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  • 1
    Electronic Resource
    Electronic Resource
    The role of geometric considerations in the diamond-cubic boron nitride heteroepitaxial system (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2679-2681 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the methods and results of a theoretical study of the diamond-cubic boron nitride [BNcub] heteroepitaxial system. We introduce a general, geometric reciprocal space technique for evaluating candidate epitaxial configurations, and a novel system of essentially geometric criteria to order them from most to least likely to occur. In the diamond- BNcub system, it is found that low index like planes require a relatively small strain of 1.37% from bulk parameters. The unlike epitaxial configuration which pairs diamond{100} with BNcub{221} and yields two-dimensional coincidence with the same strain is favored above other low index mixed configurations. The essentially geometric nature of this epitaxial system is highlighted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348663
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  • 2
    Electronic Resource
    Electronic Resource
    The electron-beam furnace: A new facility for materials science research (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 3620-3626 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The development and the test results of an electron-beam furnace for the later utilization in a microgravitational environment are reported. By just varying the deflection pattern by means of the electron-optical components two reference profiles, a gradient profile with a maximum slope of 220 K/cm, and a hot zone profile with a zone temperature of 1520 K could be established and maintained. A beam power of 550 W had to be applied to a sample made of massive Ta for the gradient profile, for creating a hot zone profile an input power of only 250 W onto a sample with a ceramic core was sufficient. A continuous pyrometric measurement system with a high local and time resolution has been realized. By temperature sensing of the sample with this system an intrinsic feature of electron-beam heating could be directly observed, the sharply localized energy deposition at the sample surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144239
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  • 3
    Electronic Resource
    Electronic Resource
    Particle production at high energies in the Cardy pomeron model (1992)
    Springer
    The European physical journal 56 (1992), S. 643-652 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Particle production at very high energies inhh, hA andAB collisions is studied in the framework of the pomeron model with a strong self-interaction proposed by Cardy. It is shown that the interaction between pomerons substancially damps the production rate one nuclei, the multiplicities forhA collisions becomingA-independent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01474739
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  • 4
    Electronic Resource
    Electronic Resource
    On the description of multiple measurements of an unstable state (1992)
    Springer
    Foundations of physics 22 (1992), S. 617-630 
    Details
    ISSN: 1572-9516
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The nondecay probability of an unstable particle at a definite moment of time is investigated provided this particle existed at all earlier observation moments separated with the time interval Δ. Using the usual postulates for quantum measurements it is proved that this probability is described by the exponential function of Δ〉0, and it tends to 1 as Δ → 0. An approximate formula is found for the effective decay width Γ(Δ) appearing in the case of multiple measurements. It is shown that Γ(Δ) → 0 as Δ → 0. For Δ → ∞, the width Γ(Δ) → Γ0, with Γ0 being the standard decay with in Weisskopf-Wigner theory. At finite δ's Γ(Δ) may be smaller or greater than Γ0 depending on the parameters of the theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00732925
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  • 5
    Electronic Resource
    Electronic Resource
    Full field flow visualization and computer-aided velocity measurements in a bank of cylinders in a wind tunnel (1992)
    Springer
    Experiments in fluids 13 (1992), S. 117-127 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The full field flow tracking (FFFT) method that is presented in this paper uses a laser-generated, mechanically strobed planar sheet of light, a low luminosity TV camera coupled with a long distance microscope, and a computer-controlled videorecorder to study non-intrusively and qualitatively the flow structures in a bank of cylinders that are placed in a wind tunnel. This setup simulates an upscale version of the geometry of internal cooling passageways characteristic of small air-cooled radial turbines. The qualitative images supplied by the FFFT system are processed by means of a computer-integrated image quantification (CIIQ) method into quantitative information, trajectories and velocities, that describes the flow upstream of and within the bank of cylinders. The tracking method is lagrangian in concept, and permits identification and tracking of the same particle, thus facilitating construction of time dependent trajectories and the calculation of true velocities and accelerations. The error analysis evaluates the accuracy with which the seed particles follow the flow and the errors incurred during the quantitative processing of the raw data derived from the FFFT/ CIIQ method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218157
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  • 6
    Electronic Resource
    Electronic Resource
    Nonlinear shell formulations for complete three-dimensional constitutive laws including composites and laminates (1994)
    Springer
    Computational mechanics 15 (1994), S. 1-18 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract One objective of the present study is to use arbitrary complete 3-dimensional constitutive equations without reduction or manipulation in nonlinear plate and shell analysis. The obvious consequence, namely the extension of a conventional 5-parameter shell formulation with Reissner-Mindlin kinematics to a 6-parameter formulation including the full set of stress and strain state does not solve the problem because a significant error in bending dominated cases occurs. To avoid this error the transverse normal strain is allowed to vary linearly across the thickness. This so-called 7-parameter theory recently proposed in the group of the authors resorts to the Enhanced Assumed Strain concept and preserves the basic features of a displacement formulation. The 7-parameter formulation is extended to the simulation of the response of laminated structures with arbitrarily large displacements and rotations. Following the main idea of the concept, it is sufficient to formulate a complete 3-dimensional material law which considers the layered setup of the shell. Finally, a layer-wise so-called multidirector model is developed which is well suited to grasp local interlaminar effects. In this formulation the displacement interpolation across the thickness is extended to a C0-continuous field described by a layer-wise Reissner-Mindlin kinematics. The purpose of the multidirector formulation is twofold: Firstly the higher order kinematics satisfies the same requirements discussed for the 7-parameter theory and allows also to use complete 3-dimensional material laws. Secondly it is appropriate to simulate laminates with extreme differences of the thicknesses or dissimilar material properties of each layer with sufficient accuracy. These are situations where formulations with C1-continuous displacement fields across the thickness fail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350285
