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THz radiationeffectively probes biological tissue water content due to its high sensibility to polar molecules. Skin and basal cell carcinoma (BCC), both rich in water, have been extensively studied in the THz range. Typically, the Double Debye model is used to study their dielectric permittivity. This work focuses on the viability of the multipole Cole-Cole model as an alternative dielectric model. To determine the best fit parameters, we used a genetic algorithm-based approach, solving a least squares problem. Compared with the Double Debye model, a maximum reduction of the RMSE value up to more than 50% and maximum relative percentage errors of 2.8% have been measured for both second and third order Cole-Cole models. Since the errors of the second and third order Cole-Cole models are similar, a two-poles model is enough to describe the behaviour both tissues from 0.2 THz to 2 THz.

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Maize kernels were treated using two varieties of drying methodologies, namely combined hot air- and vacuum-drying (HAVD) and natural drying (ND). We performed frequency sweep tests, modified Cole-Cole (MCC) analysis, and frequency-temperature superposition (FTS) on these kernels. The kernels' elastic and viscous properties for ND were higher than those for HAVD. The heterogeneous nature of maize kernel may account for the curvature in MCC plot for the kernel treated by HAVD 75 °C and the failure of FTS. MCC analysis was more sensitive than FTS. The kernel treated by HAVD 75 °C demonstrated thermorheologically simple behavior across the entire temperature range (30-45 °C) in both MCC analysis and FTS. The frequency scale for the kernel treated using HAVD 75 °C was broadened by up to 70,000 Hz. The relaxation processes in the kernel treated by HAVD 75 °C were determined to be mainly associated with subunits of molecules or molecular strands. The data herein could be utilized for maize storage and processing.

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To evaluate the thermal stability of composite polymer-modified asphalt, thermoplastic elastomer styrene-butadiene rubber (SBR)/polypropylene (PP) pellets were prepared using a hot-melt blending technique, with butyl rubber powder and waste polypropylene pellets as raw materials. The effects of different evaluation indexes on the thermal stability of SBR/PP-modified asphalt were investigated using a frequency scan test and a multi-stress creep recovery (MSCR) test, and the compatibility of SBR/PP particles with asphalt was studied using the Cole-Cole diagram and microstructure images. The tests show that, firstly, the performance grade (PG) classification of asphalt can be improved by adding an SBR/PP thermoplastic elastomer to enhance the adaptability of asphalt in high- and low-temperature environments, and the evaluation separation index can reflect the high-temperature storage stability of composite-modified asphalt more reasonably. Additionally, the larger the rubber-to-plastic ratio the worse the high-temperature thermal stability of composite-modified asphalt. Moreover, the addition of additives to the composite particles can promote the SBR/PP particles in the asphalt to be more uniformly dispersed, forming a more desirable microstructure and improving the thermal stability of composite-modified asphalt. Ultimately, the semicircular curve of the Cole-Cole diagram can reflect the compatibility characteristics of the two-phase structure of SBR/PP-modified asphalt, which can be used as an auxiliary index to evaluate the compatibility of polymer-modified asphalt.

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In the biopharmaceutical industry, the use of mammalian cells to produce therapeutic proteins is becoming increasingly widespread. Monitoring of these cultures via different analysis techniques is essential to ensure a good quality product while respecting good manufacturing practice (GMP) regulations. Process Analytical Technologies (PAT) tools provide real-time measurements of the physiological state of the culture and enable process automation. Dielectric spectroscopy is a PAT that can be used to monitor the viable cell concentration (VCC) of living cells after processing raw permittivity data. Several modeling approaches exist and estimate biomass with different accuracy. The accuracy of the Cole-Cole and Maxwell Wagner's equations are studied here in the determination of the VCC and cell radius in Chinese hamster ovary (CHO) culture. A sensitivity analysis performed on the parameters entering the equations highlighted the importance of the cell specific parameters such as internal conductivity (σi ) and membrane capacitance (Cm ) in the accuracy of the estimation of VCC and cell radius. The most accurate optimization method found to improve the accuracy involves in-process adjustments of Cm and σi in the model equations with samplings from the bioreactor. This combination of offline and in situ data improved the estimation precision of the VCC by 69% compared to a purely mechanistic model without offline adjustments.

