Frequency dependence of the optical relaxation time in metals

1982 ◽  
Vol 25 (2) ◽  
pp. 923-930 ◽  
Author(s):  
Jeffrey B. Smith ◽  
H. Ehrenreich
Keyword(s):  
Relaxation Time ◽  
Frequency Dependence

Frequency dependence of the Drude relaxation time in metal films

1974 ◽  
Vol 9 (4) ◽  
pp. 1299-1303 ◽  
Author(s):  
S. R. Nagel ◽  
S. E. Schnatterly
Keyword(s):  
Relaxation Time ◽  
Frequency Dependence ◽  
Metal Films

Contribution to the Dielectric Behavior of Relaxers from the Surface of Nano-Order Cluster in the Materials

1997 ◽  
Vol 492 ◽  
Author(s):  
Z. -Y. Cheng ◽  
Aqiang Guo ◽  
R. S. Katiyar
Keyword(s):  
Dielectric Constant ◽  
Relaxation Time ◽  
Frequency Dependence ◽  
Relaxor Ferroelectrics ◽  
Dielectric Behavior ◽  
Experimental Results ◽  
Time Analysis ◽  
Resonance Process

ABSTRACTBased on the analysis of the dielectric behavior of relaxor ferroelectrics, it is assumed that the material has two polarization processes. Thus, a formula, which can fit the experimental results very well, is proposed to describe the temperature and frequency dependence of the dielectric constant. The fitted results show that there is a resonance process in the material and the peak of the dielectric constant is determined with both the relaxation and resonance processes. The relaxation time analysis shows that the peak of the dielectric constant indeed consists of two parts.

Frequency Dependence of Proton Spin Relaxation in Liquid Crystalline PAA

1975 ◽  
Vol 30 (4) ◽  
pp. 437-441 ◽  
Author(s):  
W. Wölfel ◽  
F. Noack ◽  
M. Stohrer
Keyword(s):  
Relaxation Time ◽  
Transition Temperature ◽  
Frequency Dependence ◽  
Spin Relaxation ◽  
Correlation Time ◽  
Liquid Crystalline ◽  
Larmor Frequency ◽  
Proton Spin ◽  
Isotropic Phase ◽  
Frequency Range

Abstract We report on measurements of the Larmor frequency dependence of the proton spin relaxation time T1 in the nematic and isotropic phase of p-azoxyanisole (frequency range: 3.8 kHz ≦ ωL/2 π≦75 MHz) . In both cases our results clearly support the Pincus-Cahane mechanism of spin relaxation by order fluctuations ("ωL−½-law") and exclude the alternative translational dif­fusion model (“ωL+½-law”). For the isotropic phase it was possible to evaluate the correlation time τ of the liquid crystalline order fluctuations from the observed T1 dispersion. As a function of the deviation ⊿ν=ν-νc from the critical nematic-isotropic transition temperature, νc= (136± 0.5)°C, we found τ=2.71·10-7-⊿ν-0.25s .

scholarly journals Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 32
Author(s):  
Pawel Zukowski ◽  
Przemyslaw Rogalski ◽  
Tomasz N. Koltunowicz ◽  
Konrad Kierczynski ◽  
Vitalii Bondariev
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Moisture Content ◽  
Frequency Dependence ◽  
Vertical Axis ◽  
Mean Value ◽  
Transformer Oil ◽  
Potential Wells ◽  
Different Temperatures ◽  
Oil Water

