WorldWideScience

Sample records for electric impedance spectroscopy

  1. Electrical impedance spectroscopy and diagnosis of tendinitis

    International Nuclear Information System (INIS)

    Yoon, Kisung; Lee, Kyeong Woo; Kim, Sang Beom; Lee, Jong Hwa; Han, Tai Ryoon; Jung, Dong Keun; Roh, Mee Sook

    2010-01-01

    There have been a number of studies that investigate the usefulness of bioelectric signals in diagnoses and treatment in the medical field. Tendinitis is a musculoskeletal disorder with a very high rate of occurrence. This study attempts to examine whether electrical impedance spectroscopy (EIS) can detect pathological changes in a tendon and find the exact location of the lesion. Experimental tendinitis was induced by injecting collagenase into one side of the patellar tendons in rabbits, while the other side was used as the control. After measuring the impedance in the tendinitis and intact tendon tissue, the dissipation factor was computed. The real component of impedance and the dissipation factor turned out to be lower in tendinitis than in intact tissues. Moreover, the tendinitis dissipation factor spectrum showed a clear difference from that of the intact tendon, indicating its usefulness as a tool for detecting the location of the lesion. Pathologic findings from the tissues that were obtained after measuring the impedance confirmed the presence of characteristics of tendinitis. In conclusion, EIS is a useful method for diagnosing tendinitis and detecting the lesion location in invasive treatment

  2. Electrical impedance spectroscopy for measuring the impedance response of carbon-fiber-reinforced polymer composite laminates

    KAUST Repository

    Almuhammadi, Khaled; Bera, Tushar Kanti; Lubineau, Gilles

    2017-01-01

    impedance spectroscopy response at various frequencies of laminates chosen to be representative of classical layups employed in composite structures. We clarify the relationship between the frequency of the electrical current, the conductivity of the surface

  3. Electrical impedance spectroscopy for measuring the impedance response of carbon-fiber-reinforced polymer composite laminates

    KAUST Repository

    Almuhammadi, Khaled

    2017-02-16

    Techniques that monitor the change in the electrical properties of materials are promising for both non-destructive testing and structural health monitoring of carbon-fiber-reinforced polymers (CFRPs). However, achieving reliable monitoring using these techniques requires an in-depth understanding of the impedance response of these materials when subjected to an alternating electrical excitation, information that is only partially available in the literature. In this work, we investigate the electrical impedance spectroscopy response at various frequencies of laminates chosen to be representative of classical layups employed in composite structures. We clarify the relationship between the frequency of the electrical current, the conductivity of the surface ply and the probing depth for different CFRP configurations for more efficient electrical signal-based inspections. We also investigate the effect of the amplitude of the input signal.

  4. Electrical impedance spectroscopy (EIS)-based evaluation of biological tissue phantoms to study multifrequency electrical impedance tomography (Mf-EIT) systems

    KAUST Repository

    Bera, Tushar Kanti; Nagaraju, J.; Lubineau, Gilles

    2016-01-01

    . In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity

  5. Biological Cell Identification by Integrating Micro-Fluidics, Electrical Impedance Spectroscopy and Stochastic Estimation

    Science.gov (United States)

    2007-03-01

    Karolinska Institutet in Stockholm entitled "Skin Cancer as Seen by Electrical Impedance" [1]. The thesis describes Åberg�s experiments to detect skin cancer...ska Institutet , 2004. 2. Ayli¤e, H. Edward, et al. �Electric Impedance Spectroscopy Using Microchannels with Integrated Metal Electrodes

  6. Electrical impedance tomography spectroscopy method for characterising particles in solid-liquid phase

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yanlin [Department of Thermal Energy Engineering, College of Mechanical and Transportation Engineering, China University of Petroleum, Beijing, 102249 (China); Wang, Mi [Institute of Particle Science and Engineering, School of Process, Environmental and Materials Engineering, University of Leeds, Leeds LS2 9JT (China); Yao, Jun [School of Energy Research, Xiamen University, Xiamen 361005 (China)

    2014-04-11

    Electrical impedance tomography (EIT) is one of the process tomography techniques to provide an on-line non-invasive imaging for multiphase flow measurement. With EIT measurements, the images of impedance real part, impedance imaginary part, phase angle, and magnitude can be obtained. However, most of the applications of EIT in the process industries rely on the conductivity difference between two phases in fluids to obtain the concentration profiles. It is not common to use the imaginary part or phase angle due to the dominant change in conductivity or complication in the use of other impedance information. In a solid-liquid two phases system involving nano- or submicro-particles, characterisation of particles (e.g. particle size and concentration) have to rely on the measurement of impedance phase angle or imaginary part. Particles in a solution usually have an electrical double layer associated with their surfaces and can form an induced electrical dipole moment due to the polarization of the electrical double layer under the influence of an alternating electric field. Similar to EIT, electrical impedance spectroscopy (EIS) measurement can record the electrical impedance data, including impedance real part, imaginary part and phase angle (θ), which are caused by the polarization of the electrical double layer. These impedance data are related to the particle characteristics e.g. particle size, particle and ionic concentrations in the aqueous medium, therefore EIS method provides a capability for characterising the particles in suspensions. Electrical impedance tomography based on EIS measurement or namely, electrical impedance tomography spectroscopy (EITS) could image the spatial distribution of particle characteristics. In this paper, a new method, including test set-up and data analysis, for characterisation of particles in suspensions are developed through the experimental approach. The experimental results on tomographic imaging of colloidal particles

  7. on the electrical properties of ZnO by impedance spectroscopy

    Indian Academy of Sciences (India)

    The electrical properties of Zn 1 − x Ca x O ( x = 0 , 0.01 , 0.02 and 0.03) nanoceramics synthesized by solidstate reactionmethod were investigated by complex impedance spectroscopy (CIS) from room temperature to 500 ∘ C. Structural analysis of the synthesized material using the X-ray diffraction technique suggests that ...

  8. Coplanar Electrode Layout Optimized for Increased Sensitivity for Electrical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Clausen, Casper Hyttel; Skands, Gustav Erik; Bertelsen, Christian Vinther

    2015-01-01

    This work describes an improvement in the layout of coplanar electrodes for electrical impedance spectroscopy. We have developed, fabricated, and tested an improved electrode layout, which improves the sensitivity of an impedance flow cytometry chip. The improved chip was experimentally tested...... and compared to a chip with a conventional electrode layout. The improved chip was able to discriminate 0.5 mu m beads from 1 mu m as opposed to the conventional chip. Furthermore, finite element modeling was used to simulate the improvements in electrical field density and uniformity between the electrodes...... of the new electrode layout. Good agreement was observed between the model and the obtained experimental results....

  9. Electrical impedance spectroscopy (EIS)-based evaluation of biological tissue phantoms to study multifrequency electrical impedance tomography (Mf-EIT) systems

    KAUST Repository

    Bera, Tushar Kanti

    2016-03-18

    Abstract: Electrical impedance tomography (EIT) phantoms are essential for the calibration, comparison and evaluation of the EIT systems. In EIT, the practical phantoms are typically developed based on inhomogeneities surrounded by a homogeneous background to simulate a suitable conductivity contrast. In multifrequency EIT (Mf-EIT) evaluation, the phantoms must be developed with the materials which have recognizable or distinguishable impedance variations over a wide range of frequencies. In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity are analyzed. A number of practical phantoms with different tissue inhomogeneities and different inhomogeneity configurations are developed and the multifrequency impedance imaging is studied with the Mf-EIT system to evaluate the phantoms. The conductivity of the vegetable inhomogeneities reconstructed from the EIT imaging is compared with the conductivity values obtained from the EIS studies. Experimental results obtained from multifrequency EIT reconstruction demonstrate that the electrical impedance of all the biological tissues inhomogenity decreases with frequency. The potato tissue phantom produces better impedance image in high frequency ranges compared to the cucumber phantom, because the cucumber impedance at high frequency becomes lesser than that of the potato at the same frequency range. Graphical Abstract: [Figure not available: see fulltext.] © 2016 The Visualization Society of Japan

  10. Electrical Impedance Spectroscopy for Electro-Mechanical Characterization of Conductive Fabrics

    Directory of Open Access Journals (Sweden)

    Tushar Kanti Bera

    2014-06-01

    Full Text Available When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS. We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor.

  11. Determination of salt content in various depth of pork chop by electrical impedance spectroscopy

    International Nuclear Information System (INIS)

    Kaltenecker, P; Szöllösi, D; Vozáry, E; Friedrich, L

    2013-01-01

    The salt concentration was determined inside of pork chop both by electrical impedance spectroscopy and by a conventional chemical method (according to Mohr). The pork chop in various depths (4 mm, 10 mm, 20 mm and 25 mm) was punctured with two stainless steel electrodes. The length of electrodes was 60 mm, and they were insulated along the length except 1 cm section on the end, so the measurement of impedance was realized in various depths. The magnitude and phase angle of impedance were measured with a HP 4284A and a HP 4285A LCR meters from 30 Hz up to 1 MHz and from 75 kHz up to 30 MHz frequency range, respectively at 1 V voltage. The distance between the electrodes was 1 cm. The impedance magnitude decreased as the salt concentration increased. The magnitude of open-short corrected impedance values at various frequencies (10 kHz, 100 kHz, 125 kHz, 1.1 MHz and 8 MHz) showed a good correlation with salt content determined by chemical procedure. The electrical impedance spectroscopy seems a prospective method for determination the salt concentration inside the meat in various depths during the curing procedure.

  12. Coplanar Electrode Layout Optimized for Increased Sensitivity for Electrical Impedance Spectroscopy

    Directory of Open Access Journals (Sweden)

    Casper Hyttel Clausen

    2014-12-01

    Full Text Available This work describes an improvement in the layout of coplanar electrodes for electrical impedance spectroscopy. We have developed, fabricated, and tested an improved electrode layout, which improves the sensitivity of an impedance flow cytometry chip. The improved chip was experimentally tested and compared to a chip with a conventional electrode layout. The improved chip was able to discriminate 0.5 μm beads from 1 μm as opposed to the conventional chip. Furthermore, finite element modeling was used to simulate the improvements in electrical field density and uniformity between the electrodes of the new electrode layout. Good agreement was observed between the model and the obtained experimental results.

  13. Current source enhancements in Electrical Impedance Spectroscopy (EIS) to cancel unwanted capacitive effects

    Science.gov (United States)

    Zarafshani, Ali; Bach, Thomas; Chatwin, Chris; Xiang, Liangzhong; Zheng, Bin

    2017-03-01

    Electrical Impedance Spectroscopy (EIS) has emerged as a non-invasive imaging modality to detect and quantify functional or electrical properties related to the suspicious tumors in cancer screening, diagnosis and prognosis assessment. A constraint on EIS systems is that the current excitation system suffers from the effects of stray capacitance having a major impact on the hardware subsystem as the EIS is an ill-posed inverse problem which depends on the noise level in EIS measured data and regularization parameter in the reconstruction algorithm. There is high complexity in the design of stable current sources, with stray capacitance reducing the output impedance and bandwidth of the system. To confront this, we have designed an EIS current source which eliminates the effect of stray capacitance and other impacts of the capacitance via a variable inductance. In this paper, we present a combination of operational CCII based on a generalized impedance converter (OCCII-GIC) with a current source. The aim of this study is to use the EIS system as a biomedical imaging technique, which is effective in the early detection of breast cancer. This article begins with the theoretical description of the EIS structure, current source topologies and proposes a current conveyor in application of a Gyrator to eliminate the current source limitations and its development followed by simulation and experimental results. We demonstrated that the new design could achieve a high output impedance over a 3MHz frequency bandwidth when compared to other types of GIC circuits combined with an improved Howland topology.

  14. Tissue characterization using electrical impedance spectroscopy data: a linear algebra approach.

    Science.gov (United States)

    Laufer, Shlomi; Solomon, Stephen B; Rubinsky, Boris

    2012-06-01

    In this study, we use a new linear algebra manipulation on electrical impedance spectroscopy measurements to provide real-time information regarding the nature of the tissue surrounding the needle in minimal invasive procedures. Using a Comsol Multiphysics three-dimensional model, a phantom based on ex vivo animal tissue and in vivo animal data, we demonstrate how tissue inhomogeneity can be characterized without any previous knowledge of the electrical properties of the different tissues, except that they should not be linearly dependent on a certain frequency range. This method may have applications in needle biopsies, radiation seeds, or minimally invasive surgery and can reduce the number of computer tomography or magnetic resonance imaging images. We conclude by demonstrating how this mathematical approach can be useful in other applications.

  15. Tissue characterization using electrical impedance spectroscopy data: a linear algebra approach

    International Nuclear Information System (INIS)

    Laufer, Shlomi; Solomon, Stephen B; Rubinsky, Boris

    2012-01-01

    In this study, we use a new linear algebra manipulation on electrical impedance spectroscopy measurements to provide real-time information regarding the nature of the tissue surrounding the needle in minimal invasive procedures. Using a Comsol Multiphysics three-dimensional model, a phantom based on ex vivo animal tissue and in vivo animal data, we demonstrate how tissue inhomogeneity can be characterized without any previous knowledge of the electrical properties of the different tissues, except that they should not be linearly dependent on a certain frequency range. This method may have applications in needle biopsies, radiation seeds, or minimally invasive surgery and can reduce the number of computer tomography or magnetic resonance imaging images. We conclude by demonstrating how this mathematical approach can be useful in other applications. (paper)

  16. Non-invasive assessment of radiation injury with electrical impedance spectroscopy

    International Nuclear Information System (INIS)

    Osterman, K Sunshine; Hoopes, P Jack; De Lorenzo, Christine; Gladstone, David J; Paulsen, Keith D

    2004-01-01

    A detailed understanding of non-targeted normal tissue response is necessary for the optimization of radiation treatment plans in cancer therapy. In this study, we evaluate the ability of electrical impedance spectroscopy (EIS) to non-invasively determine and quantify the injury response in soft tissue after high dose rate (HDR) irradiation, which is characterized by large localized dose distributions possessing steep spatial gradients. The HDR after-loading technique was employed to irradiate small volumes of muscle tissue with single doses (26-52 Gy targeted 5 mm away from the source). Impedance measurements were performed on 29 rats at 1, 2 and 3 month post-irradiation, employing 31 frequencies in the 1 kHz to 1 MHz range. Over the first 3 months, conductivity increased by 48% and 26% following target doses of 52 Gy and 26 Gy 5 mm from the HDR source, respectively. Injury, assessed independently through a grid-based scoring method showed a quadratic dependence on distance from source. A significant injury (50% of cells atrophied, necrotic or degenerating) in 1.2% of the volume, accompanied by more diffuse injury (25% of cells atrophied, necrotic or degenerating) in 9% of the tissue produced a conductivity increase of 0.02 S m -1 (8% over a baseline of 0.24 S m -1 ). This was not statistically significant at p 0.01. Among treatment groups, injury differences in 22% of the volume led to statistically significant differences in conductivity of 0.07 S m -1 (23% difference in conductivity). Despite limitations, the success of EIS in detecting responses in a fraction of the tissue probed, during these early post-irradiation time-points, is encouraging. Electrical impedance spectroscopy may provide a useful metric of atrophy and the development of fibrosis secondary to radiation that could be further developed into a low-cost imaging method for radiotherapy monitoring and assessment

  17. Electrical impedance spectroscopy as a potential tool for recovering bone porosity

    International Nuclear Information System (INIS)

    Bonifasi-Lista, C; Cherkaev, E

    2009-01-01

    This paper deals with the recovery of porosity of bone from measurements of its effective electrical properties. The microstructural information is contained in the spectral measure in the Stieltjes representation of the bone effective complex permittivity or complex conductivity and can be recovered from the measurements over a range of frequencies. The problem of reconstruction of the spectral measure is very ill-posed and requires the use of regularization techniques. We apply the method to the effective electrical properties of cancellous bone numerically calculated using micro-CT images of human vertebrae. The presented method is based on an analytical approach and does not rely on correlation analysis nor on any a priori model of the bone micro-architecture. However the method requires a priori knowledge of the properties of the bone constituents (trabecular tissue and bone marrow). These properties vary from patient to patient. To address this issue, a sensitivity analysis of the technique was performed. Normally distributed random noise was added to the data to simulate uncertainty in the properties of the constituents and possible experimental errors in measurements of the effective properties. The values of porosity calculated from effective complex conductivity are in good agreement with the true values of bone porosity even assuming high level errors in the estimation of the bone components. These results prove the future potential of electrical impedance spectroscopy for in vivo monitoring of level and treatment of osteoporosis.

  18. Electrical impedance spectroscopy for quality assessment of meat and fish: A review on basic principles, measurement methods, and recent advances

    Science.gov (United States)

    Electrical impedance spectroscopy (EIS), as an effective analytical technique for electrochemical system, has shown a wide application for food quality and safety assessment recently. Individual differences of livestock cause high variation in quality of raw meat and fish and their commercialized pr...

  19. Detection of Potential Induced Degradation in c-Si PV Panels Using Electrical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Oprea, Matei-lon; Spataru, Sergiu; Sera, Dezso

    2016-01-01

    This work, for the first time, investigates an Impedance Spectroscopy (IS) based method for detecting potential-induced degradation (PID) in crystalline silicon photovoltaic (c-Si PV) panels. The method has been experimentally tested on a set of panels that were confirmed to be affected by PID...

  20. Novel microfluidic system for online monitoring of biofilm dynamics by electrical impedance spectroscopy and amperometry

    Science.gov (United States)

    Bruchmann, Julia; Sachsenheimer, Kai; Schwartz, Thomas; Rapp, Bastian E.

    2016-03-01

    Biofilm formation is ubiquitous in nature where microorganisms attach to surfaces and form highly adapted and protected communities. In technical and industrial systems like drinking water supply, food production or shipping industry biofilms are a major cause of product contamination, biofouling, and biocorrosion. Therefore, understanding of biofilm formation and means of preventing biofilm formation is important to develop novel biofilm treatment strategies. A system allowing directly online detection and monitoring biofilm formation is necessary. However, until today, there are little to none technical systems featuring a non-destructive real-time characterization of biofilm formation in a highthroughput manner. This paper presents such a microfluidic system based on electrical impedance spectroscopy (EIS) and amperomertic current measurement. The sensor consists of four modules, each housing 24 independent electrodes within 12 microfluidic channels. Attached biomass on the electrodes is monitored as increased inhibition in charge transfer by EIS and a change in metabolic activity is measured as change in produced electric current by amperometry. This modular sensor system is highly adaptable and suitable for a broad range of microbiological applications. Among others, biofilm formation processes can be characterized online, biofilm manipulation like inactivation or destabilization can be monitored in real-time and gene expression can be analyzed in parallel. The use of different electrode designs allows effective biofilm studies during all biofilm phases. The whole system was recently extended by an integrated pneumatic microfluidic pump which enables easy handling procedures. Further developments of this pumping module will allow a fully- automated computer-controlled valving and pumping.

  1. Electrical conductivity and transport properties of cement-based materials measured by impedance spectroscopy

    Science.gov (United States)

    Shane, John David

    The use of Impedance Spectroscopy (IS) as a tool to evaluate the electrical and transport properties of cement-based materials was critically evaluated. Emphasis was placed on determining the efficacy of IS by applying it as a tool to investigate several families of cement-based materials. Also, the functional aspects of electroding and null corrections were also addressed. The technique was found to be advantageous for these analyses, especially as a non-destructive, in-situ, rapid test. Moreover, key insights were gained into several cement-based systems (e.g., cement mortars and oil-well grouts) as well as the effect that certain testing techniques can have on materials (e.g., the rapid chloride permeability test). However, some limitations of IS were identified. For instance, improper electroding of samples can lead to erroneous results and incorrect interpretations for both two-point and multi-point measurements. This is an area of great importance, but it has received very little attention in the literature. Although the analysis of cement/electrode techniques is in its infancy, much progress was made in gaining a full understand of how to properly and reliably connect electrodes to cement-based materials. Through the application of IS to materials such as oil-well grouts, cement mortars and concretes, a great deal of valuable information about the effectiveness of IS has been gained. Oil-well cementing is somewhat limited by the inability to make measurements in the well-bore. By applying IS to oil-well grouts in a laboratory environment, it was demonstrated that IS is a viable technique with which to test the electrical and transport properties of these materials in-situ. Also, IS was shown to have the ability to measure the electrical conductivity of cement mortars with such accuracy, that very subtle changes in properties can be monitored and quantified. Through the use of IS and theoretical models, the complex interplay between the interfacial transition

  2. Classification of thyroid nodules using a resonance-frequency-based electrical impedance spectroscopy: progress assessment

    Science.gov (United States)

    Zheng, Bin; Tublin, Mitchell E.; Lederman, Dror; Klym, Amy H.; Brown, Erica D.; Gur, David

    2012-02-01

    The incidence of thyroid cancer is rising faster than other malignancies and has nearly doubled in the United States (U.S.) in the last 30 years. However, classifying between malignant and benign thyroid nodules is often difficult. Although ultrasound guided Fine Needle Aspiration Biopsy (FNAB) is considered an excellent tool for triaging patients, up to 25% of FNABs are inconclusive. As a result, definitive diagnosis requires an exploratory surgery and a large number of these are performed in the U.S. annually. It would be extremely beneficial to develop a non-invasive tool or procedure that could assist in assessing the likelihood of malignancy of otherwise indeterminate thyroid nodules, thereby reducing the number of exploratory thyroidectomies that are performed under general anesthesia. In this preliminary study we demonstrate a unique hand-held Resonance-frequency based Electrical Impedance Spectroscopy (REIS) device with six pairs of detection probes to detect and classify thyroid nodules using multi-channel EIS output signal sweeps. Under an Institutional Review Board (IRB)-approved case collection protocol, this REIS device is being tested in our clinical facility and we have been collecting an initial patient data set since March of this year. Between March and August of 2011, 65 EIS tests were conducted on 65 patients. Among these cases, six depicted pathology-verified malignant cells. Our initial assessment indicates the feasibility of easily applying this REIS device and measurement approach in a very busy clinical setting. The measured resonance frequency differences between malignant and benign nodules could potentially make it possible to accurately classify indeterminate thyroid nodules.

  3. Electrical Impedance Tomography Technology

    Data.gov (United States)

    National Aeronautics and Space Administration — The goal for the Electrical Impedance Tomography Technology (EITT) project is to develop a reliable portable, lightweight device providing two-dimensional...

  4. Electrical Impedance Spectroscopy for Detection of Cells in Suspensions Using Microfluidic Device with Integrated Microneedles

    Directory of Open Access Journals (Sweden)

    Muhammad Asraf Mansor

    2017-02-01

    Full Text Available In this study, we introduce novel method of flow cytometry for cell detection based on impedance measurements. The state of the art method for impedance flow cytometry detection utilizes an embedded electrode in the microfluidic to perform measurement of electrical impedance of the presence of cells at the sensing area. Nonetheless, this method requires an expensive and complicated electrode fabrication process. Furthermore, reuse of the fabricated electrode also requires an intensive and tedious cleaning process. Due to that, we present a microfluidic device with integrated microneedles. The two microneedles are placed at the half height of the microchannel for cell detection and electrical measurement. A commercially-available Tungsten needle was utilized for the microneedles. The microneedles are easily removed from the disposable PDMS (Polydimethylsiloxane microchannel and can be reused with a simple cleaning process, such as washing by ultrasonic cleaning. Although this device was low cost, it preserves the core functionality of the sensor, which is capable of detecting passing cells at the sensing area. Therefore, this device is suitable for low-cost medical and food safety screening and testing process in developing countries.

  5. Electrical and Dielectric Properties of Polyaniline and Polyaniline/Montmorillonite Nanocomposite Prepared by Solid Reaction Using Spectroscopy Impedance

    Directory of Open Access Journals (Sweden)

    Imene Bekri-Abbes

    2015-01-01

    Full Text Available The combination of two components with uniform distribution in nanoscale is expected to facilitate wider applications of the material. In this study, polyaniline (PAn and polyaniline/montmorillonite (Mt nanocomposite were prepared by solid reaction using persulfate of ammonium as oxidant. The phase composition and morphology of the nanocomposite were characterized by FTIR, UV-visible spectroscopy, X-ray diffractometer, thermal gravimetric analysis, and scanning electron microscopy. The electrical and dielectric properties were determined using spectroscopy impedance. The analysis of UV-visible and FTIR spectroscopy demonstrated that aniline chloride has been polymerized into PAn in its conducting emeraldine form. Thermogravimetric analysis suggested that PAn chains intercalated in the clay host are more thermally stable than those of free PAn prepared by solid-solid reaction. Electrical measurements were carried out using the complex impedance technique in the frequency range of 10−2 to 104 Hz at different temperatures. The ac conductivity data of different nanocomposites were analyzed as a function of frequency and temperature. It has been found that the incorporation of inorganic clay phase into polyaniline matrix has an effect on the electrical and dielectric properties of the nanomaterial.

  6. High temperature impedance spectroscopy of barium stannate

    Indian Academy of Sciences (India)

    ... differential thermal analysis, thermogravimetric analysis and Fourier transform infrared techniques. Electrical properties were studied using a.c. impedance spectroscopy technique in the temperature range of 50–650 °C and frequency range of 10 Hz–13 MHz. The complex impedance plots at temperature ≥ 300 °C show ...

  7. Electric and dielectric behavior of copper-chromium layered double hydroxide intercalated with dodecyl sulfate anions using impedance spectroscopy

    Science.gov (United States)

    Elhatimi, Wafaa; Bouragba, Fatima Zahra; Lahkale, Redouane; Sadik, Rachid; Lebbar, Nacira; Siniti, Mostapha; Sabbar, Elmouloudi

    2018-05-01

    The Cu2Cr-DS-LDH hybrid was successfully prepared by the anion exchange method at room temperature. The structure, the chemical composition and the physico-chemical properties of the sample were determined using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and inductively coupled plasma (ICP). In this work, the electrical and dielectric properties investigated are determined using impedance spectroscopy (IS) in a frequency range of 1 Hz to 1 MHz. Indeed, the Nyquist diagram modelized by an electrical equivalent circuit showed three contributions attributed respectively to the polarization of grains, grains boundaries and interface electrode-sample. This modelization allowed us to determine the intrinsic electrical parameters of the hybrid (resistance, pseudo-capacitance and relaxation time). The presence of the non-Debye relaxation phenomena was confirmed by the frequency analysis of impedance. Moreover, the evolution of the alternating current conductivity (σac) studied obeys the double power law of Jonscher. The ionic conduction of this material was generated through a jump movement by translation of the charge carriers. As for the dielectric behavior of the material, the evolution of dielectric constant as a function of frequency shows relatively high values in a frequency range between 10 Hz and 1 KHz. The low values of the loss tangent obtained in this frequency zone can valorize this LDH hybrid.

  8. Assay based on electrical impedance spectroscopy to discriminate between normal and cancerous mammalian cells

    Science.gov (United States)

    Giana, Fabián Eduardo; Bonetto, Fabián José; Bellotti, Mariela Inés

    2018-03-01

    In this work we present an assay to discriminate between normal and cancerous cells. The method is based on the measurement of electrical impedance spectra of in vitro cell cultures. We developed a protocol consisting on four consecutive measurement phases, each of them designed to obtain different information about the cell cultures. Through the analysis of the measured data, 26 characteristic features were obtained for both cell types. From the complete set of features, we selected the most relevant in terms of their discriminant capacity by means of conventional statistical tests. A linear discriminant analysis was then carried out on the selected features, allowing the classification of the samples in normal or cancerous with 4.5% of false positives and no false negatives.

  9. Microwave Impedance Spectroscopy and Temperature Effects on the Electrical Properties of Au/BN/C Interfaces

    Directory of Open Access Journals (Sweden)

    Hazem K. Khanfar

    2017-01-01

    Full Text Available In the current study, an Au/BN/C microwave back-to-back Schottky device is designed and characterized. The device morphology and roughness were evaluated by means of scanning electron and atomic force microscopy. As verified by the Richardson–Schottky current conduction transport mechanism which is well fitted to the experimental data, the temperature dependence of the current-voltage characteristics of the devices is dominated by the electric field assisted thermionic emission of charge carriers over a barrier height of ~0.87 eV and depletion region width of ~1.1 μm. Both the depletion width and barrier height followed an increasing trend with increasing temperature. On the other hand, the alternating current conductivity analysis which was carried out in the frequency range of 100–1400 MHz revealed the domination of the phonon assisted quantum mechanical tunneling (hopping of charge carriers through correlated barriers (CBH. In addition, the impedance and power spectral studies carried out in the gigahertz-frequency domain revealed a resonance-antiresonance feature at frequency of  ~1.6 GHz. The microwave power spectra of this device revealed an ideal band stop filter of notch frequency of  ~1.6 GHz. The ac signal analysis of this device displays promising characteristics for using this device as wave traps.

  10. Probing the biocompatibility of MoS2 nanosheets by cytotoxicity assay and electrical impedance spectroscopy

    Science.gov (United States)

    Shah, Pratikkumar; Narayanan, Tharangattu N.; Li, Chen-Zhong; Alwarappan, Subbiah

    2015-08-01

    Transition metal dichalgogenides such as MoS2 have recently emerged as hot two-dimensional (2D) materials due to their superior electronic and catalytic properties. Recently, we have reported the usefulness of MoS2 nanosheets toward the electrochemical detection of neurotransmitters and glucose (Narayanan et al 2014 Nanotechnology 25 335702). Furthermore, there are reports available in the literature that demonstrate the usefulness of MoS2 nanosheets for biosensing and energy storage applications (Zhu et al 2013 J. Am. Chem. Soc. 135 5998-6001 Pumera and Loo 2014 Trends Anal. Chem. 61 49-53 Lee et al 2014 Sci. Rep. 4 7352; Stephenson et al 2014 Energy Environ. Sci. 7 209-31). Understanding the cytotoxic effect of any material is very important prior to employing them for any in vivo biological applications such as implantable sensors, chips, or carriers for drug delivery and cell imaging purposes. Herein, we report the cytotoxicity of the MoS2 nanosheets based on the cytotoxic assay results and electrical impedance analysis using rat pheochromocytoma cells (PC12) and rat adrenal medulla endothelial cells (RAMEC). Our results indicated that the MoS2 nanosheets synthesized in our work are safe 2D nanosheets for futuristic biomedical applications.

  11. Electrical biopsy of irradiated intestinal tissue with a simple electrical impedance spectroscopy system for radiation enteropathy in rats—a pilot study

    International Nuclear Information System (INIS)

    Huang, Yu-Jie; Lu, Yi-Yu; Chen, Cheng-Yu; Cheng, Kuo-Sheng; Huang, Eng-Yen

    2011-01-01

    Electrical impedance is one of the most often used parameters for characterizing material properties, especially in biomedical applications. Electrical impedance spectroscopy (EIS), used for revealing both resistive and capacitive characteristics, is good for use in tissue characterization. In this study, a portable and simple EIS system based on a commercially available chip was used to assess rat intestinal tissues following irradiation. The EIS results were fitted to a resistor and capacitor electrical circuit model to solve the electrical properties of the tissue. The variation in the tissue's electrical characteristics was compared to the morphological and histological findings. From the experimental results, it was clear that the electrical properties, based on receiver operation curve analysis, demonstrated good detection performance relative to the histological changes. The electrical parameters of the tissues could be used to distinguish the tissue's status for investigation, which introduced a concept of 'electrical biopsy', and this 'electrical biopsy' approach may be used to complement histological examinations

  12. Determination of energy band diagram and charge carrier mobility of white emitting polymer from optical, electrical and impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mohd Sarjidan, M.A., E-mail: mohd.arif@um.edu.my; Mohd Mokhtar, H.A.; Abd Majid, W.H., E-mail: q3haliza@um.edu.my

    2015-03-15

    A single-layer white polymer light-emitting device (WPLED) has been fabricated using spin coating technique. The device was constructed as ITO/PEDOT:PSS(50 nm)/SPW-111(50 nm)/LiF(1 nm)/Al(100 nm). Indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS) are used as the transparent anode. SPW-111 is fabricated as a white emissive layer and lithium fluoride (LiF) and aluminum (Al) are used as reflecting cathode. Energy band diagram of the device was estimated from a combination of ultraviolet–visible (UV–vis) and current–voltage (J–V) analyses. Charge carrier mobility (μ) of PLED was evaluated using negative differential susceptance (−ΔB) method from impedance spectroscopy (IS) analysis. The calculated μ of the SPW-111 device is in the magnitude of 10{sup −6} cm{sup 2}/V/s. - Highlights: • Single layer PLED has been fabricated with spin-coating technique and device performance has been evaluated. • Energy band diagram of the SPW-111 is estimated from optical and electrical analyses. • Charge carrier mobility of the SPW-111 materials is obtained by impedance spectroscopy.

  13. Improvement of Depth Profiling into Biotissues Using Micro Electrical Impedance Spectroscopy on a Needle with Selective Passivation.

    Science.gov (United States)

    Yun, Joho; Kim, Hyeon Woo; Lee, Jong-Hyun

    2016-12-21

    A micro electrical impedance spectroscopy (EIS)-on-a-needle for depth profiling (μEoN-DP) with a selective passivation layer (SPL) on a hypodermic needle was recently fabricated to measure the electrical impedance of biotissues along with the penetration depths. The SPL of the μEoN-DP enabled the sensing interdigitated electrodes (IDEs) to contribute predominantly to the measurement by reducing the relative influence of the connection lines on the sensor output. The discrimination capability of the μEoN-DP was verified using phosphate-buffered saline (PBS) at various concentration levels. The resistance and capacitance extracted through curve fitting were similar to those theoretically estimated based on the mixing ratio of PBS and deionized water; the maximum discrepancies were 8.02% and 1.85%, respectively. Depth profiling was conducted using four-layered porcine tissue to verify the effectiveness of the discrimination capability of the μEoN-DP. The magnitude and phase between dissimilar porcine tissues (fat and muscle) were clearly discriminated at the optimal frequency of 1 MHz. Two kinds of simulations, one with SPL and the other with complete passivation layer (CPL), were performed, and it was verified that the SPL was advantageous over CPL in the discrimination of biotissues in terms of sensor output.

  14. Improvement of Depth Profiling into Biotissues Using Micro Electrical Impedance Spectroscopy on a Needle with Selective Passivation

    Directory of Open Access Journals (Sweden)

    Joho Yun

    2016-12-01

    Full Text Available A micro electrical impedance spectroscopy (EIS-on-a-needle for depth profiling (μEoN-DP with a selective passivation layer (SPL on a hypodermic needle was recently fabricated to measure the electrical impedance of biotissues along with the penetration depths. The SPL of the μEoN-DP enabled the sensing interdigitated electrodes (IDEs to contribute predominantly to the measurement by reducing the relative influence of the connection lines on the sensor output. The discrimination capability of the μEoN-DP was verified using phosphate-buffered saline (PBS at various concentration levels. The resistance and capacitance extracted through curve fitting were similar to those theoretically estimated based on the mixing ratio of PBS and deionized water; the maximum discrepancies were 8.02% and 1.85%, respectively. Depth profiling was conducted using four-layered porcine tissue to verify the effectiveness of the discrimination capability of the μEoN-DP. The magnitude and phase between dissimilar porcine tissues (fat and muscle were clearly discriminated at the optimal frequency of 1 MHz. Two kinds of simulations, one with SPL and the other with complete passivation layer (CPL, were performed, and it was verified that the SPL was advantageous over CPL in the discrimination of biotissues in terms of sensor output.

  15. Electrical Impedance Spectroscopy for Quality Assessment of Meat and Fish: A Review on Basic Principles, Measurement Methods, and Recent Advances

    Directory of Open Access Journals (Sweden)

    Xin Zhao

    2017-01-01

    Full Text Available Electrical impedance spectroscopy (EIS, as an effective analytical technique for electrochemical system, has shown a wide application for food quality and safety assessment recently. Individual differences of livestock cause high variation in quality of raw meat and fish and their commercialized products. Therefore, in order to obtain the definite quality information and ensure the quality of each product, a fast and on-line detection technology is demanded to be developed to monitor product processing. EIS has advantages of being fast, nondestructive, inexpensive, and easily implemented and shows potential to develop on-line detecting instrument to replace traditional methods to realize time, cost, skilled persons saving and further quality grading. This review outlines the fundamental theories and two common measurement methods of EIS applied to biological tissue, summarizes its application specifically for quality assessment of meat and fish, and discusses challenges and future trends of EIS technology applied for meat and fish quality assessment.

  16. Electrical impedance tomography

    Science.gov (United States)

    Lobo, Beatriz; Hermosa, Cecilia; Abella, Ana

    2018-01-01

    Continuous assessment of respiratory status is one of the cornerstones of modern intensive care unit (ICU) monitoring systems. Electrical impedance tomography (EIT), although with some constraints, may play the lead as a new diagnostic and guiding tool for an adequate optimization of mechanical ventilation in critically ill patients. EIT may assist in defining mechanical ventilation settings, assess distribution of tidal volume and of end-expiratory lung volume (EELV) and contribute to titrate positive end-expiratory pressure (PEEP)/tidal volume combinations. It may also quantify gains (recruitment) and losses (overdistention or derecruitment), granting a more realistic evaluation of different ventilator modes or recruitment maneuvers, and helping in the identification of responders and non-responders to such maneuvers. Moreover, EIT also contributes to the management of life-threatening lung diseases such as pneumothorax, and aids in guiding fluid management in the critical care setting. Lastly, assessment of cardiac function and lung perfusion through electrical impedance is on the way. PMID:29430443

  17. Microelectrical Impedance Spectroscopy for the Differentiation between Normal and Cancerous Human Urothelial Cell Lines: Real-Time Electrical Impedance Measurement at an Optimal Frequency

    Directory of Open Access Journals (Sweden)

    Yangkyu Park

    2016-01-01

    Full Text Available Purpose. To distinguish between normal (SV-HUC-1 and cancerous (TCCSUP human urothelial cell lines using microelectrical impedance spectroscopy (μEIS. Materials and Methods. Two types of μEIS devices were designed and used in combination to measure the impedance of SV-HUC-1 and TCCSUP cells flowing through the channels of the devices. The first device (μEIS-OF was designed to determine the optimal frequency at which the impedance of two cell lines is most distinguishable. The μEIS-OF trapped the flowing cells and measured their impedance at a frequency ranging from 5 kHz to 1 MHz. The second device (μEIS-RT was designed for real-time impedance measurement of the cells at the optimal frequency. The impedance was measured instantaneously as the cells passed the sensing electrodes of μEIS-RT. Results. The optimal frequency, which maximized the average difference of the amplitude and phase angle between the two cell lines (p<0.001, was determined to be 119 kHz. The real-time impedance of the cell lines was measured at 119 kHz; the two cell lines differed significantly in terms of amplitude and phase angle (p<0.001. Conclusion. The μEIS-RT can discriminate SV-HUC-1 and TCCSUP cells by measuring the impedance at the optimal frequency determined by the μEIS-OF.