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Carasau bread is a flat bread, typical of Sardinia (Italy). The market of this food product has a large growth potential, and its industry is experiencing a revolution, characterized by digitalization and automation. To monitor the quality of this food product at different manufacturing stages, microwave sensors and devices could be a cost-effective solution. In this framework, knowledge of the microwave response of Carasau dough is required. Thus far, the analysis of the microwave response of Carasau doughs through dielectric spectroscopy has been limited to the dynamics of fermentation. In this work, we aim to perform complex dielectric permittivity measurements up to 8.5 GHz, investigating and modeling the role of water amount, salt and yeast concentrations on the spectra of this food product. A third-order Cole-Cole model was used to interpret the microwave response of the different samples, resulting in a maximum error of 1.58% and 1.60% for the real and imaginary parts of permittivity, respectively. Thermogravimetric analysis was also performed to support the microwave spectroscopy investigation. We found that dielectric properties of Carasau bread doughs strongly depend on the water content. The analysis highlighted that an increase in water quantity tends to increase the bounded water fraction at the expense of the free water fraction. In particular, the free water amount in the dough is not related to the broadening parameter γ2 of the second pole, whereas the bound water weight fraction is more evident in the γ2 and σdc parameters. An increase in electrical conductivity was observed for increasing water content. The microwave spectrum of the real part of the complex permittivity is slightly affected by composition, while large variation in the imaginary part of the complex dielectric permittivity can be identified, especially for frequencies below 4 GHz. The methodology and data proposed and reported in this work can be used to design a microwave sensor for retrieving the composition of Carasau bread doughs through their dielectric signature.

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Different doping elements have been used to enhance the dielectric properties of BaTiO3 ceramic. In this work, the effect of substitution of Ba by Bi in A site and Ti by Fe in B site on structural, dielectric and electrical properties of Ba1-xBixTi0.80Fe0·20O3 ceramics at (x = 0.00, 0.05, 0.10 and 0.15) was investigated by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy (SEM), Mössbauer spectroscopy as well as dielectric measurements. The Rietveld refinement results revealed that the prepared compounds crystallize in both tetragonal (P4mm) and hexagonal (P63/mmc) phases for x = 0.00 and 0.05 while at x = 0.10 and 0.15, the hexagonal phase disappears and only the tetragonal phase is fitted. The Raman spectra confirmed the disappearance of hexagonal phase in benefit of tetragonal phase as the Bi3+ substitution increases. Based on Mössbauer analyses results, all the samples are in paramagnetic state at room temperature and the Fe is oxidized under Fe3+ without the presence of Fe2+ or Fe4+ ions. The dielectric measurements as function of temperature are studied and tree broad and relaxor phase transitions were detected: from rhombohedral to orthorhombic phase TR-O and to tetragonal ferroelectric phase TO-T then to cubic paraelectric phase Tm. These phase transitions were displaced to the lower temperature with increasing of Bi3+ substitution. The values of ε'r increase gradually with increasing of Bi3+contents which confirmed the enhancement of dielectric properties of BaTi0·80Fe0·20O3 by Bi substitution on Ba site. The diffuse phase transitions were described by fitting the modified Uchino relation. The Cole-Cole analyses showed that both the grain and grain boundaries resistivity values are higher for Bi3+ substituted samples which are responsible to the dielectric properties improvement.

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This paper examines the effect of finger fat pad thickness on the accuracy performance of complementary split-ring resonator (CSRR)-based microwave sensors for non-invasive blood glucose level detection. For this purpose, a simplified four-layer Cole-Cole model along with a CSRR-based microwave sensor have been comprehensively analyzed and validated through experimentation. Computed scattering parameter (S-parameter) responses to different fat layer thicknesses are employed to verify the concordance of the studied model with the measurement results. In this respect, a figure of merit (FM) based on the normalized squared difference is introduced to assess the accuracy of the considered Cole-Cole model. We have demonstrated that the analyzed model agrees closely with the experimental validation. In fact, the maximum error difference for all five fingertips does not exceed 1.73 dB over the entire frequency range of interest, from 1 GHz to 4 GHz.

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We present a systematic study of the lithium-ion transport upon the mixed manganese-iron oxide phosphate glasses 3Li2O-xMn2O3-(2-x)Fe2O3-3P2O5(LMxF2−xPO; 0≤ x ≤2.0) proposed for the use in a cathode for lithium secondary batteries. The glasses have been fabricated using a solid reaction process. The electrical characteristics of the glass samples have been characterized by electrical impedance in the frequency range from 100 Hz to 30 MHz and temperature from 30 °C to 240 °C. Differential thermal analysis and X-ray diffraction were used to determine the thermal and structural properties. It has been observed that the dc conductivity decreases, but the activation energies of dc and ac and the glass-forming ability increase with the increasing Mn2O3 content in LMxF2−xPO glasses. The process of the ionic conduction and the relaxation in LMxF2−xPO glasses are determined by using power−law, Cole−Cole, and modulus methods. The Li+ ions migrate via the conduction pathway of the non-bridging oxygen formed by the depolymerization of the mixed iron−manganese−phosphate network structure. The mixed iron−manganese content in the LMxF2−xPO glasses constructs the sites with different depths of the potential well, leading to low ionic conductivity.

