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  • 1
    Electronic Resource
    Electronic Resource
    Homogeneous fine-grained Mn-Zn ferrites by sintering of colloidally precipitated powders (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5644-5646 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Colloidally precipitated powders were investigated for the synthesis of chemically homogeneous, uniformly fine-grained Mn-Zn ferrites. The process consists of the atomized dispersion of an aqueous solution of Mn, Zn, and Fe nitrates in an agitated solution of 1M ammonium hydroxide. This results in the coprecipitation of a fine colloidal mixture of Mn, Zn, and Fe hydroxides. The mixture is filtered, washed, dried, and heat treated to form agglomerated powders. The agglomerated powders are reduced in size and sintered after cold compaction. Sintering was performed at temperatures of 1100–1250 °C with oxygen partial pressures from 0 to 500 ppm in argon. Magnetic permeability and disaccommodation were measured on selected samples after an initial 0.5–5.0 Oe decaying sinusoidal field was applied to the specimens to excite time varying permeability. The permeability variation depended strongly on the magnitude of this excitation; both disaccommodation and accommodation were observed. The duplex structure typically associated with severe discontinuous grain growth was not observed for either of the two compositions examined over the range of sintering temperatures studied. Low levels of porosity were seen in samples sintered at 1150 and 1250 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342521
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  • 2
    Electronic Resource
    Electronic Resource
    Chemically homogeneous fine-grained Mn-Zn ferrites by spray drying (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5665-5665 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chemically and structurally uniform Mn-Zn ferrites have been produced using powders synthesized by the spray decomposition of mixed, aqueous Mn, Fe, and Zn nitrate solutions. The particle size of the as-formed powder depended strongly on the metal ion concentration in solution; higher concentrations produced larger sizes. The as-formed particles are spherical, internally hollow, and consisted mostly of Fe2O3. A 900 °C, 6-h argon treatment removed the internal void space and converted the particles mostly to the ferrite spinel phase. Sintering of compacts from heat-treated powders produced microstructures superior to those from as-formed powders. Uniform, fine-grained materials, with a densification level comparable to that of commercial sintered ferrite, have been produced at the very low sintering temperature of 1100 °C. Preliminary work indicates that a higher initial permeability is obtained when a higher sintering temperature was used and the level of its disaccommodation depended on the oxygen partial pressure present during sintering. Both "accommodation'' and disaccommodation were observed in the permeability; their magnitudes depended on the peak value of the applied excitation field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342264
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  • 3
    Electronic Resource
    Electronic Resource
    Defect generation in silicon dioxide from soft x-ray synchrotron radiation (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1145-1151 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Generation of fixed positive charge, neutral electron traps, and fixed negative charge in SiO2 due to exposure to monochromatic x-ray radiation in the photon energy range from 300 to 1000 eV in a synchrotron source is reported upon. At a constant exposure level of 2×107 rads, the number of defects generated is approximately independent of x-ray photon energy. The generated defects, independent of x-ray radiation energy, show normal post-metal annealing characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341876
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic anisotropy energy in single crystal Y1.8Er0.2Fe14B (invited) (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3139-3139 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: There has been considerable interest in tetragonal R2Fe14B compounds as a basis for a new class of permanent magnet materials because of the unusually large energy products they exhibit at room temperature for certain rare-earth substitutions. The origin of the high-energy products is directly related to the large saturation magnetization and magnetic anisotropy energy. The magnetocrystalline anisotropy energy is believed to be directly related to an interaction between the 4f-electrons and the crystal field: however, to date few if any direct comparisons have been made between the experimental magnetic anisotropy and crystal field theory. The reason being that the large anisotropy energy makes it very difficult to use conventional torque magnetometry techniques to determine the angular dependence of the magnetic free energy, particularly at low temperatures where the higher-order terms become important. In this investigation we determine the angular dependence of the magnetic free energy as a function of temperature for Y1.8Er0.2Fe14B using high field (6 T) torque magnetometry techniques and make a direct comparison of the free energy with the energy calculated using a model based on crystal field theory. Y1.8Er0.2Fe14B was chosen because the Fe and Er sublattice anisotropy energies nearly cancel at low temperatures making it possible to measure anisotropy. Excellent agreement was obtained between the model and experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340867
