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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2093-2096 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plates of β-NbD0.7 were irradiated with single pulses of a KrF excimer laser having a wavelength of 248.4 nm. The power level was varied from roughly 0.1 to 1 GW/cm2. The pulse length was about 15 ns. The irradiated areas at low and medium power displayed individual hydrogen (deuterium) blisters which started overlapping at higher power levels. Calculation of the thermal diffusivity showed that a surface layer roughly 0.6 μm thick was heated during the pulse. Applying Bechtel's formula [J. Appl. Phys. 46, 1585 (1975)] for the temperature increase in the heated layer demonstrated that melting of the heated layer must have occurred during the pulse. The formation of hydrogen (deuterium) blisters is understandable in terms of the very high equilibrium vapor pressure of the hydrides near the melting temperature. A model for the formation of the blisters is presented.
    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 74 (1993), S. 4371-4374 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Implantation of hydrogen at 600 °C into GaAs at 8 keV and at high doses resulted in the formation of a two-layer structure. The topmost layer roughly extended in depth to the range of the protons and exhibited a high concentration of loops, hydrogen bubbles, decorated dislocations, and faults. Occasional microsplits on {110} were observed. The deeper layer contained pressurized hydrogen platelets on {111}. These results are critically compared with previous results obtained with cold implanted and subsequently annealed GaAs. The present observations are also discussed in relation to the theoretical treatment by d'Olieslaeger [J. Mater. Sci. 23, 2697 (1988)]. Estimates of the importance of arsine production are also presented.
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 2814-2818 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report a molecular dynamics investigation of the glass transition temperature in selenium at pressures ranging from 0 to 6 GPa as a function of the quench rate, Qr. For moderate pressures the specific volume of the glass depends strongly on the quench rate, whereas the specific enthalpy varies only little. We find for both volume and energy a linear dependence on the quench-rate-dependent glass transition temperature. The slopes of these curves reflect the different energy scales of void formation, inter- and intrachain interactions. The extrapolated glass transition temperatures for quench rates of order K/s agree with the experimental ones within 20%. Applying a pressure of 1 GPa the glass transition temperature is raised by 37 K. For the same Qr, the transition temperature Tg is much higher for simulations using fixed volume conditions (NVT ensemble) than for the ones using fixed pressure (NPT ensemble) when one compares results for equal pressure at T=0. © 2002 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 3236-3242 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present an investigation of the vibrational density of states (VDOS) of selenium calculated using two different methods. First we compute the VDOS from the velocity autocorrelation and study its evolution with the temperature. Secondly we compute it from the dynamical matrix. This latter method leads to imaginary frequencies for finite temperatures. In the literature these frequencies are called unstable and are related to the diffusion and/or the anharmonicity. We investigate the character of these frequencies, asking whether they are localized or extended, more acoustic or optic. We show that, below a temperature-dependent threshold frequency, they are similar to their real low-frequency counterparts. The temperature evolution of the number of these modes changes at the glass transition. © 2001 American Institute of Physics.
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  • 5
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mean velocity and Reynolds-stress profiles were measured in the incompressible turbulent boundary layer with zero pressure gradient on the aerodynamically smooth sidewall of the German–Dutch windtunnel. Data were taken at Reynolds numbers Reδ2, based on momentum thickness δ2 of 2×104, 4×104, and 6×104 by means of four different types of hot-wire probes (three-wire probes, X wire, and normal-wire probes). There are also measurements of skin friction and of spectra. The data compare well with the few available other measurements, and all profiles show independence of Reynolds number in the outer region of the boundary layer when plotted against y/Δ, where Δ is the Rotta–Clauser length. © 1995 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2187-2194 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: As a tool for screening large numbers of biological samples by means of amplification (e.g., Qβ or PCR) we have constructed a thermocycler that includes optionally a 96-channel or 960-channel glass fiber fluorimeter (combined with a cooled charge-coupled-device camera). We briefly describe the system integration of all components like liquid handling, thermostats, an x,y,z robot arm, and the glass fiber fluorimeter. The integrated glass fiber fluorimeter allows sensitive on-line measurements in 960 channels within 5 s. Two different screening procedures were carried out. In a first experiment PCR reactions were done in the presence of the known PCR inhibitor hematin and its suppressor transferrin. The system was used to titrate the suppressor with the inhibitor hematin in order to determine the maximum inhibitor concentration tolerated at a given suppressor concentration. We processed 96 PCR samples in parallel with 11 different concentration steps. In a second experiment the 960-channel glass fiber fluorimeter was used to monitor on line the amplification of the Qβ system in the presence or absence of an inhibitor (heparin). Since the doubling time of Qβ RNA variants is about 20 s, on-line detection is crucial for the experimental setup. The evolution of new RNA species adapted to high inhibitor concentrations could be proved by comparison of the fluorimetric signal and electrophoresis. © 1997 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 7587-7590 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on long-term creep experiments on dilute tantalum tritides at room temperature. Significant deviations of the recorded strain rates from isotropic swelling are found above approximately 30 MPa. We attribute this room-temperature creep to a stress-induced preferential dislocation loop punching by bubbles in crystallographic directions close the stress axis. Quantitative estimates show that this mechanism can indeed account for the observed creep rates.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 1116-1117 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The gas-handling system of a simple, inexpensive gas chromatograph is described suitable for the safe and fast purity analysis of tritium gas.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2206-2210 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Semi-insulating liquid-encapsulated Czochralski grown GaAs wafers were implanted at room temperature with protons at energies of 2, 4, and 30 keV at doses up to 1×1018 cm−2. Without using further annealing treatments the samples were inspected, also using cross-sectional techniques, by transmission electron microscopy. Surface amorphization of the bombarded GaAs was found. Excess hydrogen precipitates in the form of large bubbles in the amorphous layer. Nearly spherical hydrogen bubbles were detected in the crystalline layer below the amorphous zone. At 30 keV, pressurized bubble rafts, where a certain number of bubbles are located in the plane of a microcrack, were detected. The recent observations of similar bubble rafts by Neethling and Snyman [J. Mater. Sci. 23, 2697 (1988)] and the present rafts are discussed in the light of the theoretical treatment by d'Olieslaeger et al. [Philos. Mag. B 63, 1321 (1991)]. The bubble rafts have presumably been produced by the collapse of pressurized hydrogen-filled microcracks.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 729-731 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The expansion of the tritide TaT0.37 at 10 K was measured using strain gauge dilatometry. The volume increase as expressed by ΔvHe/Ω = 0.26 may be attributed to a random distribution of single interstitial 3He atoms. To the knowledge of the authors this is the first direct measurement of the volume requirement of interstitial 3He in a metal. For purposes of comparison swelling of the same sample was also measured at room temperature. Here, however, 3He atoms cluster and form bubbles leading to ΔvHe/Ω ≈ 0.38, which represents the volume requirement of 3He in a bubble. Conversion of this value to a pressure normalized to the shear modulus μ yields in p/μ=0.22 which is in excellent agreement with other recent experimental and theoretical work on the pressure required for dislocation loop punching.
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