Time Domain Dielectric Spectroscopy Research Articles

Analysis and application of time domain dielectric spectroscopy based on wavelet transform

At present, the time domain dielectric spectroscopy is mainly used to analyze thin liquids or materials composed of molecular orderly substances. The various relaxation processes need to be unrelated or be superposed linearly. But it will be clearly limited when the method is applied to the complex heterogeneous mixture analysis. In order to widen its scope of application, the analysis method is improved in this paper by using the wavelet transform. Through the analysis of the oil-water mixture, the experimental results show that the time domain dielectric spectroscopy based on wavelet transform can not only offer the whole spectral information but exhibit the time domain and frequency domain information of various components. Therefore, the analysis method of time domain dielectric spectroscopy based on wavelet transform can be used to analyze complex heterogeneous mixtures.

A Hybrid Filtering Scheme for Proper Denoising of Real-time Data in Dielectric Spectroscopy

Condition monitoring of different power equipment with noninvasive and nondestructive techniques, such as dielectric spectroscopy, has become one of the important facets of power system reliability. This is increasingly becoming essential for predicting the insulation condition and probable future failure of power apparatus. Noise contamination, being one of the major problems in these measurements, should be treated judiciously. The paper proposes a simple but versatile real-time denoising scheme for this kind of signals of dielectric spectroscopy in time domain namely, polarization-depolarization current (PDC) and recovery voltage (RV), through a hybrid filtering technique using weighted median (WM) filter along with low pass digital infinite impulse response (IIR) filter. The proposed filter is able to remove real- life, random, high frequency noises as well as spurious impulse signals while preserving any step change in the signal. The performance of the proposed scheme is judged through experimentation using a real-time, automated computer controlled test setup for condition monitoring of transformers and the results show that it performs efficiently on different types of signals of dielectric spectroscopy in time domain, namely, PDC and RV.

Percolation of polar nanoregions: A dynamic approach to the ferroelectric phase transition

The percolative nature of the ferroelectric phase transition in a potassium tantalate niobate (KTN) crystal is studied using time domain dielectric spectroscopy. A relaxation process linked to the off-center niobium ions is observed. The dynamic nature of this relaxation shows well defined temperature regimes in which it progresses from independent (Arrhenius) to cooperative (Vogel–Fulcher–Tammann) behavior. A recursive fractal model was applied in order to interpret the data obtained from the dielectric measurements. The structural parameters, ν and μ, derived from the correlation functions, enable the investigation of the onset of the phase transition in terms of the fractal dimensions of the polarization excitation.

Ultrashort electric pulse induced changes in cellular dielectric properties

The interaction of nanosecond duration pulsed electric fields (nsPEFs) with biological cells, and the models describing this behavior, depend critically on the electrical properties of the cells being pulsed. Here, we used time domain dielectric spectroscopy to measure the dielectric properties of Jurkat cells, a malignant human T-cell line, before and after exposure to five 10ns, 150kV/cm electrical pulses. The cytoplasm and nucleoplasm conductivities decreased dramatically following pulsing, corresponding to previously observed rises in cell suspension conductivity. This suggests that electropermeabilization occurred, resulting in ion transport from the cell’s interior to the exterior. A delayed decrease in cell membrane conductivity after the nsPEFs possibly suggests long-term ion channel damage or use dependence due to repeated membrane charging and discharging. This data could be used in models describing the phenomena at work.

Dielectric response of biconcave erythrocyte membranes to D- and L-Glucose

In this paper, we report on the influence of D- and L-glucose on the dielectric properties of native shaped (biconcave) human erythrocytes using time domain dielectric spectroscopy. The dielectric spectra of biconcave cells were analysed using a modified form of the model originally reported for spheroid particle suspensions (Asami and Yonezawa 1995 Biochim. Biophys. Acta. 1245 317–24) The observed increase in the specific membrane capacitance of the biconcave erythrocytes was correlated with an increase in the concentration of D-glucose. In contrast, no associated correlation was found to changes in the membrane capacitance with increasing concentrations of L-glucose. A similar analysis of the dielectric response of osmotically swollen erythrocytes to changes in D-glucose concentration revealed a significantly different calculated specific cell membrane capacitance at elevated (>12 mM) D-glucose concentrations. The paper outlines and discusses the possible biochemical mechanisms that could be responsible for the measured dielectric properties of the erythrocyte membrane capacitances.