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The influence of pertinent parameters of a Cole-Cole model in the impedimetric assessment of cell-monolayers was investigated with respect to the significance of their individual contribution. The analysis enables conclusions on characteristics, such as intercellular junctions. Especially cold atmospheric plasma (CAP) has been proven to influence intercellular junctions which may become a key factor in CAP-related biological effects. Therefore, the response of rat liver epithelial cells (WB-F344) and their malignant counterpart (WB-ras) was studied by electrical impedance spectroscopy (EIS). Cell monolayers before and after CAP treatment were analyzed. An uncertainty quantification (UQ) of Cole parameters revealed the frequency cut-off point between low and high frequency resistances. A sensitivity analysis (SA) showed that the Cole parameters, R0 and α were the most sensitive, while Rinf and τ were the least sensitive. The temporal development of major Cole parameters indicates that CAP induced reversible changes in intercellular junctions, but not significant changes in membrane permeability. Sustained changes of τ suggested that long-lived ROS, such as H2O2, might play an important role. The proposed analysis confirms that an inherent advantage of EIS is the real time observation for CAP-induced changes on intercellular junctions, with a label-free and in situ method manner.

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Impedance spectroscopy is used for the characterization of electrochemical systems as well as for the monitoring of bioprocesses. However, the data obtained using this technique allow multiple interpretations, depending on the methodology implemented. Hence, it is necessary to establish a robust methodology to reliably follow-up biomass in fermentations. In the present work, two methodological approaches, mainly used for the characterization of electrochemical systems, were employed to characterize and determine a frequency that allows the monitoring of biomass in Bacillus thuringiensis fermentations by impedance spectroscopy. The first approach, based on a conventional analysis, revealed a single distribution with a characteristic frequency of around 2 kHz. In contrast, the second approach, based on the distribution of relaxation times, gave three distributions (A, B, and C). The C distribution, found near 9 kHz, was more related to the microbial biomass than the distribution at 2 kHz using the equivalent circuits. The time course of the B. thuringiensis fermentation was followed; bacilli, spores, glucose, and acid and base consumption for pH were determined out of line; and capacitance at 9 kHz was monitored. The correlation between the time course data and the capacitance profile indicated that the monitoring of B. thuringiensis at 9 kHz mainly corresponds to extracellular activity and, in a second instance, to the cellular concentration. These results show that it is necessary to establish a robust and reliable methodology to monitor fermentation processes by impedance spectroscopy, and the distribution of relaxation times was more appropriate. KEY POINTS: • Application of impedance spectroscopy for bioprocess monitoring • Low-frequency monitoring of biomass in fermentations • Analysis of impedance data by two methodological approaches.

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Airborne transient electromagnetic (ATEM) technology is a technique often used in mineral exploration and geological mapping. Due to inductive polarization (IP) phenomena, the ATEM response curve often shows a negative response or declines rapidly to the attenuation curve. Traditional resistivity inversion techniques do not explain the IP response of a signal well, so the negative response is usually removed during data processing, resulting in a reduced correctness and authenticity of the findings. In this paper, in the parameter inversion based on the Cole-Cole model, the Jacobian matrix chain analysis method is used to calculate, and the current waveform calculation is also considered in the inversion. The results show that compared with the perturbation method, the analysis technique can greatly reduce the calculation time and improve the inversion efficiency. In the single-point one-dimensional inversion and lateral constraint quasi-two-dimensional inversion, the Cole-Cole four-parameter forward response has strong inversion accuracy, which can successfully invert the actual exploration content and the Cole-Cole four-parameter response. Some measured sounding data in the Qingchengzi survey area of Liaoning Province, China have a negative response to IP, and the resistivity scheme cannot be used alone for inversion, but the real underground resistivity structure can be obtained through the method studied in this paper, and good exploration results can be obtained.

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Real-time estimation of physiological properties of the cell during recombinant protein production would ensure enhanced process monitoring. In this study, we explored the application of dielectric spectroscopy to track the fed-batch phase of recombinant Escherichia coli cultivation for estimating the physiological properties, namely, cell diameter and viable cell concentration (VCC). The scanning capacitance data from the dielectric spectroscopy were pre-processed using moving average. Later, it was modeled through a nonlinear theoretical Cole-Cole model and further solved using a global evolutionary genetic algorithm (GA). The parameters obtained from the GA were further applied for the estimation of the aforementioned physiological properties. The offline cell diameter and cell viability data were obtained from particle size analyzer and flow cytometry measurements to validate the Cole-Cole model. The offline VCC was calculated from the cell viability % from flow cytometry data and dry cell weight concentration. The Cole-Cole model predicted the cell diameter and VCC with an error of 1.03% and 7.72%, respectively. The proposed approach can enable the operator to take real-time process decisions to achieve desired productivity and product quality.