  18. Relaxations in Ba{sub 2}BiTaO{sub 6} ceramics investigated by impedance and electric modulus spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Joao Elias Figuereido Soares [Departamento de Fisica - CCET, Universidade Federal do Maranhao, Campus do Bacanga, 65085-580, Sao Luis -MA (Brazil); Paschoal, Carlos William de Araujo, E-mail: paschoal@ufma.br [Departamento de Fisica - CCET, Universidade Federal do Maranhao, Campus do Bacanga, 65085-580, Sao Luis -MA (Brazil); Silva, Eder Nascimento [Departamento de Fisica - CCET, Universidade Federal do Maranhao, Campus do Bacanga, 65085-580, Sao Luis -MA (Brazil); Mince, Kathryn A.; Lufaso, Michael W. [Department of Chemistry, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224 (United States)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer We have confirmed that the relaxation observed in Ba{sub 2}BiTaO{sub 6} is due to the conduction mechanism. Black-Right-Pointing-Pointer The conduction mechanism is the oxygen vacancies hopping. Black-Right-Pointing-Pointer We have explained because the activation energy for the Ba{sub 2}BiTaO{sub 6} is lower than observed for Ba{sub 2}BiSbO{sub 6} with basis in zero-point energy of both materials. Black-Right-Pointing-Pointer We have showed that a minor secondary phase is a minor secondary phase, which is common when the BBTO is obtained by ceramic method under air, does not change significantly the electrical properties of BBTO. -- Abstract: Impedance spectroscopy analysis of the dielectric properties of a Ba{sub 2}BiTaO{sub 6} ceramic was performed in the temperature range from room temperature to 500 K. The sample was prepared using conventional solid state synthesis under air and the X-ray diffraction shows the presence of Ba{sub 5}Ta{sub 4}O{sub 15} as a minor secondary phase (0.09%). The impedance data clearly show contributions of the grain and grain boundary. The results indicate that the conduction in Ba{sub 2}BiTaO{sub 6} is due to hopping of oxygen vacancies and that the impurities not influence the conduction mechanism.

  19. Validation of a multi-frequency electrical impedance tomography (mfEIT) system KHU Mark1: impedance spectroscopy and time-difference imaging

    International Nuclear Information System (INIS)

    Oh, Tong In; Koo, Hwan; Lee, Kyung Heon; Kim, Sang Min; Woo, Eung Je; Lee, Jeehyun; Kim, Sung Wan; Seo, Jin Keun

    2008-01-01

    Validation and interpretation of reconstructed images using a multi-frequency electrical impedance tomography (mfEIT) requires a conductivity phantom including imaging objects with known complex conductivity (σ + iωε) spectra. We describe imaging experiments using the recently developed mfEIT system called the KHU Mark1 with the frequency range of 10 Hz to 500 kHz. Using a bio-impedance spectroscopy (BIS) system, we first measured complex conductivity spectra of different imaging objects including saline, agar, polyacrylamide, TX151, animal hide gelatin, banana and cucumber. Based on an analysis of how conductivity and permittivity affect measured complex boundary voltages, we suggested a new complex version of a multi-frequency time-difference image reconstruction algorithm. Imaging experiments were conducted to produce time-difference images of the objects at multiple frequencies using the proposed algorithm. Images of a conductor (stainless steel) and an insulator (acrylic plastic) were used to set a common scale bar to display all images. Comparing reconstructed time-difference images at multiple frequencies with measured complex conductivity spectra, we found that they showed an overall similarity in terms of changes in complex conductivity values with respect to frequency. However, primarily due to the limitation of the difference imaging algorithm, we suggest that multi-frequency time-difference images must be interpreted in terms of relative contrast changes with respect to frequency. We propose further imaging studies using biological tissues of known complex conductivity spectra and using human subjects to find clinical applications of the mfEIT system

  20. Highly sensitive three-dimensional interdigitated microelectrode for microparticle detection using electrical impedance spectroscopy

    International Nuclear Information System (INIS)

    Chang, Fu-Yu; Chen, Ming-Kun; Jang, Ling-Sheng; Wang, Min-Haw

    2016-01-01

    Cell impedance analysis is widely used for monitoring biological and medical reactions. In this study, a highly sensitive three-dimensional (3D) interdigitated microelectrode (IME) with a high aspect ratio on a polyimide (PI) flexible substrate was fabricated for microparticle detection (e.g. cell quantity detection) using electroforming and lithography technology. 3D finite element simulations were performed to compare the performance of the 3D IME (in terms of sensitivity and signal-to-noise ratio) to that of a planar IME for particles in the sensing area. Various quantities of particles were captured in Dulbecco’s modified Eagle medium and their impedances were measured. With the 3D IME, the particles were arranged in the gap, not on the electrode, avoiding the noise due to particle position. For the maximum particle quantities, the results show that the 3D IME has at least 5-fold higher sensitivity than that of the planar IME. The trends of impedance magnitude and phase due to particle quantity were verified using the equivalent circuit model. The impedance (1269 Ω) of 69 particles was used to estimate the particle quantity (68 particles) with 98.6% accuracy using a parabolic regression curve at 500 kHz. (paper)

  1. Electrical characterization of strontium titanate borosilicate glass ceramics system with bismuth oxide addition using impedance spectroscopy

    International Nuclear Information System (INIS)

    Thakur, O.P.; Kumar, Devendra; Parkash, Om; Pandey, Lakshman

    2003-01-01

    The ac electrical data, measured in the frequency range 0.1 kHz-1 MHz, were used to study the electrical response of strontium titanate borosilicate glass ceramic system with bismuth oxide addition. Complex plane plots from these electrical data for various glass ceramic samples reveal contributions from simultaneously operating polarization mechanisms to overall dielectric behavior. The complex modulus (M * ) representation of electrical data for various glass ceramic samples were found to be more informative. Equivalent circuit models, which represent the electrical behavior of glass ceramic samples, were determined using complex non-linear least square (CNLS) fitting. An attempt has been made to understand the dielectric behavior of various glass ceramics in terms of contributions arising from different polarization processes occurring at glassy matrix, crystalline phases, glass to crystal interface region and blocking electrodes. Glass ceramics containing SrTiO 3 and TiO 2 (rutile) phases show thermally stable dielectric behavior

  2. Analysis of electrical and thermal stress effects on PCBM:P3HT solar cells by photocurrent and impedance spectroscopy modeling

    DEFF Research Database (Denmark)

    Torto, Lorenzo; Rizzo, Antonio; Cester, Andrea

    2017-01-01

    We investigated the effects of electrical stress and thermal storage by means of photocurrent, Impedance Spectroscopy and Open Circuit Voltage Decay models. The electrical stress damages only the active layer, by reducing the generation rate, the polaron separation probability and the carrier...... lifetime. The thermal stress also degrades the anode interface. This reflects on the appearance of an inflection in the I-V photocurrent shape close to the operative region....

  3. Impedance Spectroscopy of Dielectrics and Electronic Conductors

    DEFF Research Database (Denmark)

    Bonanos, Nikolaos; Pissis, Polycarpos; Macdonald, J. Ross

    2013-01-01

    Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property, such as admi......Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property......, such as admittance or dielectric constant - as a function of frequency and comparing the results with expectations based on physical, chemical, and microstructural models. This article reviews the principles and practical aspects of the technique, the representations of the results, the analysis of data......, and procedures for the correction of measurement errors. The applications of impedance spectroscopy are illustrated with examples from electroceramics and polymer-based dielectric systems. The way in which the technique is applied to the two classes of materials is compared with reference to the different models...

  4. Facts and artefacts regarding correlation between skin electrical impedance spectroscopy (EIS) and blood glucose

    International Nuclear Information System (INIS)

    Ollmar, Stig; Nicander, Ingrid; Åberg, Peter; Bolinder, Jan

    2013-01-01

    Earlier observations on possible co-variation between skin EIS and blood glucose prompted us to map and include other factors at play in the predictive model. Skin pH would be one such factor. A cohort of 20 diabetics was investigated, taking around 30 measurements spread over each of two different days 2–21 days apart. Each measurement comprises skin EIT in the frequency range 1kHz to 2.5MHz, skin pH, and immediately evaluated blood samples. There is a co-variation for some, but not all, test persons. The relationship gets stronger on the group level by adding pH-information, but is still poor or non-existent for some test persons. Non-invasive EIS measurements on skin is influenced by skin hydration, blood glucose, skin pH, body location, season, environmental factors, and variables not yet understood. Since impedance related parameters are used to estimate skin hydration, users of such devices should be aware that skin pH may influence as much as the water content of the stratum corneum.

  5. Facts and artefacts regarding correlation between skin electrical impedance spectroscopy (EIS) and blood glucose

    Science.gov (United States)

    Ollmar, Stig; Nicander, Ingrid; Åberg, Peter; Bolinder, Jan

    2013-04-01

    Earlier observations on possible co-variation between skin EIS and blood glucose prompted us to map and include other factors at play in the predictive model. Skin pH would be one such factor. A cohort of 20 diabetics was investigated, taking around 30 measurements spread over each of two different days 2-21 days apart. Each measurement comprises skin EIT in the frequency range 1kHz to 2.5MHz, skin pH, and immediately evaluated blood samples. There is a co-variation for some, but not all, test persons. The relationship gets stronger on the group level by adding pH-information, but is still poor or non-existent for some test persons. Non-invasive EIS measurements on skin is influenced by skin hydration, blood glucose, skin pH, body location, season, environmental factors, and variables not yet understood. Since impedance related parameters are used to estimate skin hydration, users of such devices should be aware that skin pH may influence as much as the water content of the stratum corneum.

  6. Impedance spectroscopy applied to the fast wounding dynamics of an electrical wound-healing assay in mammalian cells

    Science.gov (United States)

    Bellotti, Mariela I.; Giana, Fabián E.; Bonetto, Fabián J.

    2015-08-01

    Electrical wound-healing assays are often used as a means to study in vitro cell migration and proliferation. In such analysis, a cell monolayer that sits on a small electrode is electrically wounded and its spectral impedance is then continuously measured in order to monitor the healing process. The relatively slow dynamics of the cell healing have been extensively studied, while those of the much faster wounding phase have not yet been investigated. An analysis of the electrical properties of a particular cell type during this phase could give extra information about the changes in the cell membrane due to the application of the wounding current, and could also be useful to optimize the wounding regime for different cell types. The main issue when trying to register information about these dynamics is that the traditional measurement scheme employed in typical wound-healing assays doesn’t allow the simultaneous application of the wounding signal and measurement of the system’s impedance. In this paper, we overcome this limitation by implementing a measurement strategy consisting of cycles of fast alternating low- and high-voltage signals applied on electrodes covered with mammalian cells. This approach is capable of registering the fast impedance changes during the transient regime corresponding to the cell wounding process. Furthermore, these quasi-simultaneous high- and low-voltage measurements can be compared in order to obtain an empirical correlation between both quantities.

  7. Impedance spectroscopy applied to the fast wounding dynamics of an electrical wound-healing assay in mammalian cells

    International Nuclear Information System (INIS)

    Bellotti, Mariela I; Giana, Fabián E; Bonetto, Fabián J

    2015-01-01

    Electrical wound-healing assays are often used as a means to study in vitro cell migration and proliferation. In such analysis, a cell monolayer that sits on a small electrode is electrically wounded and its spectral impedance is then continuously measured in order to monitor the healing process. The relatively slow dynamics of the cell healing have been extensively studied, while those of the much faster wounding phase have not yet been investigated. An analysis of the electrical properties of a particular cell type during this phase could give extra information about the changes in the cell membrane due to the application of the wounding current, and could also be useful to optimize the wounding regime for different cell types. The main issue when trying to register information about these dynamics is that the traditional measurement scheme employed in typical wound-healing assays doesn’t allow the simultaneous application of the wounding signal and measurement of the system’s impedance. In this paper, we overcome this limitation by implementing a measurement strategy consisting of cycles of fast alternating low- and high-voltage signals applied on electrodes covered with mammalian cells. This approach is capable of registering the fast impedance changes during the transient regime corresponding to the cell wounding process. Furthermore, these quasi-simultaneous high- and low-voltage measurements can be compared in order to obtain an empirical correlation between both quantities. (paper)

  8. Electrical transport properties of CoMn0.2−xGaxFe1.8O4 ferrites using complex impedance spectroscopy

    Directory of Open Access Journals (Sweden)

    Chien-Yie Tsay

    2016-05-01

    Full Text Available In this study, we report the influence of Ga content on the microstructural, magnetic, and AC impedance properties of Co-based ferrites with compositions of CoMn0.2−xGaxFe1.8O4 (x=0, 0.1, and 0.2 prepared by the solid-state reaction method. Experimental results showed that the as-prepared Co-based ferrites had a single-phase spinel structure; the Curie temperature of Co-based ferrites decreased with increasing Ga content. All ferrite samples exhibited a typical hysteresis behavior with good values of saturation magnetization at room temperature. The electrical properties of Co-based ferrites were investigated using complex impedance spectroscopy analysis in the frequency range of 100 kHz-50 MHz at temperatures of 150 to 250 oC. The impedance analysis revealed that the magnitudes of the real part (Z’ and the imaginary part (Z” of complex impedance decreased with increasing temperature. Only one semicircle was observed in each complex impedance plane plot, which revealed that the contribution to conductivity was from the grain boundaries. It was found that the relaxation time for the grain boundary (τgb also decreased with increasing temperature. The values of resistance for the grain boundary (Rgb significantly increased with increasing Ga content, which indicated that the incorporation of Ga into Co-based ferrites enhanced the electrical resistivity.

  9. Early Detection of Cervical Intraepitelial Neoplasia in a Heterogeneos Group of Colombian Women Using Electrical Impedance Spectroscopy and the Miranda-López Algorithm

    International Nuclear Information System (INIS)

    Miranda, David A; Corzo, Sandra P; González-Correa, Carlos-A

    2012-01-01

    Electrical Impedance Spectroscopy (EIS) allows the study of the electrical properties of materials and structures such as biological tissues. EIS can be used as a diagnostic tool for the identification of pathological conditions such as cervical cancer. We used EIS in combination with genetic algorithms to characterize cervical epithelial squamous tissue in a heterogeneous sample of 56 Colombian women. All volunteers had a cytology taken for Papanicolau test and biopsy taken for histopathological analysis from those with a positive result (9 subjects). ROC analysis of the results suggest a sensitivity and specificity in the order of 0.73 and 0.86, respectively.

  10. IMPEDANCE SPECTROSCOPY OF POLYCRYSTALLINE TIN DIOXIDE FILMS

    Directory of Open Access Journals (Sweden)

    D. V. Adamchuck

    2016-01-01

    Full Text Available The aim of this work is the analysis of the influence of annealing in an inert atmosphere on the electrical properties and structure of non-stoichiometric tin dioxide films by means of impedance spectroscopy method. Non-stoichiometric tin dioxide films were fabricated by two-step oxidation of metallic tin deposited on the polycrystalline Al2O3 substrates by DC magnetron sputtering. In order to modify the structure and stoichiometric composition, the films were subjected to the high temperature annealing in argon atmosphere in temperature range 300–800 °С. AC-conductivity measurements of the films in the frequency range 20 Hz – 2 MHz were carried out. Variation in the frequency dependencies of the real and imaginary parts of the impedance of tin dioxide films was found to occur as a result of high-temperature annealing. Equivalent circuits for describing the properties of films with various structure and stoichiometric composition were proposed. Possibility of conductivity variation of the polycrystalline tin dioxide films as a result of аnnealing in an inert atmosphere was demonstrated by utilizing impedance spectroscopy. Annealing induces the recrystallization of the films, changing in their stoichiometry as well as increase of the sizes of SnO2 crystallites. Variation of electrical conductivity and structure of tin dioxide films as a result of annealing in inert atmosphere was confirmed by X-ray diffraction analysis. Analysis of the impedance diagrams of tin dioxide films was found to be a powerful tool to study their electrical properties. 

  11. Characterization of platinum catalysts supported on substoichiometric oxides of Zr, Ti and Ce by the electric impedance spectroscopy

    International Nuclear Information System (INIS)

    Eder, D.

    2003-09-01

    energy of 120 kJ/mol, their number being ten times larger than for titania. Additionally, the influence of the water vapour pressure is stronger than in TiO 2 (power -2/3). With the electric impedance spectroscopy it is possible to decouple single processes of an electrochemical system with different time scales by measuring the impedance over a large frequency range (1 'micro' Hz < f < 1 MHz). The measurements were carried out in different gas atmospheres using the 2-pole method with gold electrodes. Therefore, it was possible to study the electric behavior of the oxides in oxidizing and reducing atmospheres and under dry and wet conditions. (author)

  12. On Impedance Spectroscopy of Supercapacitors

    Science.gov (United States)

    Uchaikin, V. V.; Sibatov, R. T.; Ambrozevich, A. S.

    2016-10-01

    Supercapacitors are often characterized by responses measured by methods of impedance spectroscopy. In the frequency domain these responses have the form of power-law functions or their linear combinations. The inverse Fourier transform leads to relaxation equations with integro-differential operators of fractional order under assumption that the frequency response is independent of the working voltage. To compare long-term relaxation kinetics predicted by these equations with the observed one, charging-discharging of supercapacitors (with nominal capacitances of 0.22, 0.47, and 1.0 F) have been studied by means of registration of the current response to a step voltage signal. It is established that the reaction of devices under study to variations of the charging regime disagrees with the model of a homogeneous linear response. It is demonstrated that relaxation is well described by a fractional stretched exponent.

  13. Electrical impedance tomography: topology optimization

    International Nuclear Information System (INIS)

    Miranda, Lenine Campos

    2013-01-01

    The Electrical Impedance Tomography (EIT) is a study of body parts who use electric current. Is studied through computers resistance or conductivity of these parts, producing an image used for medical diagnosis. A body is wrapped in a blanket placed with small electrodes and receivers of electric current, potential difference. Based on data obtained from a series of measurements at the electrodes, one by one, sending and receiving, you can perform a numerical phantom, where each 'voxel' of the image formed computationally represents the impedance of biological tissue. In Brazil, studies on electrical impedance tomography (EIT) has not yet started. Such equipment are measured tensions - potential difference - between each electrode / sensor one by one, as a way to Simple Combinatorial Analysis. The sequence and the way it is measured strains are in the final image quality. Finite Element Method Interactive, whose algorithm is based on Dialectical Method. We use an initial function with the objective of maximizing the data quantitatively, for better qualitative analysis. Topology Optimization methods are used to improve the image reconstruction. Currently the study is quite primitive related to the theory that shows how to power the new science studied. The high quality images requires a difficulty in obtaining. This work is not intended for detailed for analysis in any tissue or organ specific, but in general terms. And the formation of the 2D image. 3D need a reconstructor to part. (author)

  14. Electric transport properties study of bulk BaFe{sub 12}O{sub 19} by complex impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pattanayak, R., E-mail: ranjit.p20@gmail.com [Department of Physics and Astronomy, National Institute of Technology, Rourkela, Odisha (India); Panigrahi, S. [Department of Physics and Astronomy, National Institute of Technology, Rourkela, Odisha (India); Dash, T. [CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, Odisha (India); Muduli, R.; Behera, D. [Department of Physics and Astronomy, National Institute of Technology, Rourkela, Odisha (India)

    2015-10-01

    Polycrystalline M-type hexagonal Barium ferrite (BaFe{sub 12}O{sub 19}) was prepared by the solid state reaction method. The single phase and well grain growth of micrometer range was confirmed by XRD pattern and SEM image respectively. The presence of Fe{sup 2+} and Fe{sup 3+} states were verified by XPS study. In this report, the electric transport properties of BaFe{sub 12}O{sub 19} (BaM) was systematically investigated and analyzed in the frequency range of 100 Hz to 1 MHz and temperature range of 30–200 °C. The relaxation behaviors were examined by considering both impedance and modulus formalism, to differentiate intrinsic (grain) and extrinsic (grain boundary and electrode polarization) conduction process. The co-contribution effect of grain and grain boundary was verified which appeared as a single relaxation process in the chosen frequency and temperature range. However, the sample experienced the early (even at room temperature) arrival of surface conduction which dominates over grain boundary with increasing of temperature.

  15. Battery impedance spectroscopy using bidirectional grid connected

    Indian Academy of Sciences (India)

    Keywords. Impedance spectroscopy; grid connection; battery converter; state of charge; health monitoring ... The converter is grid connected and controlled to operate at unity power factor. Additional ... Sadhana. Current Issue : Vol. 43, Issue 6.

  16. Applications of Nonlinear Electrochemical Impedance Spectroscopy (NLEIS)

    KAUST Repository

    Adler, S. B.

    2013-01-01

    This paper reviews the use of nonlinear electrochemical impedance spectroscopy (NLEIS) in the analysis of SOFC electrode reactions. By combining EIS and NLEIS, as well as other independent information about an electrode material, it becomes possible

  17. Evaluation of electrical broad bandwidth impedance spectroscopy as a tool for body composition measurement in cows in comparison with body measurements and the deuterium oxide dilution method.

    Science.gov (United States)

    Schäff, C T; Pliquett, U; Tuchscherer, A; Pfuhl, R; Görs, S; Metges, C C; Hammon, H M; Kröger-Koch, C

    2017-05-01

    Body fatness and degree of body fat mobilization in cows vary enormously during their reproduction cycle and influence energy partitioning and metabolic adaptation. The objective of the study was to test bioelectrical impedance spectroscopy (BIS) as a method for predicting fat depot mass (FDM), in living cows. The FDM is defined as the sum of subcutaneous, omental, mesenteric, retroperitoneal, and carcass fat mass. Bioelectrical impedance spectroscopy is compared with the prediction of FDM from the deuterium oxide (DO) dilution method and from body conformation measurements. Charolais × Holstein Friesian (HF; = 18; 30 d in milk) crossbred cows and 2 HF (lactating and nonlactating) cows were assessed by body conformation measurements, BIS, and the DO dilution method. The BCS of cows was a mean of 3.68 (SE 0.64). For the DO dilution method, a bolus of 0.23 g/kg BW DO (60 atom%) was intravenously injected and deuterium (D) enrichment was analyzed in plasma and whey by stabile isotope mass spectrometry, and total body water content was calculated. Impedance measurement was performed using a 4-electrode interface and time domain-based measurement system consisting of a voltage/current converter for applying current stimulus and an amplifier for monitoring voltage across the sensor electrodes. For the BIS, we used complex impedances over three frequency decades that delivers information on intra- and extracellular water and capacity of cell membranes. Impedance data (resistance of extra- and intracellular space, cell membrane capacity, and phase angle) were extracted 1) by simple curve fit to extract the resistance at direct current and high frequency and 2) by using an electrical equivalent circuit. Cows were slaughtered 7 d after BIS and D enrichment measurements and dissected for the measurement of FDM. Multiple linear regression analyses were performed to predict FDM based on data obtained from body conformation measurements, BIS, and D enrichment, and applied

  18. Battery impedance spectroscopy using bidirectional grid connected ...

    Indian Academy of Sciences (India)

    Shimul Kumar Dam

    Keywords. Impedance spectroscopy; grid connection; battery converter; state of charge; health monitoring. 1. Introduction .... the load should be within the safe range of operation specified by the ... A split capacitor damping scheme is adopted here as shown in ...... spectroscopy testing on the Advanced Technology Devel-.

  19. Magnetic, Electrical Transport and Impedance Spectroscopy Studies on Ti Substituted La0.67Sr0.33MnO3 Ceramics

    International Nuclear Information System (INIS)

    Zalita, Z.; Halim, S.A.; Lim, K.P.; Talib, Z.A.; Hishamuddin, Z.; Walter, C.P.

    2009-01-01

    La 0.67 Sr 0.33 Mn 1-x Ti x O 3 samples with x = 0.0, 0.2, 0.4 and 0.6 have been prepared using the conventional solid-state reaction method. The structure, magnetic and electrical transport properties as well as the impedance spectroscopy of the samples were investigated. The powder XRD analysis showed that all samples were single phase with rhombohedral perovskite structure. The magnetization curve suggests that the Ti substituted samples exhibit weak ferromagnetic behaviour. The highest magnetoresistance (MR) value was obtained for sample x = 0.2 at temperature 200 K and field 1 T, which was 32.5 %. Low field magnetoresistance (LFMR) effect was observed for the x = 0.0 sample. The metal-like resistivity curve for the x = 0.0 sample was best fitted with ρ = ρo + ρ2T2 equation, indicating the grain boundary effects and electron-electron scattering process contribution. Semiconductor-like transport behaviour was observed for the Ti substituted samples and can be fitted by variable range hopping (VRH) and small polaron hopping (SPH) mechanisms. The activation energy of the samples increased when the Ti composition increased. An equivalent circuit was proposed for the impedance plot with a series of two parallel RC circuits. The grain, grain boundary and electrode resistance values increased with Ti composition due to the reduction of the Mn 3+ / Mn 4+ ratio. (author)

  20. Electrical impedance tomography of electrolysis.

    Directory of Open Access Journals (Sweden)

    Arie Meir

    Full Text Available The primary goal of this study is to explore the hypothesis that changes in pH during electrolysis can be detected with Electrical Impedance Tomography (EIT. The study has relevance to real time control of minimally invasive surgery with electrolytic ablation. To investigate the hypothesis, we compare EIT reconstructed images to optical images acquired using pH-sensitive dyes embedded in a physiological saline agar gel phantom treated with electrolysis. We further demonstrate the biological relevance of our work using a bacterial E.Coli model, grown on the phantom. The results demonstrate the ability of EIT to image pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E.coli model. The results are promising, and invite further experimental explorations.

  1. Determination of Peukert's Constant Using Impedance Spectroscopy: Application to Supercapacitors.

    Science.gov (United States)

    Mills, Edmund Martin; Kim, Sangtae

    2016-12-15

    Peukert's equation is widely used to model the rate dependence of battery capacity, and has recently attracted attention for application to supercapacitors. Here we present a newly developed method to readily determine Peukert's constant using impedance spectroscopy. Impedance spectroscopy is ideal for this purpose as it has the capability of probing electrical performance of a device over a wide range of time-scales within a single measurement. We demonstrate that the new method yields consistent results with conventional galvanostatic measurements through applying it to commercially available supercapacitors. Additionally, the novel method is much simpler and more precise, making it an attractive alternative for the determination of Peukert's constant.

  2. Electrochemical Impedance Spectroscopy Of Metal Alloys

    Science.gov (United States)

    Macdowell, L. G.; Calle, L. M.

    1993-01-01

    Report describes use of electrochemical impedance spectroscopy (EIS) to investigate resistances of 19 alloys to corrosion under conditions similar to those of corrosive, chloride-laden seaside environment of Space Transportation System launch site. Alloys investigated: Hastelloy C-4, C-22, C-276, and B-2; Inconel(R) 600, 625, and 825; Inco(R) G-3; Monel 400; Zirconium 702; Stainless Steel 304L, 304LN, 316L, 317L, and 904L; 20Cb-3; 7Mo+N; ES2205; and Ferralium 255. Results suggest electrochemical impedance spectroscopy used to predict corrosion performances of metal alloys.

  3. Study of Electrical Transport Properties of Thin Films Used as HTL and as Active Layer in Organic Solar Cells, through Impedance Spectroscopy Measurements

    Directory of Open Access Journals (Sweden)

    Camilo A. Otalora

    2016-01-01

    Full Text Available Impedance spectroscopy (IS is used for studying the electrical transport properties of thin films used in organic solar cells with structure ITO/HTL/active layer/cathode, where PEDOT:PSS (poly(3,4-ethylenedioxythiophene:polystyrene sulfonic acid and CuPC (tetrasulfonated copper-phthalocyanine were investigated as HTL (hole transport layer and P3HT:PCBM (poly-3-hexylthiophene:phenyl-C61-butyric acid methyl ester blends prepared from mesitylene and chlorobenzene based solutions were studied as active layer and Ag and Al were used as cathode. The study allowed determining the influence of the type of solvent used for the preparation of the active layer as well as the speed at which the solvents are removed on the carriers mobility. The effect of exposing the layer of P3HT to the air on its mobility was also studied. It was established that samples of P3HT and P3HT:PCBM prepared using mesitylene as a solvent have mobility values significantly higher than those prepared from chlorobenzene which is the solvent most frequently used. It was also determined that the mobility of carriers in P3HT films strongly decreases when this sample is exposed to air. In addition, it was found that the electrical properties of P3HT:PCBM thin films can be improved by removing the solvent slowly which is achieved by increasing the pressure inside the system of spin-coating during the film growth.

  4. Possibilities of electrical impedance tomography in gynecology

    International Nuclear Information System (INIS)

    Trokhanova O V; Chijova Y A; Okhapkin M B; Korjenevsky A V; Tuykin T S

    2013-01-01

    The paper describes results of comprehensive EIT diagnostics of mammary glands and cervix. The data were obtained from examinations of 170 patients by EIT system MEM (multi-frequency electrical impedance mammograph) and EIT system GIT (gynecological impedance tomograph). Mutual dependence is discussed.

  5. Transition metal oxide as anode interface buffer for impedance spectroscopy

    Science.gov (United States)

    Xu, Hui; Tang, Chao; Wang, Xu-Liang; Zhai, Wen-Juan; Liu, Rui-Lan; Rong, Zhou; Pang, Zong-Qiang; Jiang, Bing; Fan, Qu-Li; Huang, Wei

    2015-12-01

    Impedance spectroscopy is a strong method in electric measurement, which also shows powerful function in research of carrier dynamics in organic semiconductors when suitable mathematical physical models are used. Apart from this, another requirement is that the contact interface between the electrode and materials should at least be quasi-ohmic contact. So in this report, three different transitional metal oxides, V2O5, MoO3 and WO3 were used as hole injection buffer for interface of ITO/NPB. Through the impedance spectroscopy and PSO algorithm, the carrier mobilities and I-V characteristics of the NPB in different devices were measured. Then the data curves were compared with the single layer device without the interface layer in order to investigate the influence of transitional metal oxides on the carrier mobility. The careful research showed that when the work function (WF) of the buffer material was just between the work function of anode and the HOMO of the organic material, such interface material could work as a good bridge for carrier injection. Under such condition, the carrier mobility measured through impedance spectroscopy should be close to the intrinsic value. Considering that the HOMO (or LUMO) of most organic semiconductors did not match with the work function of the electrode, this report also provides a method for wide application of impedance spectroscopy to the research of carrier dynamics.

  6. Impedance spectroscopy of ceramic solid electrolytes

    International Nuclear Information System (INIS)

    Muccillo, R.; Cosentino, I.C.; Florio, D.Z. de; Franca, Y.V.

    1996-01-01

    The Impedance Spectroscopy (IS) technique has been used to the study of Th O 2 :Y 2 O 3 , Zr O 2 :La 2 O 3 and Zr O 2 :Y 2 O 3 solid electrolytes. The results show that solid solution has been attained, grain boundaries act as oxygen-ion blockers, and the importance of the IS technique to study phase transformation in ceramics. (author)

  7. Applications of Nonlinear Electrochemical Impedance Spectroscopy (NLEIS)

    KAUST Repository

    Adler, S. B.

    2013-08-31

    This paper reviews the use of nonlinear electrochemical impedance spectroscopy (NLEIS) in the analysis of SOFC electrode reactions. By combining EIS and NLEIS, as well as other independent information about an electrode material, it becomes possible to establish quantitative links between electrochemical kinetics and materials properties, even when systems are unstable with time. After a brief review of the method, this paper summarizes recent results analyzing the effects of Sr segregation in thin-film LSC electrodes. © The Electrochemical Society.

  8. Study of electrical properties of Sc doped BaFe12O19 ceramic using dielectric, impedance, modulus spectroscopy and AC conductivity

    Science.gov (United States)

    Gupta, Surbhi; Deshpande, S. K.; Sathe, V. G.; Siruguri, V.

    2018-04-01

    We present dielectric, complex impedance, modulus spectroscopy and AC conductivity studies of the compound BaFe10Sc2O19 as a function of temperature and frequency to understand the conduction mechanism. The variation in complex dielectric constant with frequency and temperature were analyzed on the basis of Maxwell-Wagner-Koop's theory and charge hopping between ferrous and ferric ions. The complex impedance spectroscopy study shows only grain contribution whereas complex modulus plot shows two semicircular arcs which indicate both grain and grain boundary contributions in conduction mechanism. AC conductivity has also been evaluated which follows the Jonscher's law. The activation energy calculated from temperature dependence of DC conductivity comes out to be Ea˜ 0.31eV.

  9. Electrical Impedance Measurements of PZT Nanofiber Sensors

    Directory of Open Access Journals (Sweden)

    Richard Galos

    2017-01-01

    Full Text Available Electrical impedance measurements of PZT nanofiber sensors were performed using a variety of methods over a frequency spectrum ranging from DC to 1.8 GHz. The nanofibers formed by electrospinning with diameters ranging from 10 to 150 nm were collected and integrated into sensors using microfabrication techniques. Special matching circuits with ultrahigh input impedance were fabricated to produce low noise, measurable sensor outputs. Material properties including resistivity and dielectric constant are derived from the impedance measurements. The resulting material properties are also compared with those of individual nanofibers being tested using conductive AFM and Scanning Conductive Microscopy.

  10. Cervical cancer detection by electrical impedance in a Colombian setting

    International Nuclear Information System (INIS)

    A Miranda, David; P Corzo, Sandra; Correa, C A González

    2013-01-01

    Electrical properties of normal and neoplastic cervical tissues in a heterogeneous group of 56 Colombian women were studied by electrical impedance spectroscopy and a model based on the Generalized Effective-Medium Theory of Induced Polarization (GEMTIP). Differences between the electrical bioimpedance spectra were correlated with cellular and tissue parameters. The analysis performed by the proposed model suggest that the number of different types of cellular layers that form the biological tissue, the intracellular and extracellular conductivity could be used to explain the differences between electrical bioimpedance spectra in normal and neoplastic tissues.

  11. Electrochemical impedance spectroscopy of polynucleotide adsorption

    Czech Academy of Sciences Publication Activity Database

    Strašák, Luděk; Dvořák, Jakub; Hasoň, Stanislav; Vetterl, Vladimír

    2002-01-01

    Roč. 56, 1/2 (2002), s. 37-41 ISSN 1567-5394 R&D Projects: GA AV ČR IAA4004002; GA AV ČR IBS5004107; GA ČR GV204/97/K084 Grant - others:GA FRVŠ(XC) G40583; GA FRVŠ(XC) F40564 Institutional research plan: CEZ:AV0Z5004920 Keywords : electrochemical impedance spectroscopy * DNA adsorption * poly A adsorption Subject RIV: BO - Biophysics Impact factor: 1.463, year: 2002

  12. Method for conducting nonlinear electrochemical impedance spectroscopy

    Science.gov (United States)

    Adler, Stuart B.; Wilson, Jamie R.; Huff, Shawn L.; Schwartz, Daniel T.

    2015-06-02

    A method for conducting nonlinear electrochemical impedance spectroscopy. The method includes quantifying the nonlinear response of an electrochemical system by measuring higher-order current or voltage harmonics generated by moderate-amplitude sinusoidal current or voltage perturbations. The method involves acquisition of the response signal followed by time apodization and fast Fourier transformation of the data into the frequency domain, where the magnitude and phase of each harmonic signal can be readily quantified. The method can be implemented on a computer as a software program.

  13. Laboratory scale tests of electrical impedence tomography

    International Nuclear Information System (INIS)

    Binley, A; Daily, W; LaBredcque, D; Ramirez, A.

    1998-01-01

    Electrical impedance tomographs (magnitude and phase) of known, laboratory-scale targets are reported. Three methods are used to invert electrical impedance data and their tomographs compared. The first method uses an electrical resistance tomography (ERT) algonthm (designed for DC resistivity inversion) to perform impedance magnitude inversion and a linearized perturbation approach (PA) to invert the imaginary part. The second approximate method compares ERT magnitude inversions at two frequencies and uses the frequency effect (FE) to compute phase tomographs. The third approach, electrrcal impedance tomography (EIT), employs fully complex algebra to account for the real and imaginary components of electrical impedance data. The EIT approach provided useful magnitude and phase images for the frequency range of 0.0625 to 64 Hz; images for higher frequencies were not reliable. Comparisons of the ERT and EIT magnitude images show that both methods provided equivalent results for the water blank, copper rod and PVC rod targets. The EIT magnitude images showed better spatial resolutron for a sand-lead mixture target. Phase images located anomalies of both high and low contrast IP and provided better spatial resolution than the magnitude images. When IP was absent from the data, the EIT algorithm reconstructed phase values consistent with the data noise levels

  14. Application of impedance spectroscopy to SOFC research

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, G.; Mason, T.O. [Northwestern Univ., Evanston, IL (United States); Pederson, L.R. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-12-31

    With the resurgence of interest in solid oxide fuel cells and other solid state electrochemical devices, techniques originally developed for characterizing aqueous systems are being adapted and applied to solid state systems. One of these techniques, three-electrode impedance spectroscopy, is particularly powerful as it allows characterization of subcomponent and interfacial properties. Obtaining accurate impedance spectra, however, is difficult as reference electrode impedance is usually non-negligible and solid electrolytes typically have much lower conductance than aqueous solutions. Faidi et al and Chechirlian et al have both identified problems associated with low conductivity media. Other sources of error are still being uncovered. Ford et al identified resistive contacts with large time constants as a possibility, while Me et al showed that the small contact capacitance of the reference electrode was at fault. Still others show that instrument limitations play a role. Using the voltage divider concept, a simplified model that demonstrates the interplay of these various factors, predicts the form of possible distortions, and offers means to minimize errors is presented.

  15. Electrochemical Impedance Spectroscopy in Solid State Ionics: Recent Advances

    NARCIS (Netherlands)

    Boukamp, Bernard A.

    2004-01-01

    Electrochemical Impedance Spectroscopy (EIS) has become an important research tool in Solid State Ionics. Some new developments are highlighted: new methods of automatic parameter extraction from impedance measurements are briefly discussed. The Kramers–Kronig data validation test presents another

  16. Microstructure and electrical properties of slug-type resistors based on B4C and TiC - ESCA - XPS and impedance spectroscopy investigations

    International Nuclear Information System (INIS)

    Klimiec, E.; Zaraska, W.; Stobiecki, T.; Bak, W.; Starzyk, F.

    2000-01-01

    The microstructure and electrical properties of slug-type resistors based on B 4 C and TiC were investigated. From XPS measurements was deducted that Ti in TiO 2 is in intermediate oxidation number between Ti +4 and Ti +3 . The impedance of both type of resistors is independent on frequency in the range from 10 3 to 10 4 Hz, only very subtle differences above 10 4 Hz are observed. The metallic type conductivity in TiC and semiconducting in B 4 C was established. (author)

  17. Corrosion Study Using Electrochemical Impedance Spectroscopy

    Science.gov (United States)

    Farooq, Muhammad Umar

    2003-01-01

    Corrosion is a common phenomenon. It is the destructive result of chemical reaction between a metal or metal alloy and its environment. Stainless steel tubing is used at Kennedy Space Center for various supply lines which service the orbiter. The launch pads are also made of stainless steel. The environment at the launch site has very high chloride content due to the proximity to the Atlantic Ocean. Also, during a launch, the exhaust products in the solid rocket boosters include concentrated hydrogen chloride. The purpose of this project was to study various alloys by Electrochemical Impedance Spectroscopy in corrosive environments similar to the launch sites. This report includes data and analysis of the measurements for 304L, 254SMO and AL-6XN in primarily neutral 3.55% NaCl. One set of data for 304L in neutral 3.55%NaCl + 0.1N HCl is also included.

