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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 52 (1997), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Thirteen patients were monitored for nocturnal body position (supine vs. side) and arterial oxygen saturation pre-operatively and on the second postoperative night after major abdominal surgery. The number of positional changes were significantly decreased after operation (p 〈 0.05) with a trend towards more time spent in the supine position (p = 0.1). Individual mean arterial oxygen saturation decreased postoperatively (p 〈 0.05) but without a difference between the supine and side positions (p = 0.9). Pre-operatively, episodic desaturations were significantly more frequent in the supine position than on the side (p 〈 0.05) but not postoperatively. Pain was the most frequent reason for decreased nocturnal movements.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4107-4117 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a detailed study of the recently discovered modulation at frequencies of hundreds of MHz of an electron beam produced by a plasma cathode. The plasma cathode consists of a ferroelectric disk sample [BaTiO3 or Pb(Zr, Ti)O3] that is placed in a cylindrical metal box having an output window covered by a grid. The plasma is prepared by an incomplete discharge that was ignited by a few kV driving pulse applied across the ferroelectric disk. It was shown that the current modulation appears only when the driving pulse is applied to the front gridded electrode of the ferroelectric sample and the solid rear electrode is grounded. The modulation spectrum is quite narrow (≤3%), with harmonics at frequencies up to a few GHz. The basic frequency of modulation was found to be dependent on the length of the feed cable to the sample. Investigation of the plasma and the beam modulation properties and their dependence on the experimental parameters is presented. The results indicate the formation of a plasma at the vicinity of the front electrode of the ferroelectric sample during the modulation. The results are discussed within the frame of electrons oscillating in the potential well created by the positively charged plasma having feedback coupling with the input cable. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1202-1211 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of negative ions on the collisionless electrostatic ion cyclotron instability (EICI) is investigated analytically and numerically. The singly ionized negative ion species has mass greater than or equal to the mass of the singly ionized positive ion species. Standard linear Vlasov theory is used to estimate the critical electron drift velocity. It is shown that the critical drifts for the excitation of both the light and heavy ion EIC modes decrease as the relative density of negative ions increases. Our results are compared with available negative ion plasma experiments concerning the EICI, and possible applications to experiments in the ionosphere are briefly discussed. © 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)
    Physics of Plasmas 5 (1998), S. 3786-3788 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of longitudinal boundaries on electrostatic instabilities driven by an ion beam in a dusty plasma is considered. In analogy with instabilities in electron-ion plasma diodes, in this case both the low-frequency ion-space-charge waves and ion-dust waves can be unstable. The growth rates and ion current thresholds are estimated. The present investigation should help to design a large scale dusty plasma device to study these low-frequency analogs of instabilities in bounded beam-plasma systems. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 644-649 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low frequency drift instabilities are investigated in a dusty magnetized plasma with negatively charged grains in which locally there is an electron density gradient which is opposite in sign to a dust density gradient. Frequencies less than the ion gyrofrequency but much larger than the dust gyrofrequency are considered. Two different equilibria are considered that are characterized by ρd≥Lnd, where ρd is the dust gyroradius and Lnd is the dust density scale length. Instabilities analogous to the universal instability and to the lower-hybrid-drift instability (with the lower-hybrid frequency in this case associated with the dust) are investigated. Possible applications to dusty space plasmas such as the spoke regions of Saturn's B-ring are discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The issue of lateral stress measurements, with piezoresistance gauges, is discussed by Feng et al. [J. Appl. Phys. 82, 2845 (1997)] and Feng and Gupta [J. Appl. Phys. 83, 747 (1998)] using 2D numerical simulations. The purpose of this Comment is to highlight the difficulties with these simulations and to emphasize some of the results obtained in these articles, which strongly support our analytical approach to the subject. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 4612-4617 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In situ microscopic and spectroscopic studies of samples allow us to understand the mechanisms and measure kinetics of phase transformations in materials. We use a light microscope and a Raman microspectrometer to study phase transformations induced by contact loading. Many interesting phenomena occur in materials during indentation that can only be analyzed during indentation, in situ. By analyzing what occurs to ceramics and semiconductors in situ we can gain valuable insight into the mechanisms and kinetics of phase transformation. A microindentation device has been designed and fabricated to achieve these objectives. The microindentation device can provide the means to study pressure-induced phase transformations in real time. The basic design of the device is adaptable to several configurations, so that the device may be used in a wide variety of applications. The device consists of a piezoelectric actuator (piezoelectric translator), load cell, linear microscrew stage, translation stage containing the specimen mount and specimen holder, and diamond-tip indenter. For the first time, an indentation tester has been coupled with a Raman microspectrometer to conduct in situ studies of pressure-induced phase transformations. This article describes the design, operation, and experimentation of a microindentation device for the in situ analysis of pressure-induced phase transformations in materials. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2550-2553 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present the first results of use of the high power x-rays from an insertion device beamline at the Advanced Photon Source for welding. X-rays with energies between 3 and 200 keV and power densities greater than 10 000 W/cm2 can penetrate deeply into most materials and thus can be used as volumetric heating sources. In this article we show results of bead-on-plate welds of a 3.3-mm-thick Al/Al2O3 metal-matrix composite and discuss results obtained for other materials. The potential of x-rays for welding is also discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 2251-2256 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Conversion of an electron microprobe for use as an x-ray microtomograph is described. Only minor modifications are required, indeed several of the utilities of the microprobe can be used to ensure high resolution radiography and tomography. System performance was evaluated by analysis of glass fiber reinforced polymer composites and of a carbonate reservoir rock. Individual glass fibers of 10 and 20 μm diameter are clearly visible in the former. In the latter, comparison with scanning electron micrographs shows reliable reconstruction of external morphology. In addition, internal pore structure can be studied a posteriori using the tomography data. Spatial resolutions in radiography of better than 3 μm and in tomography of 10 μm have been demonstrated. Further improvements to the detector system and increased data handling capacity are possible to achieve 1 μm resolution tomographic images. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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