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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1489-1496 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The local environment of Cm3+ in a borosilicate glass has been probed by a combination of laser spectroscopy, structural modeling, and extended x-ray absorption fine structure (EXAFS) spectroscopy. The Stark splitting for the Cm f–f state transitions is significantly larger than the inhomogeneous line broadening that results from the disordered environment. As a result, the Cm optical spectrum can be fit using an effective operator Hamiltonian to obtain a set of crystal-field parameters. The fitting procedure, which requires the use of a descent-in-symmetry approach, provides a set of parameters for a best fit within tetragonal symmetry. These parameters are then linked to the local environment of Cm through exchange-charge modeling (ECM) of crystal field interactions. Cm in our borosilicate glass is best modeled with six oxygen ions with approximately tetragonal symmetry, and at an average distance of 2.31 (3) Å. The results of crystal-field modeling are supported by EXAFS results. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 96 (1989), S. 0 
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. Forty primigravid womcn aged 15–45 years were randomly allocated to receive either an intravaginal pessary of 3 mg prostaglandin E, (PGE2) or an intracervical 5-mm laminaria tent (LT) 12–16 h before termination of pregnancy at 6–14 weeks gestation. The degree of dilatation of the cervix a t operation and its resistance t o further dilatation during the procedure were assessed by a ‘blind’ operator. Laminaria tents were more effective in achieving dilatation and softening of the cervix than were PGE2 pessaries and in 40% of women no further dilatation was necessary. There were no associated side-effects or complications. A cervical tear occurred in two of 20 patients treated with PGE2 pessaries and all 20 required further dilatation of the cervix. Laminaria tents provide a simple. safe, acceptable and effective means of ‘ripening’ the cervix prior to termination of early pregnancy.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 96 (1989), S. 0 
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 379-382 
    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 x radiation in the photon energy range below 41 eV from a synchrotron source is reported. For constant incident x-radiation exposure levels of 120 mJ/cm2 with both monochromatic and broadband radiation, the number of defects generated in the monitoring devices was at or below the detection limit of the equipment. This is in sharp contrast with the results obtained at photon energies above 300 eV reported earlier [C. K. Williams, A. Reisman, P. K. Bhattacharya, and W. Ng, J. Appl. Phys. 64, 1145 (1988)] in which a large number of each of the three defects mentioned above were generated. The lack of damage indicates that the problems associated with x-ray-induced insulator damage due to x-ray lithography may be solved by tailoring the photon energy, provided suitable mask and photoresist materials can be developed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2014-2016 
    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
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4723-4729 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A modified version of the atomic force microscope is introduced that enables a precise measurement of the force between a tip and a sample over a tip-sample distance range of 30–150 A(ring). As an application, the force signal is used to maintain the tip-sample spacing constant, so that profiling can be achieved with a spatial resolution of 50 A(ring). A second scheme allows the simultaneous measurement of force and surface profile; this scheme has been used to obtain material-dependent information from surfaces of electronic materials.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The principal factors that limit intensities of short-lived radioactive ion beams produced by the isotope separator on-line technique are time delays due to diffusion of radioactive species from solid or liquid target materials and their effusive-flow transport to the ion source. Although diffusion times can be reduced by proper design of short diffusion length, highly refractory targets, effusive-flow times are more difficult to assess. After diffusion from the target material, the species must travel through the target material and vapor transport system to the ion source. The time required for effusive-flow transport to the ion source depends on the conduction path, chemical reactions between the species and target material and materials of construction, as well as the physical size and geometry of the transport system. We have developed a fast valve (0.1 ms closing time) for introducing gaseous or vapor-state species into the target/vapor transport/ion source/system that permits measurement of effusive-flow times for any gaseous or vaporous species (chemically active or chemically inactive) through any vapor transport system, independent of size and geometry. Characteristic times are determined from the exponential decay of the momentum analyzed ion beam intensity for the species during effusive flow through the vapor transport system under evaluation. This article describes the effusive-flow apparatus and presents characteristic time spectra and characteristic effusive-flow time data for noble gases flowing through a serial-flow target reservoir system. © 2002 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)
    Journal of Applied Physics 66 (1989), S. 5801-5804 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper, the effects on insulated gate field-effect transistor device characteristics due to implantation of silicon into the gate insulator have been studied. Contrary to what one might have expected in an oxygen-deficient insulator, the primary defects generated, as detected by optically assisted injection of electrons into the gate insulators of damaged devices, are large quantities, as much as 1.3×1012 cm−2, of neutral electron traps (NET). Secondary types of defects found appear to be fixed negative charge, approximately 2.3×1011 cm−2 in the worse case, and a smaller amount of fixed positive charge (FPC), approximately 1.7×1011 cm−2 in the worse case. It was found that none of these defects could be removed by employing conventional postmetal annealing conditions in forming gas (10% H2, 90% N2) at 400 °C for up to 60 min. The defects created by ion implantation appear to be quite different from those created by x-ray or electron irradiation, where large quantities of FPC and NET are generated which can be annealed in a similar postmetal annealing cycles.
    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 64 (1988), S. 5644-5646 
    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
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