  18. Electrochemical impedance spectroscopy of oxidized porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Mula, Guido, E-mail: guido.mula@unica.it [Dipartimento di Fisica, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Tiddia, Maria V. [Dipartimento di Fisica, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Ruffilli, Roberta [Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Falqui, Andrea [Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Palmas, Simonetta; Mascia, Michele [Dipartimento di Ingegneria Meccanica Chimica e dei Materiali, Università degli Studi di Cagliari, Piazza d' Armi, 09126 Cagliari (Italy)

    2014-04-01

    We present a study of the electrochemical oxidation process of porous silicon. We analyze the effect of the layer thickness (1.25–22 μm) and of the applied current density (1.1–11.1 mA/cm{sup 2}, values calculated with reference to the external samples surface) on the oxidation process by comparing the galvanostatic electrochemical impedance spectroscopy (EIS) measurements and the optical specular reflectivity of the samples. The results of EIS were interpreted using an equivalent circuit to separate the contribution of different sample parts. A different behavior of the electrochemical oxidation process has been found for thin and thick samples: whereas for thin samples the oxidation process is univocally related to current density and thickness, for thicker samples this is no more true. Measurements by Energy Dispersive Spectroscopy using a Scanning Electron Microscopy confirmed that the inhomogeneity of the electrochemical oxidation process is increased by higher thicknesses and higher currents. A possible explanation is proposed to justify the different behavior of thin and thick samples during the electrochemical process. - Highlights: • A multidisciplinary approach on porous Si electrochemical oxidation is proposed. • Electrochemical, optical, and structural characterizations are used. • Layer thickness and oxidation current effects are shown. • An explanation of the observed behavior is proposed.

  19. Electrical and impedance spectroscopy analysis of sol-gel derived spin coated Cu2ZnSnS4 solar cell

    Science.gov (United States)

    Gupta, Goutam Kumar; Garg, Ashish; Dixit, Ambesh

    2018-01-01

    We carried out electrical and impedance studies on solution derived Al:ZnO/ZnO/CdS/Cu2ZnSnS4/Mo/Glass multilayered solar cell structures to understand their impact on photovoltaic performance. The Cu2ZnSnS4 layer is synthesized on a molybdenum (Mo) coated soda lime glass substrate as an absorber and characterized intensively to optimize the absorber physical properties. The optimized Cu2ZnSnS4 is p-type with 5.8 × 1017 cm-3 hole carrier concentration. The depletion width of the junction is around 20.5 nm and the diffusion capacitance is ˜35.5 nF for these devices. We observed relatively large minority carrier life time ˜23 μs for these structures using open voltage decay analysis. The measured Cu2ZnSnS4/MoS2 and Cu2ZnSnS4/CdS interface resistances are 7.6 kΩ and 12.5 kΩ, respectively. The spatial inhomogeneities are considered and the corresponding resistance is ˜11.4 kΩ. The impedance measurements suggest that in conjunction with series resistance ˜350 Ω, the interface and spatial inhomogeneity resistances also give a significant contribution to the photovoltaic performance.

  20. Electrical impedance studies of uranium oxide

    International Nuclear Information System (INIS)

    Hampton, R.N.

    1986-11-01

    The thesis presents data on the electrical properties of uranium oxide at temperatures from 1700K to 4.2K, and pressures between 25 K bar and 70 K bar. The impedance data were analysed using the technique of complex plane representation to establish the conductivity and dielectric constant of uranium dioxide. The thermophysical data were compared with previously reported experimental and theoretical work on uranium dioxide and other fluorite structured oxides. (U.K.)

  1. Relating membrane potential to impedance spectroscopy

    Directory of Open Access Journals (Sweden)

    Eugen Gheorghiu

    2011-12-01

    Full Text Available Non-invasive, label-free assessment of membrane potential of living cells is still a challenging task. The theory linking membrane potential to the low frequency α dispersion exhibited by suspensions of spherical shelled particles (presenting a net charge distribution on the inner side of the shell has been pioneered in our previous studies with emphasis on the permittivity spectra. Whereas α dispersion is related to a rather large variation exhibited by the permittivity spectrum, we report that the related decrement presented by the impedance magnitude spectrum is either extremely small, or occurs (for large cells at very small frequencies (~mHz explaining the lack of experimental bioimpedance data on the matter. We stress that appropriate choice of the parameters (as revealed by the microscopic model may enable access to membrane potential as well as to other relevant parameters when investigating living cells and charged lipid vesicles. We analyse the effect on the low frequency of the permittivity and impedance spectra of: I. Parameters pertaining to cell membrane i.e. (i membrane potential (through the amount of the net charge on the inner side of the membrane, (ii size of the cells/vesicles, (iii conductivity of the membrane; II. Parameters of the extra cellular medium (viscosity and conductivity. The applicability of the study has far reaching implications for basic (life sciences (providing non-invasive access to the dynamics of relevant cell parameters as well as for biosensing applications, e.g. assessment of cytotoxicity of a wide range of stimuli. doi:10.5617/jeb.214 J Electr Bioimp, vol. 2, pp. 93-97, 2011

  2. Variational constraints for electrical-impedance tomography

    International Nuclear Information System (INIS)

    Berryman, J.G.; Kohn, R.V.

    1990-01-01

    The task of electrical-impedance tomography is to invert boundary measurements for the conductivity distribution of a body. This inverse problem can be formulated so the primary data are the measured powers dissipated across injection electrodes. Then, since these powers are minima of the pertinent (dual) variational principles, feasibility constraints can be found for the nonlinear inversion problem. When power may be measured accurately, the existence of these dual variational principles implies that any exact solution must lie at a point of intersection of the two feasibility boundaries

  3. Study on electrical impedance matching for broadband ultrasonic transducer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Geon Woo [University of Science and Technology, Daejeon (Korea, Republic of); Kim, Ki Bok [Korea Research Institute of Standards and Science, Center for Safety Measurement, Daejeon (Korea, Republic of); Baek, Kwang Sae [Elache Co., Busan (Korea, Republic of)

    2017-02-15

    Ultrasonic transducers with high resolution and resonant frequency are required to detect small defects (less than hundreds of μm) by ultrasonic testing. The resonance frequency and resolution of an ultrasonic transducer are closely related to the thickness of piezo-electric materials, backing materials, and the electric impedance matching technique. Among these factors, electrical impedance matching plays an important role because it can reduce the loss and reflection of ultrasonic energy differences in electrical impedance between an ultrasonic transducer and an ultrasonic defects detecting system. An LC matching circuit is the most frequently used electric matching method. It is necessary for the electrical impedance of an ultrasonic transducer to correspond to approximately 50 Ω to compensate the difference in electrical impedance between both connections. In this study, a 15 MHz immersion ultrasonic transducer was fabricated and an LC electrical impedance circuit was applied to that for having broad-band frequency characteristic.

  4. Theory for electrochemical impedance spectroscopy of ...

    Indian Academy of Sciences (India)

    Shweta Dhillon

    generalize phenomenological theory for the Randles-Ershler admittance at the electrode with double layer capacitance ..... impedance (equation 12) curves accounting for the elec- ..... R.K. thanks University of Delhi for the financial support.

  5. Multi-probe-based resonance-frequency electrical impedance spectroscopy for detection of suspicious breast lesions: improving performance using partial ROC optimization

    Science.gov (United States)

    Lederman, Dror; Zheng, Bin; Wang, Xingwei; Wang, Xiao Hui; Gur, David

    2011-03-01

    We have developed a multi-probe resonance-frequency electrical impedance spectroscope (REIS) system to detect breast abnormalities. Based on assessing asymmetry in REIS signals acquired between left and right breasts, we developed several machine learning classifiers to classify younger women (i.e., under 50YO) into two groups of having high and low risk for developing breast cancer. In this study, we investigated a new method to optimize performance based on the area under a selected partial receiver operating characteristic (ROC) curve when optimizing an artificial neural network (ANN), and tested whether it could improve classification performance. From an ongoing prospective study, we selected a dataset of 174 cases for whom we have both REIS signals and diagnostic status verification. The dataset includes 66 "positive" cases recommended for biopsy due to detection of highly suspicious breast lesions and 108 "negative" cases determined by imaging based examinations. A set of REIS-based feature differences, extracted from the two breasts using a mirror-matched approach, was computed and constituted an initial feature pool. Using a leave-one-case-out cross-validation method, we applied a genetic algorithm (GA) to train the ANN with an optimal subset of features. Two optimization criteria were separately used in GA optimization, namely the area under the entire ROC curve (AUC) and the partial area under the ROC curve, up to a predetermined threshold (i.e., 90% specificity). The results showed that although the ANN optimized using the entire AUC yielded higher overall performance (AUC = 0.83 versus 0.76), the ANN optimized using the partial ROC area criterion achieved substantially higher operational performance (i.e., increasing sensitivity level from 28% to 48% at 95% specificity and/ or from 48% to 58% at 90% specificity).

  6. PREFACE: XV International Conference on Electrical Bio-Impedance (ICEBI) & XIV Conference on Electrical Impedance Tomography (EIT)

    Science.gov (United States)

    Pliquett, Uwe

    2013-04-01

    . Structures down to sub-micrometer range and complex impedance measurements tools integrated at single chips are now affordable. Moreover, the introduction of alternative signals and data processing algorithms focuses on very fast and parallel electrical characterization which in turn pushes this technique to new applications and markets. Electrical impedance tomography today yields pictures in real time with a resolution that was impossible 10 years ago. The XVth International Conference on Electrical Bio-Impedance in conjunction with the XIVth Electrical Impedance Tomography ICEBI/EIT 2013 organized by the Institute for Bioprocessing and Analytical Measurement Techniques, Heilbad Heiligenstadt, Germany, together with the EIT-group at the University of Göttingen, Germany, brings world leading scientists in these fields together. It is a platform to present the latest developments in instrumentation and signal processing but also points to new applications, especially in the field of biosensors and non-linear phenomena. Two Keynote lectures will extend the view of the participants above the mainstream of bio-impedance measurement. Friederich Kremer (University of Leipzig) delivers the plenary lecture on broad bandwidth dielectric spectroscopy. New achievements in the research of ligand gated ionic channels will be presented by Klaus Benndorf (University of Jena). Leading scientists in the field of bio-impedance measurement, such as, Sverre Grimnes, Orjan Martinsen, Andrea Robitzki, Richard Bayford, Jan Gimsa and Mart Min will give lectures for students but also more experienced scientists in a pre-conference tutorial which is a good opportunity to learn or refresh the basics. List of committees Conference Chair Dr Uwe Pliquett Professor Dieter Beckmann Institut für Bioprozess- und Analysenmesstechnik eV, Rosenhof, Heilbad Heiligenstadt, Germany Technical Program Chair Maik Hiller Conventus Congressmanagement & Marketing GmbH, Carl-Pulfrich-Str. 1 - 07745 Jena Pre

  7. Characterizing aging effects of lithium ion batteries by impedance spectroscopy

    International Nuclear Information System (INIS)

    Troeltzsch, Uwe; Kanoun, Olfa; Traenkler, Hans-Rolf

    2006-01-01

    Impedance spectroscopy is one of the most promising methods for characterizing aging effects of portable secondary batteries online because it provides information about different aging mechanisms. However, application of impedance spectroscopy 'in the field' has some higher requirements than for laboratory experiments. It requires a fast impedance measurement process, an accurate model applicable with several batteries and a robust method for model parameter estimation. In this paper, we present a method measuring impedance at different frequencies simultaneously. We propose to use a composite electrode model, capable to describe porous composite electrode materials. A hybrid method for parameter estimation based on a combination of evolution strategy and Levenberg-Marquardt method allowed a robust and fast parameter calculation. Based on this approach, an experimental investigation of aging effects of a lithium ion battery was carried out. After 230 discharge/charge cycles, the battery showed a 14% decreased capacity. Modeling results show that series resistance, charge transfer resistance and Warburg coefficient changed thereby their values by approximately 60%. A single frequency impedance measurement, usually carried out at 1 kHz, delivers only information about series resistance. Impedance spectroscopy allows additionally the estimation of charge transfer resistance and Warburg coefficient. This fact and the high sensitivity of model parameters to capacity change prove that impedance spectroscopy together with an accurate modeling deliver information that significantly improve characterization of aging effects

  8. Characterizing aging effects of lithium ion batteries by impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Troeltzsch, Uwe [University of the Bundeswehr Munich Institute for Measurement and Automation, 85579 Neubiberg (Germany)]. E-mail: uwe.troeltzsch@unibw-muenchen.de; Kanoun, Olfa [University of the Bundeswehr Munich Institute for Measurement and Automation, 85579 Neubiberg (Germany); Traenkler, Hans-Rolf [University of the Bundeswehr Munich Institute for Measurement and Automation, 85579 Neubiberg (Germany)

    2006-01-20

    Impedance spectroscopy is one of the most promising methods for characterizing aging effects of portable secondary batteries online because it provides information about different aging mechanisms. However, application of impedance spectroscopy 'in the field' has some higher requirements than for laboratory experiments. It requires a fast impedance measurement process, an accurate model applicable with several batteries and a robust method for model parameter estimation. In this paper, we present a method measuring impedance at different frequencies simultaneously. We propose to use a composite electrode model, capable to describe porous composite electrode materials. A hybrid method for parameter estimation based on a combination of evolution strategy and Levenberg-Marquardt method allowed a robust and fast parameter calculation. Based on this approach, an experimental investigation of aging effects of a lithium ion battery was carried out. After 230 discharge/charge cycles, the battery showed a 14% decreased capacity. Modeling results show that series resistance, charge transfer resistance and Warburg coefficient changed thereby their values by approximately 60%. A single frequency impedance measurement, usually carried out at 1 kHz, delivers only information about series resistance. Impedance spectroscopy allows additionally the estimation of charge transfer resistance and Warburg coefficient. This fact and the high sensitivity of model parameters to capacity change prove that impedance spectroscopy together with an accurate modeling deliver information that significantly improve characterization of aging effects.

  9. Impedance spectroscopy of CdTe thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, Charlotte; Heisler, Christoph; Reisloehner, Udo; Ronning, Carsten; Wesch, Werner [Institute of Solid State Physics, University of Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)

    2012-07-01

    Impedance Spectroscopy (IS) is a widely used method to analyze dielectric properties of specimen as a function of frequency. Typically this characterization method delivers an equivalent circuit diagram of the device under examination to describe its electrical properties. Traditionally IS is used in coating evaluation, corrosion monitoring and in electrochemistry. During the last years the method became more important also in the field of electrical characterization of solar cells. In our work we use IS for the electrical characterization of thin film CdTe solar cells. The measurement is done at room temperature without illumination in a frequency domain from 20 Hz to 2 MHz. The samples are measured under variable forward bias. The results match insufficiently with the model of two resistor-capacitor circuits in series which is commonly used to describe the p-n junction and the blocking back contact. For better consistency, other models from the literature are used and discussed. From the results a conclusion is drawn about the properties of the solar cell such as the nature of the p-n junction or the performance of the back contact.

  10. Investigation of disorder and its effect on electrical transport in electrochemically doped polymer devices by current-voltage and impedance spectroscopy

    Science.gov (United States)

    Rahman Khan, Motiur; Anjaneyulu, P.; Koteswara Rao, K. S. R.; Menon, R.

    2017-03-01

    We report on the analysis of temperature-dependent current-voltage characteristics and impedance measurements of electrochemically doped poly(3-methylthiophene) devices at different doping levels. The extent of doping is carefully tailored such that only the bulk-limited transport mechanism prevails. A transition from exponentially distributed trap-limited transport to trap-free space-charge-limited current is observed in current-voltage conduction upon increasing the doping. The obtained trap densities (3.2  ×  1016 cm-3 and 8.6  ×  1015 cm-3) and trap energies (31.7 meV and 16.6 meV) for different devices signify the variation in disorder with doping, which is later supported by impedance measurements. Impedance-frequency data for various devices can not be explained using the parallel resistance-capacitance (RC) model in the equivalent circuit. However, this was established by incorporating a constant phase element Q (CPE) instead of the capacitance parameter. It should be emphasized that low doping devices in particular are best simulated with two CPE elements, while the data related to other devices are fitted well with a single CPE element. It is also observed from evaluated circuit parameters that the spatial inhomogeneity and disorder are the cause of variability in different samples, which has an excellent correlation with the temperature-dependent current-voltage characteristics.

  11. Application of electrochemical impedance spectroscopy to monitor seawater fouling on stainless steels and copper alloys

    International Nuclear Information System (INIS)

    Feron, D.

    1991-01-01

    Electrochemical impedance spectroscopy may be applied to detect and to follow seawater fouling. Experiments have been conducted with natural seawater flowing inside tube-electrodes at temperatures between 30 deg C and 85 deg C. With stainless steel tubes, mineral and organic foulings have been followed; a linear relationship between the dry weight of the organic fouling and its electrical resistance, has been observed. On copper alloy tubes, only mineral deposits have occurred and so have been detected by impedance spectroscopy. (Author). 5 refs., 6 figs

  12. Electrochemical Characterization of a PEMEC Using Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Elsøe, Katrine; Grahl-Madsen, L.; Hjelm, Johan

    2017-01-01

    In this study, electrochemical impedance spectroscopy (EIS) is applied in combination with cyclic voltammetry (CV) and current density – cell voltage curves (iV-curves) to investigate the processes contributing to the total impedance of a polymer electrolyte membrane electrolysis cell (PEMEC). i......V-curves were linear above 0.35 A cm−2 implying ohmic processes to be performance limiting, however the impedance spectra showed three arcs indicating three electrochemical reactions at these conditions not to be purely ohmic, but also to have capacitive properties. A hypothesis that the composite Ir...

  13. Characterization of Zircaloy-4 oxide layers by impedance spectroscopy

    International Nuclear Information System (INIS)

    Barberis, P.

    1999-01-01

    Two Zircaloy-4 type alloys with different tin contents (0.5 and 1.2 wt%) have been oxidized in autoclave (400 C in steam) for several durations (1-140 days). The film has been characterized by electrochemical impedance spectroscopy (EIS). Several soaking times have been investigated (up to 40 days). The Cole-Cole representation has been used to display and study the data. A simple electrical model has been derived from the observed spectra: the electrical circuit includes two RC loops in series, whose capacitances are frequency dispersed. It is thoroughly related to the layer structure. It has been shown that even before the kinetic transition, the film is constituted of three parts: an inner layer which is compact, an outer layer subdivided in an external region immediately soaked by the electrolyte, and an internal one in which electrolyte diffusion processes can take place. The kinetic transition is interpreted in terms of an abrupt 'compacity' change, both layers degrading at this point. The alloy with high tin content exhibits higher dispersive properties of the oxide layer formed on it, in correlation with its faster oxidation kinetics. (orig.)

  14. Impedance-spectroscopy analysis and piezoelectric properties of Pb2KNb5O15 ceramics

    International Nuclear Information System (INIS)

    Rao, K. Sambasiva; Murali Krishna, P.; Swarna Latha, T.; Madhava Prasad, D.

    2006-01-01

    Preparation, dielectric, piezoelectric, hysteresis, impedance spectroscopy and AC conductivity studies in the Pb 0.8 K 0.4 Nb 2 O 6 ferroelectric ceramic have been presented. The Pb 1-x K 2x Nb 2 O 6 (PKN) characterized for ferroelectric and impedance spectroscopy studies from room temperature to 600 deg. C. The sample shows a single phase with orthorhombic structure from X-ray diffraction studies. The Cole-Cole plots and electric modulus plots at different temperatures are drawn. The results obtained from the impedance spectroscopy are analyzed, to understand the conductivity behavior of PKN. The piezoelectric constant, d 33 , has been found to be 75 x 10 -12 C/N

  15. Broadband electrical impedance matching for piezoelectric ultrasound transducers.

    Science.gov (United States)

    Huang, Haiying; Paramo, Daniel

    2011-12-01

    This paper presents a systematic method for designing broadband electrical impedance matching networks for piezoelectric ultrasound transducers. The design process involves three steps: 1) determine the equivalent circuit of the unmatched piezoelectric transducer based on its measured admittance; 2) design a set of impedance matching networks using a computerized Smith chart; and 3) establish the simulation model of the matched transducer to evaluate the gain and bandwidth of the impedance matching networks. The effectiveness of the presented approach is demonstrated through the design, implementation, and characterization of impedance matching networks for a broadband acoustic emission sensor. The impedance matching network improved the power of the acquired signal by 9 times.

  16. Investigation of disorder and its effect on electrical transport in electrochemically doped polymer devices by current–voltage and impedance spectroscopy

    International Nuclear Information System (INIS)

    Khan, Motiur Rahman; Koteswara Rao, K S R; Menon, R; Anjaneyulu, P

    2017-01-01

    We report on the analysis of temperature-dependent current–voltage characteristics and impedance measurements of electrochemically doped poly(3-methylthiophene) devices at different doping levels. The extent of doping is carefully tailored such that only the bulk-limited transport mechanism prevails. A transition from exponentially distributed trap-limited transport to trap-free space-charge-limited current is observed in current–voltage conduction upon increasing the doping. The obtained trap densities (3.2  ×  10 16 cm −3 and 8.6  ×  10 15 cm −3 ) and trap energies (31.7 meV and 16.6 meV) for different devices signify the variation in disorder with doping, which is later supported by impedance measurements. Impedance–frequency data for various devices can not be explained using the parallel resistance–capacitance ( RC ) model in the equivalent circuit. However, this was established by incorporating a constant phase element Q (CPE) instead of the capacitance parameter. It should be emphasized that low doping devices in particular are best simulated with two CPE elements, while the data related to other devices are fitted well with a single CPE element. It is also observed from evaluated circuit parameters that the spatial inhomogeneity and disorder are the cause of variability in different samples, which has an excellent correlation with the temperature-dependent current–voltage characteristics. (paper)

  17. Detailed characterization of anode-supported SOFCs by impedance spectroscopy

    DEFF Research Database (Denmark)

    Barfod, R.; Mogensen, Mogens Bjerg; Klemensø, Trine

    2007-01-01

    Anode-supported thin electrolyte cells are studied by electrochemical impedance spectroscopy (EIS). The aim is to describe how the losses of this type of cells are distributed at low current density (around open-circuit voltage) as a function of temperature. An equivalent circuit consisting...

  18. Impedance spectroscopy studies of Silver Doped Cadmium Sulphide Nanocrystallites

    Science.gov (United States)

    Sivanand, R.; Chellammal, S.; Manivannan, S.

    2018-02-01

    Using co-precipitation method, cadmium sulphide (CdS) and silver doped cadmium sulphide (CdS;Ag) was prepared. By using energy-dispersive X-ray analysis (EDXA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) to analyse the structural characterization of the prepared samples. The energy-dispersive X-ray analysis (EDXA) measurement is used to confirm, the presence of elements in prepared samples. There is no peaks of other impurity were detected. The average size of nanoparticles was calculated by scherrer formula. SEM photographs indicate that the nanopowders consist of well dispersed agglomerates of grains with a narrow size distribution, whereas the sizes of the individual particles are between 5 and 12 nm. The synthesized samples have been structurally analysed by X-ray diffraction method. The peaks in the XRD pattern are in good matches with the standard values of JCPDS file and other impurity peaks of crystalline phases were not detected. Scanning electron microscopy (SEM) measurement is used for the morphological studies. Electrical conductivity studies are analysed by Impedance spectroscopy measurement and also calculate the activation energies at low and high temperature for prepared samples.

  19. Study of Paclitaxel-Treated HeLa Cells by Differential Electrical Impedance Flow Cytometry

    Directory of Open Access Journals (Sweden)

    Julie Kirkegaard

    2014-08-01

    Full Text Available This work describes the electrical investigation of paclitaxel-treated HeLa cells using a custom-made microfluidic biosensor for whole cell analysis in continuous flow. We apply the method of differential electrical impedance spectroscopy to treated HeLa cells in order to elucidate the changes in electrical properties compared with non-treated cells. We found that our microfluidic system was able to distinguish between treated and non-treated cells. Furthermore, we utilize a model for electrical impedance spectroscopy in order to perform a theoretical study to clarify our results. This study focuses on investigating the changes in the electrical properties of the cell membrane caused by the effect of paclitaxel. We observe good agreement between the model and the obtained results. This establishes the proof-of-concept for the application in cell drug therapy.

  20. Mathematical modeling of the electrochemical impedance spectroscopy in lithium ion battery cycling

    International Nuclear Information System (INIS)

    Xie, Yuanyuan; Li, Jianyang; Yuan, Chris

    2014-01-01

    Electrochemical impedance spectroscopy (EIS) has been widely utilized as an experimental method for understanding the internal mechanisms and aging effect of lithium ion battery. However, the impedance interpretation still has a lot of difficulties. In this study, a multi-physics based EIS simulation approach is developed to study the cycling effect on the battery impedance responses. The SEI film growth during cycling is coherently coupled with the complicated charge, mass and energy transport processes. The EIS simulation is carried out by applying a perturbation voltage on the electrode surface, and the numerical results on cycled cells are compared with the corresponding experimental data. The effect of electrical double layer, electrode open circuit potential as well as the diffusivity of binary electrolyte are simulated on battery impedance responses. The influence of different SEI growth rate, thermal conditions and charging-discharging rate during cycling are also studied. This developed method can be potentially utilized for interpretation and analysis of experimental EIS results

  1. Impedance spectroscopy studies of surface engineered TiO2 ...

    Indian Academy of Sciences (India)

    Administrator

    Impedance; nanoTiO2; self-assembled monolayers; electrical resistivity; permittivity. 1. Introduction ... search studies showed that nanostructured TiO2 ceramics possess ..... tion handbook (ed) J Cazes (New York: Marcel Dekker). 3rd ed, p ...

  2. Lactate threshold by muscle electrical impedance in professional rowers

    Science.gov (United States)

    Jotta, B.; Coutinho, A. B. B.; Pino, A. V.; Souza, M. N.

    2017-04-01

    Lactate threshold (LT) is one of the physiological parameters usually used in rowing sport training prescription because it indicates the transitions from aerobic to anaerobic metabolism. Assessment of LT is classically based on a series of values of blood lactate concentrations obtained during progressive exercise tests and thus has an invasive aspect. The feasibility of noninvasive LT estimative through bioelectrical impedance spectroscopy (BIS) data collected in thigh muscles during rowing ergometer exercise tests was investigated. Nineteen professional rowers, age 19 (mean) ± 4.8 (standard deviation) yr, height 187.3 ± 6.6 cm, body mass 83 ± 7.7 kg, and training experience of 7 ± 4 yr, were evaluated in a rowing ergometer progressive test with paired measures of blood lactate concentration and BIS in thigh muscles. Bioelectrical impedance data were obtained by using a bipolar method of spectroscopy based on the current response to a voltage step. An electrical model was used to interpret BIS data and to derive parameters that were investigated to estimate LT noninvasively. From the serial blood lactate measurements, LT was also determined through Dmax method (LTDmax). The zero crossing of the second derivative of kinetic of the capacitance electrode (Ce), one of the BIS parameters, was used to estimate LT. The agreement between the LT estimates through BIS (LTBIS) and through Dmax method (LTDmax) was evaluated using Bland-Altman plots, leading to a mean difference between the estimates of just 0.07 W and a Pearson correlation coefficient r = 0.85. This result supports the utilization of the proposed method based on BIS parameters for estimating noninvasively the lactate threshold in rowing.

  3. Electrical Impedance Tomography Technology (EITT) Project

    Science.gov (United States)

    Oliva-Buisson, Yvette J.

    2014-01-01

    Development of a portable, lightweight device providing two-dimensional tomographic imaging of the human body using impedance mapping. This technology can be developed to evaluate health risks and provide appropriate medical care on the ISS, during space travel and on the ground.

  4. Impedance spectroscopy of tripolar concentric ring electrodes with Ten20 and TD246 pastes.

    Science.gov (United States)

    Nasrollaholhosseini, Seyed Hadi; Herrera, Daniel Salazar; Besio, Walter G

    2017-07-01

    Electrodes are used to transform ionic currents to electrical currents in biological systems. Modeling the electrode-electrolyte interface could help to optimize the performance of the electrode interface to achieve higher signal to noise ratios. There are previous reports of accurate models for single-element biomedical electrodes. In this paper, we measured the impedance on both tripolar concentric ring electrodes and standard cup electrodes by electrochemical impedance spectroscopy (EIS) using both Ten20 and TD246 electrode paste. Furthermore, we applied the model to prove that the model can predict the performance of the electrode-electrolyte interface for tripolar concentric ring electrodes (TCRE) that are used to record brain signals.

  5. Ionic conductivity measurements of zirconia under pressure using impedance spectroscopy

    International Nuclear Information System (INIS)

    Takebe, H; Sakamoto, D; Ohtaka, O; Fukui, H; Yoshiasa, A; Yamanaka, T; Ota, K; Kikegawa, T

    2002-01-01

    We have set up an electrical conductivity measurement system under high-pressure and high-temperature conditions with a multi-anvil high-pressure apparatus using an AC complex impedance method. With this system, we have successfully measured the electrical conductivity of stabilized ZrO 2 (Y 2 O 3 -ZrO 2 solid solution) under pressures up to 5 GPa in the temperature range from 300 to 1200 K. The electrical conductivities obtained under pressure are compatible with those of previous results measured at ambient pressure

  6. A new lithium-ion battery internal temperature on-line estimate method based on electrochemical impedance spectroscopy measurement

    Science.gov (United States)

    Zhu, J. G.; Sun, Z. C.; Wei, X. Z.; Dai, H. F.

    2015-01-01

    The power battery thermal management problem in EV (electric vehicle) and HEV (hybrid electric vehicle) has been widely discussed, and EIS (electrochemical impedance spectroscopy) is an effective experimental method to test and estimate the status of the battery. Firstly, an electrochemical-based impedance matrix analysis for lithium-ion battery is developed to describe the impedance response of electrochemical impedance spectroscopy. Then a method, based on electrochemical impedance spectroscopy measurement, has been proposed to estimate the internal temperature of power lithium-ion battery by analyzing the phase shift and magnitude of impedance at different ambient temperatures. Respectively, the SoC (state of charge) and temperature have different effects on the impedance characteristics of battery at various frequency ranges in the electrochemical impedance spectroscopy experimental study. Also the impedance spectrum affected by SoH (state of health) is discussed in the paper preliminary. Therefore, the excitation frequency selected to estimate the inner temperature is in the frequency range which is significantly influenced by temperature without the SoC and SoH. The intrinsic relationship between the phase shift and temperature is established under the chosen excitation frequency. And the magnitude of impedance related to temperature is studied in the paper. In practical applications, through obtaining the phase shift and magnitude of impedance, the inner temperature estimation could be achieved. Then the verification experiments are conduced to validate the estimate method. Finally, an estimate strategy and an on-line estimation system implementation scheme utilizing battery management system are presented to describe the engineering value.

  7. Electrical impedance spectroscopy measurements to estimate the ...

    Indian Academy of Sciences (India)

    Administrator

    The reviews of these studies were presented by Kahraman ... kind of solid or liquid material: ionic, semi-conducting, mixed electronic–ionic and .... the rock sample and its response was measured at room temperature. Figure 5 indicates the ...

  8. Impedance-Source Networks for Electric Power Conversion Part II

    DEFF Research Database (Denmark)

    Siwakoti, Yam P.; Peng, Fang Zheng; Blaabjerg, Frede

    2015-01-01

    Impedance-source networks cover the entire spectrum of electric power conversion applications (dc-dc, dc-ac, ac-dc, ac-ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance......-source-network-based power converters has been covered in a previous paper and main topologies were discussed from an application point of view. Now Part II provides a comprehensive review of the most popular control and modulation strategies for impedance-source network-based power converters/inverters. These methods...

  9. Effect of Intravenous Infusion Solutions on Bioelectrical Impedance Spectroscopy.

    Science.gov (United States)

    Yap, Jason; Rafii, Mahroukh; Azcue, Maria; Pencharz, Paul

    2017-05-01

    Bioelectrical impedance (BIA) is often used to measure body fluid spaces and thereby body composition. However, in acute animal studies, we found that impedance was driven by the saline content of intravenous (IV) fluids and not by the volume. The aim of the study was to investigate the effect of 3 different fluids acutely administered on the change in impedance, specifically resistance (R). Nine healthy adults participated in 3 treatment (0.9% saline, 5% dextrose, and a mixture of 0.3% saline + 3.3% dextrose) experiments on nonconsecutive days. They all received 1 L of one of the treatments intravenously over a 1-hour period. Repeated BIA measurements were performed prior to IV infusion and then every 5 minutes for the 1-hour infusion period, plus 3 more measurements up to 15 minutes after the completion of the infusion. The change in R in the 0.9% saline infusion experiment was significantly lower than that of the glucose and mixture treatment ( P < .001). Bioelectrical impedance spectroscopy and BIA measure salt rather than the volume changes over the infusion period. Hence, in patients receiving IV fluids, BIA of any kind (single frequency or multifrequency) cannot be used to measure body fluid spaces or body composition.

  10. Fuzzy modeling of electrical impedance tomography images of the lungs

    International Nuclear Information System (INIS)

    Tanaka, Harki; Ortega, Neli Regina Siqueira; Galizia, Mauricio Stanzione; Borges, Joao Batista; Amato, Marcelo Britto Passos

    2008-01-01

    Objectives: Aiming to improve the anatomical resolution of electrical impedance tomography images, we developed a fuzzy model based on electrical impedance tomography's high temporal resolution and on the functional pulmonary signals of perfusion and ventilation. Introduction: Electrical impedance tomography images carry information about both ventilation and perfusion. However, these images are difficult to interpret because of insufficient anatomical resolution, such that it becomes almost impossible to distinguish the heart from the lungs. Methods: Electrical impedance tomography data from an experimental animal model were collected during normal ventilation and apnoea while an injection of hypertonic saline was administered. The fuzzy model was elaborated in three parts: a modeling of the heart, the pulmonary ventilation map and the pulmonary perfusion map. Image segmentation was performed using a threshold method, and a ventilation/perfusion map was generated. Results: Electrical impedance tomography images treated by the fuzzy model were compared with the hypertonic saline injection method and computed tomography scan images, presenting good results. The average accuracy index was 0.80 when comparing the fuzzy modeled lung maps and the computed tomography scan lung mask. The average ROC curve area comparing a saline injection image and a fuzzy modeled pulmonary perfusion image was 0.77. Discussion: The innovative aspects of our work are the use of temporal information for the delineation of the heart structure and the use of two pulmonary functions for lung structure delineation. However, robustness of the method should be tested for the imaging of abnormal lung conditions. Conclusions: These results showed the adequacy of the fuzzy approach in treating the anatomical resolution uncertainties in electrical impedance tomography images. (author)

  11. Mitochondrial membrane studies using impedance spectroscopy with parallel pH monitoring.

    Directory of Open Access Journals (Sweden)

    Divya Padmaraj

    Full Text Available A biological microelectromechanical system (BioMEMS device was designed to study complementary mitochondrial parameters important in mitochondrial dysfunction studies. Mitochondrial dysfunction has been linked to many diseases, including diabetes, obesity, heart failure and aging, as these organelles play a critical role in energy generation, cell signaling and apoptosis. The synthesis of ATP is driven by the electrical potential across the inner mitochondrial membrane and by the pH difference due to proton flux across it. We have developed a tool to study the ionic activity of the mitochondria in parallel with dielectric measurements (impedance spectroscopy to gain a better understanding of the properties of the mitochondrial membrane. This BioMEMS chip includes: 1 electrodes for impedance studies of mitochondria designed as two- and four-probe structures for optimized operation over a wide frequency range and 2 ion-sensitive field effect transistors for proton studies of the electron transport chain and for possible monitoring other ions such as sodium, potassium and calcium. We have used uncouplers to depolarize the mitochondrial membrane and disrupt the ionic balance. Dielectric spectroscopy responded with a corresponding increase in impedance values pointing at changes in mitochondrial membrane potential. An electrical model was used to describe mitochondrial sample's complex impedance frequency dependencies and the contribution of the membrane to overall impedance changes. The results prove that dielectric spectroscopy can be used as a tool for membrane potential studies. It can be concluded that studies of the electrochemical parameters associated with mitochondrial bioenergetics may render significant information on various abnormalities attributable to these organelles.

  12. On the Usage of Cyclic Voltammetry and Impedance Spectroscopy for Measuring the Concentration of Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Manuel Fiedler

    2015-02-01

    Full Text Available This article describes sensors for concentration measurement based on the electro- chemical properties of the liquid being measured. Herein two electrical methods, namely cyclic voltammetry and impedance spectroscopy, are being presented. The measurement can be performed quasi simultaneously using the same measurement medium. Further optimization of the combined methods is possible by adapting the geometric design of the electrode structure, the electrode material, the optional passivation and the electric coupling (galvanically or capacitively. In summary, by combining multiple sensory principles on a device it becomes possible to analyze mixtures of substances contained in a solution with respect to their composition.

  13. A comparison study of electrodes for neonate electrical impedance tomography

    International Nuclear Information System (INIS)

    Rahal, Mohamad; Demosthenous, Andreas; Khor, Joo Moy; Tizzard, Andrew; Bayford, Richard

    2009-01-01

    Electrical impedance tomography (EIT) is an imaging technique that has the potential to be used for studying neonate lung function. The properties of the electrodes are very important in multi-frequency EIT (MFEIT) systems, particularly for neonates, as the skin cannot be abraded to reduce contact impedance. In this work, the impedance of various clinical electrodes as a function of frequency is investigated to identify the optimum electrode type for this application. Six different types of self-adhesive electrodes commonly used in general and neonatal cardiology have been investigated. These electrodes are Ag/AgCl electrodes from the Ambu® Cardiology Blue sensors range (BR, NF and BRS), Kendall (KittyCat(TM) and ARBO®) and Philips 13953D electrodes. In addition, a textile electrode without gel from Textronics was tested on two subjects to allow comparison with the hydrogel-based electrodes. Two- and four-electrode measurements were made to determine the electrode-interface and tissue impedances, respectively. The measurements were made on the back of the forearm of six healthy adult volunteers without skin preparation with 2.5 cm electrode spacing. Impedance measurements were carried out using a Solartron SI 1260 impedance/gain-phase analyser with a frequency range from 10 Hz to 1 MHz. For the electrode-interface impedance, the average magnitude decreased with frequency, with an average value of 5 kΩ at 10 kHz and 337 Ω at 1 MHz; for the tissue impedance, the respective values were 987 Ω and 29 Ω. Overall, the Ambu BRS, Kendall ARBO® and Textronics textile electrodes gave the lowest electrode contact impedance at 1 MHz. Based on the results of the two-electrode measurements, simple RC models for the Ambu BRS and Kendall-ARBO and Textronics textile electrodes have been derived for MFEIT applications

  14. Electrical impedance tomography of the 1995 OGI gasoline release

    International Nuclear Information System (INIS)

    Daily, W.; Ramirez, A.

