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  • Articles  (14)
  • Dielectric properties
  • Springer  (13)
  • American Chemical Society  (1)
  • American Institute of Physics (AIP)
  • 1
    Electronic Resource
    Electronic Resource
    Excess permittivities, excess refractive indices and NMR spectroscopic studies of solutions of 1,2-dibromoethane in aromatic hydrocarbons (1991)
    Springer
    Journal of solution chemistry 20 (1991), S. 257-269 
    Details
    ISSN: 1572-8927
    Keywords: Dielectric properties ; refractive indices ; permittivities ; dipole moments ; excess functions ; binary mixtures ; NMR spectroscopic studies ; equilibrium constants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Excess permittivities and excess refractive indices data for solutions of 1,2-dibromoethane (DBE) in benzene, toluene, o-xylene, m-xylene and p-xylene over the whole composition range at 25°C have been obtained. The analysis of excess dielectric properties suggests the existence of weak electron donor-acceptor type interactions between 1,2-dibromoethane (DBE) and aromatic hydrocarbons. The equilibrium constants and the dipole moments of the DBE-aromatic hydrocarbon complexes in solutions have been evaluated. Strneght of interaction increases with electron donating power of aromatic hydrocarbons. NMR spectroscopic studies made on these binary liquid systems also provide evidence for the existence of weak electron donor-acceptor type specific interactions between DBE and aromatic hydrocarbons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00649534
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of fast neutrons on dielectric properties of pure and gelatin doped-poly (vinyl alcohol) films (2000)
    Springer
    Journal of polymer research 7 (2000), S. 149-153 
    Details
    ISSN: 1572-8935
    Keywords: Fast neutrons ; Dielectric properties ; Poly(vinyl alcohol) ; Electric dipole moment ; Activation energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Cast thin films of pure and gelatin doped poly(vinyl alcohol) (PVA) with concentrations of 2, 5, 7, 10, and 15 wt% were prepared and subjected to fast neutron fluences in the range of 105–108 n/cm2. The dielectric constant (ε′), dielectric loss tangent (tanδ) and a.c. electrical conductivity (σa,c) were investigated as a function of field frequency and temperature for all samples before and after irradiation. A clear glass transition peak was observed in ε′(T) and tanδ(T) curves. The irregular shift in the position of the glass transition temperature (Tg) in tanδ spectra with increasing neutron fluence can be attributed to either degradation or the predominance of the crosslinking process. The electric dipole moment and activation energy were calculated for pure and gelatin doped PVA samples before and after neutron irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10965-006-0114-z
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  • 3
    Electronic Resource
    Electronic Resource
    Enhanced dielectric properties of modified Ta2O5 thin films (1999)
    Springer
    Materials research innovations 2 (1999), S. 299-302 
    Details
    ISSN: 1433-075X
    Keywords: Key words Tantalum oxide ; Thin film ; Dielectric properties ; Insulating properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Tantalum oxide (Ta2O5) is a promising high dielectric constant material for the DRAM applications because of its ease of integration compared to other complex oxide dielectrics. The dielectric constant and thermal stability characteristics of bulk Ta2O5 samples were reported to enhance significantly through small substitutions of Al2O3. However, this improvement in the dielectric constant of (1-x)Ta2O5-xAl2O3 is not clearly understood. The present research attempts to explain the higher dielectric constant of (1-x)Ta2O5-xAl2O3 by fabricating thin films with enhanced dielectric properties. A higher dielectric constant of 42.8 was obtained for 0.9Ta2O5–0.1Al2O3 thin films compared to that reported for pure Ta2O5 (25–30). This increase was shown to be closely related to a-axis orientation. Pure Ta2O5 thin films with similar a-axis orientation also exhibited a high dielectric constant of 51.7, thus confirming the orientation effect. The leakage current properties and the reliability characteristics were also found to be improved with Al2O3 addition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100190050101
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  • 4
    Electronic Resource
    Electronic Resource
    Computation of the dielectric tensor of a magnetized maxwellian plasma in the case of large Larmor radius effects (1991)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 881-890 
    Details
    ISSN: 0392-6737
    Keywords: Dielectric properties ; Electromagnetic wave propagation in plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary It is shown how to deduce an asymptotic form of the Gordeev dispersion function of a Maxwellian plasma in a magnetic field, in the limit in which the Larmor radius parameter approaches infinity on the complex plane. This asymptotic form is necessary in the numerical computation of the elements of the plasma dielectric tensor in all physical circumstances characterized by large Larmor radius effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457175
