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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 3633-3638 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reversible structural relaxation has been studied in (Fe1−xNix)80B10Si10 by differential scanning calorimetry and x-ray diffraction. It is found that surface crystallization plays a major role in inhibiting reversibility. In consequence, previously published data have presented a misleading picture about the composition dependence of the reversible effect in Fe-Ni-B-Si, which simply increases monotonically with Ni composition. There is no evidence that chemical short-range order plays any role in reversibility, and the data have been quantitatively modeled by simply assuming that reversible relaxation is caused by the thermal repopulation of excited structural states.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 39 (1998), S. 5098-5111 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Though, in contrast to standard quantum field theory (QFT), the tensor-algebra over the test-function space of hyperfunction quantum field theory has no local structure, the localization properties of states on this algebra can be used to derive asymptotic Abelianness in spacelike directions. Again, in contrast to standard QFT, the closure of (Hermitian) field operators can destroy localization properties. This problem is addressed in a natural modification of the definition of the closure, called the local closure. This allows one, in conjunction with asymptotic Abelianness, to define a proper reduction of the field algebra to the subspace of the translation invariant states, and to investigate the dimension of this subspace. © 1998 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 30 (1989), S. 2340-2359 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The choice of the class E' of generalized functions on space-time in which to formulate general relativistic quantum field theory (QFT) is discussed. A first step is to isolate a set of conditions on E' that allows a formulation of QFT in otherwise the same way as the original proposal by Wightman [Ark. Fys. 28, 129 (1965)], where E' is the class of tempered distributions. It is stressed that the formulation of QFT in which E' equals the class of Fourier hyperfunctions on space-time meets the following requirements: (A) Fourier hyperfunctions generalize tempered distributions thus allowing more singular fields as suggested by concrete models; (B) Fourier hyperfunction quantum fields are localizable both in space-time and in energy-momentum space thus allowing the physically indispensable standard interpretation of Poincaré covariance, local commutativity, and localization of energy-momentum spectrum; and (C) in Fourier hyperfunction quantum field theory almost all the basic structural results of "standard'' QFT (existence of a PCT operator, spin-statistics theorems, existence of a scattering operator, etc.) hold. Finally, a short introduction to that part of Fourier hyperfunction theory needed in this context is given.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 2456-2469 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dissociation of fast nitrogen molecules with kinetic energies ranging from 200 to 2000 eV/atom was studied for grazing collisions with various fcc surfaces. At these energies, the dissociation is caused by vibrational and rotational excitation, the latter being favored for scattering along the surface semichannels. N2 is chemically inert and interacts mainly elastically with the surfaces. A controversial question is the role of the dynamic screening of the molecular constituents by the bulk electron gas during the dissociation process. Another interesting issue is the dependence of the dissociation probability on the azimuthal scattering angle—the fragmentation is highest for the low indexed direction. We treat both problems, by comparing results obtained from the different surfaces Pd(110), Ag(110), and Pt(110). The experimental data are compared to molecular dynamics simulations based on realistic interaction potentials as obtained from density functional theory calculations. The potentials are improved by adding an explicit dependence of the intramolecular bond strength on the molecule surface distance z, which leads to excellent agreement of experiment and simulations. © 2000 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 9634-9638 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We propose a simple model for photoinduced charge transfer in conducting polymer C60 composites. Our model consists of coupled Su–Schrieffer–Heeger models for a single polymer chain and a C60 molecule. We have included the coupling of the molecular vibrations to the π electrons but have neglected explicit electron–electron interaction. Using adiabatic and nonadiabatic molecular dynamics, we find photoinduced electron transfer takes place in 200–300 fs. This is consistent with an experimental upper bound of 300 fs. Nonadiabatic effects tend to average out pronounced oscillatory behavior in the adiabatic calculations. © 1997 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3215-3222 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Vitreous selenium is used extensively for light detection. Its photoconducting properties are altered by structural relaxation near room temperature. X-ray diffraction, densiometry, and calorimetry are used to determine the change of the glass state during relaxation. Annealing for 24 h at 300 K increases the density by 0.14% and lowers the enthalpy by 105 J/mol. The structure factor of cast samples was measured before and after annealing, and reverse Monte Carlo models of the structure of selenium glass were generated to match the data for the quenched and annealed states. Atoms in amorphous selenium are arranged in randomly oriented chains. In the model clusters annealing effects are found by analyzing inter- and intrachain distances, bond angle distributions, and dihedral angle distributions. The average bond length remains unchanged upon annealing, while the distribution of bond lengths becomes narrower by 1.2%. Distances between atoms in adjacent chains decrease by about 0.03%, i.e., the selenium chains move closer together, and the distribution of interchain distances becomes narrower. Bond angles within the chains are affected slightly. The mean bond angle decreases by 0.016°, which indicates a greater folding of the selenium chains and represents an evolution towards the angles found in crystalline selenium phases. The bond angle distribution for the annealed state is 0.006° narrower. © 2001 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2978-2983 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: At the early stage of mechanical alloying of α-Fe and ε-Co lamellar layers of the initial phases are formed. As the thickness of the layers decreases the interdiffusion of the elements starts and a disordered crystalline Fe-Co solid solution is formed. The progress of the solid state reaction has been monitored by Mössbauer spectroscopy, x-ray diffraction, and measurements of the saturation magnetization. The experimental data allow calculation of the change of fractions of material with different local compositions as the alloying proceeds. The main results are that Co diffuses into the α-Fe while Fe does not diffuse into the ε-Co. In spite of a much lower negative heat of mixing, the reaction proceeds in a similar way to the formation of amorphous NiZr during mechanical alloying.
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