    1996-01-01

    Electrical impedance tomography (EIT) was used to image the plume resulting from a release of 378 liters (100 gallons) of gasoline into a sandy acquifer. Images were made in 5 planes before and 5 times during the release, to generate a detailed picture of the spatial as well as the temporal development of the plume as it spread at the water table. Information of the electrical impedance (both in phase and out of phase voltages) was used or several different frequencies to produce images. We observed little dispersion in the images either before or after the gasoline entered the acquifer. Likewise, despite some laboratory measurements of impedances, there was no evidence of a change in the reactance in the soil because of the gasoline

  15. Electrical impedance of layered atherosclerotic plaques on human aortas

    NARCIS (Netherlands)

    C.J. Slager (Cornelis); A.C. Phaff; C.E. Essed; N. Bom (Klaas); J.C.H. Schuurbiers (Johan); P.W.J.C. Serruys (Patrick)

    1992-01-01

    textabstractElectrical impedance measurements were performed on 13 atherosclerotic human aortic segments at 67 measuring spots in order to determine whether or not on the basis of these data a distinction can be made between atherosclerotic lesions and normal tissue. Stenosis localization and

  16. Study of Paclitaxel-Treated HeLa Cells by Differential Electrical Impedance Flow Cytometry

    DEFF Research Database (Denmark)

    Kirkegaard, Julie; Clausen, Casper Hyttel; Rodriguez-Trujíllo, Romén

    2014-01-01

    This work describes the electrical investigation of paclitaxel-treated HeLa cells using a custom-made microfluidic biosensor for whole cell analysis in continuous flow. We apply the method of differential electrical impedance spectroscopy to treated HeLa cells in order to elucidate the changes...... on investigating the changes in the electrical properties of the cell membrane caused by the effect of paclitaxel. We observe good agreement between the model and the obtained results. This establishes the proof-of-concept for the application in cell drug therapy....

  17. An Electrochemical Impedance Spectroscopy System for Monitoring Pineapple Waste Saccharification

    Directory of Open Access Journals (Sweden)

    Claudia Conesa

    2016-02-01

    Full Text Available Electrochemical impedance spectroscopy (EIS has been used for monitoring the enzymatic pineapple waste hydrolysis process. The system employed consists of a device called Advanced Voltammetry, Impedance Spectroscopy & Potentiometry Analyzer (AVISPA equipped with a specific software application and a stainless steel double needle electrode. EIS measurements were conducted at different saccharification time intervals: 0, 0.75, 1.5, 6, 12 and 24 h. Partial least squares (PLS were used to model the relationship between the EIS measurements and the sugar determination by HPAEC-PAD. On the other hand, artificial neural networks: (multilayer feed forward architecture with quick propagation training algorithm and logistic-type transfer functions gave the best results as predictive models for glucose, fructose, sucrose and total sugars. Coefficients of determination (R2 and root mean square errors of prediction (RMSEP were determined as R2 > 0.944 and RMSEP < 1.782 for PLS and R2 > 0.973 and RMSEP < 0.486 for artificial neural networks (ANNs, respectively. Therefore, a combination of both an EIS-based technique and ANN models is suggested as a promising alternative to the traditional laboratory techniques for monitoring the pineapple waste saccharification step.

  18. Electrical impedance along connective tissue planes associated with acupuncture meridians

    Directory of Open Access Journals (Sweden)

    Hammerschlag Richard

    2005-05-01

    Full Text Available Abstract Background Acupuncture points and meridians are commonly believed to possess unique electrical properties. The experimental support for this claim is limited given the technical and methodological shortcomings of prior studies. Recent studies indicate a correspondence between acupuncture meridians and connective tissue planes. We hypothesized that segments of acupuncture meridians that are associated with loose connective tissue planes (between muscles or between muscle and bone visible by ultrasound have greater electrical conductance (less electrical impedance than non-meridian, parallel control segments. Methods We used a four-electrode method to measure the electrical impedance along segments of the Pericardium and Spleen meridians and corresponding parallel control segments in 23 human subjects. Meridian segments were determined by palpation and proportional measurements. Connective tissue planes underlying those segments were imaged with an ultrasound scanner. Along each meridian segment, four gold-plated needles were inserted along a straight line and used as electrodes. A parallel series of four control needles were placed 0.8 cm medial to the meridian needles. For each set of four needles, a 3.3 kHz alternating (AC constant amplitude current was introduced at three different amplitudes (20, 40, and 80 μAmps to the outer two needles, while the voltage was measured between the inner two needles. Tissue impedance between the two inner needles was calculated based on Ohm's law (ratio of voltage to current intensity. Results At the Pericardium location, mean tissue impedance was significantly lower at meridian segments (70.4 ± 5.7 Ω compared with control segments (75.0 ± 5.9 Ω (p = 0.0003. At the Spleen location, mean impedance for meridian (67.8 ± 6.8 Ω and control segments (68.5 ± 7.5 Ω were not significantly different (p = 0.70. Conclusion Tissue impedance was on average lower along the Pericardium meridian, but not

  19. Ferroelectric relaxor behaviour and impedance spectroscopy of Bi2O3-doped barium zirconium titanate ceramics

    Science.gov (United States)

    Mahajan, Sandeep; Thakur, O P; Bhattacharya, D K; Sreenivas, K

    2009-03-01

    Bi2O3-doped barium zirconate titanate ceramics, Ba1-xBix(Zr0.05Ti0.95)O3, have been prepared by the conventional solid-state reaction method. The ferroelectric relaxor behaviour and dielectric properties have been investigated in detail. By XRD analysis, it is suggested that up to x = 0.04, Bi3+ substitutes A-site ion, and thereafter with higher Bi3+ content, it enters the B-site sub lattice. Substitution of Bi3+ ions induces ferroelectric relaxor behaviour and the degree of relaxation behaviour increases with bismuth concentration. The remanent polarization and strain behaviour show a slight increase with the substitution level. The degree of hysteresis (strain versus electric field) also reduces from 21.4% to 4.6% with bismuth substitution. Impedance measurements were made on the prepared sample over a wide range of temperatures (300-723 K) and frequencies (40 Hz-1 MHz), which show the presence of both bulk and grain boundary effects in the material. The bulk and grain boundary conductivities determined from impedance study indicate the Arrhenius-type thermally activated process. Impedance spectroscopy is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries to the complex impedance of a ceramic system, accurately estimating its electrical conductivity as well as its corresponding activation energies and drawing conclusions on its structural properties.

  20. Ferroelectric relaxor behaviour and impedance spectroscopy of Bi2O3-doped barium zirconium titanate ceramics

    International Nuclear Information System (INIS)

    Mahajan, Sandeep; Thakur, O P; Bhattacharya, D K; Sreenivas, K

    2009-01-01

    Bi 2 O 3 -doped barium zirconate titanate ceramics, Ba 1-x Bi x (Zr 0.05 Ti 0.95 )O 3 , have been prepared by the conventional solid-state reaction method. The ferroelectric relaxor behaviour and dielectric properties have been investigated in detail. By XRD analysis, it is suggested that up to x = 0.04, Bi 3+ substitutes A-site ion, and thereafter with higher Bi 3+ content, it enters the B-site sub lattice. Substitution of Bi 3+ ions induces ferroelectric relaxor behaviour and the degree of relaxation behaviour increases with bismuth concentration. The remanent polarization and strain behaviour show a slight increase with the substitution level. The degree of hysteresis (strain versus electric field) also reduces from 21.4% to 4.6% with bismuth substitution. Impedance measurements were made on the prepared sample over a wide range of temperatures (300-723 K) and frequencies (40 Hz-1 MHz), which show the presence of both bulk and grain boundary effects in the material. The bulk and grain boundary conductivities determined from impedance study indicate the Arrhenius-type thermally activated process. Impedance spectroscopy is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries to the complex impedance of a ceramic system, accurately estimating its electrical conductivity as well as its corresponding activation energies and drawing conclusions on its structural properties.

  1. Damage detection and conductivity evolution in carbon nanofiber epoxy via electrical impedance tomography

    International Nuclear Information System (INIS)

    Tallman, T N; Wang, K W; Gungor, S; Bakis, C E

    2014-01-01

    Utilizing electrically conductive nanocomposites for integrated self-sensing and health monitoring is a promising area of structural health monitoring (SHM) research wherein local changes in conductivity coincide with damage. In this research we conduct proof of concept investigations using electrical impedance tomography (EIT) for damage detection by identifying conductivity changes and by imaging conductivity evolution in a carbon nanofiber (CNF) filled epoxy composite. CNF/epoxy is examined because fibrous composites can be manufactured with a CNF/epoxy matrix thereby enabling the entire matrix to become self-sensing. We also study the mechanisms of conductivity evolution in CNF/epoxy through electrical impedance spectroscopy (EIS) testing. The results of these tests indicate that thermal expansion is responsible for conductivity evolution in a CNF/epoxy composite. (paper)

  2. Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography

    International Nuclear Information System (INIS)

    Grasland-Mongrain, Pol; Destrempes, François; Cloutier, Guy; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril

    2015-01-01

    Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an ‘acousto-electrical speckle’ in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging. (paper)

  3. Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography

    Science.gov (United States)

    Grasland-Mongrain, Pol; Destrempes, François; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy

    2015-05-01

    Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an ‘acousto-electrical speckle’ in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.

  4. On-line monitoring of the crystallization process: relationship between crystal size and electrical impedance spectra

    International Nuclear Information System (INIS)

    Zhao, Yanlin; Yao, Jun; Wang, Mi

    2016-01-01

    On-line monitoring of crystal size in the crystallization process is crucial to many pharmaceutical and fine-chemical industrial applications. In this paper, a novel method is proposed for the on-line monitoring of the cooling crystallization process of L-glutamic acid (LGA) using electrical impedance spectroscopy (EIS). The EIS method can be used to monitor the growth of crystal particles relying on the presence of an electrical double layer on the charged particle surface and the polarization of double layer under the excitation of alternating electrical field. The electrical impedance spectra and crystal size were measured on-line simultaneously by an impedance analyzer and focused beam reflectance measurement (FBRM), respectively. The impedance spectra were analyzed using the equivalent circuit model and the equivalent circuit elements in the model can be obtained by fitting the experimental data. Two equivalent circuit elements, including capacitance ( C 2 ) and resistance ( R 2 ) from the dielectric polarization of the LGA solution and crystal particle/solution interface, are in relation with the crystal size. The mathematical relationship between the crystal size and the equivalent circuit elements can be obtained by a non-linear fitting method. The function can be used to predict the change of crystal size during the crystallization process. (paper)

  5. Cell Electrical Impedance as a Novel Approach for Studies on Senescence Not Based on Biomarkers

    Directory of Open Access Journals (Sweden)

    Jung-Joon Cha

    2016-01-01

    Full Text Available Senescence of cardiac myocytes is frequently associated with heart diseases. To analyze senescence in cardiac myocytes, a number of biomarkers have been isolated. However, due to the complex nature of senescence, multiple markers are required for a single assay to accurately depict complex physiological changes associated with senescence. In single cells, changes in both cytoplasm and cell membrane during senescence can affect the changes in electrical impedance. Based on this phenomenon, we developed MEDoS, a novel microelectrochemical impedance spectroscopy for diagnosis of senescence, which allows us to precisely measure quantitative changes in electrical properties of aging cells. Using cardiac myocytes isolated from 3-, 6-, and 18-month-old isogenic zebrafish, we examined the efficacy of MEDoS and showed that MEDoS can identify discernible changes in electrical impedance. Taken together, our data demonstrated that electrical impedance in cells at different ages is distinct with quantitative values; these results were comparable with previously reported ones. Therefore, we propose that MEDoS be used as a new biomarker-independent methodology to obtain quantitative data on the biological senescence status of individual cells.

  6. Electrical impedance measured changes in thoracic fluid content during thoracentesis

    DEFF Research Database (Denmark)

    Petersen, J R; Jensen, B V; Drabaek, H

    1994-01-01

    In patients (seven females and 11 males) with pleural effusion due to pulmonary (n = 13) or cardiac disease (n = 5) the change in baseline transthoracic impedance (Z0) was measured by electrical impedance (BoMed's NCCOM-3, 70 kHz) during thoracentesis. Data were obtained before and after withdrawal...... of each 500 ml, and at the end of the thoracentesis. We found a close linear correlation (r = 0.97) between changes in Z0 and the volume of aspirated pleural effusion (y = 0.415.x+0.093). The variability of the estimated thoracic fluid volumes was analysed with a plot of the residuals from the regression...... line, and we found that changes in thoracic fluid volume estimated by impedance technique would be within +/- 302 ml (= 2 SD). However, the absolute value of Z0 before thoracentesis could not differentiate the group of patients with pleural effusion from normal subjects (n = 28)....

  7. Tunable Impedance Spectroscopy Sensors via Selective Nanoporous Materials.

    Energy Technology Data Exchange (ETDEWEB)

    Nenoff, Tina M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Small, Leo J [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-09-01

    Impedance spectroscopy was leveraged to directly detect the sorption of I 2 by selective adsorption into nanoporous metal organic frameworks (MOF). Films of three different types of MOF frameworks, respectively, were drop cast onto platinum interdigitated electrodes, dried, and exposed to gaseous I 2 at 25, 40, or 70 C. The MOF frameworks varied in topology from small pores (equivalent to I 2 diameter) to large pore frameworks. The combination of the chemistry of the framework and pore size dictated quantity and kinetics of I 2 adsorption. Air, argon, methanol, and water were found to produce minimal changes in ZIF-8 impedance. Independent of MOF framework characteristics, all resultant sensors showed high response to I 2 in air. As an example of sensor output, I 2 was readily detected at 25 C in air within 720 s of exposure, using an un-optimized sensor geometry with a small pored MOF. Further optimization of sensor geometry, decreasing MOF film thicknesses and maximizing sensor capacitance, will enable faster detection of trace I 2 .

  8. Design of a wideband CMOS impedance spectroscopy ASIC analog front-end for multichannel biosensor interfaces.

    Science.gov (United States)

    Valente, Virgilio; Dai Jiang; Demosthenous, Andreas

    2015-08-01

    This paper presents the preliminary design and simulation of a flexible and programmable analog front-end (AFE) circuit with current and voltage readout capabilities for electric impedance spectroscopy (EIS). The AFE is part of a fully integrated multifrequency EIS platform. The current readout comprises of a transimpedance stage and an automatic gain control (AGC) unit designed to accommodate impedance changes larger than 3 order of magnitude. The AGC is based on a dynamic peak detector that tracks changes in the input current over time and regulates the gain of a programmable gain amplifier in order to optimise the signal-to-noise ratio. The system works up to 1 MHz. The voltage readout consists of a 2 stages of fully differential current-feedback instrumentation amplifier which provide 100 dB of CMRR and a programmable gain up to 20 V/V per stage with a bandwidth in excess of 10MHz.

  9. Development of electrochemical impedance spectroscopy based sensing system for DEHP detection

    KAUST Repository

    Zia, Asif I.

    2011-11-01

    This research work presents a real time and non invasive technique to detect Di(2-ethylhexyl) phthalate (DEHP)content in purified water and quantify its concentration by Electrochemical Impedance Spectroscopy(E.I.S.). Planar Inter-digital capacitive sensor is employed to evaluate conductivity, permeability and dielectric properties of material under test. This sensor, consisting of inter-digitated microelectrodes, is fabricated on silicon substrate using thin-film Microelectromechanical system (MEMS) based semiconductor device fabrication technology. Impedance spectrums are obtained with various concentrations of DEHP in purified water by using an electric circuit in order to extract sample conductance. Relationship of sample conductance with DEHP concentration is studied in this research work which enables us to show the ability of E.I.S. to detect DEHP concentration in water and hence can be applied in water treatment process for contamination quantification. © 2011 IEEE.

  10. Nanostructured ZnO films: A study of molecular influence on transport properties by impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sappia, Luciano D.; Trujillo, Matias R. [Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET, Chacabuco 461, T4000ILI San Miguel de Tucumán (Argentina); Laboratorio de Medios e Interfases (LAMEIN), Departamento de Bioingeniería, Fac. de Cs. Exactas y Tecnología, Universidad Nacional de Tucumán, Av. Independencia 1800, 4000 San Miguel de Tucumán (Argentina); Lorite, Israel [Division of Superconductivity and Magnetism, Institute for Experimental Physics II, University of Leipzig, Linnéstrasse 5, 04103 Leipzig (Germany); Madrid, Rossana E., E-mail: rmadrid@herrera.unt.edu.ar [Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET, Chacabuco 461, T4000ILI San Miguel de Tucumán (Argentina); Laboratorio de Medios e Interfases (LAMEIN), Departamento de Bioingeniería, Fac. de Cs. Exactas y Tecnología, Universidad Nacional de Tucumán, Av. Independencia 1800, 4000 San Miguel de Tucumán (Argentina); Tirado, Monica [NanoProject and Laboratorio de Nanomateriales y Propiedades Dieléctricas, Departamento de Física, Universidad Nacional de Tucumán, Avenida Independencia 1800, Tucumán (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); and others

    2015-10-15

    Graphical abstract: - Highlights: • We study electrical transport in nanostructured ZnO films by impedance spectroscopy. • Bioaggregates on the surface produce strong changes in film transport properties. • This behavior is explained by modeling data with RC parallel circuits. • Electrical responses of ZnO films to aggregates are promising for biosensing. - Abstract: Nanomaterials based on ZnO have been used to build glucose sensors due to its high isoelectric point, which is important when a protein like Glucose Oxidase (GOx) is attached to a surface. It also creates a biologically friendly environment to preserve the activity of the enzyme. In this work we study the electrical transport properties of ZnO thin films (TFs) and single crystals (SC) in contact with different solutions by using impedance spectroscopy. We have found that the composition of the liquid, by means of the charge of the ions, produces strong changes in the transport properties of the TF. The enzyme GOx and phosphate buffer solutions have the major effect in the conduction through the films, which can be explained by the entrapment of carriers at the grain boundaries of the TFs. These results can help to design a new concept in glucose biosensing.

  11. Magnetoacoustic tomographic imaging of electrical impedance with magnetic induction

    OpenAIRE

    Xia, Rongmin; Li, Xu; He, Bin

    2007-01-01

    Magnetoacoustic tomography with magnetic induction (MAT-MI) is a recently introduced method for imaging tissue electrical impedance properties by integrating magnetic induction and ultrasound measurements. In the present study, we have developed a focused cylindrical scanning mode MAT-MI system and the corresponding reconstruction algorithms. Using this system, we demonstrated 3-dimensional MAT-MI imaging in a physical phantom, with cylindrical scanning combined with ultrasound focusing, and ...

  12. Determination of SoH of Lead-Acid Batteries by Electrochemical Impedance Spectroscopy

    Directory of Open Access Journals (Sweden)

    Monika Kwiecien

    2018-05-01

    Full Text Available The aging mechanisms of lead-acid batteries change the electrochemical characteristics. For example, sulfation influences the active surface area, and corrosion increases the resistance. Therefore, it is expected that the state of health (SoH can be reflected through differentiable changes in the impedance of a lead-acid battery. However, for lead-acid batteries, no reliable SoH algorithm is available based on single impedance values or the spectrum. Additionally, the characteristic changes of the spectrum during aging are unknown. In this work, lead-acid test cells were aged under specific cycle regimes known as AK3.4, and periodic electrochemical impedance spectroscopy (EIS measurements and capacity tests were conducted. It was examined that single impedance values increased linearly with capacity decay, but with varying slopes depending on the pre-history of the cell and measurement frequency of impedance. Thereby, possible reasons for ineffective SoH estimation were found. The spectra were fitted to an equivalent electrical circuit containing, besides other elements, an ohmic and a charge-transfer resistance of the negative electrode. The linear increase of the ohmic resistance and the charge-transfer resistance were characterized for the performed cyclic aging test. Results from chemical analysis confirmed the expected aging process and the correlation between capacity decay and impedance change. Furthermore, the positive influence of charging on the SoH could be detected via EIS. The results presented here show that SoH estimation using EIS can be a viable technique for lead-acid batteries.

  13. An impedance spectroscopy investigation of nanocrystalline CsPbBr{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Vitale, G. [Department of Electronic Engineering and INFM, University of Rome ' Roma Tre' , Via della Vasca Navale 84, 00146 Rome (Italy); Conte, G. [Department of Electronic Engineering and INFM, University of Rome ' Roma Tre' , Via della Vasca Navale 84, 00146 Rome (Italy)]. E-mail: gconte@ele.uniroma3.it; Aloe, P. [Department of Physics and INFM, University of Rome ' Roma Tre' , Via della Vasca Navale 84, 00146 Rome (Italy); Somma, F. [Department of Physics and INFM, University of Rome ' Roma Tre' , Via della Vasca Navale 84, 00146 Rome (Italy)

    2005-12-15

    Thin films of CsPbBr{sub 3} were prepared by co-evaporation of CsBr and PbBr{sub 2} powders. Deposited materials are constituted by nanometer-sized crystals as evidenced by atomic force microscopy and X ray diffraction. Impedance spectroscopy measurements, aimed to study the dielectric relaxation processes and transport mechanisms at grain boundary and grain interior, reveal a complex response of the material both on the frequency and on the temperature variations. DC current voltage curves are ohmic for applied electric field strength up to 2 x 10{sup 6} V/cm. The DC conductivity Arrhenius plot gives a value of the activation energy equal to 0.85 eV, smaller then that expected for an intrinsic semiconductor. On the other hand, impedance measurements on a wide frequency range and at different temperatures can be reduced to a single master curve addressing hopping transport mechanism and dielectric relaxation processes being active. Finally, a simple model based on multiple Voigt's elements has been used to fit the impedance spectroscopy data and to evaluate relevant material parameters.

  14. Magnetoacoustic tomographic imaging of electrical impedance with magnetic induction

    Science.gov (United States)

    Xia, Rongmin; Li, Xu; He, Bin

    2007-08-01

    Magnetoacoustic tomography with magnetic induction (MAT-MI) is a recently introduced method for imaging tissue electrical impedance properties by integrating magnetic induction and ultrasound measurements. In the present study, the authors have developed a focused cylindrical scanning mode MAT-MI system and the corresponding reconstruction algorithms. Using this system, they demonstrated a three-dimensional MAT-MI imaging approach in a physical phantom, with cylindrical scanning combined with ultrasound focusing, and the ability of MAT-MI in imaging electrical conductivity properties of biological tissue.

  15. Study of charge-carrier relaxation in a disordered organic semiconductor by simulating impedance spectroscopy

    NARCIS (Netherlands)

    Mesta, M.; Cottaar, J.; Coehoorn, R.; Bobbert, P.A.

    2014-01-01

    Impedance spectroscopy is a very sensitive probe of nonstationary charge transport governed by charge-carrier relaxation in devices of disordered organic semiconductors. We simulate impedance spectroscopy measurements of hole-only devices of a polyfluorene-based disordered organic semiconductor by

  16. Characterization of Bi4Ge3O12 single crystal by impedance spectroscopy

    Directory of Open Access Journals (Sweden)

    Zélia Soares Macedo

    2003-12-01

    Full Text Available Bi4Ge3O12 (bismuth germanate - BGO single crystals were produced by the Czochralski technique and their electrical and dielectric properties were investigated by impedance spectroscopy. The isothermal ac measurements were performed for temperatures from room temperature up to 750 °C, but only the data taken above 500 °C presented a complete semicircle in the complex impedance diagrams. Experimental data were fitted to a parallel RC equivalent circuit, and the electrical conductivity was obtained from the resistivity values. Conductivity values from 5.4 × 10(9 to 4.3 × 10-7 S/cm were found in the temperature range of 500 to 750 °C. This electrical conductivity is thermally activated, following the Arrhenius law with an apparent activation energy of (1.41 ± 0.04 eV. The dielectric properties of BGO single crystal were also studied for the same temperature interval. Permittivity values of 20 ± 2 for frequencies higher than 10³ Hz and a low-frequency dispersion were observed. Both electric and dielectric behavior of BGO are typical of systems in which the conduction mechanism dominates the dielectric response.

  17. Electrochemical impedance spectroscopy of supercapacitors: A novel analysis approach using evolutionary programming

    Science.gov (United States)

    Oz, Alon; Hershkovitz, Shany; Tsur, Yoed

    2014-11-01

    In this contribution we present a novel approach to analyze impedance spectroscopy measurements of supercapacitors. Transforming the impedance data into frequency-dependent capacitance allows us to use Impedance Spectroscopy Genetic Programming (ISGP) in order to find the distribution function of relaxation times (DFRT) of the processes taking place in the tested device. Synthetic data was generated in order to demonstrate this technique and a model for supercapacitor ageing process has been obtained.

  18. Impedance spectroscopy study of dehydrated chitosan and chitosan containing LiClO4

    International Nuclear Information System (INIS)

    Costa, M.M.; Terezo, A.J.; Matos, A.L.; Moura, W.A.; Giacometti, Jose A.; Sombra, A.S.B.

    2010-01-01

    Cast films of chitosan and chitosan containing LiClO 4 were characterized using Fourier transform infrared spectroscopy and the thermogravimetric technique. The electric properties of hydrated and dehydrated films were investigated with impedance spectroscopy in the frequency range from 0.1 Hz to 1 MHz, at temperatures varying from 30 to 110 o C. The frequency dependence of the impedance for dehydrated chitosan and chitosan containing LiClO 4 films indicated ionic conduction. Two relaxation peaks were evident on the imaginary curve of the electric modulus, which were assigned to ionic conduction. The peak at higher frequency was found for chitosan and chitosan containing LiClO 4 films. The peak at lower frequency was attributed to Li + conduction since it appeared only for the chitosan containing LiClO 4 . The peak frequency varied with the temperature according to an Arrhenius process with activation energies of circa of 0.6 and 0.45 eV, for H + and Li + conduction, respectively.

  19. A LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) for biological tissue impedance analysis and equivalent circuit modelling

    KAUST Repository

    Bera, Tushar Kanti

    2016-12-05

    Under an alternating electrical signal, biological tissues produce a complex electrical bioimpedance that is a function of tissue composition and applied signal frequencies. By studying the bioimpedance spectra of biological tissues over a wide range of frequencies, we can noninvasively probe the physiological properties of these tissues to detect possible pathological conditions. Electrical impedance spectroscopy (EIS) can provide the spectra that are needed to calculate impedance parameters within a wide range of frequencies. Before impedance parameters can be calculated and tissue information extracted, impedance spectra should be processed and analyzed by a dedicated software program. National Instruments (NI) Inc. offers LabVIEW, a fast, portable, robust, user-friendly platform for designing dataanalyzing software. We developed a LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) to analyze the electrical impedance spectra for tissue characterization in medical, biomedical and biological applications. Here, we test, calibrate and evaluate the performance of LEBISDI on the impedance data obtained from simulation studies as well as the practical EIS experimentations conducted on electronic circuit element combinations and the biological tissue samples. We analyze the Nyquist plots obtained from the EIS measurements and compare the equivalent circuit parameters calculated by LEBISDI with the corresponding original circuit parameters to assess the accuracy of the program developed. Calibration studies show that LEBISDI not only interpreted the simulated and circuitelement data accurately, but also successfully interpreted tissues impedance data and estimated the capacitive and resistive components produced by the compositions biological cells. Finally, LEBISDI efficiently calculated and analyzed variation in bioimpedance parameters of different tissue compositions, health and temperatures. LEBISDI can also be used for human tissue

  20. A LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) for biological tissue impedance analysis and equivalent circuit modelling

    KAUST Repository

    Bera, Tushar Kanti; Jampana, Nagaraju; Lubineau, Gilles

    2016-01-01

    Under an alternating electrical signal, biological tissues produce a complex electrical bioimpedance that is a function of tissue composition and applied signal frequencies. By studying the bioimpedance spectra of biological tissues over a wide range of frequencies, we can noninvasively probe the physiological properties of these tissues to detect possible pathological conditions. Electrical impedance spectroscopy (EIS) can provide the spectra that are needed to calculate impedance parameters within a wide range of frequencies. Before impedance parameters can be calculated and tissue information extracted, impedance spectra should be processed and analyzed by a dedicated software program. National Instruments (NI) Inc. offers LabVIEW, a fast, portable, robust, user-friendly platform for designing dataanalyzing software. We developed a LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) to analyze the electrical impedance spectra for tissue characterization in medical, biomedical and biological applications. Here, we test, calibrate and evaluate the performance of LEBISDI on the impedance data obtained from simulation studies as well as the practical EIS experimentations conducted on electronic circuit element combinations and the biological tissue samples. We analyze the Nyquist plots obtained from the EIS measurements and compare the equivalent circuit parameters calculated by LEBISDI with the corresponding original circuit parameters to assess the accuracy of the program developed. Calibration studies show that LEBISDI not only interpreted the simulated and circuitelement data accurately, but also successfully interpreted tissues impedance data and estimated the capacitive and resistive components produced by the compositions biological cells. Finally, LEBISDI efficiently calculated and analyzed variation in bioimpedance parameters of different tissue compositions, health and temperatures. LEBISDI can also be used for human tissue

  1. Polarization study on doped lanthanum gallate electrolyte using impedance spectroscopy

    Science.gov (United States)

    Gong, Wenquan; Gopalan, Srikanth; Pal, Uday B.

    2004-06-01

    Alternating current complex impedance spectroscopy studies were conducted on symmetrical cells of the type [gas, electrode/La1-x Sr x Ga1-y Mg y O3 (LSGM) electrolyte/electrode, gas]. The electrode materials were slurry-coated on both sides of the LSGM electrolyte support. The electrodes selected for this investigation are candidate materials for solid oxide fuel cell (SOFC) electrodes. Cathode materials include La1-x Sr x MnO3 (LSM), La1-x Sr x Co y Fe1-y O3 (LSCF), a two-phase particulate composite consisting of LSM and doped-lanthanum gallate (LSGM), and LSCF + LSGM. Pt metal electrodes were also used for the purpose of comparison. Anode material investigated was the Ni + Ce0.85Gd0.15O2 composite. The study revealed important details pertaining to the charge-transfer reactions that occur in such electrodes. The information obtained can be used to design electrodes for intermediate temperature SOFCs based on LSGM electrolytes.

  2. Interrogation of the rat mammary gland using intraductal impedance spectroscopy

    International Nuclear Information System (INIS)

    Young, E F; Quinn, D A; Davies, R J

    2010-01-01

    Extant technologies for the detection of breast cancer exploit changes in the morphology of the mammary ductal epithelial network and can involve ionizing radiation. Intraductal surveillance of mammary epithelium has the potential to allow for earlier detection based on changes in function of the epithelium. This study investigated the feasibility of using intraductal impedance spectroscopy (IIS) to assess changes in resistance in the mammary epithelium in a small group of female rats in resting, pregnant and ultimately lactating states. In resting rats, intraductal surveillance was able to detect only a single resistive capacitance (RC). In pregnant animals, a second RC became evident in the frequency range between 1 and 190 Hz. The real resistance of this low frequency RC increased when measurements were made after the animals had begun lactating. Equivalent circuit modeling revealed this increase to be a 1.7-fold change from pregnancy to lactation. A model of tight junction closure in the context of ductal expansion is proposed. These results suggest that physiologic measurements can be made in rodent mammary epithelium using this technique allowing for assessment of function in normal and disease states

  3. Impedance Spectroscopy and FTIR Studies of PEG - Based Polymer Electrolytes

    Directory of Open Access Journals (Sweden)

    Anji Reddy Polu

    2011-01-01

    Full Text Available Ionic conductivity of poly(ethylene glycol (PEG - ammonium chloride (NH4Cl based polymer electrolytes can be enhanced by incorporating ceramic filler TiO2 into PEG-NH4Cl matrix. The electrolyte samples were prepared by solution casting technique. FTIR studies indicates that the complex formation between the polymer, salt and ceramic filler. The ionic conductivity was measured using impedance spectroscopy technique. It was observed that the conductivity of the electrolyte varies with TiO2 concentration and temperature. The highest room temperature conductivity of the electrolyte of 7.72×10−6 S cm-1 was obtained at 15% by weight of TiO2 and that without TiO2 filler was found to be 9.58×10−7 S cm−1. The conductivity has been improved by 8 times when the TiO2 filler was introduced into the PEG–NH4Cl electrolyte system. The conductance spectra shows two distinct regions: a dc plateau and a dispersive region. The temperature dependence of the conductivity of the polymer electrolytes seems to obey the VTF relation. The conductivity values of the polymer electrolytes were reported and the results were discussed. The imaginary part of dielectric constant (εi decreases with increase in frequency in the low frequency region whereas frequency independent behavior is observed in the high frequency region.

  4. Non-foster impedance matching sensitivity of electrically small electric and magnetic spherical dipole antennas

    DEFF Research Database (Denmark)

    Yoon, Ick-Jae; Christensen, S.; Zhurbenko, Vitaliy

    2016-01-01

    The impedance bandwidth (BW) improvement property of a self-resonant folded spherical helix electric dipole and a spherical split ring (SSR) magnetic dipole is compared when a negative reactance element is loaded on the parasitic resonator of the antennas. They have the same electrical size of ka...

  5. Monotonicity-based electrical impedance tomography for lung imaging

    Science.gov (United States)

    Zhou, Liangdong; Harrach, Bastian; Seo, Jin Keun

    2018-04-01

    This paper presents a monotonicity-based spatiotemporal conductivity imaging method for continuous regional lung monitoring using electrical impedance tomography (EIT). The EIT data (i.e. the boundary current-voltage data) can be decomposed into pulmonary, cardiac and other parts using their different periodic natures. The time-differential current-voltage operator corresponding to the lung ventilation can be viewed as either semi-positive or semi-negative definite owing to monotonic conductivity changes within the lung regions. We used these monotonicity constraints to improve the quality of lung EIT imaging. We tested the proposed methods in numerical simulations, phantom experiments and human experiments.

  6. Recent Progress on the Factorization Method for Electrical Impedance Tomography

    Directory of Open Access Journals (Sweden)

    Bastian Harrach

    2013-01-01

    method was introduced by Kirsch for inverse scattering problems and extended to electrical impedance tomography (EIT by Brühl and Hanke. Since these pioneering works, substantial progress has been made on the theoretical foundations of the method. The necessary assumptions have been weakened, and the proofs have been considerably simplified. In this work, we aim to summarize this progress and present a state-of-the-art formulation of the Factorization Method for EIT with continuous data. In particular, we formulate the method for general piecewise analytic conductivities and give short and self-contained proofs.

  7. INVESTIGATION OF CEMENT CONCRETE CONGLOMERATE SOLIDIFICATION PROCESS BY IMPEDANCE SPECTROSCOPY METHOD

    Directory of Open Access Journals (Sweden)

    S. N. Bandarenka

    2015-01-01

    Full Text Available One of the most prospective directions in preservation  and increase of service live of  road pavements is a construction of  automobile roads with cement concrete surface. Modern tendencies for provision of road construction quality presuppose a necessity to control processes of solidification and subsequent destruction of the material while forming and using cement concrete conglomerate being considered as a basic element of the road surface.  Multiyear practical experience of  automobile road operation using cement concrete pavements reveals an importance for monitoring  such processes as formation and destruction of cement concrete materials. An impedance spectroscopy method has been tried out and proposed as a tool for solution of the given problem.Experimental samples of cement concrete have been prepared for execution of tests, graded silica sand and granite chippings with particle size from 0.63 to 2.5 mm have been used as a fine aggregate in the samples. Dependencies of resistance (impedance on AC-current frequency  have been studied for samples of various nature and granulometric composition. The Gamry  G300 potentiostat has been used for measurement of complex impedance value. A spectrum analysis and calculation of equivalent circuit parameters calculation have been carried out while using EIS Spectrum Analyzer program.Comparison of impedance spectra for the prepared cement concrete samples have made it possible to reveal tendencies in changing spectrum parameters during solidification and subsequent contact with moisture in respect of every type of the sample. An equivalent electrical circuit has been developed that  characterizes physical and chemical processes which are accompanied by charge transfer in cement concrete conglomerate. The paper demonstrates a possibility to use an impedance spectroscopy for solution of a number of actual problems in the field of cement concrete technology problems. Particularly, the problems

  8. Development of an enrofloxacin immunosensor based on label-free electrochemical impedance spectroscopy.

    Science.gov (United States)

    Wu, Ching-Chou; Lin, Chia-Hung; Wang, Way-Shyan

    2009-06-30

    Enrofloxacin is the most widespread antibiotic in the fluoroquinolone family. As such, the development of a rapid and sensitive method for the determination of trace amounts of enrofloxacin is an important issue in the health field. The interaction of the enrofloxacin antigen to a specific antibody (Ab) immobilized on an 11-mercapto-undecanoic acid-coated gold electrode was quantified by electrochemical impedance spectroscopy. Two equivalent circuits were separately used to interpret the obtained impedance spectra. These circuits included one resistor in series with one parallel circuit comprised of a resistor and a capacitor (1R//C), and one resistor in series with two parallel RC circuits (2R//C). The results indicate that the antigen-antibody reaction analyzed using the 1R//C circuit provided a more sensitive resistance increment against the enrofloxacin concentration than that of the 2R//C circuit. However, the 2R//C circuit provided a better fitting for impedance spectra, and therefore supplies more detailed results of the enrofloxacin-antibody interaction, causing the increase of electron transfer resistance selectively to the modified layer, and not the electrical double layer. The antibody-modified electrode allowed for analysis of the dynamic linear range of 1-1000 ng/ml enrofloxacin with a detection limit of 1 ng/ml. The reagentless and label-free impedimetric immunosensors provide a simple and sensitive detection method for the specific determination of enrofloxacin.

  9. Impedance Spectroscopy and AC Conductivity Studies of Bulk 3-Amino-7-(dimethylamino)-2-methyl-hydrochloride

    Science.gov (United States)

    El-Shabaan, M. M.

    2018-02-01

    Impedance spectroscopy and alternating-current (AC) conductivity (σ AC) studies of bulk 3-amino-7-(dimethylamino)-2-methyl-hydrochloride (neutral red, NR) have been carried out over the temperature (T) range from 303 K to 383 K and frequency (f) range from 0.5 kHz to 5 MHz. Dielectric data were analyzed using the complex impedance (Z *) and complex electric modulus (M *) for bulk NR at various temperatures. The impedance loss peaks were found to shift towards high frequencies, indicating an increase in the relaxation time (τ 0) and loss in the material, with increasing temperature. For each temperature, a single depressed semicircle was observed at high frequencies, originating from the bulk transport, and a spike in the low-frequency region, resulting from the electrode effect. Fitting of these curves yielded an equivalent circuit containing a parallel combination of a resistance R and constant-phase element (CPE) Q. The carrier transport in bulk NR is governed by the correlated barrier hopping (CBH) mechanism, some parameters of which, such as the maximum barrier height (W M), charge density (N), and hopping distance (r), were determined as functions of both temperature and frequency. The frequency dependence of σ AC at different temperatures indicated that the conduction in bulk NR is a thermally activated process. The σ AC value at different frequencies increased linearly with temperature.

  10. Application of impedance spectroscopy method for analysis of benzanol fuels

    Directory of Open Access Journals (Sweden)

    Mamykin A. V.

