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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 612-614 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-dependent two-magnon scattering was previously proposed as a mechanism to explain the large magnitude of the ferrimagnetic resonance (FMR) linewidth of barium ferrite as a function of frequency. In the present work, it is shown that a quantum mechanical mechanism like the Kasuya–Le Craw process (KL)1 but with the phonon excitation replaced by a single-particle excitation of a trigonal site iron ion, which moves in an anharmonic potential well, gives a linewidth contribution of less than a tenth of an Oersted and proportional to the frequency, as in the KL mechanism. We conclude, based on this work and our previous work on the KL mechanism, that neither of these mechanisms can explain the observed FMR linewidths in barium ferrite at any frequency.
    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 69 (1991), S. 6183-6185 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two microscopic models have been proposed to explain the large intrinsic linewidth of barium ferrite. The first is a two-magnon scattering process due to an intrinsic disorder associated with the unique trigonal bipyramidal site in the crystal. [E. Tsantes and L. M. Silber, J. Appl. Phys. 63, 3350 (1988)]. The second is the Kasuya–LeCraw relaxation process [S. P. Marshall, J. B. Sokoloff, and C. Vittoria, IEEE Trans. Magn. MAG-25, 3491 (1989)]. Both of these processes involve modulation of the single-ion anisotropy. Analytical calculations using simplified models for the acoustic magnon and phonon spectra fail to account for the linewidths characteristic of barium ferrite. In order to understand both of these relaxation processes as they relate to barium ferrite, we have calculated the full phonon spectrum for this crystal based on the rigid-ion model. The calculated reflectivity compares well with the infrared reflectivity data that we have taken. Using phonon modes that we have calculated and the magnon modes calculated previously [S. P. Marshall and J. B. Sokoloff, J. Appl. Phys. 67, 2017 (1990)], we have calculated the ferromagnetic resonance linewidth on the basis of the Kasuya–LeCraw mechanism and two-magnon scattering by fluctuating 2b-site ions. We find that the trigonal-site disorder scattering mechanism is able to account for the observed magnitude of the linewidth.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2659-2665 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The mathematical analysis of a device for measurement of the conductivity of cylindrical samples is given. This analysis involves calculation of the geometrical factor by evaluating Fourier series of circular and cylindrical harmonics. The results derived are applicable to a wide range of cylindrical samples shapes, including the limiting cases of thin disks and infinitely long rods. Full consideration is given to the finite size of current-bearing electrodes and deviations from two-dimensional current distribution that arise when the electrode width is less than the length of the cylinder. The range of sample geometries in which these deviations are significant is determined.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Routine Arrhythmia Inductions in Patients with ICDs. Introduction: The value of ventricular arrhythmia inductions as part of routine implantable cardioverter defibrillator (ICD) follow-up in new-generation pectoral ICDs is unknown Methods and Results: We performed a retrospective analysis of a prospectively collected database analyzing data from 153 patients with pectoral ICDs who had routine arrhythmia inductions at predismissal, and 3 months and 1 year after implantation. Routine predismissal ventricular fibrillation (VF) induction yielded important findings in 8.8% of patients, all in patients with implantation defibrillation threshold (DFT) ≥ 15 J or with concomitant pacemaker systems. At 3 months and 1 year, routine VF induction yielded important findings in 5.9% and 3.8% of tested patients, respectively, all in patients who had high DFT on prior testing. Ventricular tachycardia (VT) induction at predismissal, and 3 months and 1 year after implantation resulted in programming change in 37.4%, 28.1%, and 13.8% of tested patients, almost all in patients with inducible VT on baseline electrophysiologic study and clinical episodes since implantation. Conclusion: Although helpful in identifying potentially important ICD malfunctions, routine arrhythmia inductions during the first year after ICD implantation may not be necessary in all cases. VF inductions have a low yield in patients with previously low DFTs who lack concomitant pacemakers. VT inductions have a low yield in patients without baseline Inducible VT and in the absence of clinical events. Definite recommendations regarding patient selection must await larger prospective studies as well as consensus in the medical community about what comprises an acceptable risk justifying avoidance of the costs and inconveniences of routine arrhythmia inductions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 11 (2000), S. 0 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: ICD Therapy. Although it has become clear that implantable cardioverter defibrillators (ICDs) are effective, important challenges remain for the physician. Due to the limitations of available risk stratification tools, patient selection for primary sudden death prevention remains controversial in many populations. Additionally, the proliferation of device choices has led to challenges in matching the appropriate device to the individual patient: device size is balanced against longevity: the advantages of dual chamber systems is weighed against their increased complexity; physician and patient preferences in device implant site are constrained by site-dependent effects on defibrillation effectiveness and lead failure rates; and special consideration must be given to the patient with a preexisting pacemaker. After ICD placement, determination of appropriate follow-up frequency and methodology to assess device function must be considered. This article will review patient selection, device implant site selection, device-device interactions, single versus dual chamber ICD selection, and follow-up.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 693 (1993), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of chemical & engineering data 17 (1972), S. 412-415 
    ISSN: 1520-5134
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5534-5534 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to determine whether barium ferrite will be suitable for microwave and millimeter wave device applications, it is essential to calculate the intrinsic ferrimagnetic resonance linewidth for perfect single crystals of this compound. The two mechanisms believed to be responsible for the intrinsic linewidth of barium ferrite, the Kasuya–LeCraw1 two-magnon one-phonon process and the two-magnon scattering caused by the time fluctuations of 2b site (trigonal symmetry site) ions,2 require knowledge of the magnon dispersion relations throughout the Brillouin zone, and not just near the zone center. We describe the calculations of the spin-wave spectrum for barium ferrite, which is a highly complex exchange-coupled hexagonal ferrimagnetic compound, using a method similar to that used by Harris for YIG.3 The exchange integrals are calculated by fitting the Weiss molecular field approximation to the sublattice magnetizations while including single-ion anisotropy. The value for the space-averaged stiffness constant as calculated from the acoustic mode of the spin-wave spectrum is 2.5×10−9 Oe cm4.
    Type of Medium: Electronic Resource
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