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  • 1
    Digitale Medien
    Digitale Medien
    Modeling ferroelectric capacitor switching with asymmetric nonperiodic input signals and arbitrary initial conditions (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2849-2860 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The switching behavior of ferroelectric capacitors experiencing arbitrary time-dependent electric fields and arbitrary initial conditions is investigated both theoretically and experimentally. A general approach for modeling incomplete dipole switching in ferroelectric capacitors is used to derive equations describing the electrical behavior of a simple characterization circuit with arbitrary initial conditions and arbitrary time-dependent applied voltages. The equations include four experimentally determined parameters: the remanent and spontaneous polarizations, the coercive field, and the ferroelectric dielectric constant. Once these model parameters are determined from a single high-frequency sinusoidal hysteresis loop, model predictions are made with no adjustable parameters. The circuit behavior for both sinusoidal and trapezoidal input signals is computed, including asymmetric and nonperiodic signals as well as several different initial conditions. The accuracy of the model predictions is quantitatively verified with experimental data. The approach is also utilized to model the switching behavior of a ferroelectric capacitor containing a sheet of space charge. It is found that hysteresis loop distortions resulting from ionizing radiation resemble those caused by a sheet of space charge. This quantitative modeling capability facilitates the optimization of the design of ferroelectric memory circuits by minimizing the amount of required electrical testing and characterization. It can also be used to facilitate the identification and understanding of degradation mechanisms occurring in ferroelectric thin films.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349348
    Standort Signatur Einschränkungen Verfügbarkeit
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    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    Device modeling of ferroelectric capacitors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6463-6471 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A physically based methodology is developed for modeling the behavior of electrical circuits containing nonideal ferroelectric capacitors. The methodology is illustrated by modeling the discrete ferroelectric capacitor as a stacked dielectric structure, with switching ferroelectric and nonswitching dielectric layers. Electrical properties of a modified Sawyer–Tower circuit are predicted by the model. Distortions of hysteresis loops due to resistive losses as a function of input signal frequency are accurately predicted by the model. The effect of signal amplitude variations predicted by the model also agree with experimental data. The model is used as a diagnostic tool to demonstrate that cycling degradation, at least for the sample investigated, cannot be modeled by the formation of nonswitching dielectric layer(s) or the formation of conductive regions near the electrodes, but is consistent with a spatially uniform reduction in the number of switching dipoles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346845
    Standort Signatur Einschränkungen Verfügbarkeit
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    Artikel (Nationallizenzen)
    Volltext
  • 3
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    Amelioration of salt-induced vascular dysfunction in mesenteric arteries of Dahl salt-sensitive rats by missense mutation of extracellular superoxide dismutase (2014)
    The American Physiological Society (APS)
    Details
    Publikationsdatum: 2014-02-03
    Beschreibung: Superoxide dismutase (SOD) enzymes, including extracellular SOD (ecSOD), are important for scavenging superoxide radicals (O 2 ·– ) in the vasculature. This study investigated vascular control in rats [SS-Sod 3 m1Mcwi (ecSOD E124D )] with a missense mutation that alters a single amino acid (E124D) of ecSOD that produces a malfunctioning protein in the salt-sensitive (Dahl SS) genetic background. We hypothesized that this mutation would exacerbate endothelial dysfunction due to elevated vascular O 2 ·– levels in SS, even under normal salt (NS; 0.4% NaCl) conditions. Aortas of ecSOD E124D rats fed standard rodent chow showed enhanced sensitivity to phenylephrine and reduced relaxation to acetylcholine (ACh) vs. SS rats. Endothelium-dependent dilation to ACh was unaffected by the mutation in small mesenteric arteries of ecSOD E124D rats fed NS diet, and mesenteric arteries of ecSOD E124D rats were protected from endothelial dysfunction during short-term (3–5 days) high-salt (HS; 4% NaCl) diet. ACh-induced dilation of mesenteric arteries of ecSOD E124D rats and SS rats fed NS diet was inhibited by N G -nitro- l -arginine methyl ester and/or by H 2 O 2 scavenging with polyethylene glycol-catalase at higher concentrations of ACh. Total SOD activity was significantly higher in ecSOD E124D rats vs. SS controls fed HS diet, most likely reflecting a compensatory response to loss of a functional ecSOD isoform. These findings indicate that, contrary to its effect in the aorta, this missense mutation of ecSOD in the SS rat genome has no negative effect on vascular function in small resistance arteries, but instead protects against salt-induced endothelial dysfunction, most likely via compensatory mechanisms involving an increase in total SOD activity.
    Print ISSN: 0363-6135
    Digitale ISSN: 1522-1539
    Thema: Medizin
    Publiziert von The American Physiological Society (APS)
    Standort Signatur Einschränkungen Verfügbarkeit
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