    2015-06-01

    Full Text Available The authors have developed a method for express control of three component «gasoline-alcohol-water» fuel mixtures based on the spectral impedance investigation of benzanol mixture in the frequency range of 500 Hz — 10 kHz. A correlation dependence between the dielectric constant and the specific resistance of the fuel mixture on content of ethanol and water in the mixture has been found. On the basis of this dependence a calibration nomogram to quantify the gasoline and water-alcohol components content in the test benzanol fuel in the actual range of concentrations has been formed. The nomogram allows determining the water-alcohol and gasoline parts in the analyzed fuel with an error of no more than 1% vol., while the strength of water-alcohol solution is determined with an error of no more than 0.8% vol. The obtained nomogram can also give information about critical water content in the benzanol fuel to prevent its eventual phase separation. It is shown that the initial component composition of different gasoline brands has no significant effect on the electrical characteristics of the studied benzanol fuels, which makes the evaluation of alcohol and water content in the fuel sufficiently accurate. for practical applications.

  11. Multiple biopsy probe sampling enabled minimally invasive electrical impedance tomography

    International Nuclear Information System (INIS)

    Shini, Mohanad; Rubinsky, Boris

    2008-01-01

    Biopsies are a reliable method for examining tissues and organs inside the body, in particular for detection of tumors. However, a single biopsy produces only limited information on the site from which it is taken. Therefore, tumor detection now employs multiple biopsy samplings to examine larger volumes of tissue. Nevertheless, even with multiple biopsies, the information remains discrete, while the costs of biopsy increase. Here we propose and evaluate the feasibility of using minimally invasive medical imaging as a means to overcome the limitations of discrete biopsy sampling. The minimally invasive medical imaging technique employs the biopsy probe as electrodes for measurements of electrical impedance tomography relevant data during each biopsy sampling. The data from multiple samplings are combined and used to produce an EIT image of the tissue. Two- and three-dimensional mathematical simulations confirm that the minimally invasive medical imaging technique can produce electrical impedance tomography images of the tissues between the biopsy probe insertion sites. We show that these images can detect tumors that would be missed with multiple biopsy samplings only, and that the technique may facilitate the detection of tumors with fewer biopsies, thereby reducing the cost of cancer detection

  12. Sintering and thermal ageing studies of zirconia - yttria ceramics by impedance spectroscopy

    International Nuclear Information System (INIS)

    Florio, Daniel Zanetti de

    1998-01-01

    ZrO 2 :8 mol %Y 2 O 3 solid electrolyte ceramic pellets have been prepared with powders of three different origins: a Nissan (Japan) commercial powder, a powder obtained by the coprecipitation technique at IPEN, and the mixing of powder oxides (ZrO 2 produced at a Pilot Plant at IPEN and 99.9% pure Y 2 O 3 of USA origin). These starting powders have been analysed by the following techniques: X-ray fluorescence for yttrium content, X-ray diffraction for structural phase content, sedimentation for particle size distribution, gas adsorption (BET) for surface area determination, and transmission electron microscopy for average particle size determination. Pressed ceramic pellets have been analysed by dilatometry to evaluate the sintering stages. Sintered pellets have been characterized by X-ray diffraction for phase analysis and scanning electron microscopy for grain morphology analysis. Impedance spectroscopy analysis have been carried out to follow thermal ageing of zirconia-yttria solid electrolyte at 600 deg C, the working temperature of permanent oxygen sensor, and to study sintering kinetics. The main results show that ageing at 600 deg C decreases the emf sensor response in the first 100 h to a steady value. Moreover, sintering studies by impedance spectroscopy allowed for finding correlations between electrical parameters, sintering kinetics and grain growth mechanisms. (author)

  13. Microfluidic Impedance Flow Cytometry Enabling High-Throughput Single-Cell Electrical Property Characterization

    Science.gov (United States)

    Chen, Jian; Xue, Chengcheng; Zhao, Yang; Chen, Deyong; Wu, Min-Hsien; Wang, Junbo

    2015-01-01

    This article reviews recent developments in microfluidic impedance flow cytometry for high-throughput electrical property characterization of single cells. Four major perspectives of microfluidic impedance flow cytometry for single-cell characterization are included in this review: (1) early developments of microfluidic impedance flow cytometry for single-cell electrical property characterization; (2) microfluidic impedance flow cytometry with enhanced sensitivity; (3) microfluidic impedance and optical flow cytometry for single-cell analysis and (4) integrated point of care system based on microfluidic impedance flow cytometry. We examine the advantages and limitations of each technique and discuss future research opportunities from the perspectives of both technical innovation and clinical applications. PMID:25938973

  14. Four-Wire Impedance Spectroscopy on Planar Zeolite/Chromium Oxide Based Hydrocarbon Gas Sensors

    Directory of Open Access Journals (Sweden)

    Ralf Moos

    2007-11-01

    Full Text Available Impedometric zeolite hydrocarbon sensors with a chromium oxide intermediatelayer show a very promising behavior with respect to sensitivity and selectivity. Theunderlying physico-chemical mechanism is under investigation at the moment. In order toverify that the effect occurs at the electrode and that zeolite bulk properties remain almostunaffected by hydrocarbons, a special planar setup was designed, which is very close to realsensor devices. It allows for conducting four-wire impedance spectroscopy as well as two-wire impedance spectroscopy. Using this setup, it could be clearly demonstrated that thesensing effect can be ascribed to an electrode impedance. Furthermore, by combining two-and four-wire impedance measurements at only one single frequency, the interference of thevolume impedance can be suppressed and an easy signal evaluation is possible, withouttaking impedance data at different frequencies.

  15. Bias Voltage-Dependent Impedance Spectroscopy Analysis of Hydrothermally Synthesized ZnS Nanoparticles

    Science.gov (United States)

    Dey, Arka; Dhar, Joydeep; Sil, Sayantan; Jana, Rajkumar; Ray, Partha Pratim

    2018-04-01

    In this report, bias voltage-dependent dielectric and electron transport properties of ZnS nanoparticles were discussed. ZnS nanoparticles were synthesized by introducing a modified hydrothermal process. The powder XRD pattern indicates the phase purity, and field emission scanning electron microscope image demonstrates the morphology of the synthesized sample. The optical band gap energy (E g = 4.2 eV) from UV measurement explores semiconductor behavior of the synthesized material. The electrical properties were performed at room temperature using complex impedance spectroscopy (CIS) technique as a function of frequency (40 Hz-10 MHz) under different forward dc bias voltages (0-1 V). The CIS analysis demonstrates the contribution of bulk resistance in conduction mechanism and its dependency on forward dc bias voltages. The imaginary part of the impedance versus frequency curve exhibits the existence of relaxation peak which shifts with increasing dc forward bias voltages. The dc bias voltage-dependent ac and dc conductivity of the synthesized ZnS was studied on thin film structure. A possible hopping mechanism for electrical transport processes in the system was investigated. Finally, it is worth to mention that this analysis of bias voltage-dependent dielectric and transport properties of as-synthesized ZnS showed excellent properties for emerging energy applications.

  16. Impedance spectroscopy study of N719-sensitized ZnO-based solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Pauporté, Th., E-mail: thierry-pauporte@chimie-paristech.fr [Laboratoire d' Electrochimie, Chimie des Interfaces et Modélisation pour l' Energie, Ecole Nationale Supérieure de Chimie de Paris, 11 rue P. et M. Curie, 75231 Paris cedex 05 (France); Magne, C. [Laboratoire d' Electrochimie, Chimie des Interfaces et Modélisation pour l' Energie, Ecole Nationale Supérieure de Chimie de Paris, 11 rue P. et M. Curie, 75231 Paris cedex 05 (France); Saint-Gobain Recherche, 39 quai Lucien Lefranc, 93303 Aubervilliers Cedex (France)

    2014-06-02

    ZnO porous films prepared by electrodeposition and by sol–gel techniques have been sensitized by the N719 dye and used as photoelectrode in dye-sensitized solar cells. Similar stationary current–voltage characteristics have been measured for films having two drastically different morphologies and nanostructures. The solar cells have been studied by impedance spectroscopy over large frequency and applied voltage ranges in order to elucidate the inherent correlation between the photoelectrode structure and properties. The electrical response has been analyzed using an ad-hoc electrical model to extrapolate the electronic structure and charge carrier kinetic properties of the photoelectrodes. The two films exhibit very different density distributions of their trap states below the conduction band edge. Moreover, their electron lifetimes and transport times vary differently with the DOS due to different surface and conduction properties. The charge collection efficiency has been calculated by two different approaches, one being derived from first principles. Very high values are reported in all cases. Globally, the limitation of N719/ZnO solar cell performances is related to their open circuit voltage and their short circuit current. The latter point is discussed in the light of our impedance results and photoelectrode light absorption data. - Highlights: • Exponential trap state distribution • Electron transport and recombination depend on oxide preparation route. • Charge collection efficiency modeling • Very high charge collection efficiency in N719/ZnO dye-sensitized solar cells • ZnO cell performance limitations.

  17. Fractional calculus model of electrical impedance applied to human skin.

    Science.gov (United States)

    Vosika, Zoran B; Lazovic, Goran M; Misevic, Gradimir N; Simic-Krstic, Jovana B

    2013-01-01

    Fractional calculus is a mathematical approach dealing with derivatives and integrals of arbitrary and complex orders. Therefore, it adds a new dimension to understand and describe basic nature and behavior of complex systems in an improved way. Here we use the fractional calculus for modeling electrical properties of biological systems. We derived a new class of generalized models for electrical impedance and applied them to human skin by experimental data fitting. The primary model introduces new generalizations of: 1) Weyl fractional derivative operator, 2) Cole equation, and 3) Constant Phase Element (CPE). These generalizations were described by the novel equation which presented parameter [Formula: see text] related to remnant memory and corrected four essential parameters [Formula: see text] We further generalized single generalized element by introducing specific partial sum of Maclaurin series determined by parameters [Formula: see text] We defined individual primary model elements and their serial combination models by the appropriate equations and electrical schemes. Cole equation is a special case of our generalized class of models for[Formula: see text] Previous bioimpedance data analyses of living systems using basic Cole and serial Cole models show significant imprecisions. Our new class of models considerably improves the quality of fitting, evaluated by mean square errors, for bioimpedance data obtained from human skin. Our models with new parameters presented in specific partial sum of Maclaurin series also extend representation, understanding and description of complex systems electrical properties in terms of remnant memory effects.

  18. Fractional calculus model of electrical impedance applied to human skin.

    Directory of Open Access Journals (Sweden)

    Zoran B Vosika

    Full Text Available Fractional calculus is a mathematical approach dealing with derivatives and integrals of arbitrary and complex orders. Therefore, it adds a new dimension to understand and describe basic nature and behavior of complex systems in an improved way. Here we use the fractional calculus for modeling electrical properties of biological systems. We derived a new class of generalized models for electrical impedance and applied them to human skin by experimental data fitting. The primary model introduces new generalizations of: 1 Weyl fractional derivative operator, 2 Cole equation, and 3 Constant Phase Element (CPE. These generalizations were described by the novel equation which presented parameter [Formula: see text] related to remnant memory and corrected four essential parameters [Formula: see text] We further generalized single generalized element by introducing specific partial sum of Maclaurin series determined by parameters [Formula: see text] We defined individual primary model elements and their serial combination models by the appropriate equations and electrical schemes. Cole equation is a special case of our generalized class of models for[Formula: see text] Previous bioimpedance data analyses of living systems using basic Cole and serial Cole models show significant imprecisions. Our new class of models considerably improves the quality of fitting, evaluated by mean square errors, for bioimpedance data obtained from human skin. Our models with new parameters presented in specific partial sum of Maclaurin series also extend representation, understanding and description of complex systems electrical properties in terms of remnant memory effects.

  19. Magnetic resonance electrical impedance tomography for determining electric field distribution during electroporation

    International Nuclear Information System (INIS)

    Kranjc, Matej; Miklavcic, Damijan; Bajd, Franci; Serša, Igor

    2013-01-01

    Electroporation is a phenomenon caused by externally applied electric field to cells that results in an increase of cell membrane permeability to various molecules. Accurate coverage of the tissue with a sufficiently large electric field presents one of the most important conditions for successful membrane permeabilization. Applications based on electroporation would greatly benefit with a method for monitoring the electric field, especially if it could be done in situ. As the membrane electroporation is a consequence of an induced transmembrane potential, which is directly proportional to the local electric field, we have been investigating current density imaging and magnetic resonance electrical impedance tomography techniques to determine the electric field distribution during electroporation. In this paper, we present comparison of current density and electric field distribution in an agar phantom and in a liver tissue exposed to electroporation pulses. As expected, a region of increased electrical conductivity was observed in the liver tissue exposed to sufficiently high electric field but not in agar phantom.

  20. Revisiting the electrochemical impedance spectroscopy of magnesium with online inductively coupled plasma atomic emission spectroscopy.

    Science.gov (United States)

    Shkirskiy, Viacheslav; King, Andrew D; Gharbi, Oumaïma; Volovitch, Polina; Scully, John R; Ogle, Kevin; Birbilis, Nick

    2015-02-23

    The electrochemical impedance of reactive metals such as magnesium is often complicated by an obvious inductive loop with decreasing frequency of the AC polarising signal. The characterisation and ensuing explanation of this phenomenon has been lacking in the literature to date, being either ignored or speculated. Herein, we couple electrochemical impedance spectroscopy (EIS) with online atomic emission spectroelectrochemistry (AESEC) to simultaneously measure Mg-ion concentration and electrochemical impedance spectra during Mg corrosion, in real time. It is revealed that Mg dissolution occurs via Mg(2+) , and that corrosion is activated, as measured by AC frequencies less than approximately 1 Hz approaching DC conditions. The result of this is a higher rate of Mg(2+) dissolution, as the voltage excitation becomes slow enough to enable all Mg(2+) -enabling processes to adjust in real time. The manifestation of this in EIS data is an inductive loop. The rationalisation of such EIS behaviour, as it relates to Mg, is revealed for the first time by using concurrent AESEC. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. An Electrochemical Impedance Spectroscopy Study on a Lithium Sulfur Pouch Cell

    DEFF Research Database (Denmark)

    Stroe, Daniel Loan; Knap, Vaclav; Swierczynski, Maciej Jozef

    2016-01-01

    The impedance behavior of a 3.4 Ah pouch Lithium-Sulfur cell was extensively characterized using the electrochemical impedance spectroscopy (EIS) technique. EIS measurements were performed at various temperatures and over the entire state-of-charge (SOC) interval without applying a superimposed DC...

  2. Monitoring thoracic fluid content using bioelectrical impedance spectroscopy and Cole modeling

    NARCIS (Netherlands)

    Dovancescu, Silviu; Saporito, Salvatore; Herold, Ingeborg H.F.; Korsten, H.H.M.; Aarts, Ronald M.; Mischi, Massimo

    2017-01-01

    Heart failure is a chronic disease marked by frequenthospitalizations due to pulmonary fluid congestion. Monitoringthe thoracic fluid status may favor the detection of fluidcongestion in an early stage and enable targeted preventivemeasures. Bioelectrical impedance spectroscopy (BIS) has beenused in

  3. Development of electrochemical impedance spectroscopy based sensing system for DEHP detection

    KAUST Repository

    Zia, Asif I.; Mohd. Syaifudin, A. R.; Mukhopadhyay, Subhas Chandra; Al-Bahadly, Ibrahim H.; Yu, Paklam; Gooneratne, Chinthaka Pasan; Kosel, Jü rgen

    2011-01-01

    This research work presents a real time and non invasive technique to detect Di(2-ethylhexyl) phthalate (DEHP)content in purified water and quantify its concentration by Electrochemical Impedance Spectroscopy(E.I.S.). Planar Inter-digital capacitive

  4. Weighted least-squares criteria for electrical impedance tomography

    International Nuclear Information System (INIS)

    Kallman, J.S.; Berryman, J.G.

    1992-01-01

    Methods are developed for design of electrical impedance tomographic reconstruction algorithms with specified properties. Assuming a starting model with constant conductivity or some other specified background distribution, an algorithm with the following properties is found: (1) the optimum constant for the starting model is determined automatically; (2) the weighted least-squares error between the predicted and measured power dissipation data is as small as possible; (3) the variance of the reconstructed conductivity from the starting model is minimized; (4) potential distributions with the largest volume integral of gradient squared have the least influence on the reconstructed conductivity, and therefore distributions most likely to be corrupted by contact impedance effects are deemphasized; (5) cells that dissipate the most power during the current injection tests tend to deviate least from the background value. The resulting algorithm maps the reconstruction problem into a vector space where the contribution to the inversion from the background conductivity remains invariant, while the optimum contributions in orthogonal directions are found. For a starting model with nonconstant conductivity, the reconstruction algorithm has analogous properties

  5. Influence of compressive stress in TGO layer on impedance spectroscopy from TBC coatings

    Energy Technology Data Exchange (ETDEWEB)

    Kang, To; Zhang, Jianhai; Yuan, Maodan; Song, Sungjin; Kim, Hakjoon; Kim, Yongseok; Seok, Changsung [Sungkyunkwan Univ., Suwon (Korea, Republic of)

    2013-02-15

    Impedance spectroscopy is a non destructive evaluation (NDE) method first proposed and developed for evaluating TGO layers with compressive stress inside thermally degraded plasma sprayed thermal barrier coatings (PS TBCs). A bode plot (phase angle ({Dirac_h}) vs. frequency (f)) was used to investigate the TGO layer on electrical responses. In our experimental study, the phase angle of Bode plots is sensitive for detecting TGO layers while applying compressive stress on thermal barrier coatings. It is difficult to detect TGO layers in samples isothermally aged for 100hrs and 200hrs without compressive stress, and substantial change of phase was observed these samples with compressive stress. Also, the frequency shift of the phase angle and change of the phase angle are observed in samples isothermally aged for more than 400hrs.

  6. Investigation of steel passivation in inhibited cooling waters by electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    Gusmano, G.; Montesperelli, G.; Traversa, E.

    1992-01-01

    The corrosion of mild steel, which is one of the main problems in industrial cooling equipments, is greatly influenced by total alkalinity, pH and oxygen concentration. The low concentration of oxygen present in natural waters and the low solubility of CaCO 3 greatly affect the passivation mechanism, hindering the growth of a compact and protective film. The all-organic inhibitors, which have the property of supersaturating waters with CaCO 3 , overcome this problem. In this paper the electrical characteristics of the protective film formed by this kind of inhibitors in the presence of different levels of carbonatic alkalinity and at different pH values is studied by Electrochemical Impedance Spectroscopy

  7. Monitoring the evolution of boron doped porous diamond electrode on flexible retinal implant by OCT and in vivo impedance spectroscopy

    International Nuclear Information System (INIS)

    Hébert, Clément; Cottance, Myline; Degardin, Julie; Scorsone, Emmanuel; Rousseau, Lionel; Lissorgues, Gaelle; Bergonzo, Philippe; Picaud, Serge

    2016-01-01

    Nanocrystalline Boron doped Diamond proved to be a very attractive material for neural interfacing, especially with the retina, where reduce glia growth is observed with respect to other materials, thus facilitating neuro-stimulation over long terms. In the present study, we integrated diamond microelectrodes on a polyimide substrate and investigated their performances for the development of neural prosthesis. A full description of the microfabrication of the implants is provided and their functionalities are assessed using cyclic voltammetry and electrochemical impedance spectroscopy. A porous structure of the electrode surface was thus revealed and showed promising properties for neural recording or stimulation. Using the flexible implant, we showed that is possible to follow in vivo the evolution of the electric contact between the diamond electrodes and the retina over 4 months by using electrochemical impedance spectroscopy. The position of the implant was also monitored by optical coherence tomography to corroborate the information given by the impedance measurements. The results suggest that diamond microelectrodes are very good candidates for retinal prosthesis. - Highlights: • Microfabrication of porous diamond electrode on flexible retinal implant • Electrochemical characterization of microelectrode for neural interfacing • In vivo impedance spectroscopy of retinal tissue

  8. Monitoring the evolution of boron doped porous diamond electrode on flexible retinal implant by OCT and in vivo impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hébert, Clément, E-mail: clement.hebert@icn2.cat [CEA-LIST, Diamond Sensors Laboratory, Gif-sur-Yvette 91191 (France); Cottance, Myline [Université Paris-Est, ESYCOM-ESIEE Paris, Noisy le Grand (France); Degardin, Julie [INSERM, U968, Institut de la Vision, Paris (France); Scorsone, Emmanuel [CEA-LIST, Diamond Sensors Laboratory, Gif-sur-Yvette 91191 (France); Rousseau, Lionel; Lissorgues, Gaelle [Université Paris-Est, ESYCOM-ESIEE Paris, Noisy le Grand (France); Bergonzo, Philippe [CEA-LIST, Diamond Sensors Laboratory, Gif-sur-Yvette 91191 (France); Picaud, Serge [INSERM, U968, Institut de la Vision, Paris (France)

    2016-12-01

    Nanocrystalline Boron doped Diamond proved to be a very attractive material for neural interfacing, especially with the retina, where reduce glia growth is observed with respect to other materials, thus facilitating neuro-stimulation over long terms. In the present study, we integrated diamond microelectrodes on a polyimide substrate and investigated their performances for the development of neural prosthesis. A full description of the microfabrication of the implants is provided and their functionalities are assessed using cyclic voltammetry and electrochemical impedance spectroscopy. A porous structure of the electrode surface was thus revealed and showed promising properties for neural recording or stimulation. Using the flexible implant, we showed that is possible to follow in vivo the evolution of the electric contact between the diamond electrodes and the retina over 4 months by using electrochemical impedance spectroscopy. The position of the implant was also monitored by optical coherence tomography to corroborate the information given by the impedance measurements. The results suggest that diamond microelectrodes are very good candidates for retinal prosthesis. - Highlights: • Microfabrication of porous diamond electrode on flexible retinal implant • Electrochemical characterization of microelectrode for neural interfacing • In vivo impedance spectroscopy of retinal tissue.

  9. A neural network image reconstruction technique for electrical impedance tomography

    International Nuclear Information System (INIS)

    Adler, A.; Guardo, R.

    1994-01-01

    Reconstruction of Images in Electrical Impedance Tomography requires the solution of a nonlinear inverse problem on noisy data. This problem is typically ill-conditioned and requires either simplifying assumptions or regularization based on a priori knowledge. This paper presents a reconstruction algorithm using neural network techniques which calculates a linear approximation of the inverse problem directly from finite element simulations of the forward problem. This inverse is adapted to the geometry of the medium and the signal-to-noise ratio (SNR) used during network training. Results show good conductivity reconstruction where measurement SNR is similar to the training conditions. The advantages of this method are its conceptual simplicity and ease of implementation, and the ability to control the compromise between the noise performance and resolution of the image reconstruction

  10. Electrical impedance tomography with compensation for electrode positioning variations

    International Nuclear Information System (INIS)

    Blott, B.H.; Daniell, G.J.; Meeson, S.

    1998-01-01

    Ideally electrical impedance tomography (EIT) should not be oversensitive to electrode positions, but this conflicts with efforts to produce high-resolution images. Two procedures are presented that balance reducing the sensitivity to electrode position errors with generating practicable EIT images. The first provides a criterion based on electrode sensitivity for regularizing the reconstruction through spectral expansion. The main consequences of this are that smoother images are produced and the number of artefacts and their magnitude are generally reduced. The second modification uses the recorded data to compensate for electrode movements that have occurred after the reference data were measured. Image smoothness is used as the criterion for the readjustment. Computer simulation tests have shown that this modification produces improved image fidelity. (author)

  11. Applications of Electrical Impedance Tomography (EIT): A Short Review

    Science.gov (United States)

    Kanti Bera, Tushar

    2018-03-01

    Electrical Impedance Tomography (EIT) is a tomographic imaging method which solves an ill posed inverse problem using the boundary voltage-current data collected from the surface of the object under test. Though the spatial resolution is comparatively low compared to conventional tomographic imaging modalities, due to several advantages EIT has been studied for a number of applications such as medical imaging, material engineering, civil engineering, biotechnology, chemical engineering, MEMS and other fields of engineering and applied sciences. In this paper, the applications of EIT have been reviewed and presented as a short summary. The working principal, instrumentation and advantages are briefly discussed followed by a detail discussion on the applications of EIT technology in different areas of engineering, technology and applied sciences.

  12. Assessment of breast tumor size in electrical impedance scanning

    International Nuclear Information System (INIS)

    Kim, Sungwhan

    2012-01-01

    Electrical impedance scanning (EIS) is a newly introduced imaging technique for early breast cancer detection. In EIS, we apply a sinusoidal voltage between a hand-held electrode and a scanning probe placed on the breast skin to make current travel through the breast. We measure induced currents (Neumann data) through the scanning probe. In this paper, we investigate the frequency-dependent behavior of the induced complex potential and show how the frequency differential of the current measurement on the scanning probe reflects the contrast in complex conductivity values between surrounding and cancerous tissues. Furthermore, we develop the formula for breast tumor size using the frequency differential of the current measurement and provide its feasibility. (paper)

  13. Duality reconstruction algorithm for use in electrical impedance tomography

    International Nuclear Information System (INIS)

    Abdullah, M.Z.; Dickin, F.J.

    1996-01-01

    A duality reconstruction algorithm for solving the inverse problem in electrical impedance tomography (EIT) is described. In this method, an algorithm based on the Geselowitz compensation (GC) theorem is used first to reconstruct an approximate version of the image. It is then fed as a first guessed data to the modified Newton-Raphson (MNR) algorithm which iteratively correct the image until a final acceptable solution is reached. The implementation of the GC and MNR based algorithms using the finite element method will be discussed. Reconstructed images produced by the algorithm will also be presented. Consideration is also given to the most computationally intensive aspects of the algorithm, namely the inversion of the large and sparse matrices. The methods taken to approximately compute the inverse ot those matrices will be outlined. (author)

  14. Electrochemical properties and electrochemical impedance spectroscopy of polypyrrole-coated platinum electrodes

    Directory of Open Access Journals (Sweden)

    M. Fall

    2006-12-01

    Full Text Available Polypyrrole (PPy films of different thickness were characterized by electrochemical impedance spectroscopy (EIS measurements in acetonitrile and aqueous solutions, containing 0.1 M NaClO4 or sodium dodecylsulfate as the dopant. The PPy films were electrochemically deposited on Pt, and their electrochemical properties studied by cyclic voltammetry. Impedance spectra were obtained at potentials ranging from 0 to 0.8 V/SCE. The EIS data were fitted using two different equivalent electrical circuits (depending on the nature of the dopant. They involve a diffusive capacitance, which increased with the passing charge during electrosynthesis (i.e. film thickness for ClO4--doped PPy, but was practically unaffected by the film thickness in the case of SDS-doped PPy. Also, a double-layer capacitance was found only in the circuit of ClO4--doped PPy. It increased with the film thickness, and showed a minimum near the open-circuit potential. Finally the charge-transfer resistance (Rct obtained with SDS is nearly 200-fold higher than that obtained with ClO4- in the same solvent (H2O. With the same dopant (ClO4-, Rct is about five times higher in acetonitrile relative to water. All these EIS results of the different types of PPy suggest a relation with the wettability of the polymer.

  15. Utilisation of electrical impedance tomography in breast cancer diagnosis.

    Science.gov (United States)

    Raneta, O; Ondruš, D; Bella, V

    2012-01-01

    Breast cancer presents a serious medical and social problem worldwide. Early detection is key to effective breast cancer treatment. Therefore, scientists are consistently looking for new diagnostic techniques that would be more efficient, easy to use and safe for the patient. The main task of this study was to evaluate the feasibility of a novel low-cost non-invasive technique called electrical impedance tomography (EIT) and to determine whether EIT can qualitatively supplement the existing traditional imaging techniques in the process of breast cancer diagnostics. Randomly selected patients with mammographic and/or sonographic abnormalities were involved into the study. In total, 808 patients aged 18-94 (mean 54) years participated in the survey. Exclusion criteria involved previous breast surgery, breast core biopsy or fine needle aspiration within the last 1 and 3 months, respectively. Furthermore, patients with implanted electrically powered devices (cardioverter, pacemaker) and patients previously treated by chemo-radiotherapy were also excluded. The EIT examination was performed using the electrical impedance computer mammograph MEIK developed by the Institute of Radio Engineering and Electronics, Russian Academy of Sciences. The following results were obtained: sensitivity of EIT was 87%, X-ray mammography (MMG) 89% and ultrasonography (USG) 91%; specificity of EIT was 85%, MMG 91% and USG 84%. Negative predictive value (NPV) of all three modalities showed nearly equal values, with slight advantage of the USG. MMG had the highest positive predictive (PPV) value (83%), EIT had the lowest (63%). Sensitivity increased to 96% and 98%, respectively, when combinations EIT+MMG and EIT+USG were used. The specificity increased to 79% for EIT+MMG and 71% for EIT+USG. EIT+MMG and EIT+USG NPV remained the same. PPV was 65% and 58%, respectively for the EIT+MMG and EIT+USG combination. Our study findings are comparable to those of other similar studies. Although the EIT

  16. Electrical impedance tomography imaging using a priori ultrasound data

    Directory of Open Access Journals (Sweden)

    Soleimani Manuchehr

    2006-02-01

    Full Text Available Abstract Background Different imaging systems (e.g. electrical, magnetic, and ultrasound rely on a wide variety of physical properties, and the datasets obtained from such systems provide only partial information about the unknown true state. One approach is to choose complementary imaging systems, and to combine the information to achieve a better representation. Methods This paper discusses the combination of ultrasound and electrical impedance tomography (EIT information. Ultrasound reflection signals are good at locating sharp acoustic density changes associated with the boundaries of objects. Some boundaries, however, may be indeterminable due to masking from intermediate boundaries or because they are outside the ultrasound beam. Conversely, the EIT data contains relatively low-quality information, but it includes the whole region enclosed by the electrodes. Results Results are shown from a narrowband level-set method applied to 2D and 3D EIT incorporating limited angle ultrasound time of flight data. Conclusion The EIT reconstruction is shown to be faster and more accurate using the additional edge information from both one and four transducer ultrasound systems.

  17. Electrical impedance tomography system: an open access circuit design

    Directory of Open Access Journals (Sweden)

    Soleimani Manuchehr

    2006-05-01

    Full Text Available Abstract Background This paper reports a simple 2-D system for electrical impedance tomography EIT, which works efficiently and is low cost. The system has been developed in the Sharif University of Technology Tehran-Iran (for the author's MSc Project. Methods The EIT system consists of a PC in which an I/O card is installed with an external current generator, a multiplexer, a power supply and a phantom with an array of electrodes. The measurement system provides 12-bit accuracy and hence, suitable data acquisition software has been prepared accordingly. The synchronous phase detection method has been implemented for voltage measurement. Different methods of image reconstruction have been used with this instrument to generate electrical conductivity images. Results The results of simulation and real measurement of the system are presented. The reconstruction programs were written in MATLAB and the data acquisition software in C++. The system has been tested with both static and dynamic mode in a 2-D domain. Better results have been produced in the dynamic mode of operation, due to the cancellation of errors. Conclusion In the spirit of open access publication the design details of this simple EIT system are made available here.

  18. Electrochemical impedance spectroscopy for quantitative interface state characterization of planar and nanostructured semiconductor-dielectric interfaces

    Science.gov (United States)

    Meng, Andrew C.; Tang, Kechao; Braun, Michael R.; Zhang, Liangliang; McIntyre, Paul C.

    2017-10-01

    The performance of nanostructured semiconductors is frequently limited by interface defects that trap electronic carriers. In particular, high aspect ratio geometries dramatically increase the difficulty of using typical solid-state electrical measurements (multifrequency capacitance- and conductance-voltage testing) to quantify interface trap densities (D it). We report on electrochemical impedance spectroscopy (EIS) to characterize the energy distribution of interface traps at metal oxide/semiconductor interfaces. This method takes advantage of liquid electrolytes, which provide conformal electrical contacts. Planar Al2O3/p-Si and Al2O3/p-Si0.55Ge0.45 interfaces are used to benchmark the EIS data against results obtained from standard electrical testing methods. We find that the solid state and EIS data agree very well, leading to the extraction of consistent D it energy distributions. Measurements carried out on pyramid-nanostructured p-Si obtained by KOH etching followed by deposition of a 10 nm ALD-Al2O3 demonstrate the application of EIS to trap characterization of a nanostructured dielectric/semiconductor interface. These results show the promise of this methodology to measure interface state densities for a broad range of semiconductor nanostructures such as nanowires, nanofins, and porous structures.

  19. Electrical Impedance Spectroscopic Studies on Broiler Chicken Tissue Suitable for the Development of Practical Phantoms in Multifrequency EIT

    Directory of Open Access Journals (Sweden)

    Tushar Kanti Bera

    2011-06-01

    Full Text Available Phantoms are essential for assessing the system performance in Electrical Impedance Tomography (EIT. Saline phantoms with insulator inhomogeneity fail to mimic the physiological structure of real body tissue in several aspects. Saline or any other salt solutions are purely resistive and hence studying multifrequency EIT systems cannot be assessed with saline phantoms because the response of the purely resistive materials do not change over frequency. Animal tissues show a variable response over a wide band of signal frequency due to their complex physiological and physiochemical structures and hence they can suitably be used as bathing medium and inhomogeneity in the phantoms of multifrequency EIT system. An efficient assessment of a multifrequency EIT system with real tissue phantom needs a prior knowledge of the impedance profile of the bathing medium as well as the inhomogeneity. In this direction Electrical Impedance Spectroscopy (EIS of broiler chicken muscle tissue paste and broiler chicken fat tissue is conducted from 10 Hz to 2 MHz using an impedance analyzer and their impedance profiles are thoroughly studied. Results show that the broiler chicken muscle tissue paste is less resistive than the fat tissue and hence it can be successfully used as the bathing medium of the phantoms for resistivity imaging in multifrequency EIT. Fat tissue is found more resistive than the muscle tissue which makes it more suitable for the inhomogeneity in phantoms of resistivity imaging study. doi:10.5617/jeb.174 J Electr Bioimp, vol. 2, pp. 48-63, 2011

  20. Altered electrode degradation with temperature in LiFePO4/mesocarbon microbead graphite cells diagnosed with impedance spectroscopy

    International Nuclear Information System (INIS)

    Klett, Matilda; Zavalis, Tommy Georgios; Kjell, Maria H.; Lindström, Rakel Wreland; Behm, Mårten; Lindbergh, Göran

    2014-01-01

    Highlights: • Aging of LiFePO 4 /mesocarbon microbead graphite cells from hybrid electric vehicle cycling. • Electrode degradation evaluated post-mortem by impedance spectroscopy and physics-based modeling. • Increased temperature promotes different degradation processes on the electrode level. • Conductive carbon degradation at 55 °C in the LiFePO 4 electrode. • Mesocarbon microbead graphite electrode degraded by cycling rather than temperature. - Abstract: Electrode degradation in LiFePO 4 /mesocarbon microbead graphite (MCMB) pouch cells aged at 55 °C by a synthetic hybrid drive cycle or storage is diagnosed and put into context with previous results of aging at 22 °C. The electrode degradation is evaluated by means of electrochemical impedance spectroscopy (EIS), measured separately on electrodes harvested from the cells, and by using a physics-based impedance model for aging evaluation. Additional capacity measurements, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) are used in the evaluation. At 55 °C the LiFePO 4 electrode shows increased particle/electronic conductor resistance, for both stored and cycled electrodes. This differs from results obtained at 22 °C, where the electrode suffered lowered porosity, particle fracture, and loss of active material. For graphite, only cycling gave a sustained effect on electrode performance at 55 °C due to lowered porosity and changes of surface properties, and to greater extent than at low temperature. Furthermore, increased current collector resistance also contributes to a large part of the pouch cell impedance when aged at increased temperatures. The result shows that increased temperature promotes different degradation on the electrode level, and is an important implication for high temperature accelerated aging. In light of the electrode observations, the correlation between full-cell and electrode impedances is discussed

  1. Electrothermal impedance spectroscopy measurement on high power LiMO2/Li4Ti5O12 battery cell with low bandwidth test setup

    DEFF Research Database (Denmark)

    Swierczynski, Maciej Jozef; Stroe, Daniel Loan; Stanciu, Tiberiu

    2015-01-01

    be executed on-line (e.g. in the electric vehicle Battery Management System). The Electrothermal Impedance Spectroscopy (ETIS) can be used as a relatively simple and fast method for non-destructive parametrization of the battery thermal models. However, the ETIS requires expensive galvanostat with high...

  2. Sparsity reconstruction in electrical impedance tomography: An experimental evaluation

    KAUST Repository

    Gehre, Matthias

    2012-02-01

    We investigate the potential of sparsity constraints in the electrical impedance tomography (EIT) inverse problem of inferring the distributed conductivity based on boundary potential measurements. In sparsity reconstruction, inhomogeneities of the conductivity are a priori assumed to be sparse with respect to a certain basis. This prior information is incorporated into a Tikhonov-type functional by including a sparsity-promoting ℓ1-penalty term. The functional is minimized with an iterative soft shrinkage-type algorithm. In this paper, the feasibility of the sparsity reconstruction approach is evaluated by experimental data from water tank measurements. The reconstructions are computed both with sparsity constraints and with a more conventional smoothness regularization approach. The results verify that the adoption of ℓ1-type constraints can enhance the quality of EIT reconstructions: in most of the test cases the reconstructions with sparsity constraints are both qualitatively and quantitatively more feasible than that with the smoothness constraint. © 2011 Elsevier B.V. All rights reserved.

  3. Practical human abdominal fat imaging utilizing electrical impedance tomography.

    Science.gov (United States)

    Yamaguchi, T; Maki, K; Katashima, M

    2010-07-01

    The fundamental cause of metabolic syndrome is thought to be abdominal obesity. Accurate diagnosis of abdominal obesity can be done by an x-ray computed tomography (CT) scan. But CT is expensive, bulky and entails the risks involved with radiation. To overcome such disadvantages, we attempted to develop a measuring device that could apply electrical impedance tomography to abdominal fat imaging. The device has 32 electrodes that can be attached to a subject's abdomen by a pneumatic mechanism. That way, electrode position data can be acquired simultaneously. An applied alternating current of 1.0 mArms was used at a frequency of 500 kHz. Sensed voltage data were carefully filtered to remove noise and processed to satisfy the reciprocal theorem. The image reconstruction software was developed concurrently, applying standard finite element methods and the Marquardt method to solve the mathematical inverse problem. The results of preliminary experiments showed that abdominal subcutaneous fat and the muscle surrounding the viscera could be imaged in humans. While our imaging of visceral fat was not of sufficient quality, it was suggested that we will be able to develop a safe and practical abdominal fat scanner through future improvements.