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of sodium concentration on changes of membrane capacitance associated with the electrogenic ion transport by the Na,K-ATPase (1998)
    Springer
    European biophysics journal 27 (1998), S. 605-617 
    Details
    ISSN: 1432-1017
    Keywords: Key words Na ; K-ATPase ; Membrane capacitance ; Dielectric properties ; Ion movement ; Electrogenicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Electrogenic ion transport by the Na,K-ATPase was investigated in a model system of protein-containing membrane fragments adsorbed to a lipid bilayer. Transient Na+ currents were induced by photorelease of ATP from inactive caged ATP. This process was accompanied by a capacitance change of the membrane system. Two methods were applied to measure capacitances in the frequency range 1 to 6000 Hz. The frequency dependent capacitance increment, ΔC, was of sigmoidal shape and decreased at high frequencies. The midpoint frequency, f 0, depended on the ionic strength of the buffer. At 150 mm NaCl f 0 was about 200 Hz and decreased to 12 Hz at high ionic strength (1 M). At low frequencies (f≪f 0) the capacitance increment became frequency independent. It was, however, dependent on Na+ concentration and on the membrane potential which was generated by the charge transferred. A simple model is presented to analyze the experimental data quantitatively as a function of two parameters, the capacitance of the adsorbed membrane fragments, C P, and the potential of maximum capacitance increment, ψ 0. Below 5 mm Na+ a negative capacitance change was detected which may be assigned to electrogenic Na+ binding to cytoplasmic sites. It could be shown that the results obtained by experiments with the presented alternating current method contain the information which is determined by current-relaxation experiments with cell membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050172
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  • 6
    Electronic Resource
    Electronic Resource
    Microwave Spectroscopy of Myocardial Ischemia and Infarction. 2. Biophysical Reconstruction (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 55-60 
    Details
    ISSN: 1573-9686
    Keywords: Myocardial ischemia ; Infarction ; Dielectric properties ; Resistance ; Water content ; Biophysical reconstruction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The proposed dielectrical relaxation model of the myocardium in the microwave spectrum has been verified both on test solutions and on normal canine myocardium. Furthermore, the model was utilized to reconstruct the changes in tissue properties (including myocardial bulk resistance and water content) following myocardial acute ischemia and chronic infarction. It was shown that the reconstructed myocardial resistance and water content correlate dynamically with the process of the development of acute myocardial ischemic injury. In chronic cases the reconstructed resistance and water content of infarcted myocardium are significantly different from that of normal myocardium: the resistance is lower and water content is higher than in normal myocardium. © 2000 Biomedical Engineering Society. PAC00: 8764-t, 8719Xx
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.254
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of electrical mixture rules for composites (1986)
    Springer
    Colloid & polymer science 264 (1986), S. 1030-1050 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric properties ; heterogeneous mixtures ; composite permittivity ; mixture rules ; ellipsoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Firstly the basic theoretical methods of calculating the dielectric properties of heterogeneous mixtures are discussed. These are the mean field and effective medium theories and integral methods. Formulae are presented for systems containing parallel oriented ellipsoids and for randomly oriented ellipsoidal systems. Theoretical formulae are divided into two sub-groups: symmetric equations for statistical mixtures and asymmetric equations for matrix-inclusion type composites. In the former case only the relative amount of the components is important, in the second case phase inversion results in a change of the dielectric properties. Formulae are compared numerically using spherical and spheroidal systems with sharply different components (permittivity ratio is 1 ∶ 100). In the case of asymmetric formulae the effect of phase inversion is studied as well. Percolation behaviour predicted by the equations is demonstrated and discussed. Functional shapes are compared in relation to the theoretical differences. Finally, experimental data are compared with the theoretical results, advantages and drawbacks of the various formulae are discussed. For spherical systems the simplest mean field formula yields somewhat worse values than effective medium or integral equations. The Looyenga equation does not work very well if the permittivity difference is high. For nonspherical systems the fit is better in general, even the simplest formula works satisfactorily. The shape independence predicted by the Looyenga theory for randomly oriented ellipsoids is in conflict with experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410321