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A new version of the DielParamFit program [J. Colloid Interface Sci. 419 (2014) 102-106] for the fitting of a superposition of dispersion terms to measured dielectric data is presented. It extends its applicability to a wide range of new systems by allowing the use of up to three Havriliak-Negami dispersions, each of which can be readily transformed into Debye, Cole-Cole, or Cole-Davidson terms. Moreover, it greatly enhances its usability by means of a graphic interface that displays the measured data together with the model spectra allowing to iteratively adjust the chosen terms and guess parameter values guided by a live view of the obtained results. The DielParamFit_2 program executable file for Microsoft Windows is available upon request from the author.

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Double-dispersion impedance models are important for the accurate fitting of spectral impedance measurements in Electrical Impedance Spectroscopy (EIS). While the Cole-Cole model is the most widely known, it is possible to define double-dispersion Cole-Davidson and Havriliak-Negami models as well. In this work, we show that more freedom can be exercised when these three models are combined together and that this combination can be done in various forms. Experimental results using a two-stage optimization algorithm applied on the suggested models are provided.

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The most important parameter in bioprocesses is biomass, where not only the quantity produced in a culture but also the behavior that is presented are important concerns. It is clear that conditions of operation in a bioreactor affect biomass production, but how operation conditions affect the measurement of biomass on-line is of special interest. We studied the effect of bioreactor operating condition variations on model parameters using impedance spectroscopy for biomass monitoring. The model parameters analyzed were capacitance, resistance, alpha (α), conductivity delta (∆σ) and critical frequency (fc). These model parameters were obtained by fitting data from impedance measurements to an equivalent circuit model and Cole-Cole conductivity model. The effect of operating conditions on the medium with no cells was estimated by the percentage of change in each model parameter. The operating conditions with the most significant percentage of change were determined, by comparing to the percentage of change of the same model parameters obtained, during a fermentation of Bacillus thuringiensis as a cellular model. Equivalent circuit parameters were mainly affected by variation in pH, temperature and aeration, whereas Cole-Cole parameters were affected by variation in agitation, aeration, temperature and pH. Therefore, any variation in these operating conditions (within the test interval) during a fermentation may generate changes in monitoring parameters, which will not be a direct consequence of any change in the properties of the biomass.

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Diagnosis in the early stage of breast cancer is crucial for the onset of preliminary treatment. Non-radiative bioimpedance measurement in the microwave frequency range can contribute to electrode-medium interface error and the malaise of electrode placement on the patient to take measurements. These reasons account for alternate diagnosis procedure and improved reliability of retrieved mensuration. Non-invasive optical diagnosis in the near infra-red (NIR) and visible light of the electromagnetic range is the shifting paradigm for healthcare diagnosis. An accurate quantitative measurement is unparalleled to circumvent false positives. The focus of this paper is to perform quantitative mathematical analysis for bioimpedance and optical properties for sample breast cancer cells for meticulous interpretation of malignant cell diagnosis. The analytical solution of the Cole-Cole plot, relaxation frequency, and capacitance measurement showed reliability with previous experimental findings. The dissimilitude of the frequency-dependent refractive index measurement of the malignant and healthy cell can be used by clinicians for pronouncement. The diffusion theory is also used to interpret the pathlength of the source light particle and the absorption property of the malignant cell. The synergistic analytical solutions of the bioimpedance and optical parameters can be used by licensed Physicians or Clinical Practitioners (CP) to meticulously interpret the diagnosis result. The quantitative parameters obtained from the dispersed bandwidth range from microwave to visible light offers a comprehensive understanding of the biophysical properties of the malignant cell.