  4. Practical human abdominal fat imaging utilizing electrical impedance tomography

    International Nuclear Information System (INIS)

    Yamaguchi, T; Katashima, M; Maki, K

    2010-01-01

    The fundamental cause of metabolic syndrome is thought to be abdominal obesity. Accurate diagnosis of abdominal obesity can be done by an x-ray computed tomography (CT) scan. But CT is expensive, bulky and entails the risks involved with radiation. To overcome such disadvantages, we attempted to develop a measuring device that could apply electrical impedance tomography to abdominal fat imaging. The device has 32 electrodes that can be attached to a subject's abdomen by a pneumatic mechanism. That way, electrode position data can be acquired simultaneously. An applied alternating current of 1.0 mArms was used at a frequency of 500 kHz. Sensed voltage data were carefully filtered to remove noise and processed to satisfy the reciprocal theorem. The image reconstruction software was developed concurrently, applying standard finite element methods and the Marquardt method to solve the mathematical inverse problem. The results of preliminary experiments showed that abdominal subcutaneous fat and the muscle surrounding the viscera could be imaged in humans. While our imaging of visceral fat was not of sufficient quality, it was suggested that we will be able to develop a safe and practical abdominal fat scanner through future improvements

  5. An Effective Measured Data Preprocessing Method in Electrical Impedance Tomography

    Directory of Open Access Journals (Sweden)

    Chenglong Yu

    2014-01-01

    Full Text Available As an advanced process detection technology, electrical impedance tomography (EIT has widely been paid attention to and studied in the industrial fields. But the EIT techniques are greatly limited to the low spatial resolutions. This problem may result from the incorrect preprocessing of measuring data and lack of general criterion to evaluate different preprocessing processes. In this paper, an EIT data preprocessing method is proposed by all rooting measured data and evaluated by two constructed indexes based on all rooted EIT measured data. By finding the optimums of the two indexes, the proposed method can be applied to improve the EIT imaging spatial resolutions. In terms of a theoretical model, the optimal rooting times of the two indexes range in [0.23, 0.33] and in [0.22, 0.35], respectively. Moreover, these factors that affect the correctness of the proposed method are generally analyzed. The measuring data preprocessing is necessary and helpful for any imaging process. Thus, the proposed method can be generally and widely used in any imaging process. Experimental results validate the two proposed indexes.

  6. Video rate electrical impedance tomography of vascular changes: preclinical development

    International Nuclear Information System (INIS)

    Halter, Ryan; Hartov, Alex; Paulsen, Keith

    2008-01-01

    Peripheral vasculature disease is strongly correlated with cardiovascular-associated mortality. Monitoring circulation health, especially in the peripheral limbs, is vital to detecting clinically significant disease at a stage when it can still be addressed through medical intervention. Electrical impedance tomography (EIT) maps the electrical properties of tissues within the body and has been used to image dynamically varying physiology, including blood flow. Here, we suggest that peripheral vasculature health can be monitored with EIT by imaging the hemodynamics of peripheral vessels and the surrounding tissues during reactive hyperemia testing. An analysis based on distinguishability theory is presented that indicates that an EIT system capable of making measurements with a precision of 50 µV may be able to detect small changes in vessel size associated with variations in blood flow. An EIT system with these precision capabilities is presented that is able to collect data at frame rates exceeding 30 fps over a broad frequency range up to 10 MHz. The system's high speed imaging performance is verified through high contrast phantom experiments and through physiological imaging of induced ischemia with a human forearm. Region of interest analysis of the induced ischemia images shows a marked decrease in conductivity over time, changing at a rate of approximately −3 × 10 −7 S m −1 s −1 , which is the same order of magnitude as reported in the literature. The distinguishability analysis suggests that a system such as the one developed here may provide a means to characterize the hemodynamics associated with blood flow through the peripheral vasculature

  7. Real-time sensing of epithelial cell-cell and cell-substrate interactions by impedance spectroscopy on porous substrates

    Energy Technology Data Exchange (ETDEWEB)

    Mondal, D.; RoyChaudhuri, C., E-mail: chirosreepram@yahoo.com [Department of Electronics and Telecommunication Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103 (India); Pal, D. [Department of Aerospace Engineering and Applied Mechanics, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103 (India)

    2015-07-28

    Oxidized porous silicon (PS) is a common topographical biocompatible substrate that potentially provides a distinct in vitro environment for better understanding of in vivo behavior. But in the reported studies on oxidized PS, cell-cell and cell-substrate interactions have been detected only by fluorescent labeling. This paper is the first attempt to investigate real-time sensing of these interactions on HaCaT cells by label-free impedance spectroscopy on oxidized PS of two pore diameters (50 and 500 nm). One of the major requirements for successful impedance spectroscopy measurement is to restrict the channeling of electric field lines through the pores. To satisfy this criterion, we have designed the pore depths after analyzing the penetration of the medium by using computational fluid dynamics simulation. A distributed electrical model was also developed for estimating the various cellular attributes by considering a pseudorandom distribution of pores. It is observed from the impedance measurements and from the model that the proliferation rate increases for 50 nm pores but decreases for 500 nm pores compared to that for planar substrates. The rate of decrease in cell substrate separation (h) in the initial stage is more than the rate of increase in cell-cell junction resistance (R{sub b}) corresponding to the initial adhesion phase of cells. It is observed that R{sub b} and h are higher for 50 nm pores than those for planar substrates, corresponding to the fact that substrates more conducive toward cell adhesion encourage cell-cell interactions than direct cell-substrate interactions. Thus, the impedance spectroscopy coupled with the proposed theoretical framework for PS substrates can sense and quantify the cellular interactions.

  8. Real-time sensing of epithelial cell-cell and cell-substrate interactions by impedance spectroscopy on porous substrates

    International Nuclear Information System (INIS)

    Mondal, D.; RoyChaudhuri, C.; Pal, D.

    2015-01-01

    Oxidized porous silicon (PS) is a common topographical biocompatible substrate that potentially provides a distinct in vitro environment for better understanding of in vivo behavior. But in the reported studies on oxidized PS, cell-cell and cell-substrate interactions have been detected only by fluorescent labeling. This paper is the first attempt to investigate real-time sensing of these interactions on HaCaT cells by label-free impedance spectroscopy on oxidized PS of two pore diameters (50 and 500 nm). One of the major requirements for successful impedance spectroscopy measurement is to restrict the channeling of electric field lines through the pores. To satisfy this criterion, we have designed the pore depths after analyzing the penetration of the medium by using computational fluid dynamics simulation. A distributed electrical model was also developed for estimating the various cellular attributes by considering a pseudorandom distribution of pores. It is observed from the impedance measurements and from the model that the proliferation rate increases for 50 nm pores but decreases for 500 nm pores compared to that for planar substrates. The rate of decrease in cell substrate separation (h) in the initial stage is more than the rate of increase in cell-cell junction resistance (R b ) corresponding to the initial adhesion phase of cells. It is observed that R b and h are higher for 50 nm pores than those for planar substrates, corresponding to the fact that substrates more conducive toward cell adhesion encourage cell-cell interactions than direct cell-substrate interactions. Thus, the impedance spectroscopy coupled with the proposed theoretical framework for PS substrates can sense and quantify the cellular interactions

  9. Electrochemical impedance spectroscopy investigation on indium tin oxide films under cathodic polarization in NaOH solution

    International Nuclear Information System (INIS)

    Gao, Wenjiao; Cao, Si; Yang, Yanze; Wang, Hao; Li, Jin; Jiang, Yiming

    2012-01-01

    The electrochemical corrosion behaviors of indium tin oxide (ITO) films under the cathodic polarization in 0.1 M NaOH solution were investigated by electrochemical impedance spectroscopy. The as-received and the cathodically polarized ITO films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction for morphological, compositional and structural studies. The results showed that ITO films underwent a corrosion process during the cathodic polarization and the main component of the corrosion products was body-centered cubic indium. The electrochemical impedance parameters were related to the effect of the cathodic polarization on the ITO specimens. The capacitance of ITO specimens increased, while the charge transfer resistance and the inductance decreased with the increase of the polarization time. The proposed mechanism indicated that the corrosion products (metallic indium) were firstly formed during the cathodic polarization and then absorbed on the surface of the ITO film. As the surface was gradually covered by indium particles, the corrosion process was suppressed. - Highlights: ► Cathodic polarization of indium tin oxide (ITO) in 0.1 M NaOH. ► Cathodic polarization studied with electrochemical impedance spectroscopy. ► ITO underwent a corrosion attack during cathodic polarization, indium was observed. ► Electrochemical parameters of ITO were obtained using equivalent electrical circuit. ► A corrosion mechanism is proposed.

  10. Electrochemical impedance spectroscopy on nanostructured carbon electrodes grown by supersonic cluster beam deposition

    International Nuclear Information System (INIS)

    Bettini, Luca Giacomo; Bardizza, Giorgio; Podestà, Alessandro; Milani, Paolo; Piseri, Paolo

    2013-01-01

    Nanostructured porous films of carbon with density of about 0.5 g/cm 3 and 200 nm thickness were deposited at room temperature by supersonic cluster beam deposition (SCBD) from carbon clusters formed in the gas phase. Carbon film surface topography, determined by atomic force microscopy, reveals a surface roughness of 16 nm and a granular morphology arising from the low kinetic energy ballistic deposition regime. The material is characterized by a highly disordered carbon structure with predominant sp2 hybridization as evidenced by Raman spectroscopy. The interface properties of nanostructured carbon electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy employing KOH 1 M solution as aqueous electrolyte. An increase of the double layer capacitance is observed when the electrodes are heat treated in air or when a nanostructured nickel layer deposited by SCBD on top of a sputter deposited film of the same metal is employed as a current collector instead of a plain metallic film. This enhancement is consistent with an improved charge injection in the active material and is ascribed to the modification of the electrical contact at the interface between the carbon and the metal current collector. Specific capacitance values up to 120 F/g have been measured for the electrodes with nanostructured metal/carbon interface.

  11. Electrochemical impedance spectroscopy on nanostructured carbon electrodes grown by supersonic cluster beam deposition

    Energy Technology Data Exchange (ETDEWEB)

    Bettini, Luca Giacomo; Bardizza, Giorgio; Podesta, Alessandro; Milani, Paolo; Piseri, Paolo, E-mail: piseri@mi.infn.it [Universita degli Studi di Milano, Dipartimento di Fisica and CIMaINa (Italy)

    2013-02-15

    Nanostructured porous films of carbon with density of about 0.5 g/cm{sup 3} and 200 nm thickness were deposited at room temperature by supersonic cluster beam deposition (SCBD) from carbon clusters formed in the gas phase. Carbon film surface topography, determined by atomic force microscopy, reveals a surface roughness of 16 nm and a granular morphology arising from the low kinetic energy ballistic deposition regime. The material is characterized by a highly disordered carbon structure with predominant sp2 hybridization as evidenced by Raman spectroscopy. The interface properties of nanostructured carbon electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy employing KOH 1 M solution as aqueous electrolyte. An increase of the double layer capacitance is observed when the electrodes are heat treated in air or when a nanostructured nickel layer deposited by SCBD on top of a sputter deposited film of the same metal is employed as a current collector instead of a plain metallic film. This enhancement is consistent with an improved charge injection in the active material and is ascribed to the modification of the electrical contact at the interface between the carbon and the metal current collector. Specific capacitance values up to 120 F/g have been measured for the electrodes with nanostructured metal/carbon interface.

  12. Electrochemical impedance spectroscopy on nanostructured carbon electrodes grown by supersonic cluster beam deposition

    Science.gov (United States)

    Bettini, Luca Giacomo; Bardizza, Giorgio; Podestà, Alessandro; Milani, Paolo; Piseri, Paolo

    2013-02-01

    Nanostructured porous films of carbon with density of about 0.5 g/cm3 and 200 nm thickness were deposited at room temperature by supersonic cluster beam deposition (SCBD) from carbon clusters formed in the gas phase. Carbon film surface topography, determined by atomic force microscopy, reveals a surface roughness of 16 nm and a granular morphology arising from the low kinetic energy ballistic deposition regime. The material is characterized by a highly disordered carbon structure with predominant sp2 hybridization as evidenced by Raman spectroscopy. The interface properties of nanostructured carbon electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy employing KOH 1 M solution as aqueous electrolyte. An increase of the double layer capacitance is observed when the electrodes are heat treated in air or when a nanostructured nickel layer deposited by SCBD on top of a sputter deposited film of the same metal is employed as a current collector instead of a plain metallic film. This enhancement is consistent with an improved charge injection in the active material and is ascribed to the modification of the electrical contact at the interface between the carbon and the metal current collector. Specific capacitance values up to 120 F/g have been measured for the electrodes with nanostructured metal/carbon interface.

  13. Applications for Electrical Impedance Tomography (EIT) and Electrical Properties of the Human Body.

    Science.gov (United States)

    Lymperopoulos, Georgios; Lymperopoulos, Panagiotis; Alikari, Victoria; Dafogianni, Chrisoula; Zyga, Sofia; Margari, Nikoletta

    2017-01-01

    Electrical Impedance Tomography (EIT) is a promising application that displays changes in conductivity within a body. The basic principle of the method is the repeated measurement of surface voltages of a body, which are a result of rolling injection of known and small-volume sinusoidal AC current to the body through the electrodes attached to its surface. This method finds application in biomedicine, biology and geology. The objective of this paper is to present the applications of Electrical Impedance Tomography, along with the method's capabilities and limitations due to the electrical properties of the human body. For this purpose, investigation of existing literature has been conducted, using electronic databases, PubMed, Google Scholar and IEEE Xplore. In addition, there was a secondary research phase, using paper citations found during the first research phase. It should be noted that Electrical Impedance Tomography finds use in a plethora of medical applications, as the different tissues of the body have different conductivities and dielectric constants. Main applications of EIT include imaging of lung function, diagnosis of pulmonary embolism, detection of tumors in the chest area and diagnosis and distinction of ischemic and hemorrhagic stroke. EIT advantages include portability, low cost and safety, which the method provide, since it is a noninvasive imaging method that does not cause damage to the body. The main disadvantage of the method, which blocks its wider spread, appears in the image composition from the voltage measurements, which are conducted by electrodes placed on the periphery of the body, because the injected currents are affected nonlinearly by the general distribution of the electrical properties of the body. Furthermore, the complex impedance of the skin-electrode interface can be modelled by using a capacitor and two resistor, as a result of skin properties. In conclusion, Electrical Impedance Tomography is a promising method for the

  14. Impedance spectroscopy as a method for evaluation of lithium-thionyl chloride cells

    Energy Technology Data Exchange (ETDEWEB)

    Kanevskii, L.S.; Bagotzky, V.S.; Nizhnikovskii, E.A. [Frumkin Institute of Electrochemistry, Moscow (Russian Federation)

    1995-04-01

    Impedance spectroscopy was evaluated as a method for ascertaining the state of constituent components of Li-thionyl chloride cells. No unambiguous correlation between impedance characteristics and residual capacity was detected as a result of investigation of a large population of different size and capacity Li-thionyl chloride cells. Impedance studies of nonpolarized lithium electrodes in operating cells resulted in a conclusion that the diagnostics of Li-thionyl chloride cells is extremely difficult, due to the specific nature of lithium passivation in operating cells and the influence on this process exerted by sulfur dioxide generated during discharge.

  15. Static and Dynamic Measurement of Dopamine Adsorption in Carbon Fiber Microelectrodes Using Electrochemical Impedance Spectroscopy.

    Science.gov (United States)

    Rivera-Serrano, Nilka; Pagan, Miraida; Colón-Rodríguez, Joanisse; Fuster, Christian; Vélez, Román; Almodovar-Faria, Jose; Jiménez-Rivera, Carlos; Cunci, Lisandro

    2018-02-06

    In this study, electrochemical impedance spectroscopy was used for the first time to study the adsorption of dopamine in carbon fiber microelectrodes. In order to show a proof-of-concept, static and dynamic measurements were taken at potentials ranging from -0.4 to 0.8 V versus Ag|AgCl to demonstrate the versatility of this technique to study dopamine without the need of its oxidation. We used electrochemical impedance spectroscopy and single frequency electrochemical impedance to measure different concentrations of dopamine as low as 1 nM. Moreover, the capacitance of the microelectrodes surface was found to decrease due to dopamine adsorption, which is dependent on its concentration. The effect of dissolved oxygen and electrochemical oxidation of the surface in the detection of dopamine was also studied. Nonoxidized and oxidized carbon fiber microelectrodes were prepared and characterized by optical microscopy, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Optimum working parameters of the electrodes, such as frequency and voltage, were obtained for better measurement. Electrochemical impedance of dopamine was determined at different concentration, voltages, and frequencies. Finally, dynamic experiments were conducted using a flow cell and single frequency impedance in order to study continuous and real-time measurements of dopamine.

  16. Adaptive Filtering to Enhance Noise Immunity of Impedance and Admittance Spectroscopy: Comparison with Fourier Transformation

    Science.gov (United States)

    Stupin, Daniil D.; Koniakhin, Sergei V.; Verlov, Nikolay A.; Dubina, Michael V.

    2017-05-01

    The time-domain technique for impedance spectroscopy consists of computing the excitation voltage and current response Fourier images by fast or discrete Fourier transformation and calculating their relation. Here we propose an alternative method for excitation voltage and current response processing for deriving a system impedance spectrum based on a fast and flexible adaptive filtering method. We show the equivalence between the problem of adaptive filter learning and deriving the system impedance spectrum. To be specific, we express the impedance via the adaptive filter weight coefficients. The noise-canceling property of adaptive filtering is also justified. Using the RLC circuit as a model system, we experimentally show that adaptive filtering yields correct admittance spectra and elements ratings in the high-noise conditions when the Fourier-transform technique fails. Providing the additional sensitivity of impedance spectroscopy, adaptive filtering can be applied to otherwise impossible-to-interpret time-domain impedance data. The advantages of adaptive filtering are justified with practical living-cell impedance measurements.

  17. Discerning apical and basolateral properties of HT-29/B6 and IPEC-J2 cell layers by impedance spectroscopy, mathematical modeling and machine learning.

    Directory of Open Access Journals (Sweden)

    Thomas Schmid

    Full Text Available Quantifying changes in partial resistances of epithelial barriers in vitro is a challenging and time-consuming task in physiology and pathophysiology. Here, we demonstrate that electrical properties of epithelial barriers can be estimated reliably by combining impedance spectroscopy measurements, mathematical modeling and machine learning algorithms. Conventional impedance spectroscopy is often used to estimate epithelial capacitance as well as epithelial and subepithelial resistance. Based on this, the more refined two-path impedance spectroscopy makes it possible to further distinguish transcellular and paracellular resistances. In a next step, transcellular properties may be further divided into their apical and basolateral components. The accuracy of these derived values, however, strongly depends on the accuracy of the initial estimates. To obtain adequate accuracy in estimating subepithelial and epithelial resistance, artificial neural networks were trained to estimate these parameters from model impedance spectra. Spectra that reflect behavior of either HT-29/B6 or IPEC-J2 cells as well as the data scatter intrinsic to the used experimental setup were created computationally. To prove the proposed approach, reliability of the estimations was assessed with both modeled and measured impedance spectra. Transcellular and paracellular resistances obtained by such neural network-enhanced two-path impedance spectroscopy are shown to be sufficiently reliable to derive the underlying apical and basolateral resistances and capacitances. As an exemplary perturbation of pathophysiological importance, the effect of forskolin on the apical resistance of HT-29/B6 cells was quantified.

  18. Fuel flow distribution in SOFC stacks revealed by impedance spectroscopy

    DEFF Research Database (Denmark)

    Mosbæk, Rasmus Rode; Hjelm, Johan; Barfod, Rasmus

    2014-01-01

    As SOFC technology is moving closer to a commercial break through, methods to measure the “state-of-health” of operating stacks are becoming of increasing interest. This requires application of advanced methods for detailed electrical and electrochemical characterization during operation. An oper......As SOFC technology is moving closer to a commercial break through, methods to measure the “state-of-health” of operating stacks are becoming of increasing interest. This requires application of advanced methods for detailed electrical and electrochemical characterization during operation...... utilizations. The fuel flow distribution provides important information about the operating limits of the stack when high electrical efficiency is required....

  19. The effect of interface state continuum on the impedance spectroscopy of semiconductor heterojunctions

    International Nuclear Information System (INIS)

    Brus, V V

    2013-01-01

    A quantitative analysis of the impedance spectroscopy of semiconductor heterojunctions was carried out in the presence of interface state continuum at the heterojunction interface. A comparison of the impedance spectroscopy of semiconductor heterojunctions simulated in the context of the interface state continuum model with that simulated in the scope of the single-level state model was carried and possible misinterpretations were considered. The previously proposed approaches for the determination of the interface-state-related parameters and for the calculation of the actual barrier capacitance (the single-level state model) were modified in order to take into account the effect of interface state continuum. (paper)

  20. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    Bertram, F.; Evertsson, J.; Messing, M. E.; Mikkelsen, A.; Lundgren, E.; Zhang, F.; Pan, J.; Carlà, F.; Nilsson, J.-O.

    2014-01-01

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  1. Impedance spectroscopy on xerogel layer for chemical sensing

    Czech Academy of Sciences Publication Activity Database

    Abdelghani, A.; Cherif, K.; Jaffrezic-Renault, N.; Matějec, Vlastimil

    2006-01-01

    Roč. 26, 2/3 (2006), s. 542-545 ISSN 0928-4931. [MADICA 2004. Tunis, 29.11.2004-01.12.2004] Institutional research plan: CEZ:AV0Z2067918 Keywords : demodulation * chemical sensors * aerogels * spectroscopy * sol-gel processing Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 1.325, year: 2006

  2. Impedance-Source Networks for Electric Power Conversion Part I

    DEFF Research Database (Denmark)

    Siwakoti, Yam P.; Peng, Fang Zheng; Blaabjerg, Frede

    2015-01-01

    power chain, which may improve the reliability and performance of the power system. The first part of this paper provides a comprehensive review of the various impedance-source-networks-based power converters and discusses the main topologies from an application point of view. This review paper...... is the first of its kind with the aim of providing a “one-stop” information source and a selection guide on impedance-source networks for power conversion for researchers, designers, and application engineers. A comprehensive review of various modeling, control, and modulation techniques for the impedance...

  3. Accurate position estimation methods based on electrical impedance tomography measurements

    Science.gov (United States)

    Vergara, Samuel; Sbarbaro, Daniel; Johansen, T. A.

    2017-08-01

    Electrical impedance tomography (EIT) is a technology that estimates the electrical properties of a body or a cross section. Its main advantages are its non-invasiveness, low cost and operation free of radiation. The estimation of the conductivity field leads to low resolution images compared with other technologies, and high computational cost. However, in many applications the target information lies in a low intrinsic dimensionality of the conductivity field. The estimation of this low-dimensional information is addressed in this work. It proposes optimization-based and data-driven approaches for estimating this low-dimensional information. The accuracy of the results obtained with these approaches depends on modelling and experimental conditions. Optimization approaches are sensitive to model discretization, type of cost function and searching algorithms. Data-driven methods are sensitive to the assumed model structure and the data set used for parameter estimation. The system configuration and experimental conditions, such as number of electrodes and signal-to-noise ratio (SNR), also have an impact on the results. In order to illustrate the effects of all these factors, the position estimation of a circular anomaly is addressed. Optimization methods based on weighted error cost functions and derivate-free optimization algorithms provided the best results. Data-driven approaches based on linear models provided, in this case, good estimates, but the use of nonlinear models enhanced the estimation accuracy. The results obtained by optimization-based algorithms were less sensitive to experimental conditions, such as number of electrodes and SNR, than data-driven approaches. Position estimation mean squared errors for simulation and experimental conditions were more than twice for the optimization-based approaches compared with the data-driven ones. The experimental position estimation mean squared error of the data-driven models using a 16-electrode setup was less

  4. A Harmonic Impedance Measurement System for Reduction of Harmonics in the Electricity Grid

    NARCIS (Netherlands)

    Heskes, P.J.M.; Myrzik, J.M.A.; Kling, W.L.

    2009-01-01

    This paper describes the development of a Complex Harmonic Impedance Measurement system, called the CHIME-system. This system performs on-line impedance measurements in the electricity grid and will be designed for implementation in Digital Signal Processor (DSP) control systems of grid-connected

  5. A harmonic impedance measurement system for reduction of harmonics in the electricity grid

    NARCIS (Netherlands)

    Heskes, P.J.M.; Myrzik, J.M.A.; Kling, W.L.

    2009-01-01

    This paper describes the development of a Complex Harmonic Impedance Measurement system, called the CHIME-system. This system performs on-line impedance measurements in the electricity grid and will be designed for implementation in Digital Signal Processor (DSP) control systems of grid-connected

  6. Regional pressure volume curves by electrical impedance tomography in a model of acute lung injury

    NARCIS (Netherlands)

    Kunst, P. W.; Böhm, S. H.; Vazquez de Anda, G.; Amato, M. B.; Lachmann, B.; Postmus, P. E.; de Vries, P. M.

    2000-01-01

    OBJECTIVE: A new noninvasive method, electrical impedance tomography (EIT), was used to make pressure-impedance (PI) curves in a lung lavage model of acute lung injury in pigs. The lower inflection point (LIP) and the upper deflection point (UDP) were determined from these curves and from the

  7. Electrochemical impedance spectroscopy of nanoporous anodic alumina template

    International Nuclear Information System (INIS)

    Shahzad, K.

    2010-01-01

    Room temperature EIS characterization of nanoporous anodic alumina prepared at 40 V and 60 V has been done in 0.3 M oxalic acid solution. Rapid decrease in impedance was observed for the template prepared at 40 V. EIS study of porous anodic alumina template prepared in 0.3 M oxalic acid has been done in different electrolytes. Templates prepared in 0.3 M sulfuric acid solution were also characterized for comparison. Rapid decrease in the thickness of nonporous anodic film was observed with an increase of aggressiveness of electrolyte. Temperature based systematic study of EIS measurement has been done for porous anodic alumina template at different temperatures. Formation of micropores was observed in the nanoporous anodic alumina film formed on aluminum in 0.3 M oxalic acid solution which accelerates the dissolution rate with increase of measurement temperature. In addition to these, electropolishing behavior of pure aluminum has also been studied in different electrolytes and it was observed that electropolishing conditions prior to anodization are extremely important. (author)

  8. Electrochemical Impedance Spectroscopy Investigation of the Anodic Functionalities and Processes in LSCM-CGO-Ni Systems

    KAUST Repository

    Boulfrad, Samir

    2015-07-17

    Electrochemical impedance spectroscopy was used to characterize anode compositions made of (La0.75Sr0.25)0.97Cr0.5Mn0.5O3 (LSCM) and gadolinia doped ceria (CGO) with and without additional submicron Ni, or exsoluted Ni nanoparticles. In addition, the effects of the anode gas flow rate and the working temperature were investigated. Higher content of the ionic conductor leads to a decrease of the impedance in the frequency range from 100 Hz to 10 Hz. The effect of the catalyst component was investigated while keeping the electronic conductivity unchanged in the tested materials. Enhanced catalytic activity was demonstrated to considerably decrease the impedance especially in the frequency range between 100 Hz to 1 Hz. The change in the gas flow rate affects mainly the impedance bellow 1 Hz. © The Electrochemical Society.

  9. Cycle aging studies of lithium nickel manganese cobalt oxide-based batteries using electrochemical impedance spectroscopy

    NARCIS (Netherlands)

    Maheshwari, Arpit; Heck, Michael; Santarelli, Massimo

    2018-01-01

    The cycle aging of a commercial 18650 lithium-ion battery with graphite anode and lithium nickel manganese cobalt (NMC) oxide-based cathode at defined operating conditions is studied by regular electrochemical characterization, electrochemical impedance spectroscopy (EIS) and post-mortem analysis.

  10. Electrochemical bond cleavage in pesticide ioxynil. Kinetic analysis by voltammetry and impedance spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Sokolová, R.; Giannarelli, S.; Fanelli, N.; Pospíšil, Lubomír

    2017-01-01

    Roč. 49, SI C (2017), s. 134-138 ISSN 0324-1130 Institutional support: RVO:61388963 Keywords : electrochemical impedance spectroscopy * rate constant * self-protonation * faradaic phase angle * halogen cleavage * EC processes fitting Subject RIV: CG - Electrochemistry OBOR OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis) Impact factor: 0.238, year: 2016

  11. Electrochemical bond cleavage in pesticide ioxynil. Kinetic analysis by voltammetry and impedance spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Sokolová, Romana; Giannarelli, S.; Fanelli, N.; Pospíšil, Lubomír

    2017-01-01

    Roč. 49, C (2017), s. 134-138 ISSN 0324-1130 R&D Projects: GA ČR(CZ) GA14-05180S Institutional support: RVO:61388955 Keywords : electrochemical impedance spectroscopy * rate constant * self-protonation Subject RIV: CG - Electrochemistry OBOR OECD: Physical chemistry Impact factor: 0.238, year: 2016

  12. The New Method of the PV Panels Fault Detection Using Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Symonowicz, Joanna Karolina; Riedel, Nicholas; Thorsteinsson, Sune

    The aim of our project is to develop a new method for photovoltaic (PV) panel fault detection based on analyzing impedance spectroscopy (IS) spectra. Although this technique was successful in assessing the state of degradation of fuel cells and batteries, it has never been applied to PV cells...

  13. Li Insertion Into Li-Ti-O Spinels: Voltammetric and Electrochemical Impedance Spectroscopy Study

    Czech Academy of Sciences Publication Activity Database

    Krtil, Petr; Fattakhova, Dina

    2001-01-01

    Roč. 148, č. 9 (2001), s. A1045-A1050 ISSN 0013-4651 R&D Projects: GA ČR GA203/99/0879 Institutional research plan: CEZ:AV0Z4040901 Keywords : Li insertion * impedance spectroscopy * Frumkin insertion isotherm Subject RIV: CG - Electrochemistry Impact factor: 2.033, year: 2001

  14. Electrochemical impedance spectroscopy of polycrystalline boron doped diamond layers with hydrogen and oxygen terminated surface

    Czech Academy of Sciences Publication Activity Database

    Vlčková Živcová, Zuzana; Petrák, Václav; Frank, Otakar; Kavan, Ladislav

    2015-01-01

    Roč. 55, MAY 2015 (2015), s. 70-76 ISSN 0925-9635 R&D Projects: GA ČR GA13-31783S Institutional support: RVO:61388955 ; RVO:68378271 Keywords : Boron doped diamond * Electrochemical impedance spectroscopy * Aqueous electrolyte solution Subject RIV: CG - Electrochemistry Impact factor: 2.125, year: 2015

  15. Modelling of a High Temperature PEM Fuel Cell Stack using Electrochemical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Jespersen, Jesper Lebæk; Kær, Søren Knudsen

    2008-01-01

    This work presents the development of an equivalent circuit model of a 65 cell high temperature PEM (HTPEM) fuel cell stack using Electrochemical Impedance Spectroscopy (EIS). The HTPEM fuel cell membranes used are PBI-based and uses phosphoric acid as proton conductor. The operating temperature...

  16. Simultaneous reconstruction of outer boundary shape and conductivity distribution in electrical impedance tomography

    KAUST Repository

    Hyvö nen, Nuutti

    2016-01-01

    The simultaneous retrieval of the exterior boundary shape and the interior admittivity distribution of an examined body in electrical impedance tomography is considered. The reconstruction method is built for the complete electrode model

  17. Extraction of electrical characteristics from pixels of multifrequency electrical impedance tomographs

    International Nuclear Information System (INIS)

    Fitzgerald, A.J.; Thomas, B.J.; Cornish, B.H.; Michael, G.J.

    1996-01-01

    Full text: Multi-frequency electrical impedance tomography (MFEIT) is a modality that provides images of the change in the electrical response of tissue at a number of discrete frequencies relative to the response at a selected reference frequency (H Griffiths and A Ahmed, Clin. Phys. Physiol. Meas. 8A:103-107, 1987). This method overcomes the need, when forming in vivo static images, to measure or calculate the voltage profiles of a resistive, homogeneous reference medium and therefore avoids the errors introduced due to boundary shape and electrode location inaccuracies. Information on the spectral response of the tissue is contained within the pixel values, hence characteristics of the tissues and the state of health can be obtained by extracting this information from in vivo MFEIT images. Griffith and Jossinet (Physiol Meas. 15A: 59-63, 1994) used computer modelling to demonstrate that the Cole-Cole plot (variations of resistance and reactance with frequency) can be extracted from pixel values of MFEIT images provided the reference set was obtained from a purely resistive and homogeneous medium. To date it has not been possible to extract true Cole-Cole plots from in vivo MFEIT images because tissue contains a reactive component of impedance which introduces an unknown phase angle into the reference data set. Instead, an impedance spectrum, equivalent to a Cole-Cole plot rotated about the origin by the unknown phase angle, may be extracted. A correction for this rotation of the Cole-Cole plot is necessary since parameters derived from the impedance spectrum do not accurately reflect the electrical response of the imaged tissue. We have developed two distinct methods to determine this unknown phase angle and hence enable the extraction of parameters that more accurately reflect the true electrical response of tissue from in vivo MFEIT images. The first method is an empirical method based on observation of the distribution of frequency data around the Cole

  18. AC impedance spectroscopy of NASICON type Na3Fe2(PO4)3 ceramic

    Science.gov (United States)

    Mandal, Biswajit; Thakur, A. K.

    2018-05-01

    Super ionic conductors (e.g.; A3M2(XO4)3, A=Li, Na) have received attention in applied research due to their interesting electrochemical property and inherently high ionic conductivity [1]. However, structural and compatibility requirements for fast ion transport is stringent and it plays a crucial role. In A3M2(XO4)3, a suitable cage formation in the crystal framework due to corner sharing arrangement of XO4 tetrahedra and MO6 octahedra creates voids that acts as host/guest site for cation transport. In this work, we report Nasicon structure Na3Fe2(PO4)3 (NFP) prepared via sol-gel route mediated by citric acid. Structural analysis confirmed that NFP sample belongs to monoclinic crystal structure having Cc space group (S. G. No 9) with lattice parameters, a=15.106 Å, b=8.722 Å, c=8.775 Å and β=124.96°. Electrical properties of the prepared sample have been studied by AC impedance spectroscopy technique. The AC conductivity results indicated typical signature of ionically conducting system.

  19. Empirical Modeling of Lithium-ion Batteries Based on Electrochemical Impedance Spectroscopy Tests

    International Nuclear Information System (INIS)

    Samadani, Ehsan; Farhad, Siamak; Scott, William; Mastali, Mehrdad; Gimenez, Leonardo E.; Fowler, Michael; Fraser, Roydon A.

    2015-01-01

    Highlights: • Two commercial Lithium-ion batteries are studied through HPPC and EIS tests. • An equivalent circuit model is developed for a range of operating conditions. • This model improves the current battery empirical models for vehicle applications • This model is proved to be efficient in terms of predicting HPPC test resistances. - ABSTRACT: An empirical model for commercial lithium-ion batteries is developed based on electrochemical impedance spectroscopy (EIS) tests. An equivalent circuit is established according to EIS test observations at various battery states of charge and temperatures. A Laplace transfer time based model is developed based on the circuit which can predict the battery operating output potential difference in battery electric and plug-in hybrid vehicles at various operating conditions. This model demonstrates up to 6% improvement compared to simple resistance and Thevenin models and is suitable for modeling and on-board controller purposes. Results also show that this model can be used to predict the battery internal resistance obtained from hybrid pulse power characterization (HPPC) tests to within 20 percent, making it suitable for low to medium fidelity powertrain design purposes. In total, this simple battery model can be employed as a real-time model in electrified vehicle battery management systems

  20. Label-Free Aptasensor for Lysozyme Detection Using Electrochemical Impedance Spectroscopy

    Directory of Open Access Journals (Sweden)

    Dionisia Ortiz-Aguayo

    2018-01-01

    Full Text Available This research develops a label-free aptamer biosensor (aptasensor based on graphite-epoxy composite electrodes (GECs for the detection of lysozyme protein using Electrochemical Impedance Spectroscopy (EIS technique. The chosen immobilization technique was based on covalent bonding using carbodiimide chemistry; for this purpose, carboxylic moieties were first generated on the graphite by electrochemical grafting. The detection was performed using [Fe(CN6]3−/[Fe(CN6]4− as redox probe. After recording the frequency response, values were fitted to its electric model using the principle of equivalent circuits. The aptasensor showed a linear response up to 5 µM for lysozyme and a limit of detection of 1.67 µM. The sensitivity of the established method was 0.090 µM−1 in relative charge transfer resistance values. The interference response by main proteins, such as bovine serum albumin and cytochrome c, has been also characterized. To finally verify the performance of the developed aptasensor, it was applied to wine analysis.

  1. Label-Free Aptasensor for Lysozyme Detection Using Electrochemical Impedance Spectroscopy.

    Science.gov (United States)

    Ortiz-Aguayo, Dionisia; Del Valle, Manel

    2018-01-26

    This research develops a label-free aptamer biosensor (aptasensor) based on graphite-epoxy composite electrodes (GECs) for the detection of lysozyme protein using Electrochemical Impedance Spectroscopy (EIS) technique. The chosen immobilization technique was based on covalent bonding using carbodiimide chemistry; for this purpose, carboxylic moieties were first generated on the graphite by electrochemical grafting. The detection was performed using [Fe(CN)₆] 3- /[Fe(CN)₆] 4- as redox probe. After recording the frequency response, values were fitted to its electric model using the principle of equivalent circuits. The aptasensor showed a linear response up to 5 µM for lysozyme and a limit of detection of 1.67 µM. The sensitivity of the established method was 0.090 µM -1 in relative charge transfer resistance values. The interference response by main proteins, such as bovine serum albumin and cytochrome c, has been also characterized. To finally verify the performance of the developed aptasensor, it was applied to wine analysis.

  2. Charge Carrier Conduction Mechanism in PbS Quantum Dot Solar Cells: Electrochemical Impedance Spectroscopy Study.

    Science.gov (United States)

    Wang, Haowei; Wang, Yishan; He, Bo; Li, Weile; Sulaman, Muhammad; Xu, Junfeng; Yang, Shengyi; Tang, Yi; Zou, Bingsuo

    2016-07-20

    With its properties of bandgap tunability, low cost, and substrate compatibility, colloidal quantum dots (CQDs) are becoming promising materials for optoelectronic applications. Additionally, solution-processed organic, inorganic, and hybrid ligand-exchange technologies have been widely used in PbS CQDs solar cells, and currently the maximum certified power conversion efficiency of 9.9% has been reported by passivation treatment of molecular iodine. Presently, there are still some challenges, and the basic physical mechanism of charge carriers in CQDs-based solar cells is not clear. Electrochemical impedance spectroscopy is a monitoring technology for current by changing the frequency of applied alternating current voltage, and it provides an insight into its electrical properties that cannot be measured by direct current testing facilities. In this work, we used EIS to analyze the recombination resistance, carrier lifetime, capacitance, and conductivity of two typical PbS CQD solar cells Au/PbS-TBAl/ZnO/ITO and Au/PbS-EDT/PbS-TBAl/ZnO/ITO, in this way, to better understand the charge carriers conduction mechanism behind in PbS CQD solar cells, and it provides a guide to design high-performance quantum-dots solar cells.

  3. Improved system for identifying biological tissue temperature using electrical impedance tomography

    Directory of Open Access Journals (Sweden)

    Korolyuk Evgeniy

    2018-01-01

    Full Text Available This paper proposes a cheap and compact medical system that determines the temperature of an object using broadband impedance tomography. This system can be used in medicine to visualize ice structure in tissue during cryosurgical operations, as well as for fault diagnosis and location in studied industrial objects. These effects are achieved by measuring electrical impedance between electrode pairs in the measuring chamber. The assembled prototype is compact, consumes little power, and allows to non-invasively determine the impedance of a target object in real time. The research included experimental studies to determine the dependence of the impedance spectrum of saline water and muscle tissue on temperature in broad band spectrum, which allowed to obtain the dependence of total electrical impedance of target objects on temperature.