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement of in-plane magnetization by force microscopy (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1446-1448 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present data which show that the magnetic force microscope is capable of detecting the component of the magnetic field parallel to the surface of a sample under study. Images of bits in a Co-alloy thin-film disk and of laser-written bits in a TbFe film were taken with a magnetized tip tilted at 45° with respect to the surface normal. In both cases the asymmetric part of the image of a domain is interpreted in terms of gradients in the in-plane component of the magnetic field. The bits written in the Co-alloy disk were decorated with small magnetized particles, allowing identification of the domain boundaries and the asymmetric component of the force microscope image due to in-plane magnetization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99964
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  • 6
    Electronic Resource
    Electronic Resource
    Noise reduction technique for scanning tunneling microscopy (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1503-1505 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Noise stemming from mechanical vibration, electronic noise, or low frequency (1/f power spectrum) inherent in the tunneling process, often limits the resolution, speed, or range of application of scanning tunneling microscopy (STM). We demonstrate a technique for minimizing the effect of these noise sources on the STM image. In our method, the tunneling tip is vibrated parallel to the sample surface at a frequency f0, above that of the feedback response frequency. Two signals are obtained simultaneously: the conventional topography, and a differential image corresponding to the amplitude of current modulation at f0. The resultant ac signal can be simply related to the normal STM topographic image, with significant improvement in the signal-to-noise ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99940
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  • 7
    Electronic Resource
    Electronic Resource
    Pulse radiolysis studies of berkelium(III): preparation and identification of berkelium(II) in aqueous perchlorate media (1988)
    s.l. : American Chemical Society
    Inorganic chemistry 27 (1988), S. 597-598 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00277a005
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  • 8
    Electronic Resource
    Electronic Resource
    Juvenile polyposis–a precancerous condition (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Histopathology 13 (1988), S. 0 
    Details
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Clinical and pathological findings in 87 patients with juvenile polyposis have been reviewed; 1032 polyps were available from 80 of these patients; 840 were typical spherical juvenile polyps whereas 169 differed in being multilobulated or showing a villous configuration; 79 (46.7%) of the latter contained foci of epithelial dysplasia whereas only 76 (9.0%) of the typical juvenile polyps were dysplastic. The series also included 21 adenomas and two hyperplastic (metaplastic) polyps. The demonstration of dysplasia provides a histogenetic mechanism for the evolution of colorectal cancer from hamartomatous polyps; 18 juvenile polyposis patients have developed colorectal cancer at a mean age of 34 years (range 15–59). The clinical outcome was generally poor. No clinical or pathological distinction could be made between polyposis patients with and without colorectal cancer. Thus, the development of cancer in juvenile polyposis appears to be a random event. A working definition of juvenile polyposis is provided: (1) more than five juvenile polyps of the colorectum; and/or (2) juvenile polyps throughout the gastrointestinal tract; and/or (3) any number of juvenile polyps with a family history of juvenile polyposis. It is suggested that the condition should be treated as seriously as familial adenomatous polyposis except that regular colonoscopic surveillance may obviate the need for prophylactic colectomy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2559.1988.tb02093.x
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  • 9
    Electronic Resource
    Electronic Resource
    Ayer's Influence on the Lexicographers (1988)
    Cambridge : Cambridge University Press
    Philosophy 63 (1988), S. 536-537 
    Details
    ISSN: 0031-8191
    Source: Cambridge Journals Digital Archives
    Topics: Philosophy
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S0031819100043862
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  • 10
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    HARNDEN, The Parish Registers of Herefordshire (Book Review) (1988)
    London : Periodicals Archive Online (PAO)
    Archives. 18:80 (1988:Oct.) 230 
    Details
    ISSN: 0003-9535
    Topics: Information Science and Librarianship
    Notes: REVIEWS
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:0013-1988-018-80-000015
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