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  • 7
    Electronic Resource
    Electronic Resource
    Statoliths pull on microfilaments (1993)
    Springer
    Protoplasma 172 (1993), S. 38-42 
    Details
    ISSN: 1615-6102
    Keywords: Actin filaments ; Chara rhizoid ; Cytochalasin ; Microgravity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous videomicroscopy ofChara rhizoids during parabolic flights of rockets showed that the weightless statoliths moved basipetally. A hypothesis was offered that the removal of gravity force disturbed the initial balance between this force and the basipetally acting forces generated in a dynamic interaction of statoliths with microfilaments (MFs). The prediction of this hypothesis that the statoliths would not be displaced basipetally during the microgravity phase (MG-phase) after disorganizing the MFs was tested by videomicroscopy of a rhizoid treated with cytochalasin D (CD) immediately before the flight. The prediction was fully supported by the flight experiment. Additionally, by chemical fixation of many rhizoids at the end of the MG-phase it was shown that all rhizoids treated with CD before the flight had statoliths at the same location, i.e., sedimented on the apical cell wall, while all untreated rhizoids had statoliths considerably displaced basipetally from their normal position. Thus, a dynamical interaction involving shearing forces between MFs and statoliths appears highly probable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403719
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  • 8
    Electronic Resource
    Electronic Resource
    Centrifugation causes adaptation of microfilaments Studies on the transport of statoliths in gravity sensingChara rhizoids (1993)
    Springer
    Protoplasma 174 (1993), S. 50-61 
    Details
    ISSN: 1615-6102
    Keywords: Actin ; Adaptation ; Chara rhizoids ; Gravitropism ; Microfilaments ; Polarity ; Statoliths
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The actin cytoskeleton is involved in the positioning of statoliths in tip growingChara rhizoids. The balance between the acropetally acting gravity force and the basipetally acting net out-come of cytoskeletal force results in the dynamically stable position of the statoliths 10–30 μm above the cell tip. A change of the direction and/or the amount of one of these forces in a vertically growing rhizoid results in a dislocation of statoliths. Centrifugation was used as a tool to study the characteristics of the interaction between statoliths and microfilaments (MFs). Acropetal and basipetal accelerations up to 6.5 g were applied with the newly constructed slow-rotating-centrifuge-microscope (NIZEMI). Higher accelerations were applied by means of a conventional centrifuge, namely acropetally 10–200 g and basipetally 10–70 g. During acropetal accelerations (1.4–6 g), statoliths were displaced to a new stable position nearer to the cell vertex (12–6.5 μm distance to the apical cell wall, respectively), but they did not sediment on the apical cell wall. The original position of the statoliths was reestablished within 30 s after centrifugation. Sedimentation of statoliths and reduction of the growth rates of the rhizoids were observed during acropetal accelerations higher than 50 g. When not only the amount but also the direction of the acceleration were changed in comparison to the natural condition, i.e., during basipetal accelerations (1.0–6.5 g), statoliths were displaced into the subapical zone (up to 90 μm distance to the apical cell wall); after 15–20 min the retransport of statoliths to the apex against the direction of acceleration started. Finally, the natural position in the tip was reestablished against the direction of continuous centrifugation. Retransport was observed during accelerations up to 70 g. Under the 1 g condition that followed the retransported statoliths showed an up to 5-fold increase in sedimentation time onto the lateral cell wall when placed horizontally. During basipetal centrifugations ⩾ 70 g all statoliths entered the basal vacuolar part of the rhizoid where they were cotransported in the streaming cytoplasm. It is concluded that the MF system is able to adapt to higher mass accelerations and that the MF system of the polarly growing rhizoid is polarly organized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01404042
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  • 9
    Electronic Resource
    Electronic Resource
    Cytoplasmic streaming inChara rhizoids (1991)
    Springer
    Protoplasma 165 (1991), S. 121-126 
    Details
    ISSN: 1615-6102
    Keywords: Chara (rhizoid) ; Cytoplasmic streaming ; Gravity (effect on streaming) ; Microfilaments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In-vivo videomicroscopy ofChara rhizoids under 10–4g demonstrated that gravity affected the velocities of cytoplasmic streaming. Both, the acropetal and basipetal streaming velocities increased on the change to microgravity. The endogenous difference in the velocities of the oppositely directed cytoplasmic streams was maintained under microgravity, yet the difference was diminished as the basipetal streaming velocity increased more than the acropetal streaming velocity. Direction and structure of microfilaments labeled by rhodamine-phalloidin had not changed after 6 min of microgravity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322282
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  • 10
    Electronic Resource
    Electronic Resource
    String fusion and particle production at high energies: Monte-Carlo string fusion model (1994)
    Springer
    The European physical journal 63 (1994), S. 507-516 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The theoretical basis to build a Monte-Carlo string model, which includes string fusion phenomena, is presented. The model intends for simulations of multiple particle production inhh,hA andAA collision at ultrahigh energies. Calculations reveal that string fusion leads to a reduction in total particle multiplicities and to a baryon enhancement. The effect grows with energy and atomic numbers of the projectile and target.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01580331
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