  4. Proton and O sup(2-) ion diffusion studied by γ-γ angular correlation and by impedance spectroscopy

    International Nuclear Information System (INIS)

    Oliveira Damasceno, O. de.

    1988-01-01

    The interaction of sup(181) Ta quadrupole momentum with electric field gradient was measured by perturbed angular correlation spectroscopy in polycrystalline samples of hafnium hydride and hafnium oxide. The measurements were done as function of the temperature, in cubic and tetragonal phases of hafnium hydride. In the cubic phase, spin relaxation effects related to proton diffusion with activation energy of 0.43 ± 0.05eV were observed, and in the tetragonal phase, the interaction was purely static. The hafnium oxide was studied in cubic phase stabilized by addition of calcium oxide or magnesium oxide. Relaxation effects probably due to O sup(2-) ion diffusion were verified. The protonic conduction in K H sub(2) PO sub(4) was studied by impedance spectroscopy, in pellets prepared by melting or powder compression using silver and platinum electrodes. In the case of silver electrodes, in the low frequency region, the impedance spectrum tends to a 45 sup(0) typical line of the diffusion process. It was attributed to hydrogen injection in the electrode. Heating k H sub(2) PO sub(4) at about 230 sup(0)C modifies significantly the electric properties. Two relaxation annealing reduced conductivities to constant values independently of preparation method. (author)

  5. Electrochemical impedance spectroscopy: An effective tool for a fast microbiological diagnosis

    International Nuclear Information System (INIS)

    Ramirez, Nardo; Regueiro, Angel; Arias, Olimpia; Contreras, Rolando

    2009-01-01

    Dielectric spectroscopy, also called electrochemical impedance spectroscopy, is traditionally used in monitoring corrosion and electro-deposition processes in the coating and characterization assessment of many kinds of sensors and semi-conductors. Its application in biotechnology for the characterization of cell cultures has, however, been notably expanded in the last decade. As a transductional principle, impedance has been applied in the field of microbiology as a means of detecting and quantifying pathogenic bacteria. This paper reviews the state-of-the-art of Impedance Microbiology, its progress and its applications for the detection of foodborne pathogenic bacteria, including the use of interdigitated microelectrodes, the development of chip-based impedance microbiology and the integration of impedance biosensors along with other techniques such as dielectrophoresis and electropermeabilization. Reference is made to basic components, definitions and principles of this technique, as well as to the explanation of the components and principles for cell culture design and the use of equivalent circuits for the analysis of the systems based on this alternative. (Author)

  6. Drilling electrode for real-time measurement of electrical impedance in bone tissues.

    Science.gov (United States)

    Dai, Yu; Xue, Yuan; Zhang, Jianxun

    2014-03-01

    In order to prevent possible damages to soft tissues, reliable monitoring methods are required to provide valuable information on the condition of the bone being cut. This paper describes the design of an electrical impedance sensing drill developed to estimate the relative position between the drill and the bone being drilled. The two-electrode method is applied to continuously measure the electrical impedance during a drill feeding movement: two copper wire brushes are used to conduct electricity in the rotating drill and then the drill is one electrode; a needle is inserted into the soft tissues adjacent to the bone being drilled and acts as another electrode. Considering that the recorded electrical impedance is correlated with the insertion depth of the drill, we theoretically calculate the electrode-tissue contact impedance and prove that the rate of impedance change varies considerably when the drill bit crosses the boundary between two different bone tissues. Therefore, the rate of impedance change is used to determine whether the tip of the drill is located in one of cortical bone, cancellous bone, and cortical bone near a boundary with soft tissue. In vitro experiments in porcine thoracic spines were performed to demonstrate the feasibility of the impedance sensing drill. The experimental results indicate that the drill, used with the proposed data-processing method, can provide accurate and reliable breakthrough detection in the bone-drilling process.

  7. Cationic effect on dye-sensitized solar cell properties using electrochemical impedance and transient absorption spectroscopy techniques

    International Nuclear Information System (INIS)

    Gupta, Ravindra Kumar; Bedja, Idriss

    2017-01-01

    Redox-couple polymer electrolytes, (poly(ethylene oxide)-succinonitrile) blend/MI-I 2 , where M  =  Li or K, were prepared by the solution cast method. Owing to the plasticizing property of K + ions, the K + ion-based electrolyte exhibited better electrical conductivity than the Li + ion-based electrolyte, which did however exhibit better photovoltaic properties. Electrochemical impedance spectroscopy revealed faster redox species diffusions and interfacial processes in the Li + ion-based dye-sensitized solar cells than in the K + ion-based ones. Transient absorption spectroscopy ascertained faster dye-regeneration by the Li + ion-based electrolyte than the K + ion-based electrolyte. (paper)

  8. Magnetic resonance electrical impedance tomography for measuring electrical conductivity during electroporation

    International Nuclear Information System (INIS)

    Kranjc, M; Miklavčič, D; Bajd, F; Serša, I

    2014-01-01

    The electroporation effect on tissue can be assessed by measurement of electrical properties of the tissue undergoing electroporation. The most prominent techniques for measuring electrical properties of electroporated tissues have been voltage–current measurement of applied pulses and electrical impedance tomography (EIT). However, the electrical conductivity of tissue assessed by means of voltage–current measurement was lacking in information on tissue heterogeneity, while EIT requires numerous additional electrodes and produces results with low spatial resolution and high noise. Magnetic resonance EIT (MREIT) is similar to EIT, as it is also used for reconstruction of conductivity images, though voltage and current measurements are not limited to the boundaries in MREIT, hence it yields conductivity images with better spatial resolution. The aim of this study was to investigate and demonstrate the feasibility of the MREIT technique for assessment of conductivity images of tissues undergoing electroporation. Two objects were investigated: agar phantoms and ex vivo liver tissue. As expected, no significant change of electrical conductivity was detected in agar phantoms exposed to pulses of all used amplitudes, while a considerable increase of conductivity was measured in liver tissue exposed to pulses of different amplitudes. (paper)

  9. Synthesis, characterization and impedance spectroscopy study of magnetite/epoxidized natural rubber nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Tan, W.L. [Nanoscience Research Laboratory, School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang (Malaysia); Abu Bakar, M., E-mail: bmohamad@usm.my [Nanoscience Research Laboratory, School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang (Malaysia)

    2013-06-05

    Highlights: ► The Fe{sub 3}O{sub 4}/ENR nanocomposites have not been synthesized and reported. ► Nanocomposites were obtained via in situ synthesis of Fe{sub 3}O{sub 4} in the presence of ENR. ► The use of ENR enabled control of the size of Fe{sub 3}O{sub 4} particles to <20 nm. ► Conductivity of the nanocomposites increases with the increase in Fe{sub 3}O{sub 4} loading. ► The equivalent circuit for the nanocomposites is proposed and discussed. -- Abstract: The magnetite (Fe{sub 3}O{sub 4}) particles were synthesized in situ in the presence of epoxidized natural rubber (ENR) to produce the various Fe{sub 3}O{sub 4}/ENR nanocomposites. The X-ray diffraction (XRD) analysis confirmed the existence of Fe{sub 3}O{sub 4} particles in the composites. The FTIR and DSC studies suggested that no chemical interactions between the particles and the matrix. The SEM and X-mapping micrographs revealed that the Fe{sub 3}O{sub 4} particles were distributed within the ENR matrix. The ENR matrix exerts control on the Fe{sub 3}O{sub 4} particles with a size of <20 nm in the composites. The Fe{sub 3}O{sub 4} particles also affect the electrical properties of the composites. Impedance spectroscopy studies show that the electrical conductivity of the nanocomposites increases with the increase in Fe{sub 3}O{sub 4} loading in the composite. The equivalent circuit for the Fe{sub 3}O{sub 4}/ENR nanocomposites is proposed and discussed.

  10. An introductory study using impedance spectroscopy technique with polarizable microelectrode for amino acids characterization

    Science.gov (United States)

    Chin, K. B.; Chi, I.; Pasalic, J.; Huang, C.-K.; Barge, Laura M.

    2018-04-01

    Portable, low power, yet ultra-sensitive life detection instrumentations are vital to future astrobiology flight programs at NASA. In this study, initial attempts to characterize amino acids in an aqueous environment by electrochemical impedance spectroscopy (EIS) using polarizable (blocking) electrodes in order to establish a means of detection via their electrical properties. Seven amino acids were chosen due to their scientific importance in demonstrating sensitivity levels in the range of part per billion concentration. Albeit more challenging in real systems of analyst mixtures, we found individual amino acids in aqueous environment do exhibit some degree of chemical and physical uniqueness to warrant characterization by EIS. The polar amino acids (Asp, Glu, and His) exhibited higher electrochemical activity than the non-polar amino acids (Ala, Gly, Val, and Leu). The non-polar amino acids (Gly and Ala) also exhibited unique electrical properties which appeared to be more dependent on physical characteristics such as molecular weight and structure. At concentrations above 1 mM where the amino acids play a more dominant transport role within the water, the conductivity was found to be more sensitive to concentrations. At lower concentrations activity with water. As revealed by equivalent circuit modeling, the relaxation times showed a 1-2 order of magnitude difference between polar and non-polar amino acids. The pseudo-capacitance from EIS measurements on sample mixtures containing salt water and individual amino acids revealed the possibility for improvement in amino acid selectivity using gold nanoporous surface enhanced electrodes. This work establishes important methodologies for characterizing amino acids using EIS combined with microscale electrodes, supporting the case for instrumentation development for life detection and origin of life programs.

  11. From TER to trans- and paracellular resistance: lessons from impedance spectroscopy.

    Science.gov (United States)

    Günzel, Dorothee; Zakrzewski, Silke S; Schmid, Thomas; Pangalos, Maria; Wiedenhoeft, John; Blasse, Corinna; Ozboda, Christopher; Krug, Susanne M

    2012-06-01

    In epithelia and endothelia, overall resistance (TER) is determined by all ion-conductive structures, such as membrane channels, tight junctions, and the intercellular space, whereas the epithelial capacitance is due to the hydrophobic phase of the plasma membrane. Impedance means alternating current resistance and, in contrast to ohmic resistance, takes into account that, e.g., capacitors become increasingly conductive with increasing frequency. Impedance spectroscopy uses the association of the capacitance with the transcellular pathway to distinguish between this capacitive pathway and purely conductive components (tight junctions, subepithelium). In detail, one-path impedance spectroscopy distinguishes the resistance of the epithelium from the resistance of subepithelial tissues. Beyond that, two-path impedance spectroscopy allows for the separation of paracellular resistance (governed by tight junctional properties) from transcellular resistance (determined by conductive structures residing in the cell membranes). The present paper reviews the basic principles of these techniques, some historic milestones, as well as recent developments in epithelial physiology. © 2012 New York Academy of Sciences.

  12. Characterization of the mechanical behavior of human skin by means of impedance spectroscopy

    Science.gov (United States)

    Pavšelj, N.; Mitar, M.; Hart, F. X.; Miklavčič, D.

    2010-04-01

    There is increased interest for the use of impedance spectroscopy to measure skin dielectric properties in vivo. The aim of such measurements can be either to evaluate the hydration state of the skin, to detect diseased states such as skin cancer, to follow the progress of transdermal drug delivery, or simply to gather data on skin tissue impedance to be used in theoretical studies. However, obtaining reliable data can be difficult. Namely, skin is a highly nonhomogeneous multi-layered structure whose composition and dimensions differ depending on the location on the body and interindividual variations. Also, impedance measurements on skin are accompanied by a number of artefacts. We performed a series of impedance measurements using an Agilent/HP 4284A precision LCR meter with parallel plate electrodes pressed on the skin, at different locations on the body. We observed substantial impedance changes over the course of the measurement. These changes can be mainly attributed to skin deformation caused by the electrodes pressing against skin. The analysis showed that skin mechanical properties and layer thicknesses can be inferred from these temporal changes. Such data on mechanical properties of skin tissue give valuable extra information, crucial for successful estimation of the impedance of different skin layers.

  13. In-Plane Impedance Spectroscopy measurements in Vanadium Dioxide thin films

    Science.gov (United States)

    Ramirez, Juan; Patino, Edgar; Schmidt, Rainer; Sharoni, Amos; Gomez, Maria; Schuller, Ivan

    2012-02-01

    In plane Impedance Spectroscopy measurements have been done in Vanadium Dioxide thin films in the range of 100 Hz to 1 MHz. Our measurements allows distinguishing between the resistive and capacitive response of the Vanadium Dioxide films across the metal-insulator transition. A non ideal RC behavior was found in our thin films from room temperature up to 334 K. Around the MIT, an increase of the total capacitance is observed. A capacitor-network model is able to reproduce the capacitance changes across the MIT. Above the MIT, the system behaves like a metal as expected, and a modified equivalent circuit is necessary to describe the impedance data adequately.

  14. Ferroelectric relaxor behaviour and impedance spectroscopy of Bi{sub 2}O{sub 3}-doped barium zirconium titanate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Mahajan, Sandeep; Thakur, O P; Bhattacharya, D K [Electroceramics Group, Solid State Physics Laboratory, Lucknow Road, Delhi-110054 (India); Sreenivas, K, E-mail: omprakasht@hotmail.co [Department of Physics and Astrophysics, University of Delhi- 110007 (India)

    2009-03-21

    Bi{sub 2}O{sub 3}-doped barium zirconate titanate ceramics, Ba{sub 1-x}Bi{sub x}(Zr{sub 0.05}Ti{sub 0.95})O{sub 3}, have been prepared by the conventional solid-state reaction method. The ferroelectric relaxor behaviour and dielectric properties have been investigated in detail. By XRD analysis, it is suggested that up to x = 0.04, Bi{sup 3+} substitutes A-site ion, and thereafter with higher Bi{sup 3+} content, it enters the B-site sub lattice. Substitution of Bi{sup 3+} ions induces ferroelectric relaxor behaviour and the degree of relaxation behaviour increases with bismuth concentration. The remanent polarization and strain behaviour show a slight increase with the substitution level. The degree of hysteresis (strain versus electric field) also reduces from 21.4% to 4.6% with bismuth substitution. Impedance measurements were made on the prepared sample over a wide range of temperatures (300-723 K) and frequencies (40 Hz-1 MHz), which show the presence of both bulk and grain boundary effects in the material. The bulk and grain boundary conductivities determined from impedance study indicate the Arrhenius-type thermally activated process. Impedance spectroscopy is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries to the complex impedance of a ceramic system, accurately estimating its electrical conductivity as well as its corresponding activation energies and drawing conclusions on its structural properties.

  15. Noninvasive electrical impedance sensor for in vivo tissue discrimination at radio frequencies.

    Science.gov (United States)

    Dai, Yu; Du, Jun; Yang, Qing; Zhang, Jianxun

    2014-09-01

    Compared to traditional open surgery, minimally invasive surgery (MIS) allows for a more rapid and less painful recovery. However, the lack of significant haptic feedback in MIS can make tissue discrimination difficult. This paper tests a noninvasive electrical impedance sensor for in vivo discrimination of tissue types in MIS. The sensor consists of two stainless steel spherical electrodes used to measure the impedance spectra over the frequency range of 200 kHz to 5 MHz. The sensor helps ensure free movement on an organ surface and prevents soft tissues from being injured during impedance measurement. Since the recorded electrical impedance is correlated with the force pressed on the electrode and the mechanical property of the tissue, the electrode-tissue contact impedance is calculated theoretically. We show that the standard deviation of the impedance ratio at each frequency point is sufficient to distinguish different tissue types. Both in vitro experiment in a pig kidney and in vivo experiment in rabbit organs were performed to demonstrate the feasibility of the electrical impedance sensor. The experimental results indicated that the sensor, used with the proposed data-processing method, provides accurate and reliable biological tissue discrimination. © 2014 Wiley Periodicals, Inc.

  16. Evaluation of electrical impedance ratio measurements in accuracy of electronic apex locators.

    Science.gov (United States)

    Kim, Pil-Jong; Kim, Hong-Gee; Cho, Byeong-Hoon

    2015-05-01

    The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL). The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC) in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC.

  17. Evaluation of electrical impedance ratio measurements in accuracy of electronic apex locators

    Directory of Open Access Journals (Sweden)

    Pil-Jong Kim

    2015-05-01

    Full Text Available Objectives The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL. Materials and Methods The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Results Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Conclusions Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC.

  18. Impedance spectroscopy in biodynamics: Detection of specific cells (pathogens using immune coated electrodes

    Directory of Open Access Journals (Sweden)

    Eugen Gheorghiu

    2002-11-01

    Full Text Available We describe the theoretical and experimental approaches for monitoring the interfacial biomolecular reaction between immobilized antibody and the antigen binding partner (the analyte, or the targeted cell using Impedance Spectroscopy, IS. The key idea is to reveal the presence of the analyte by investigating the dynamics of the impedance changes at the interface between transducer and bulk during the process of antibody-antigen binding (coupling of specific compounds to sensor surface. In this work, antibody-antigen (Ab-Ag reaction was directly monitored using an impedance analyzer capable of ~ 1 measurement/second and covalent immobilization chemistry and modified electrodes in the absence of a redox probe. The proposed approach may be applicable to monitoring other surface interfacial reactions such as protein-protein interactions, DNA-DNA interactions, DNA-protein interactions and DNA-small molecule interactions.

  19. Dual-frequency electrical impedance mammography for the diagnosis of non-malignant breast disease

    International Nuclear Information System (INIS)

    Trokhanova, O V; Okhapkin, M B; Korjenevsky, A V

    2008-01-01

    Electrical impedance tomography (EIT) enables one to determine and visualize non-invasively the spatial distribution of the electrical properties of the tissues inside the body, thus providing valuable diagnostic information. The electrical impedance mammography (EIM) system is a specialized EIT system for diagnostics and imaging of the breast. While breast cancer is the main target for any investigation conducted in this area, the diagnosis of non-cancerous diseases is also very important because it opens the way to improve the quality of life for many women and it may also reduce the incidence of breast cancer through effective treatment of mastopathy. This paper presents the main results of a comprehensive examination of 166 women using four methods: multifrequency electrical impedance mammography, ultrasonic investigation, x-ray mammography and puncture biopsy. The objective of the investigation is to estimate the usefulness of multifrequency electrical impedance mammography for diagnosing dyshormonal mammary gland diseases. The results demonstrate the advantages of the multifrequency EIM method. In particular, dual-frequency electrical impedance mammography in contrast with the single-frequency variant enables one not only to diagnose mastopathy, but also allows accurate detection of its cystless form based on observation of the absence of any difference between average conductivity in both phases of the menstrual cycle. Because the cystless form of mastopathy is associated with a higher risk of cancer development, this method allows identification of a higher risk group of patients for more frequent investigations

  20. Electrical transport properties of manganese containing pyrochlore type semiconducting oxides using impedance analyses

    International Nuclear Information System (INIS)

    Sumi, S.; Prabhakar Rao, P.; Mahesh, S.K.; Koshy, Peter

    2012-01-01

    Graphical abstract: DC conductivity variation of CaCe 1−x Mn x SnNbO 7−δ (x = 0, 0.2, 0.4 and 0.6) with inverse of temperature. Variation of conductivity with Mn concentration at 600 °C is shown in the inset. Display Omitted Highlights: ► We have observed that the structural ordering as well as grain size increase with Mn substitution. ► Impedance analysis proved that a correlated barrier hopping type conduction mechanism is involved in the materials. ► Activation energy as well as electrical conductivity increases with increase in Mn substitution. ► Localization of electrons associated with Mn 2+ and structural ordering are the key factors for the increased activation energy with Mn substitution. ► All the materials showed good NTC thermistor properties. -- Abstract: A new series of manganese containing pyrochlore type semiconducting oxides CaCe 1−x Mn x SnNbO 7−δ (x = 0, 0.2, 0.4 and 0.6) have been synthesized to study the effect of Mn substitution on the structure, microstructure and electrical properties of these samples. X-ray diffraction and scanning electron microscopy studies revealed an increase of structural ordering and grain size respectively with increase of Mn substitution. Rietveld analysis and Raman spectroscopy were also employed to corroborate the XRD results. The bulk resistance measurements with temperature exhibit negative temperature coefficient behavior. The impedance analysis of the samples revealed a non-Debye type relaxation existed in the materials. The ac conductivity variation with temperature and frequency indicates a correlated barrier hopping type conduction mechanism in these materials. The barrier height and the intersite separation for hopping influence the electrical conductivity of these samples and are found to be a function of localization of electrons associated with the Mn 2+ ions and the unit cell volume respectively. The Mn substitution increases both electrical conductivity and activation energy

  1. The interaction of antimicrobial peptide LL-37 with artificial biomembranes: epifluorescence and impedance spectroscopy approach

    International Nuclear Information System (INIS)

    Neville, Frances; Cahuzac, Marjolaine; Nelson, Andrew; Gidalevitz, David

    2004-01-01

    Membrane interactions of the human antimicrobial peptide LL-37 have been studied by a variety of techniques including insertion assay, epifluorescence microscopy and impedance spectroscopy. This study makes use of lipid monolayers at the air-aqueous interface to mimic bacterial or eukaryotic membranes. It was found that LL-37 readily inserts into phosphatidylglycerol (PG) and lipid A monolayers, significantly disrupting their structure. In contrast, the structure of phosphatidylcholine (PC) monolayers remains virtually unaffected by LL-37, which is evident both from epifluorescence and electrochemical measurements. Impedance spectroscopy showed that the LL-37 rich PC monolayer remains an ideal capacitor while LL-37 enriched lipid A capacitance decreases significantly, suggesting an increase in layer thickness from peptide-lipid binding

  2. Effects of Surface and Morphological Properties of Zeolite on Impedance Spectroscopy-Based Sensing Performance

    Directory of Open Access Journals (Sweden)

    Prabir K. Dutta

    2012-10-01

    Full Text Available Measurement by impedance spectroscopy of the changes in intrazeolitic cation motion of pressed pellets of zeolite particles upon adsorption of dimethylmethylphosphonate (DMMP provides a strategy for sensing DMMP, a commonly used simulant for highly toxic organophosphate nerve agents. In this work, two strategies for improving the impedance spectroscopy based sensing of DMMP on zeolites were investigated. The first one is the use of cerium oxide (CeO2 coated on the zeolite surface to neutralize acidic groups that may cause the decomposition of DMMP, and results in better sensor recovery. The second strategy was to explore the use of zeolite Y membrane. Compared to pressed pellets, the membranes have connected supercages of much longer length scales. The zeolite membranes resulted in higher sensitivity to DMMP, but recovery of the device was significantly slower as compared to pressed zeolite pellets.

  3. Characterization by acoustic emission and electrochemical impedance spectroscopy of the cathodic disbonding of Zn coating

    International Nuclear Information System (INIS)

    Amami, Souhail; Lemaitre, Christian; Laksimi, Abdelouahed; Benmedakhene, Salim

    2010-01-01

    Galvanized steel has been tested in a synthetic sea water solution under different cathodic overprotection conditions. The generated hydrogen flux caused the damage of the metal-zinc interface and led to a progressive coating detachment. Scanning electron microscopy, electrochemical impedance spectroscopy and acoustic emission technique were used to characterize the damage chronology under different cathodic potentials. A damage mechanism was proposed and the acoustic signature related to the coating degradation was statistically identified using clustering techniques.

  4. Characterization by acoustic emission and electrochemical impedance spectroscopy of the cathodic disbonding of Zn coating

    Energy Technology Data Exchange (ETDEWEB)

    Amami, Souhail [Universite de Technologie de Compiegne, Departement de Genie Mecanique, Laboratoire Roberval, UMR 6066 du CNRS, B.P. 20529, 60206 Compiegne Cedex (France)], E-mail: souhail.amami@utc.fr; Lemaitre, Christian; Laksimi, Abdelouahed; Benmedakhene, Salim [Universite de Technologie de Compiegne, Departement de Genie Mecanique, Laboratoire Roberval, UMR 6066 du CNRS, B.P. 20529, 60206 Compiegne Cedex (France)

    2010-05-15

    Galvanized steel has been tested in a synthetic sea water solution under different cathodic overprotection conditions. The generated hydrogen flux caused the damage of the metal-zinc interface and led to a progressive coating detachment. Scanning electron microscopy, electrochemical impedance spectroscopy and acoustic emission technique were used to characterize the damage chronology under different cathodic potentials. A damage mechanism was proposed and the acoustic signature related to the coating degradation was statistically identified using clustering techniques.

  5. Label-Free Aptasensor for Lysozyme Detection Using Electrochemical Impedance Spectroscopy

    OpenAIRE

    Dionisia Ortiz-Aguayo; Manel del Valle

    2018-01-01

    This research develops a label-free aptamer biosensor (aptasensor) based on graphite-epoxy composite electrodes (GECs) for the detection of lysozyme protein using Electrochemical Impedance Spectroscopy (EIS) technique. The chosen immobilization technique was based on covalent bonding using carbodiimide chemistry; for this purpose, carboxylic moieties were first generated on the graphite by electrochemical grafting. The detection was performed using [Fe(CN)6]3−/[Fe(CN)6]4− as redox probe. Afte...

  6. Model Biological Membranes and Possibilities of Application of Electrochemical Impedance Spectroscopy for Their Characterization

    Czech Academy of Sciences Publication Activity Database

    Skalová, Štěpánka; Vyskočil, V.; Barek, J.; Navrátil, Tomáš

    2018-01-01

    Roč. 30, č. 2 (2018), s. 207-219 ISSN 1040-0397 R&D Projects: GA ČR(CZ) GA17-05387S; GA ČR GA17-03868S Institutional support: RVO:61388955 Keywords : Electrochemical impedance spectroscopy (EIS) * Liposomes * Model membrane * Phospholipid bilayer * Planar lipid bilayer * Supported lipid bilayers * Tethered lipid bilayers Subject RIV: CG - Electrochemistry OBOR OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis) Impact factor: 2.851, year: 2016

  7. Lithium-Ion Battery Power Degradation Modelling by Electrochemical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Stroe, Daniel-Ioan; Swierczynski, Maciej Jozef; Stroe, Ana-Irina

    2017-01-01

    This paper investigates the use of the electrochemical impedance spectroscopy (EIS) technique as an alternative to the DC pulses technique for estimating the power capability decrease of Lithium-ion batteries during calendar ageing. Based on results obtained from calendar ageing tests performed...... at different conditions during one to two years, a generalized model that estimates the battery power capability decrease as function of the resistance Rs increase (obtained from EIS) was proposed and successfully verified....

  8. Impedance spectroscopy evolution upon sintering of Al-rich anodising sludge-based extruded bodies

    Directory of Open Access Journals (Sweden)

    Ribeiro, M. J.

    2006-08-01

    Full Text Available Alumina based ceramic materials, containing Al-rich sludge as the major component, were processed by extrusion. The sludge derived from the wastewater treatment of aluminium anodising industrial process. Long rods were produced using a vacuum screw extruder, by a careful control of all relevant processing parameters. Then, thick discs were obtained by cutting dried selected rods, to be tested as probes for sintering-dependent electrical properties. The sintering process was followed by performing common dilatometric/thermal analyses but the evolution of electrical conductivity, estimated by impedance spectroscopy (IS, was also used for this purpose. Results show that sintering-dependent morphological evolution up to 1300ºC strongly affects the electrical behaviour of samples, and as a consequence IS seems to be a useful technique to follow the firing process.

    Los materiales cerámicos basados en alúmina, conteniendo barros ricos en Al como componente mayoritario fueron procesados por extrusión. Los barros empleados provienen de tratamientos de lavado de residuos de un proceso industrial de anodizado de aluminio. Se produjeron varillas empleando un extrusor de tornillo en vacío con control de todos los parámetros relevantes del proceso. A partir de varillas seleccionadas, se obtuvieron por corte en seco discos cerámicos para evaluar la dependencia de la sinterización y las propiedades eléctricas. El proceso de sinterización se siguió mediante ensayos dilatométricos y análisis térmicos, junto con la evolución de la conductividad eléctrica mediante espectroscopia de impedancia. Los resultados mostraron la evolución de la sinterización y la dependencia morfológica hasta 1300ºC, que afecta fuertemente a la respuesta eléctrica y como consecuencia la espectroscopia de impedancia parece ser una técnica útil en el seguimiento de los procesos de cocción.

  9. Characterization and evaluation of EB-PVD thermal barrier coatings by impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Chunxia; Liu Fushun; Gong Shengkai; Xu Huibin [School of Materials Science and Engineering, Beihang Univ., Beijing, BJ (China)

    2005-07-01

    Two layer thermal barrier coatings (TBCs) were prepared by EB-PVD (electron beam-physical vapor deposition) at different substrate temperatures in the range of 823 to 1123 K, and their microstructure was investigated with SEM and AC impedance as a function of substrate temperature and thermal cycling time. YSZ layer of all TBCs samples is in column structure, but the grain size and growth orientation are different with substrate. In this research, impedance spectra (IS) was measured as a function of thermal cycling between 1323 K and 298 K for these thermal barrier coatings. Grain boundary and bulk can be distinguished from analysis of AC impedance spectroa to provide information about the relation between microstructure and electric properties. The change in IS until failure was found to be related with the thickness, microcracks and macrocracks of TGO and the change in the interfacial of TGO/YSZ. (orig.)

  10. Numerical analysis on effective electric field penetration depth for interdigital impedance sensor

    International Nuclear Information System (INIS)

    Kim, Chon-ung; Jong, Hakchol; Ro, Cholwu; Pak, Gilhung; Im, Songil; Li, Guofeng; Li, Jie; Song, Yunho

    2013-01-01

    Interdigital (finger-like) electrodes are widely used for electrical impedance and capacitance tomography of composite dielectric materials and complex insulating structures. Because of their advantages, they are now effectively introduced as capacitance sensors into a variety of industrial branches, agriculture, medical science, biological engineering, military branches, etc. In order to effectively apply the so-called interdigital impedance sensors in practice, of great importance is to optimize the sensor design parameters such as the electric field penetration depth, signal strength and so on. The general design principles of the interdigital capacitance sensor have been discussed for a long time by many researchers. However, there is no consensus on the definition of the effective electric field penetration depth of interdigital electrode. This paper discusses how to determine the effective electric field penetration depth of interdigital sensor on the basis of the refractive principle of electric field intensity and the FEM analyses of electric field distribution and capacitance for the sensor model.

  11. Automated AC Electrical Impedance Measurement of Ceramic Oxides by means of a Lock-in Amplifier

    International Nuclear Information System (INIS)

    Al-Khawaja, S.; Al-Sous, M. B.; Nasrallah, F.

    2009-06-01

    In this study, the electrical impedance of some ceramic oxides has been investigated employing the Perkin Elmer DSP 7280 Lock-in amplifier, while recording the electric response versus frequency and temperature at constant amplitude. Via integral automation of this lock-in with other delicate electrical measuring devices, a control program has been developed to accurately and swiftly acquire the frequency response of the sample, in order to lately infer the resulting samples' impedance in volt and ampere. Two maxima peaks characterising the impedance, in the curve of the doped molybdenum oxide have been observed discerning two phases in the sample (doped with 40% of niobium oxide), which shows a remarkable relaxation related to improvement in its ionic conductivity within the solid phase, with respect to increasing frequency. (author)

  12. Experimental impedance investigation of an ultracapacitor at different conditions for electric vehicle applications

    Science.gov (United States)

    Zhang, Lei; Hu, Xiaosong; Wang, Zhenpo; Sun, Fengchun; Dorrell, David G.

    2015-08-01

    Ultracapacitors (UCs) are being increasingly deployed as a short-term energy storage device in various energy systems including uninterruptable power supplies, electrified vehicles, renewable energy systems, and wireless communication. They exhibit excellent power density and energy efficiency. The dynamic behavior of a UC, however, strongly depends on its impedance characteristics. In this paper, the impedance characteristics of a commercial UC are experimentally investigated through the well-adopted Electrochemical Impedance Spectroscopy (EIS) technique. The implications of the UC operating conditions (i.e., temperature and state of charge (SOC)) to the impedance are systematically examined. The results show that the impedance is highly sensitive to the temperature and SOC; and the temperature effect is more significant. In particular, the coupling effect between the temperature and SOC is illustrated, as well as the high-efficiency SOC window, which is highlighted. To further verify the reliability of the EIS-based investigation and to probe the sensitivity of UC parameters to the operating conditions, a dynamic model is characterized by fitting the collected impedance data. The interdependence of UC parameters (i.e., capacitance and resistance elements) on the temperature and SOC is quantitatively revealed. The impedance-based model is demonstrated to be accurate in two driving-cycle tests.

  13. The study of human bodies' impedance networks in testing leakage currents of electrical equipments

    Science.gov (United States)

    Zhang, Zhaohui; Wang, Xiaofei

    2006-11-01

    In the testing of electrical equipments' leakage currents, impedance networks of human bodies are used to simulate the current's effect on human bodies, and they are key to the preciseness of the testing result. This paper analyses and calculates three human bodies' impedance networks of measuring electric burn current, perception or reaction current, let-go current in IEC60990, by using Matlab, compares the research result of current effect thresholds' change with sine wave's frequency published in IEC479-2, and amends parameters of measuring networks. It also analyses the change of perception or reaction current with waveform by Multisim.

  14. Electrochemical impedance spectroscopy investigation on the clinical lifetime of ProTaper rotary file system.

    Science.gov (United States)

    Penta, Virgil; Pirvu, Cristian; Demetrescu, Ioana

    2014-01-01

    The main objective of the current paper is to show that electrochemical impedance spectroscopy (EIS) could be a method for evaluating and predicting of ProTaper rotary file system clinical lifespan. This particular aspect of everyday use of the endodontic files is of great importance in each dental practice and has profound clinical implications. The method used for quantification resides in the electrochemical impedance spectroscopy theory and has in its main focus the characteristics of the surface titanium oxide layer. This electrochemical technique has been adapted successfully to identify the quality of the Ni-Ti files oxide layer. The modification of this protective layer induces changes in corrosion behavior of the alloy modifying the impedance value of the file. In order to assess the method, 14 ProTaper sets utilized on different patients in a dental clinic have been submitted for testing using EIS. The information obtained in regard to the surface oxide layer has offered an indication of use and proves that the said layer evolves with each clinical application. The novelty of this research is related to an electrochemical technique successfully adapted for Ni-Ti file investigation and correlation with surface and clinical aspects.

  15. In-situ analysis of microwave conductivity and impedance spectroscopy for evaluation of charge carrier dynamics at interfaces

    Science.gov (United States)

    Choi, Wookjin; Inoue, Junichi; Tsutsui, Yusuke; Sakurai, Tsuneaki; Seki, Shu

    2017-11-01

    A unique concerted analysis comprising non-contact microwave conductivity measurements and impedance spectroscopy was developed to simultaneously assess the charge carrier mobility and injection barriers. The frequency dependence of the microwave conductivity as well as the electrical current was analyzed by applying sinusoidal voltage to determine the equivalent circuit parameters. Based on the temperature dependence of the circuit parameters, the energy of the injection barrier was estimated to be 0.4 eV with the Richardson-Schottky model, and the band-like transport was confirmed with the negative temperature coefficient with the β value of 1.4 in the intra-layer conduction of C8-BTBT. In contrast, the increase in the resistance of the C8-BTBT layer with decreasing temperature implied the occurrence of hopping-like transport in the inter-layer conduction of C8-BTBT.

  16. A new approach to electrical impedance imaging technique

    International Nuclear Information System (INIS)

    Afroj Quadir, K.; Nasir, F.; Rahman, M.; Rabbani, K.S.

    2004-09-01

    It is possible to obtain a 2 dimensional (2D) image of a volume conductor, to locate a few widely separated objects, by driving ac constant currents through two orthogonal pairs of electrodes and measuring the resulting potential differences between several diagonally placed electrodes at the centre and back-projecting their impedance values along equi-potential lines. This has been termed as Pigeon Hole Imaging (PHI). Experimental verification has been attempted using a small insulating object placed at different locations in a saline filled 2D phantom. For a 6 x 6 matrix, the image in 16 pixels in close proximity of the diagonal along which electrodes are arranged, coincide with the object positions, while they do nt for the remaining 20 pixels. We applied a new technique where image smearing patterns have been used to correct the images in 14 of these pixels while 6 pixels near the two opposite comers still remain uncertain. Thus 30 pixels out of 36 give the right object position which may be termed a success. The concept may be extended further to higher order matrices by increasing the number of diagonal electrodes. The present work mainly concentrates on the feasibility of localization of a single small object in one matrix position of the image. (author)

  17. Impedance spectroscopy and structural properties of the perovskite-like Sn(Ba,Sr)O{sub 3} stagnate

    Energy Technology Data Exchange (ETDEWEB)

    Cuervo Farfan, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia); Ciencias Basicas, Universidad Manuela Beltran, Bogota DC (Colombia); Olaya, J.J. [Departamento de Ingenieria Mecanica y Mecatronica, Universidad Nacional de Colombia, Bogota DC (Colombia); Vera Lopez, E. [Grupo de Superficies, Electroquimica y Corrosion, Universidad Pedagogica y Tecnologica de Colombia, Tunja (Colombia); Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia)

    2012-08-15

    An exhaustive study of structural, electrical and transport properties on the perovskite stagnate Sn(Ba,Sr)O{sub 3} was performed. Samples of SnBa{sub 1-x}Sr{sub x}O{sub 3} with 0{<=}x{<=}1.00 were prepared by the solid state reaction method. The crystallographic structure was studied by X-ray diffraction experiments and Rietveld refinement using the GSAS code. Results reveal the material synthesized in a cubic structure (space group Pm3-bar m, no. 221) for 0{<=}x{<=}0.50 and in an orthorhombic (space group Pnma, no. 62) for x>0.50. The approximate grain size was found from experiments' Scanning Electron Microscopy. The electric response was studied by the Impedance Spectroscopy technique from 10.0 mHz up to 0,10 MHz. Electric polarization measurements for SnSrO{sub 3} and SnBaO{sub 3} were determined through curves of polarization as a function of applied electric field, which reveal the ferroelectric character of the material. From the saturation polarization the dielectric constants of materials were calculated.

  18. Impedance spectroscopy and structural properties of the perovskite-like Sn(Ba,Sr)O3 stagnate

    International Nuclear Information System (INIS)

    Cuervo Farfán, J.; Olaya, J.J.; Vera López, E.; Landínez Téllez, D.A.; Roa-Rojas, J.

    2012-01-01

    An exhaustive study of structural, electrical and transport properties on the perovskite stagnate Sn(Ba,Sr)O 3 was performed. Samples of SnBa 1-x Sr x O 3 with 0≤x≤1.00 were prepared by the solid state reaction method. The crystallographic structure was studied by X-ray diffraction experiments and Rietveld refinement using the GSAS code. Results reveal the material synthesized in a cubic structure (space group Pm3-bar m, no. 221) for 0≤x≤0.50 and in an orthorhombic (space group Pnma, no. 62) for x>0.50. The approximate grain size was found from experiments' Scanning Electron Microscopy. The electric response was studied by the Impedance Spectroscopy technique from 10.0 mHz up to 0,10 MHz. Electric polarization measurements for SnSrO 3 and SnBaO 3 were determined through curves of polarization as a function of applied electric field, which reveal the ferroelectric character of the material. From the saturation polarization the dielectric constants of materials were calculated.