Dielectric spectroscopy of single cells: time domain analysis using Maxwell's mixture equation

Dielectric spectroscopy is a powerful tool for investigating the dielectric properties of biological particles in suspension. For low volume fractions, the dielectric properties of the particles are related to the measured properties of the suspension by Maxwell's mixture equation. A number of different techniques can be used to measure the dielectric spectrum in the frequency domain or the time domain. In time domain dielectric spectroscopy, data can be converted into the frequency domain using convolution or Fourier transform, prior to data analysis. In this paper, we present a general method for transforming Maxwell's mixture equation from the frequency domain to the time domain allowing analysis of cell dielectric properties directly in the time domain. The derivation is based on the Laplace transform of the single shell model for a spherical particle, and can be extended to the multi-shell model. For a single shelled cell two characteristic relaxation time constants are derived. The results are compared with published analytical models. We show that the original frequency dependent mixture equation can be recovered by Fourier transform back to the frequency domain. As a result, a general relationship for the dielectric response of a mixture of particles is presented which links the frequency and time domains.

Time Domain Dielectric Spectroscopy Measurements of HL-60 Cell Suspensions After Microsecond and Nanosecond Electrical Pulses

Pulsed electric fields (PEFs) above a certain voltage threshold cause electroporation for microsecond pulses and intracellular effects for submicrosecond pulses. Models describing these effects often depend on the electrical properties of the cell, which are altered by the PEF. We used time domain dielectric spectroscopy to provide data for these models and to measure effects on cell suspension conductivity. We applied single 50-/spl mu/s and 10-ns pulses to HL-60 cells, with the voltages chosen so the pulses have approximately the same energy. For 1.1-kV/cm, 50-/spl mu/s pulses, the conductivity rose within a minute after the pulse and dropped dramatically approximately 40 min after the pulse. For 78-kV/cm, 10-ns pulses, we observed a brief delay prior to the conductivity rise and noted the same drop in conductivity after approximately 40 min. For both pulse durations, higher voltages frequently led to membrane poration followed by a gradual recovery approximately 30-40 min after the pulse. For 2-kV/cm, 50-/spl mu/s pulses, we observed significantly more scatter in Trypan Blue uptake measurements due to stronger effects on the cell membrane. By using a cell model, we showed that a 50-/spl mu/s pulse caused a much larger rise in membrane conductivity than a 10-ns pulse of the same energy.

Cell Membrane Response on d-Glucose Studied by Dielectric Spectroscopy. Erythrocyte and Ghost Suspensions

The kinetics of d-glucose influence on spherical human erythrocyte and ghost suspensions, which were prepared from fresh blood provided by healthy donors, was studied by time domain dielectric spectroscopy (TDDS) in a wide physiologic range of glucose concentrations. The dielectric response of cell membranes was found to demonstrate a nonmonotonic behavior in the vicinity of 12 mM concentration of d-glucose in both cell and ghost suspensions. In contrast to spherical cells, where the membrane effect after exposure to d-glucose was reduced after 15−30 min, no reaction was detected in the case of ghosts. The possible mechanisms of glucose transport through the membrane and metabolism are discussed in this paper.

Applications of dielectric spectroscopy in time and frequency domain for HV power equipment

Dielectric spectroscopy in the time or frequency domain offers new opportunities for an off-line, on-site insulation condition assessment of HV electric power equipment and its predictive maintenance.

