stages of crystallization in the shear-field. The lengths of the needle crystals are approximately three times higher than those of the distorted zones. The values of the interface lengths between crystals and zones of lower electron density, are matching well with the lengths of the distorted zones. This result confirms the concept of defect clustering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410319
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A new quantum statistical evaluation method for time correlation functions (1989)
    Springer
    Journal of statistical physics 54 (1989), S. 765-795 
    Details
    ISSN: 1572-9613
    Keywords: Time correlation functions ; Liouville operators ; cluster expansion ; exchange effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Considering a system ofN identical interacting particles, which obey Fermi-Dirac or Bose-Einstein statistics, we derive new formulas for correlation functions of the type $$C(t) = \langle \Sigma _{i = 1}^N A_i (t) \Sigma _{j = 1}^N B_j \rangle $$ (whereB j is diagonal in the free-particle states) in the thermodynamic limit. Thereby we apply and extend a superoperator formalism, recently developed for the derivation of long-time tails in semiclassical systems. As an illustrative application, the Boltzmann equation value of the time-integrated correlation functionC(t) is derived in a straightforward manner. Due to exchange effects, the obtained t-matrix and the resulting scattering cross section, which occurs in the Boltzmann collision operator, are now functionals of the Fermi-Dirac or Bose-Einstein distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01019775
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  • 4
    Electronic Resource
    Electronic Resource
    Quantum-statistical kinetic equations (1989)
    Springer
    Journal of statistical physics 56 (1989), S. 175-201 
    Details
    ISSN: 1572-9613
    Keywords: Kinetic equations ; exchange effects ; renormalized cluster series ; quantum-statistical Boltzmann and Choh-Uhlenbeck equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Considering a homogeneous normal quantum fluid consisting of identical interacting fermions or bosons, we derive an exact quantum-statistical generalized kinetic equation with a collision operator given as explicit cluster series where exchange effects are included through renormalized Liouville operators. This new result is obtained by applying a recently developed superoperator formalism (Liouville operators, cluster expansions, symmetrized projectors,P q rule, etc.) to nonequilibrium systems described by a density operatorρ(t) which obeys the von Neumann equation. By means of this formalism a factorization theorem is proven (being essential for obtaining closed equations), and partial resummations (leading to renormalized quantities) are performed. As an illustrative application, the quantum-statistical versions (including exchange effects due to Fermi-Dirac or Bose-Einstein statistics) of the homogeneous Boltzmann (binary collisions) and Choh-Uhlenbeck (triple collisions) equations are derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01044240
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    [n + 2]-Cycloadditionsreaktionen des (Arylimino)phosphenium-Ions, [P≡NAr]+-kationische PN-Heterocyclen mit ungewöhnlicher Struktur und BindungssituationHerrn Professor Eckehard Volker Dehmlow zum 60. Geburtstag gewidmet. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1513-1517 
    Details
    ISSN: 0009-2940
    Keywords: [n + 2] Cycloadditions ; Calculations, ab initio ; Phosphenium ions ; 1,3,2,4-Diazadiphosphetidinylium salts ; Tetrazaphospholylium salts ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [n + 2] Cycloaddition Reactions of the (Arylimino)phosphenium Ion, [P≡NAr]+-Kationic PN Heterocycles with Unusual Structure and Bonding SituationThe iminophosphenium ion [P≡NAr]+ (Ar=2,4,6-tBu3C6H2) (1) reacts with aminoiminophosphanes R2N-P=NtBu (R=iPr, Me3Si) (2) and alkyl azides RN3 (R=tBu, Et3C) (6) to yield the corresponding [n + 2] cycloadducts [R2NP (NAr)P(NtBu)+ (3) and [PN(Ar)NNN(R)]+ (7), respectively. Single-crystal X-ray diffraction studies show that 3a can be considered as an intramolecular donor-acceptor complex while 7 can be regarded as a cyclic diaminophosphenium cation coupled to a diimine fragment, which is in accordance with results of ab initio calculations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260703
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    Paper (German National Licenses)
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