This article presents direct σDC and alternating σ(f) current conductivity measurements obtained by the frequency domain spectroscopy (FDS) method on cellulose-transformer oil–water nanoparticle composite with a moisture content of (5.0 ± 0.2)% by weight in a temperature range from 293.15 to 333.15 K with step of 8 K. The uncertainty of temperature maintenance during measurements was below ±0.01 K. The sample was prepared for testing in a manner as close as possible to the cellulose insulation moisturizing process in power transformers. For the analysis of the results obtained, a model of alternating and direct current hopping conductivity was used, based on the quantum phenomenon of electron tunneling between the potential wells and nanodrops of water. It was observed that on the d(logσ)/d(logf)-derived waveforms there was a clear low-frequency maximum, and a tendency to reach the next maximum in the high-frequency area was visible. On this basis it was established that the increase in conductivity takes place in two stages. It was found that the position of σ(f) waveforms in the double logarithmic coordinates is influenced by the temperature dependence both of the conductivity and of the relaxation time of the conductivity. These relationships are described with the appropriate activation energies of the conductivity and relaxation time of conductivity. Based on the analysis of experimental data using Arrhenius diagrams, average values of the activation energy of conductivity ΔWσ ≈ (0.894 ± 0.0134) eV and the relaxation time of conductivity ΔWτσ ≈ (0.869 ± 0.0107) eV were determined. The values were equal within the limits of uncertainty and their mean value was ΔW ≈ (0.881 ± 0.0140) eV. Using the mean value of the activation energy, the frequency dependence of conductivity, obtained at different temperatures, was shifted to 293.15 K. For this purpose, first the waveforms were shifted along the horizontal and then the vertical axis. It was found that after the shift the σ(f) waveforms for the different temperatures overlap perfectly. This means that the shape of the frequency dependence of the conductivity is determined by the moisture content of the pressboard. The position of the waveforms in relation to the coordinates is determined by the temperature relationships of the conductivity and the relaxation time of the conductivity.

Temporal Dynamics of Convergent Modulation at a Crustacean Neuromuscular Junction

1998 ◽  
Vol 80 (5) ◽  
pp. 2559-2570 ◽  
Author(s):  
Juan Carlos Jorge-Rivera ◽  
Kamal Sen ◽  
J. T. Birmingham ◽  
L. F. Abbott ◽  
Eve Marder
Keyword(s):  
Relaxation Time ◽  
Neuromuscular Junction ◽  
Frequency Dependence ◽  
Temporal Dynamics ◽  
Muscle Relaxation ◽  
Stimulus Frequency ◽  
Gastric Mill ◽  
Initial Amplitude ◽  
Cancer Borealis ◽  
Evoked Contractions

Jorge-Rivera, Juan Carlos, Kamal Sen, J. T. Birmingham, L. F. Abbott, and Eve Marder. Temporal dynamics of convergent modulation at a crustacean neuromuscular junction. J. Neurophysiol. 80: 2559–2570, 1998. At least 10 different substances modulate the amplitude of nerve-evoked contractions of the gastric mill 4 (gm4) muscle of the crab, Cancer borealis. Serotonin, dopamine, octopamine, proctolin, red pigment concentrating hormone, crustacean cardioactive peptide, TNRNFLRFamide, and SDRNFLRFamide increased and d-allatostatin-3 and histamine decreased the amplitude of nerve-evoked contractions. Modulator efficacy was frequency dependent; TNRNFLRFamide, proctolin, and dallatostatin-3 were more effective when the motor neuron was stimulated at 10 Hz than at 40 Hz, whereas the reverse was true for dopamine and serotonin. The modulators that were most effective at high stimulus frequencies produced a significant decrease in muscle relaxation time; those that were most effective at low stimulus frequencies produced modest increases in relaxation time. Thus modulator actions that appear redundant when examined only at one stimulus frequency are differentiated when a range of stimulus dynamics is studied. The effects of TNRNFLRFamide, serotonin, proctolin, dopamine, and d-allatostatin-3 on the amplitude and facilitation of nerve-evoked excitatory junctional potentials (EJPs) in the gm4 and gastric mill 6 (gm6) muscles were compared. The EJPs in gm4 have a large initial amplitude and show relatively little facilitation, whereas the EJPs in gm6 have a small initial amplitude and show considerable facilitation. Modulators that enhanced contractions also enhanced EJP amplitude; d-allatostatin-3 reduced EJP amplitude. The effects of these modulators on EJP amplitude were modest and showed no significant frequency dependence. This suggests that the frequency dependence of modulator action on contraction results from effects on excitation–contraction coupling. The modulators affected facilitation at these junctions in a manner consistent with a change in release probability. They produced a change in facilitation that is inversely related to their action on EJP amplitude.

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