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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1448-1457 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two-dimensional, nonequilibrium molecular dynamics simulations have been applied to study the structure of thin films grown on single-crystal Lennard-Jones substrates. The principal microstructural features to develop within these films are single vacancies and small voids which tend to be slightly elongated and to be aligned in the growth direction. Both the void volume and the mean surface roughness of the films are found to be decreasing functions of substrate temperature and deposition kinetic energy. Voids are shown to form as a consequence of both surface roughness and shadowing effects. The attraction between deposited atoms and the sides of surface depressions lead to the formation of outgrowths from the sidewalls of the surface depression. These outgrowths shadow the open void beneath them and continue to grow across the voids by interaction with the depositing atoms until a continuous bridge is formed that closes off the void. Since this bridging mechanism leaves behind a surface depression above the closed-off void, new voids tend to form above it. This leads to the alignment of voids along the film growth direction. The spacing of the resultant void tracks is correlated with the wavelength of the surface roughness. Increasing temperature and deposition kinetic energy enhancing surface mobility leads to an increase in the wavelength of the surface roughness and hence an increase in the spacing between void tracks. Edge dislocations tend to form within voids as a natural consequence of the void bridging process, however nondislocated voids are also observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5682-5690 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomistic, molecular dynamics simulations are employed to investigate the relationship between film microstructure and deposition conditions (substrate temperature, deposition kinetic energy, and deposition angle). Increasing substrate temperature and deposition kinetic energy leads to fewer voids, smaller voids, smoother surfaces, and higher film density. As the deposition angle increases, the film microstructure changes from a dense film, with few voids, to a microstructure in which nearly colinear tracks of elongated voids form and, finally, to a highly porous structure of well-formed columns. The angle along which the voids are elongated and the orientation of the void tracks are the same and increase monotonically with the deposition angle (the column angles follow the same trend as the deposition angle). Void formation, void alignment into tracks, and the columnar structure are all attributable to shadowing effects, which become more pronounced with increasing deposition angle. The variation of the column/void track angle β with deposition angle α fits well with the classical tangent law at low angles, but is overpredicted by the tangent law at α(approximately-greater-than)60°, consistent with experiment. The column angle β decreases slowly with increasing deposition kinetic energy due to increased surface mobility. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3007-3009 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonequilibrium molecular dynamics simulations have been employed to develop a mechanistic model for the development of an out-of-plane (fiber) texture in polycrystalline thin films. The depositing atoms preferentially sputter film atoms from grains with high surface energies. As the film grows, an atomic shadowing mechanism leads to the lateral growth of the grains with a height advantage—eventually leading to the occlusion of randomly oriented grains. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 217-227 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low-temperature growth and relaxation of misfitting films are analyzed on the basis of two-dimensional molecular dynamics simulations using Lennard–Jones potentials. The temporal evolution of the surface morphology and the mechanisms for misfit dislocation nucleation and stress relaxation are monitored. Pseudomorphic film growth is observed up to a critical thickness. In some cases, the formation of voids within the film relaxes some of the stress. At the critical thickness, dislocations nucleate and relax most of the misfit. The critical thickness increases with decreasing lattice mismatch and depends on the sign of the misfit. The critical thickness of compressively strained films is smaller than that of films with the same magnitude of misfit, but in tension. The mechanism of dislocation nucleation is different in tension and compression and, in all cases, is associated with the roughness of the film surface. In the compressive misfit case, dislocations nucleate by squeezing-out an atom at the base of surface depressions. In the tensile misfit case, however, the nucleation of misfit dislocations involves the concerted motion of a relatively large number of atoms, leading to insertion of an extra lattice (plane) row into an already continuous film. These results show that the critical thickness depends intimately on the film morphology which, in turn, is determined as an integral part of the film growth process. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry 26 (1934), S. 819-822 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 57 (1985), S. 2597-2599 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1196-1203 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A modified kinetic Monte Carlo computer simulation has been developed and applied to the investigation of fiber (out-of-plane) texture formation in polycrystalline thin films grown in the absence of high-energy bombarding particles. Unlike high-energy deposition, in which texture formation appears to result from a combination of preferential resputtering and self-shadowing at the film surface, the simulation results described herein indicate that texture formation in low-energy deposition is caused by a bias in surface diffusion and adsorption energies on different crystallographic faces. A net flux of atoms toward grains with high-binding-energy faces oriented along the film surface coupled with a greater probability that an atom near the interface between two grains will become attached to the high-binding-energy face produces a preferential in-plane expansion of these grains at the expense of their neighbors. The rate of texture development is shown to increase with increases in the binding energy of the preferred faces and the deposition temperature, and to decrease with increasing deposition rate and initial grain size. Voids and vacancies incorporated into the film form as a result of incomplete layer-by-layer growth induced by conditions of low surface diffusion and high deposition rate. The density of voids and vacancies, as well as the local surface roughness, varies from grain to grain within the material due to the differences in surface diffusion on the crystallographic faces exposed to the deposition flux as each layer of the various grains is formed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The DnaA protein of Escherichia coli is a multifunctional protein which, in addition to promoting initiation of replication, can regulate the initiation or termination of transcription of a variety of genes. It acts by binding to DNA at a defined sequence, termed a DnaA-box. Three candidate DnaA-boxes which occur within the essential cell-division genes, ftsQ and ftsA, have been hypothesized to mediate the response of the downstream ftsZ gene to intracellular levels of DnaA, and thus to couple the processes of initiation and cell division. We show here that, although transcription from promoters upstream of ftsZ is increased when initiation of chromosome replication is blocked by DnaA inactivation, this response is not mediated by the DnaA-boxes near these promoters, nor is it specific to DnaA. We show, furthermore, that mutational inactivation of the putative DnaA-binding sites in the fts region of the chromosome does not lead to impaired growth or reduced survival of cells.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 227 (1970), S. 141-145 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The new transplantation antigen in SV40 transformed cells is found in highest concentration in immunogenic membrane-rich subcellular fractions, and has been ...
    Type of Medium: Electronic Resource
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