Time domain dielectric spectroscopy study of biological systems

The main principles of time domain dielectric spectroscopy, its application to conductive systems and possible methods of electrode polarization corrections in time domain are introduced. A comprehensive theoretical and experimental study of static and dynamic dielectric properties of different biological systems including globular, and membrane proteins, hydrate water, human erythrocytes, and normal and malignant blood cells of different types is presented in the paper.

Dielectric spectroscopy in time and frequency domain for HV power equipment. I. Theoretical considerations

Most dangerous breakdowns are caused by the aging effects of HV insulation systems used within HV components, and there is still a lack of appropriate tools to diagnose such systems non-destructively and reliably in the field. This review introduces the theoretical background of dielectric spectroscopy in the time and frequency domains and provides an overview about the specific measuring methods based on this background. The specific methods treated are used for diagnosing electric insulation materials used in power engineering. It indicates that some of these methods may not be sufficient to gain full information about the actual conditions of a test object and that either measurements of polarization and depolarization currents (PDC in the time domain or measurements of C-tanΔ values (or complex permittivity) in the frequency domain (FDS) should be preferred to obtain a "dielectric response function" which offers much more information to judge the actual state of an insulation material or system.

Dielectric spectroscopy of Tobacco Mosaic Virus

The dielectric properties of the Tobacco Mosaic Virus (TMV) have been measured using time domain dielectric spectroscopy (TDDS) in the temperature range from 1 to 40 degrees C. A single dielectric dispersion is observed in the MHz range. The activation energy of the process is found to be in the range 1-2 kcal/mol. The experimental data could not be completely accounted for by current theoretical models, but evidence indicates that the dielectric loss arises from polarisation of charge on and around the virus.

Dielectric spectroscopy study of specific glucose influence on human erythrocyte membranes

Time domain dielectric spectroscopy has been used to study spherical erythrocytes, suspended in diluted phosphate buffered saline (PBS) buffers at varying concentrations of D- and L-glucose at 25°C. The osmolarity for each glucose solution was adapted, equalling that of a 63% PBS (183 mOsm). The strong effect of the electrode polarization was corrected using the fractal approach in time domain. For analysis of the dielectric properties of suspensions of erythrocytes, the Maxwell–Wagner model is used for small volume fractions. Values of the permittivity and conductivity of the cell membrane were obtained from a fitting procedure according to the one-shell model. The non-monotonic and specific response of membrane electric properties on D-glucose concentrations were observed, with a dramatic decrease around 12 mM. No changes of membrane properties have been observed in the presence of increasing concentrations of L-glucose, the biologically inactive enantiomer of D-glucose. The effect is thus specific to D-glucose. The possible mechanism of specific cell reaction to D-glucose is discussed in this paper.

Time domain dielectric spectroscopy of crayfish tail muscle, measured in vivo

We measured the dielectric spectra of crayfish tail muscle, in vivo, in both the time and frequency domains. We inserted a linear array of four needle electrodes (denoted 1, 2, 3 and 4) into the tail muscle. For time domain dielectric spectroscopy (TDDS), we used the MacADIOS data acquisition system to apply a voltage step of amplitude V 0 and to sample the resulting voltages across electrodes 1 and 2 and also across 3 and 4 as well as the current, I, that flowed through a series resistor during polarization and depolarization. Fourier transformation of the variation of the conductance between 2 and 3 with time yielded the capacitance and conductance spectra of the muscle from about 1 kHz down to 0.1 Hz with electrode effects presumably eliminated. A Hewlett-Packard 4192A low-frequency impedance analyzer (IA) measured directly the capacitance and conductance spectra between electrodes 2 and 3 from 100 Hz to 1 MHz. The TDDS results exhibited a strong dispersion for frequencies on the order of 10 Hz that could be characterized by a KWW response ( T∼0.1 s and β∼0.8). We modeled the IA results as a Cole–Cole dispersion with n=0.5.