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  • 8
    Electronic Resource
    Electronic Resource
    Analysis of dielectric observations of KCl-charged poly(methyl methacrylate) microcapsules using a two-component model consisting of KCl-permeable and KCl-impermeable capsules (1987)
    Springer
    Colloid & polymer science 265 (1987), S. 1054-1060 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric properties ; microcapsule ; permeability ; poly(methyl methacrylate)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Dielectric measurements were carried out on aqueous suspensions of poly(methyl methacrylate) microcapsules charged with KCl solutions to examine the KCl permeability of the microcapsules. The specimens exhibited three kinds of dielectric relaxation. Two kinds of dielectric relaxation were observed immediately after washing the specimens with distilled water. These overlapped each other when the specimen was left standing in the measuring cell for a long time. Their relaxation frequencies were affected by the KCl concentration of the suspending medium in which the specimen was kept before washing. Another relaxation was observed distinctly when the spepcimens were washed thoroughly with distilled water. Its relaxation frequency was affected by the KCl concentration of the charged solution. These results were explained by assuming that the specimens were mixtures of KCl-permeable and KCl-impermeable capsules. The theoretical analysis procedure was devised in the light of dielectric theory of interfacial polarization to estimate the parameters which characterize the structure of the specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01417462
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  • 9
    Electronic Resource
    Electronic Resource
    Dielectric properties of moist CaCO3 filled polyethylene composites (1987)
    Springer
    Colloid & polymer science 265 (1987), S. 394-405 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric properties ; composites ; humidity effect ; interfacialpolarization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The capacitance and the dielectric loss tangents of CaCO3 filled polyethylene composites were studied. Composite samples, prepared by polymerizing ethylene on the surfaces of fillers, pre-treated by polymerization catalysts, were compared to normal mechanical mixtures. Dielectric dispersion,ε′, and loss, ε″, proved to be sensitive to heating or vacuum treatment. Investigation of samples under conditions of different relative humidities showed that the dielectric dispersion is due to adsorbed water. Bothε′ and ε″ increased with decreasing frequency and the ratio of loss and dispersion was nearly constant. Dielectric data measured at different relative humidities could be represented by a single Cole-Cole plot. Samples soaked in water for different periods yielded qualitatively similar but quantitatively different Cole-Cole plots. Composite samples showed higher losses at similar humidities. Possible interpretations in terms of a molecular relaxation model, an interfacial relaxation model, including a charged double layer mechanism, percolation theory and the universal response theory were examined, but none was able to fully explain the observed phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412217
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  • 10
    Electronic Resource
    Electronic Resource
    Numerical analysis of complex dielectric mixture formulae (1988)
    Springer
    Colloid & polymer science 266 (1988), S. 11-28 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric properties ; interfacial polarization ; composites ; heterogeneousmixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract As a continuation of our earlier work (Ref. [9]) the complex (frequency dependent) dielectric behaviour of some mixture formulae are studied numerically. These include matrix-inclusion type formulae (as the Wagner-Sillars or the Bruggeman-Boyle equations), mean-field statistical mixture formulae (as the Böttcher-Hsu equation) and symmetrical integral formulae (as the Looyenga equation). The frequency dependent dielectric properties are first calculated for a model system at various particle shapes, field orientations and volume fractions. After this, the validity of these equations is checked on typical sets of experimental data. For low loss powders, the Böttcher and Looyenga equations are suggested; for emulsions, suspensions and filled polymers, the matrix-inclusion type formulae give acceptable results in most cases, while for metal-insulator composites mean-field statistical mixture formulae have to be used, as they are capable of describing the percolation phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01451527
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