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Our aim is to clarify the association of the bioelectrical impedance-derived 50-kHz phase angle (φ50 ) with electrical parameters regarding the Cole-Cole model and clinical parameters. A total of 440 sets of bioelectrical impedance data from pre- and post-hemodialysis from 157 patients were used. Resistance at infinite frequency (Rinf ), resistance at 0 frequency (R0 ), capacitance of the cell membrane (Cm), and a parameter for the distribution of the time constant (α) were examined as electrical parameters. Normally hydrated lean tissue mass as a percentage of the dry weight (PNHLT ), excess fluid mass as a percentage of the dry weight (PExF ), body mass index (BMI), age, and sex (Nsex , 0 for male, 1 for female) were examined as clinical parameters. φ50 increased with the decrease in Rinf /R0 and α and also with the increase in Cm (multiple regression coefficients [ß]: pre/post, -0.886/-0.936, -0.175/-0.212, and 0.167/0.141), which determined the ratio of intra- to extracellular fluid volume (ICV/ECV), tissue homogeneity, and total cell mass. φ50 increased with an increase in PNHLT and BMI and decrease in PExF , Nsex , and age (ß: pre/post, 0.654/0.581, 0.466/0.412, -0.483/-0.473, -0.216/-0.154, and -0.145/-0.127). The concordance correlation coefficient between φ50 for pre- and post-hemodialysis (ρ = 0.772) may be improved (ρ = 0.950) by adding a multiplication of 0.2 and PExF to φ50 for correction. φ50 may be used to estimate body composition through the association with ICV/ECV, tissue homogeneity, and total cell mass. The correction for excess fluid is essential in order to use φ50 as a marker of body composition related to nutrition.

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Background: Electrical impedance spectroscopy (EIS) is a fast, non-invasive, and safe approach for electrical impedance measurement of biomedical tissues. Applied to dental research, EIS has been used to detect tooth cracks and caries with higher accuracy than visual or radiographic methods. Recent studies have reported age-related differences in human dental tissue impedance and utilized fractional-order equivalent circuit model parameters to represent these measurements. Objective: We aimed to highlight that fractional-order equivalent circuit models with different topologies (but same number of components) can equally well model the electrical impedance of dental tissues. Additionally, this work presents an equivalent circuit network that can be realized using Electronic Industries Alliance (EIA) standard compliant RC component values to emulate the electrical impedance characteristics of dental tissues. Results: To validate the results, the goodness of fits of electrical impedance models were evaluated visually and statistically in terms of relative error, mean absolute error (MAE), root mean squared error (RMSE), coefficient of determination (R2), Nash-Sutcliffe's efficiency (NSE), Willmott's index of agreement (WIA), or Legates's coefficient of efficiency (LCE). The fit accuracy of proposed recurrent electrical impedance models for data representative of different age groups teeth dentin supports that both models can represent the same impedance data near perfectly. Significance: With the continued exploration of fractional-order equivalent circuit models to represent biological tissue data, it is important to investigate which models and model parameters are most closely associated with clinically relevant markers and physiological structures of the tissues/materials being measured and not just "fit" with experimental data. This exploration highlights that two different fractional-order models can fit experimental dental tissue data equally well, which should be considered during studies aimed at investigating different topologies to represent biological tissue impedance and their interpretation.

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We investigated the relationship between impedance parameters and skeletal muscle function in the lower extremities, as well as the effectiveness of impedance parameters in evaluating muscle quality. Lower extremity impedance of 19 healthy men (aged 23-31 years) measured using the direct segmental multi-frequency bioelectrical impedance analysis were arc-optimized using the Cole-Cole model, following which phase angle (PA), [Formula: see text], and ß were estimated. Skeletal muscle function was assessed by muscle thickness, muscle intensity, and isometric knee extension force (IKEF). IKEF was positively correlated with PA (r = 0.58, p < 0.01) and ß (r = 0.34, p < 0.05) was negatively correlated with [Formula: see text] (r = - 0.43, p < 0.01). Stepwise multiple regression analysis results revealed that PA, ß, and [Formula: see text] were correlated with IKEF independently of muscle thickness. This study suggests that arc-optimized impedance parameters are effective for evaluating muscle quality and prediction of muscle strength.

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We investigate the role of tellurite on a lithium-silicate glass 0.1 TeO2 -0.90.1 TeO2 -0.9 (Li2O-2SiO2) (LSTO) system proposed for the use in solid electrolyte for lithium ion batteries. The measurements of electrical impedance are performed in the frequency 100 Hz-30 MHz and temperature from 50 to 150 °C. The electrical conductivity of LSTO glass increases compared with that of Li2O-2SiO2 (LSO) glass due to an increase in the number of Li+ ions. The ionic hopping and relaxation processes in disordered solids are generally explained using Cole-Cole, power law and modulus representations. The power law conductivity analysis, which is driven by the modified Rayleigh equation, presents the estimation of the number of ionic charge carriers explicitly. The estimation counts for direct contribution of about a 14% increase in direct current conductivity in the case of TeO2 doping. The relaxation process by modulus analysis confirms that the cations are trapped strongly in the potential wells. Both the direct current and alternating current activation energies (0.62-0.67 eV) for conduction in the LSO glass are the same as those in the LSTO glass.