Dielectric and Calorimetric Characteristics of Bound and Free Water in Surfactant-Based Systems

ABSTRACT The hydration behavior of the system polyoxyethylene (10) oleylalcohol [C18:1 (EO)10 or Brij 97]/water/dodecane/butanol (model system B) was investigated along a dilution line for which the respective weight ratio of dodecane:butanol:Brij 97 is 3:3:4. Two experimental methods were applied: time domain dielectric spectroscopy (TDDS) and sub-zero temperature differential scanning calorimetry (SZT-DSC). Two types of bound water (with melting peaks at -25 and -11°C) were detected by SZT-DSC (using the endothermic mode), whereas TDDS revealed only one such type. Nevertheless, roughly the same total amount of bound water was estimated from these two techniques. The average number of bound water molecules per ethylene oxide (EO) group, NW/EO is 2.3 (TDDS data) or 2.5 (SZT-DSC data) in good agreement with the observation that 1–2 water layers are formed in the hydration of ethoxylated surfactants. We have also shown that butanol is involved in the formation of the bound water that melts at -25°C. We suggest that butanol molecules occupy binding sites within the second hydration shell, thereby reducing the expected total bound water content.

Electrode polarization correction in time domain dielectricspectroscopy

Three methods of electrode polarization correction developed for timedomain dielectric spectroscopy are reviewed in the paper. Two of them are basedon the representation of the parasitic double electrical layer by an additionalcapacitor connected in series with the working electrodes of the sample holder.The third one takes into account the fractal nature of electrode polarization.The advantages and limitations of each method are discussed in the review.

Study of normal and malignant white blood cells by time domain dielectric spectroscopy

The aim of this paper is to present a comprehensive theoretical and experimental study by means of time domain dielectric spectrometer (TDDS) of static and dynamic dielectric properties of normal and malignant blood cells. The successful use of the TDDS method as a tool of human cell study required a special protocol and algorithms for all stages of cell preparation, measurements and data treatment. The routine developed in this study was used in the experimental analysis of nine lines of malignant, transformed and normal lymphocytes. It was shown that dielectric permittivity, capacitance and conductivity values of the cell membrane are higher for normal lymphocytes in comparison with malignant ones.

Observation of Liquid-Crystal-Like Ferroelectric Behavior in a Biological Membrane

In this contribution, we report the application of time domain dielectric spectroscopy from 500 kHz to 1 GHz and differential scanning calorimetry to bacteriorhodopsin containing purple membrane films. The results of these measurements unexpectedly show that the oriented purple membrane has a unique liquid-crystal-like ferroelectric behavior. The dielectric behavior can be considered as soft mode relaxation processes in ferro-electric liquid crystals near smectic-C*−smectic-A phase transition. Such a phenomenon has not been previously observed in biological systems.

Investigation of Permittivity Dispersion in the Infralow-Frequency Band by Time-Domain Dielectric Spectroscopy

The transient-current method of time-domain dielectric spectroscopy, used to investigate the dispersion of the dielectric parameters of materials in the 10–4–1 Hz frequency band, and apparatus based on it, are considered. A program is developed for the mathematical processing of the results of an experiment using the numerical Fourier transformation method employing cubic splines for approximation, interpolation and extrapolation of data. The frequency spectra of Δe' and Δe'' of certain solid materials are presented.

Study of the Dynamic Structure of Native and Hydrophobized Glucose Oxidase by Time-Domain Dielectric Spectroscopy

The dynamic structures of native and hydrophobized (by covalent attachment of palmitoyl chains) glucose oxidase were studied by time-domain dielectric spectroscopy (TDDS). Analysis of the dipole correlation function for both types of the enzyme showed that the decay of the correlation function of the macromolecule motion can be presented as a sum of components corresponding to different kinds of protein motion: isotropic rotation of the protein molecule as a whole, anisotropic Brownian tumbling of subunits, and anisotropic intramolecular motion of polar groups and substructures. The slowest relaxation time was found to be longer for the modified enzyme than for the native enzyme. The dielectric strengths for all relaxation processes, as well as the dipole moment and the molecular volume, were also larger for the modified glucose oxidase. The observed differences between various types of the dipole motion for the native and modified glucose oxidase are discussed.