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  • 1985-1989  (7)
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Materialart
Erscheinungszeitraum
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  • 1
    Digitale Medien
    Digitale Medien
    A theoretical study of the dissociation of H2/Cu (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7209-7219 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We present calculations for the dissociative adsorption of hydrogen molecules on a Cu surface as a function of initial translational energy and vibrational quantum state. Classical, semiclassical, and fully quantum calculations are performed and the results compared. The potential energy surface was based upon a total energy calculation for H2 on a small Cu cluster and has been previously employed in dynamical simulations. Our results show that for low primary beam energies, dissociation occurs primarily via tunneling through the activation barrier in the vibrational coordinate. Populating the initial vibrational states is shown to enhance reactivity, but not simply by a total energy shift. By changing the hydrogen isotope it is shown that tunneling effects can persist up to quite high molecular masses. This occurs because the activation barrier lies in the vibrational coordinate, where the reduced mass of the molecule determines the dynamics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457288
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  • 2
    Digitale Medien
    Digitale Medien
    Quantum-mechanical scattering of H2 from metal surfaces: Diffraction and dissociative adsorption (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 7197-7208 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Some theoretical and experimental aspects of the interaction of H2 with metal surfaces are reviewed. A variety of model potential energy surfaces based on simple extensions to the Lennard-Jones model are presented. These potentials include activation barriers which vary across the surface unit cell giving rise to a variety of physically interesting and realistic topologies. The quantum-mechanical scattering of hydrogen and its isotopes from these potentials illustrate that it is possible, in a very simple way, to account for simultaneous sticking and diffraction at a single beam energy. The inclusion of tunneling in a realistic description of initial sticking coefficients is shown to be essential for these light gases. Finally, it is proposed that by inverting diffraction data, it should be possible to obtain key information regarding the form of the potential energy surface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.454372
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  • 3
    Digitale Medien
    Digitale Medien
    Collision induced dissociation of diatomic molecules on surfaces: A charge transfer mechanism (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 3502-3508 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A theory is presented which accounts for one of the possible mechanisms responsible for dissociative scattering of diatomic molecules from surfaces. If on the incident trajectory of the molecule, a surface-to-molecule electron transfer occurs and on the outgoing trajectory, the reverse, then the temporary negative molecular ion formed for the time duration between electron hops will displace in its intramolecular vibrational coordinate. The molecule will emerge as a vibrationally excited neutral, with some of the excited states lying within the dissociative continuum. A model is described for this process in which the center-of-mass translational motion is handled classically and the intramolecular motion via wave packet dynamics. The theory is energy and probability conserving and microscopically reversible. Dissociation probabilities calculated as a function of incident energy and system parameters are discussed in the light of experimental measurements for the system of I2 dissociatively scattered from MgO surfaces.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.450236
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  • 4
    Digitale Medien
    Digitale Medien
    Charge transfer, vibrational excitation, and dissociative adsorption in molecule–surface collisions: Classical trajectory theory (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 5203-5215 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The consequences of charge transfer processes occurring when a molecular beam of diatomic molecules is directed upon a solid surface are here considered. In analogy with resonance electron scattering from molecules or harpooning processes in atom–diatom collisions, the incident beam could either be scattered into a highly vibrationally excited molecular state, dissociatively scattered, or dissociatively adsorbed due to formation of temporary negative molecular ions which enable redistribution of the incident translation energy of the beam into intramolecular degrees of freedom. In this work, the exact classical trajectories for the diatomic molecule, including internal vibrational motion, are calculated for motion over model diabatic potential surfaces in which surface hopping due to charge transfer/harpooning is accounted for. Connections between classes of trajectories and topological features of the potential energy surfaces (PES) are illustrated. The model is used to study the average translational to vibrational energy transfer as a function of incident kinetic energy and of PES parameters. Branching ratios between scattered and dissociatively adsorbed molecules are obtained as a function of both incident translational and total energy and the role of the intermediate negative ion resonance in influencing the dynamics of molecular processes at surfaces is illustrated. Comparison with quantum mechanical theories is given in a subsequent paper.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.448645
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  • 5
    Digitale Medien
    Digitale Medien
    Isolation of α-tubulin genes from the human malaria parasite, Plasmodium falciparum: sequence analysis of α-tubulin (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Medizin
    Notizen: As a step towards indentifying exploitable differences between host and parasite at the molecular level, we have isolated and sequenced genomic clones encompassing an entire α-tubulin gene (designated α-tubulin I) from the human malaria parasite, Plasmodium falciparum. The gene, which contains two introns, encodes a product with a predicted length of 453 amino acid residues (50.3 kD). The protein sequence shows a high degree of homology to other α-tubulins, particularly that of the coccidian parasite, Toxoplasma gondii (94%), whose gene carries introns in identical positions. Only one copy of the α-tubulin I gene itself was found, although a second gene designated α-II was also identified which is closely related but which differs at both the nucleotide and amino acid sequence levels. The α-I and β-tubulin genes were found to reside on different chromosomes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00136.x
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  • 6
    Digitale Medien
    Digitale Medien
    Cloning of a β-tubulin gene from Plasmodium falciparum (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Medizin
    Notizen: We describe the isolation and characterization of a gene for β-tubulin from the malaria parasite, Plasmodium falciparum. This organism appears to contain a single gene encoding β-tubulin. A single transcript from this gene can be detected in the total RNA of the parasite's asexual blood stages. The complete sequence for the gene has been elucidated. It has two introns, one of which has a position identical to that of a related parasite, Toxoplasma gondii. The gene shows the usual preference for codons with A or T in the third position. The predicted amino acid sequence is compared with that of T. gondii and the human host. Further comparisons between these and fungal sequences of β-tubulins resistant to benomyl, a drug binding this protein, highlight differences that could be exploited in the development of parasite-specific anti-tubulin drugs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00137.x
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  • 7
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    Unbekannt
    Child-rearing attributions and efficacy among Mexican mothers and teachers (1987)
    Worcester, Mass. : Periodicals Archive Online (PAO)
    Journal of Social Psychology. 127 (1987) 499-510 
    Details
    ISSN: 0022-4545
    Thema: Psychologie , Sociologie
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:1143-1987-127-00-000038
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