  19. New equivalent-electrical circuit model and a practical measurement method for human body impedance.

    Science.gov (United States)

    Chinen, Koyu; Kinjo, Ichiko; Zamami, Aki; Irei, Kotoyo; Nagayama, Kanako

    2015-01-01

    Human body impedance analysis is an effective tool to extract electrical information from tissues in the human body. This paper presents a new measurement method of impedance using armpit electrode and a new equivalent circuit model for the human body. The lowest impedance was measured by using an LCR meter and six electrodes including armpit electrodes. The electrical equivalent circuit model for the cell consists of resistance R and capacitance C. The R represents electrical resistance of the liquid of the inside and outside of the cell, and the C represents high frequency conductance of the cell membrane. We propose an equivalent circuit model which consists of five parallel high frequency-passing CR circuits. The proposed equivalent circuit represents alpha distribution in the impedance measured at a lower frequency range due to ion current of the outside of the cell, and beta distribution at a high frequency range due to the cell membrane and the liquid inside cell. The calculated values by using the proposed equivalent circuit model were consistent with the measured values for the human body impedance.

  20. Assessing regional lung mechanics by combining electrical impedance tomography and forced oscillation technique.

    Science.gov (United States)

    Ngo, Chuong; Spagnesi, Sarah; Munoz, Carlos; Lehmann, Sylvia; Vollmer, Thomas; Misgeld, Berno; Leonhardt, Steffen

    2017-08-29

    There is a lack of noninvasive pulmonary function tests which can assess regional information of the lungs. Electrical impedance tomography (EIT) is a radiation-free, non-invasive real-time imaging that provides regional information of ventilation volume regarding the measurement of electrical impedance distribution. Forced oscillation technique (FOT) is a pulmonary function test which is based on the measurement of respiratory mechanical impedance over a frequency range. In this article, we introduce a new measurement approach by combining FOT and EIT, named the oscillatory electrical impedance tomography (oEIT). Our oEIT measurement system consists of a valve-based FOT device, an EIT device, pressure and flow sensors, and a computer fusing the data streams. Measurements were performed on five healthy volunteers at the frequencies 3, 4, 5, 6, 7, 8, 10, 15, and 20 Hz. The measurements suggest that the combination of FOT and EIT is a promising approach. High frequency responses are visible in the derivative of the global impedance index ΔZeit(t,fos). $\\Delta {Z_{{\\text{eit}}}}(t,{f_{{\\text{os}}}}).$ The oEIT signals consist of three main components: forced oscillation, spontaneous breathing, and heart activity. The amplitude of the oscillation component decreases with increasing frequency. The band-pass filtered oEIT signal might be a new tool in regional lung function diagnostics, since local responses to high frequency perturbation could be distinguished between different lung regions.

  1. Revisiting the Characterization of the Losses in Piezoelectric Materials from Impedance Spectroscopy at Resonance

    Directory of Open Access Journals (Sweden)

    Amador M. González

    2016-01-01

    Full Text Available Electronic devices using the piezoelectric effect contain piezoelectric materials: often crystals, but in many cases poled ferroelectric ceramics (piezoceramics, polymers or composites. On the one hand, these materials exhibit non-negligible losses, not only dielectric, but also mechanical and piezoelectric. In this work, we made simulations of the effect of the three types of losses in piezoelectric materials on the impedance spectrum at the resonance. We analyze independently each type of loss and show the differences among them. On the other hand, electrical and electronic engineers include piezoelectric sensors in electrical circuits to build devices and need electrical models of the sensor element. Frequently, material scientists and engineers use different languages, and the characteristic material coefficients do not have a straightforward translation to those specific electrical circuit components. To connect both fields of study, we propose the use of accurate methods of characterization from impedance measurements at electromechanical resonance that lead to determination of all types of losses, as an alternative to current standards. We introduce a simplified equivalent circuit model with electrical parameters that account for piezoceramic losses needed for the modeling and design of industrial applications.

  2. Revisiting the Characterization of the Losses in Piezoelectric Materials from Impedance Spectroscopy at Resonance.

    Science.gov (United States)

    González, Amador M; García, Álvaro; Benavente-Peces, César; Pardo, Lorena

    2016-01-26

    Electronic devices using the piezoelectric effect contain piezoelectric materials: often crystals, but in many cases poled ferroelectric ceramics (piezoceramics), polymers or composites. On the one hand, these materials exhibit non-negligible losses, not only dielectric, but also mechanical and piezoelectric. In this work, we made simulations of the effect of the three types of losses in piezoelectric materials on the impedance spectrum at the resonance. We analyze independently each type of loss and show the differences among them. On the other hand, electrical and electronic engineers include piezoelectric sensors in electrical circuits to build devices and need electrical models of the sensor element. Frequently, material scientists and engineers use different languages, and the characteristic material coefficients do not have a straightforward translation to those specific electrical circuit components. To connect both fields of study, we propose the use of accurate methods of characterization from impedance measurements at electromechanical resonance that lead to determination of all types of losses, as an alternative to current standards. We introduce a simplified equivalent circuit model with electrical parameters that account for piezoceramic losses needed for the modeling and design of industrial applications.

  3. Electrochemical Characterization and Degradation Analysis of Large SOFC Stacks by Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Mosbæk, Rasmus Rode; Hjelm, Johan; Barfod, R.

    2013-01-01

    As solid oxide fuel cell (SOFC) technology is moving closer to a commercial break through, lifetime limiting factors, and methods to measure the “state-of-health” of operating cells and stacks are becoming of increasing interest. This requires application of advanced methods for detailed...... electrochemical characterization during operation. An experimental stack with low ohmic resistance from Topsoe Fuel Cell A/S was characterized in detail using electrochemical impedance spectroscopy (EIS). An investigation of the optimal geometrical placement of the current feeds and voltage probes was carried out...... with hydrogen as fuel with 52% fuel utilization and constant current load (0.2 A cm–2) at 750 °C. Stack interconnects were coated with six different coatings to prevent chromium poisoning on the cathode side. Four repeating units (RUs) with different coatings were selected for detailed impedance analysis. EIS...

  4. Evaluation of Bioelectrical Impedance Spectroscopy for the Assessment of Extracellular Body Water

    Directory of Open Access Journals (Sweden)

    Sören Weyer

    2012-01-01

    Full Text Available This study evaluates bioelectrical impedance spectroscopy (BIS measurements to detect body fluid status. The multifrequency impedance measurements were performed in five female pigs. Animals were connected to an extracorporeal membrane oxygenation device during a lung disease experiment and fluid balance was recorded. Every 15 min the amount of fluid infusion and the weight of the urine drainage bag was recorded. From the fluid intake and output, the fluid balance was calculated. These data were compared with values calculated from a mathematical model, based on the extracellular tissue resistance and the Hanai Mixture theory. The extracellular tissue resistance was also measured with BIS. These experimental results strongly support the feasibility and clinical value of BIS for in vivo assessment of the hydration status.

  5. Electrochemical impedance spectroscopy of dodecylsulphate doped polypyrrole films in the dark and under illumination

    Directory of Open Access Journals (Sweden)

    Martini Milena

    2000-01-01

    Full Text Available The morphology, thickness, oxidation and illumination effects in dodecylsulphate doped polypyrrole films can be qualitatively observed by EIS and consist in variations of interfacial and bulk resistances and capacitances of a proposed equivalent circuit. The circuit well with the measured spectra of films obtained with 190 mC cm-2 of synthesis charge density. For thinner films the calculated values observed by electrochemical impedance spectroscopy (EIS deviate probably due to the absence of diffusion effects. The oxidation of the films diminishes the total impedance over the entire frequency range. The morphology effects are also observed in the entire spectra. The illumination effects are reversible and are observed as expected only in the reduced form of the polymer. The illumination reduces the internal resistance and the space-charge capacitance and increases the charge transfer resistance and the double layer capacitance.

  6. Multi-channel electrical impedance tomography for regional tissue hydration monitoring.

    Science.gov (United States)

    Chen, Xiaohui; Kao, Tzu-Jen; Ashe, Jeffrey M; Boverman, Gregory; Sabatini, James E; Davenport, David M

    2014-06-01

    Poor assessment of hydration status during hemodialysis can lead to under- or over-hydration in patients with consequences of increased morbidity and mortality. In current practice, fluid management is largely based on clinical assessments to estimate dry weight (normal hydration body weight). However, hemodialysis patients usually have co-morbidities that can make the signs of fluid status ambiguous. Therefore, achieving normal hydration status remains a major challenge for hemodialysis therapy. Electrical impedance technology has emerged as a promising method for hydration monitoring due to its non-invasive nature, low cost and ease-of-use. Conventional electrical impedance-based hydration monitoring systems employ single-channel current excitation (either 2-electrode or 4-electrode methods) to perturb and extract averaged impedance from bulk tissue and use generalized models from large populations to derive hydration estimates. In the present study, a prototype, single-frequency electrical impedance tomography (EIT) system with simultaneous multi-channel current excitation was used to enable regional hydration change detection. We demonstrated the capability to detect a difference in daily impedance change between left leg and right leg in healthy human subjects, who wore a compression sock only on one leg to reduce daily gravitational fluid accumulation. The impedance difference corresponded well with the difference of lower leg volume change between left leg and right leg measured by volumetry, which on average is ~35 ml, accounting for 0.7% of the lower leg volume. We have demonstrated the feasibility of using multi-channel EIT to extract hydration information in different tissue layers with minimal skin interference. Our simultaneous, multi-channel current excitation approach provides an effective method to separate electrode contact impedance and skin condition artifacts from hydration signals. The prototype system has the potential to be used in clinical

  7. Characterization of Porous WO3 Electrochromic Device by Electrochemical Impedance Spectroscopy

    Directory of Open Access Journals (Sweden)

    Chien Chon Chen

    2013-01-01

    Full Text Available This paper concerns the microstructure of the anodic tungsten oxide (WO3 and its use in an electrochromic (EC glass device. When voltages between 100 V and 160 V were applied to tungsten film for 1 h under 0.4 wt. % NaF electrolyte, porous WO3 film was formed. The film, which had a large surface area, was used as electrochromic film for EC glass. The average transmittance in a visible region of the spectrum for a 144 cm2 EC device was above 75% in the bleached state and below 40% in the colored state, respectively. Repeatability using of the colored/bleached cycles was tested good by a cyclic voltammograms method. The internal impedance values under colored and bleached states were detected and simulated using an electrical impedance spectra (EIS technique. The EC glass impedance characteristics were simulated using resistors, capacitors, and Warburg impedance. The ITO/WO3, WO3/electrolyte, electrolyte/NiO, and NiO/ITO interfaces can be simulated using a resistance capacitance (RC parallel circuits, and bulk materials such as the indium tin oxide (ITO and conducting wire can be simulated by using a series of resisters.

  8. Impedance and electrically evoked compound action potential (ECAP drop within 24 hours after cochlear implantation.

    Directory of Open Access Journals (Sweden)

    Joshua Kuang-Chao Chen

    Full Text Available Previous animal study revealed that post-implantation electrical detection levels significantly declined within days. The impact of cochlear implant (CI insertion on human auditory pathway in terms of impedance and electrically evoked compound action potential (ECAP variation within hours after surgery remains unclear, since at this time frequency mapping can only commence weeks after implantation due to factors associated with wound conditions. The study presented our experiences with regards to initial switch-on within 24 hours, and thus the findings about the milieus inside cochlea within the first few hours after cochlear implantation in terms of impedance/ECAP fluctuations. The charts of fifty-four subjects with profound hearing impairment were studied. A minimal invasive approach was used for cochlear implantation, characterized by a small skin incision (≈ 2.5 cm and soft techniques for cochleostomy. Impedance/ECAP was measured intro-operatively and within 24 hours post-operatively. Initial mapping within 24 hours post-operatively was performed in all patients without major complications. Impedance/ECAP became significantly lower measured within 24 hours post-operatively as compared with intra-operatively (p<0.001. There were no differences between pre-operative and post-operative threshold for air-conduction hearing. A significant drop of impedance/ECAP in one day after cochlear implantation was revealed for the first time in human beings. Mechanisms could be related to the restoration of neuronal sensitivity to the electrical stimulation, and/or the interaction between the matrix enveloping the electrodes and the electrical stimulation of the initial switch-on. Less wound pain/swelling and soft techniques both contributed to the success of immediate initial mapping, which implied a stable micro-environment inside the cochlea despite electrodes insertion. Our research invites further studies to correlate initial impedance/ECAP changes

  9. Effect of Electrode Belt and Body Positions on Regional Pulmonary Ventilation- and Perfusion-Related Impedance Changes Measured by Electric Impedance Tomography.

    Directory of Open Access Journals (Sweden)

    Elin Ericsson

    Full Text Available Ventilator-induced or ventilator-associated lung injury (VILI/VALI is common and there is an increasing demand for a tool that can optimize ventilator settings. Electrical impedance tomography (EIT can detect changes in impedance caused by pulmonary ventilation and perfusion, but the effect of changes in the position of the body and in the placing of the electrode belt on the impedance signal have not to our knowledge been thoroughly evaluated. We therefore studied ventilation-related and perfusion-related changes in impedance during spontaneous breathing in 10 healthy subjects in five different body positions and with the electrode belt placed at three different thoracic positions using a 32-electrode EIT system. We found differences between regions of interest that could be attributed to changes in the position of the body, and differences in impedance amplitudes when the position of the electrode belt was changed. Ventilation-related changes in impedance could therefore be related to changes in the position of both the body and the electrode belt. Perfusion-related changes in impedance were probably related to the interference of major vessels. While these findings give us some insight into the sources of variation in impedance signals as a result of changes in the positions of both the body and the electrode belt, further studies on the origin of the perfusion-related impedance signal are needed to improve EIT further as a tool for the monitoring of pulmonary ventilation and perfusion.

  10. Compensation for geometric modeling errors by positioning of electrodes in electrical impedance tomography

    DEFF Research Database (Denmark)

    Hyvönen, N.; Majander, H.; Staboulis, Stratos

    2017-01-01

    Electrical impedance tomography aims at reconstructing the conductivity inside a physical body from boundary measurements of current and voltage at a finite number of contact electrodes. In many practical applications, the shape of the imaged object is subject to considerable uncertainties...

  11. Pneumothorax in a Preterm Infant Monitored by Electrical Impedance Tomography: A Case Report

    NARCIS (Netherlands)

    Miedema, M.; Frerichs, I.; de Jongh, F. H. C.; van Veenendaal, M. B.; van Kaam, A. H.

    2011-01-01

    Electrical impedance tomography (EIT) is a noninvasive bedside tool for monitoring regional changes in ventilation. We report, for the first time, the EIT images of a ventilated preterm infant with a unilateral pneumothorax, showing a loss of regional ventilation in the affected lung during both

  12. Electrical impedance tomography in the assessment of extravascular lung water in noncardiogenic acute respiratory failure

    NARCIS (Netherlands)

    Kunst, P. W.; Vonk Noordegraaf, A.; Raaijmakers, E.; Bakker, J.; Groeneveld, A. B.; Postmus, P. E.; de Vries, P. M.

    1999-01-01

    STUDY OBJECTIVES: To establish the value of electrical impedance tomography (EIT) in assessing pulmonary edema in noncardiogenic acute respiratory failure (ARF), as compared to the thermal dye double indicator dilution technique (TDD). DESIGN: Prospective clinical study. SETTING: ICU of a general

  13. Ventilation and perfusion imaging by electrical impedance tomography: a comparison with radionuclide scanning

    NARCIS (Netherlands)

    Kunst, P. W.; Vonk Noordegraaf, A.; Hoekstra, O. S.; Postmus, P. E.; de Vries, P. M.

    1998-01-01

    Electrical impedance tomography (EIT) is a technique that makes it possible to measure ventilation and pulmonary perfusion in a volume that approximates to a 2D plane. The possibility of using EIT for measuring the left-right division of ventilation and perfusion was compared with that of

  14. Piezo-sensor self-diagnostics using electrical impedance measurements.

    Energy Technology Data Exchange (ETDEWEB)

    Park, G. H. (Gyu Hae); Farrar, C. R. (Charles R.); Rutherford, A. C. (Amanda C.); Robertson, A. N. (Amy N.)

    2004-01-01

    This paper present the piezoelectric sensor self-diagnostic procedure that performs in-situ monitoring of the operational status of piezoelectric materials (PZT) used for sensors and actuators in structural health monitoring (SHM) applications. The use of active-sensing piezoelectric materials has received considerable attention in the SHM community. A critical aspect of the piezoelectric active-sensing technologies is that usually large numbers of distributed sensors and actuators are needed to perform the required monitoring process. The sensor/actuator self-diagnostic procedure, where the sensors/actuators are confirmed to be functioning properly during operation, is therefore a critical component to successfully complete the SHM process and to minimize the false indication regarding the structural health. The basis of this procedure is to track the changes in the capacitive value of piezoelectric materials resulting from the sensor failure, which is manifested in the imaginary part of the measured electrical admittances. Furthermore, through the analytical and experimental investigation, it is confirmed that the bonding layer between the PZT and a host structure significantly contributes to the measured capacitive values. Therefore, by monitoring the imaginary part of the admittances, one can quantitatively assess the degradation of the mechanical/electrical properties of the PZT and its attachment to a host structure. This paper concludes with an experimental example to demonstrate the feasibility of the proposed sensor-diagnostic procedure.

  15. Performance evaluation of wideband bio-impedance spectroscopy using constant voltage source and constant current source

    International Nuclear Information System (INIS)

    Mohamadou, Youssoufa; Oh, Tong In; Wi, Hun; Sohal, Harsh; Farooq, Adnan; Woo, Eung Je; McEwan, Alistair Lee

    2012-01-01

    Current sources are widely used in bio-impedance spectroscopy (BIS) measurement systems to maximize current injection for increased signal to noise while keeping within medical safety specifications. High-performance current sources based on the Howland current pump with optimized impedance converters are able to minimize stray capacitance of the cables and setup. This approach is limited at high frequencies primarily due to the deteriorated output impedance of the constant current source when situated in a real measurement system. For this reason, voltage sources have been suggested, but they require a current sensing resistor, and the SNR reduces at low impedance loads due to the lower current required to maintain constant voltage. In this paper, we compare the performance of a current source-based BIS and a voltage source-based BIS, which use common components. The current source BIS is based on a Howland current pump and generalized impedance converters to maintain a high output impedance of more than 1 MΩ at 2 MHz. The voltage source BIS is based on voltage division between an internal current sensing resistor (R s ) and an external sample. To maintain high SNR, R s is varied so that the source voltage is divided more or less equally. In order to calibrate the systems, we measured the transfer function of the BIS systems with several known resistor and capacitor loads. From this we may estimate the resistance and capacitance of biological tissues using the least-squares method to minimize error between the measured transimpedance excluding the system transfer function and that from an impedance model. When tested on realistic loads including discrete resistors and capacitors, and saline and agar phantoms, the voltage source-based BIS system had a wider bandwidth of 10 Hz to 2.2 MHz with less than 1% deviation from the expected spectra compared to more than 10% with the current source. The voltage source also showed an SNR of at least 60 dB up to 2.2 MHz

  16. Impedance spectroscopy of ceramic solid electrolytes; Espectroscopia de impedancia de eletrolitos solidos ceramicos

    Energy Technology Data Exchange (ETDEWEB)

    Muccillo, R.; Cosentino, I.C.; Florio, D.Z. de; Franca, Y.V. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil). Dept. de Engenharia de Materiais

    1996-12-31

    The Impedance Spectroscopy (IS) technique has been used to the study of Th O{sub 2}:Y{sub 2} O{sub 3}, Zr O{sub 2}:La{sub 2} O{sub 3} and Zr O{sub 2}:Y{sub 2} O{sub 3} solid electrolytes. The results show that solid solution has been attained, grain boundaries act as oxygen-ion blockers, and the importance of the IS technique to study phase transformation in ceramics. (author) 6 refs., 6 figs.

  17. Dispersive electron transport in tris(8-hydroxyquinoline) aluminum (Alq3) probed by impedance spectroscopy.

    Science.gov (United States)

    Berleb, Stefan; Brütting, Wolfgang

    2002-12-31

    Electron transport in tris(8-hydroxyquinoline) aluminum (Alq3) is investigated by impedance spectroscopy under conditions of space-charge limited conduction (SCLC). Existing SCLC models are extended to include the field dependence of the charge carrier mobility and energetically distributed trap states. The dispersive nature of electron transport is revealed by a frequency-dependent mobility with a dispersion parameter alpha in the range 0.4-0.5, independent of temperature. This indicates that positional rather than energetic disorder is the dominant mechanism for the dispersive transport of electrons in Alq3.

  18. Moisture distribution computed from electrical impedance tomographic data of a bentonite clay/sand material

    International Nuclear Information System (INIS)

    Strobel, G.S.

    1995-11-01

    Moisture contents values were calculated from electrical impedance-computed tomography measurements and compared with thermocouple psychrometer moisture values. The measurements were taken, in situ and under isothermal conditions, in a bentonite clay/sand packed borehole at the Underground Research Laboratory. Two sets of impedances moisture contents were calculated from the impedance valves--independent of each other. For one set, impedance measurements were fitted to the psychrometer moisture values in a least-squares fit to a generalized calibration curve and, for the second set, an impedance-moisture relationship from laboratory calibrations was applied. The impedance-computed moisture content data showed low scatter and the trends were consistent between the three sets of values. However, the moisture content data computed from the calibration curve were more consistent with those expected from physical arguments. The moisture values from the psychrometer readings were offset and, consequently, so were those produced after applying the fitting strategy. Internal redistribution of moisture appears to have had a more significant effect on the system than did inflow at the boundary. Inflow did cause a significant change but this was localized, during this period, to the outer ∼ 0.05 m of the test hole. No comment was made as to what internal processes caused these responses. (author) 9 refs., 2 tabs., 5 figs

  19. Relationship between moisture content and electrical impedance of carrot slices during drying

    Science.gov (United States)

    Kertész, Ákos; Hlaváčová, Zuzana; Vozáry, Eszter; Staroňová, Lenka

    2015-01-01

    Electrical properties of food materials can give information about the inner structure and physiological state of biological tissues. Generally, the process of drying of fruits and vegetables is followed by weight loss. The aim of this study was to measure the impedance spectra of carrot slices during drying and to correlate impedance parameters to moisture content in different drying periods. Cylindrical slices were cut out from the carrot root along the axis. The slices were dried in a Venticell 111 air oven at 50°C. The weight of the slices was measured with a Denver SI-603 electronic analytical and precision balance. The weighing of the samples was performed every 30 min at the beginning of drying and every 60 min after the process. The moisture content of the samples was calculated on wet basis. The magnitude and phase angle of electrical impedance of the slices were measured with HP 4284A and 4285A precision LCR meters in the frequency range from 30 Hz to 1 MHz and from 75 kHz to 30 MHz, respectively, at voltage 1 V. The impedance measurement was performed after weighting. The change in the magnitude of impedance during drying showed a good correlation with the change in the moisture content.

  20. Correlation between muscle electrical impedance data and standard neurophysiologic parameters after experimental neurogenic injury

    International Nuclear Information System (INIS)

    Ahad, M; Rutkove, S B

    2010-01-01

    Previous work has shown that electrical impedance measurements of muscle can assist in quantifying the degree of muscle atrophy resulting from neuronal injury, with impedance values correlating strongly with standard clinical parameters. However, the relationship between such data and neurophysiologic measurements is unexplored. In this study, 24 Wistar rats underwent sciatic crush, with measurement of the 2–1000 kHz impedance spectrum, standard electrophysiological measures, including nerve conduction studies, needle electromyography, and motor unit number estimation (MUNE) before and after sciatic crush, with animals assessed weekly for 4 weeks post-injury. All electrical impedance values, including a group of 'collapsed' variables, in which the spectral characteristics were reduced to single values, showed reductions as high as 47.2% after sciatic crush, paralleling and correlating with changes in compound motor action potential amplitude, conduction velocity and most closely to MUNE, but not to the presence of fibrillation potentials observed on needle electromyography. These results support the concept that localized impedance measurements can serve as surrogate makers of nerve injury; these measurements may be especially useful in assessing nerve injury impacting proximal or axial muscles where standard quantitative neurophysiologic methods such as nerve conduction or MUNE cannot be readily performed

  1. TSDC and impedance spectroscopy measurements on hydroxyapatite, β-tricalcium phosphate and hydroxyapatite/β-tricalcium phosphate biphasic bioceramics

    Science.gov (United States)

    Prezas, P. R.; Melo, B. M. G.; Costa, L. C.; Valente, M. A.; Lança, M. C.; Ventura, J. M. G.; Pinto, L. F. V.; Graça, M. P. F.

    2017-12-01

    Bone grafting and surgical interventions related with orthopaedic disorders consist in a big business, generating large revenues worldwide every year. There is a need to replace the biomaterials that currently still dominate this market, i.e., autografts and allografts, due to their disadvantages, such as limited availability, need for additional surgeries and diseases transmission possibilities. The most promising replacement materials are biomaterials with bioactive properties, such as the calcium phosphate-based bioceramics group. The bioactivity of these materials, i.e., the rate at which they promote the growth and directly bond with the new host biological bone, can be enhanced through their electrical polarization. In the present work, the electrical polarization features of pure hydroxyapatite (Hap), pure β-tricalcium phosphate (β-TCP) and biphasic hydroxyapatite/β-tricalcium phosphate composites (HTCP) were analyzed by measuring thermally stimulated depolarization currents (TSDC). The samples were thermoelectrically polarized at 500 °C under a DC electric field with a magnitude of 5 kV/cm. The biphasic samples were also polarized under electric fields with different magnitudes: 2, 3, 4 and 5 kV/cm. Additionally, the depolarization processes detected in the TSDC measurements were correlated with dielectric relaxation processes observed in impedance spectroscopy (IS) measurements. The results indicate that the β-TCP crystalline phase has a considerable higher ability to store electrical charge compared with the Hap phase. This indicates that it has a suitable composition and structure for ionic conduction and establishment of a large electric charge density, providing great potential for orthopaedic applications.

  2. Analysis of mobile ionic impurities in polyvinylalcohol thin films by thermal discharge current and dielectric impedance spectroscopy

    Directory of Open Access Journals (Sweden)

    M. Egginger

    2012-12-01

    Full Text Available Polyvinylalcohol (PVA is a water soluble polymer frequently applied in the field of organic electronics for insulating thin film layers. By-products of PVA synthesis are sodium acetate ions which contaminate the polymer material and can impinge on the electronic performance when applied as interlayer dielectrics in thin film transistors. Uncontrollable voltage instabilities and unwanted hysteresis effects are regularly reported with PVA devices. An understanding of these effects require knowledge about the electronic dynamics of the ionic impurities and their influence on the dielectric properties of PVA. Respective data, which are largely unknown, are being presented in this work. Experimental investigations were performed from room temperature to 125°C on drop-cast PVA films of three different quality grades. Data from thermal discharge current (TDC measurements, polarization experiments, and dielectric impedance spectroscopy concurrently show evidence of mobile ionic carriers. Results from TDC measurements indicate the existence of an intrinsic, build-in electric field of pristine PVA films. The field is caused by asymmetric ionic double layer formation at the two different film-interfaces (substrate/PVA and PVA/air. The mobile ions cause strong electrode polarization effects which dominate dielectric impedance spectra. From a quantitative electrode polarization analysis of isothermal impedance spectra temperature dependent values for the concentration, the mobility and conductivity together with characteristic relaxation times of the mobile carriers are given. Also shown are temperature dependent results for the dc-permittivity and the electronic resistivity. The obtained results demonstrate the feasibility to partly remove contaminants from a PVA solution by dialysis cleaning. Such a cleaning procedure reduces the values of ion concentration, conductivity and relaxation frequency.

  3. Design of current source for multi-frequency simultaneous electrical impedance tomography

    Science.gov (United States)

    Han, Bing; Xu, Yanbin; Dong, Feng

    2017-09-01

    Multi-frequency electrical impedance tomography has been evolving from the frequency-sweep approach to the multi-frequency simultaneous measurement technique which can reduce measuring time and will be increasingly attractive for time-varying biological applications. The accuracy and stability of the current source are the key factors determining the quality of the image reconstruction. This article presents a field programmable gate array-based current source for a multi-frequency simultaneous electrical impedance tomography system. A novel current source circuit was realized by combining the classic current mirror based on the feedback amplifier AD844 with a differential topology. The optimal phase offsets of harmonic sinusoids were obtained through the crest factor analysis. The output characteristics of this current source were evaluated by simulation and actual measurement. The results include the following: (1) the output impedance was compared with one of the Howland pump circuit in simulation, showing comparable performance at low frequencies. However, the proposed current source makes lower demands for resistor tolerance but performs even better at high frequencies. (2) The output impedance in actual measurement below 200 kHz is above 1.3 MΩ and can reach 250 KΩ up to 1 MHz. (3) An experiment based on a biological RC model has been implemented. The mean error for the demodulated impedance amplitude and phase are 0.192% and 0.139°, respectively. Therefore, the proposed current source is wideband, biocompatible, and high precision, which demonstrates great potential to work as a sub-system in the multi-frequency electrical impedance tomography system.

  4. Development of in vivo impedance spectroscopy techniques for measurement of micropore formation following microneedle insertion.

    Science.gov (United States)

    Brogden, Nicole K; Ghosh, Priyanka; Hardi, Lucia; Crofford, Leslie J; Stinchcomb, Audra L

    2013-06-01

    Microneedles (MNs) provide a minimally invasive means to enhance skin permeability by creating micron-scale channels (micropores) that provide a drug delivery pathway. Adequate formation of the micropores is critical to the success of this unique drug delivery technique. The objective of the current work was to develop sensitive and reproducible impedance spectroscopy techniques to monitor micropore formation in animal models and human subjects. Hairless guinea pigs, a Yucatan miniature pig, and human volunteers were treated with 100 MN insertions per site following an overnight prehydration period. Repeated measurements were made pre- and post-MN treatment using dry and gel Ag/AgCl electrodes applied with light verses direct pressure to hold the electrode to the skin surface. Impedance measurements dropped significantly post-MN application at all sites (p micropore formation. In the Yucatan pig and human subjects, gel electrodes with direct pressure yielded the lowest variability (demonstrated by lower %relative standard deviation), whereas dry electrodes with direct pressure were superior in the guinea pigs. These studies confirm that impedance measurements are suitable for use in both clinical and animal research environments to monitor the formation of new micropores that will allow for drug delivery through the impermeable skin layers. Copyright © 2013 Wiley Periodicals, Inc.

  5. Electrochemical impedance spectroscopy of fully hydrated Nafion membranes at high and low hydrogen partial pressures

    International Nuclear Information System (INIS)

    Tsampas, M.N.; Brosda, S.; Vayenas, C.G.

    2011-01-01

    The proton transport mechanism in fully hydrated Nafion 117 membranes was examined via electrochemical impedance spectroscopy (EIS) and steady-state current–potential measurements both in a symmetric H 2 , Pt|Nafion|Pt, H 2 cell and in a H 2 , Pt|Nafion|Pt, air PEM fuel cell with hydrogen partial pressure values, P H 2 , varied between 0.5 kPa and 100 kPa. In agreement with recent studies it is found that for low P H 2 values the steady-state current–potential curves exhibit bistability and regions of positive slope. In these regions the Nyquist plots are found to exhibit negative real part impedance with a large imaginary component, while the Bode plots show a pronounced negative phase shift. These observations are consistent with the mechanism involving two parallel routes of proton conduction in fully hydrated Nafion membranes, one due to proton migration in the aqueous phase, the other due to proton transfer, probably involving tunneling, between adjacent sulfonate groups in narrow pores. The former mechanism dominates at high P H 2 values and the latter dominates in the low P H 2 region where the real part of the impedance is negative.

  6. Modeling and interpretation of electrical impedance spectra of dye solar cells operated under open-circuit conditions

    International Nuclear Information System (INIS)

    Kern, R.; Sastrawan, R.; Ferber, J.; Stangl, R.; Luther, J.

    2002-01-01

    Electrical impedance spectroscopy (EIS) was applied in order to investigate electrochemical nanocrystalline TiO 2 dye solar cells (DSC). Typically, three characteristic frequency peaks were observed in the spectra. These frequency peaks could be explained by variations of cell parameters and by comparison with intensity-modulated photovoltage spectroscopy (IMVS). It was shown that the low-frequency peak (in the mHz range) corresponds to the Nernstian diffusion within the electrolyte, while the middle-frequency peak (in the 10-100 Hz range) reflects the properties of the photoinjected electrons within the TiO 2 . The high-frequency peak (in the kHz range) corresponds to the charge-transfer at the platinum counter electrode. For a detailed analysis of the spectra, a model was developed which allows the evaluation of EIS spectra, measured under bias illumination and under open-circuit conditions. The influence of cell parameters such as the TiO 2 layer thickness, cell thickness, charge-transfer resistance of the platinum counter electrode, and the lifetime of the photoinjected electrons, on the impedance spectra was studied both experimentally and theoretically. Finally, it is shown that EIS is a measurement method suited well for the investigation of the long-term stability of DSC, as changes of the inner cell parameters can be revealed

  7. Polynomial Collocation for Handling an Inaccurately Known Measurement Configuration in Electrical Impedance Tomography

    DEFF Research Database (Denmark)

    Hyvönen, Niina; Kaarnioja, V.; Mustonen, L.

    2017-01-01

    The objective of electrical impedance tomography is to reconstruct the internal conductivity of a physical body based on measurements of current and potential at a finite number of electrodes attached to its boundary. Although the conductivity is the quantity of main interest in impedance...... tomography, a real-world measurement configuration includes other unknown parameters as well: The information on the contact resistances, electrode positions, and body shape is almost always incomplete. In this work, the dependence of the electrode measurements on all aforementioned model properties...

  8. Detection of thoracic vascular structures by electrical impedance tomography: a systematic assessment of prominence peak analysis of impedance changes.

    Science.gov (United States)

    Wodack, K H; Buehler, S; Nishimoto, S A; Graessler, M F; Behem, C R; Waldmann, A D; Mueller, B; Böhm, S H; Kaniusas, E; Thürk, F; Maerz, A; Trepte, C J C; Reuter, D A

    2018-02-28

    Electrical impedance tomography (EIT) is a non-invasive and radiation-free bedside monitoring technology, primarily used to monitor lung function. First experimental data shows that the descending aorta can be detected at different thoracic heights and might allow the assessment of central hemodynamics, i.e. stroke volume and pulse transit time. First, the feasibility of localizing small non-conductive objects within a saline phantom model was evaluated. Second, this result was utilized for the detection of the aorta by EIT in ten anesthetized pigs with comparison to thoracic computer tomography (CT). Two EIT belts were placed at different thoracic positions and a bolus of hypertonic saline (10 ml, 20%) was administered into the ascending aorta while EIT data were recorded. EIT images were reconstructed using the GREIT model, based on the individual's thoracic contours. The resulting EIT images were analyzed pixel by pixel to identify the aortic pixel, in which the bolus caused the highest transient impedance peak in time. In the phantom, small objects could be located at each position with a maximal deviation of 0.71 cm. In vivo, no significant differences between the aorta position measured by EIT and the anatomical aorta location were obtained for both measurement planes if the search was restricted to the dorsal thoracic region of interest (ROIs). It is possible to detect the descending aorta at different thoracic levels by EIT using an intra-aortic bolus of hypertonic saline. No significant differences in the position of the descending aorta on EIT images compared to CT images were obtained for both EIT belts.

  9. Dynamic impedance model of the skin-electrode interface for transcutaneous electrical stimulation.

    Directory of Open Access Journals (Sweden)

    José Luis Vargas Luna

    Full Text Available Transcutaneous electrical stimulation can depolarize nerve or muscle cells applying impulses through electrodes attached on the skin. For these applications, the electrode-skin impedance is an important factor which influences effectiveness. Various models describe the interface using constant or current-depending resistive-capacitive equivalent circuit. Here, we develop a dynamic impedance model valid for a wide range stimulation intensities. The model considers electroporation and charge-dependent effects to describe the impedance variation, which allows to describe high-charge pulses. The parameters were adjusted based on rectangular, biphasic stimulation pulses generated by a stimulator, providing optionally current or voltage-controlled impulses, and applied through electrodes of different sizes. Both control methods deliver a different electrical field to the tissue, which is constant throughout the impulse duration for current-controlled mode or have a very current peak for voltage-controlled. The results show a predominant dependence in the current intensity in the case of both stimulation techniques that allows to keep a simple model. A verification simulation using the proposed dynamic model shows coefficient of determination of around 0.99 in both stimulation types. The presented method for fitting electrode-skin impedance can be simple extended to other stimulation waveforms and electrode configuration. Therefore, it can be embedded in optimization algorithms for designing electrical stimulation applications even for pulses with high charges and high current spikes.

  10. A cable-free impedance and gain measurement technique for electrically small antennas

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Zhang, Jiaying; Breinbjerg, Olav

    2010-01-01

    are represented in terms of spherical wave expansions (SWEs), and the propagation is accounted for by a transmission formula. In this paper the measurement results by the proposed technique will be presented for several AUTs, including a standard gain horn antenna, a monopole antenna, and an electrically small......Impedance and gain measurements for electrically small antennas represent a great challenge due to influences of the feeding cable. The leaking current along the cable and scattering effects are two main issues caused by the feed line. In this paper, a novel cable-free antenna impedance and gain...... measurement technique for electrically small antennas is proposed. The antenna properties are extracted by measuring the signal scattered by the antenna under test (AUT), when it is loaded with three known loads. The technique is based on a rigorous electromagnetic model where the probe and AUT...

  11. High sensitivity and label-free detection of Enterovirus 71 by nanogold modified electrochemical impedance spectroscopy

    Science.gov (United States)

    Wang, Fang-Yu; Li, Hsing-Yuan; Tseng, Shing-Hua; Cheng, Tsai-Mu; Chu, Hsueh-Liang; Yang, Jyh-Yuan; Chang, Chia-Ching

    2013-03-01

    Enterovirus 71 (EV71), which is the most fulminant and invasive species of enterovirus, can cause children neurologic complications and death within 2-3 days after fever and rash developed. Besides, EV71 has high sequence similarity with Coxsackie A 16 (CA16) that makes differential diagnosis difficult in clinic and laboratory. Since conventional viral diagnostic method cannot diagnose EV71 quickly and EV71 can transmit at low viral titer, the patients might delay in treatment. A quick, high sensitive, and high specific test for EV71 detection is pivotal. Electrochemical impedance spectroscopy (EIS) has been applied for detecting bio-molecules as biosensors recently. In this study, we try to build a detection platform for EV71 detection by nanogold modified EIS probe. The result shows that our probe can detect 3.6 VP1/50 μl (one EV71 particle has 60 VP1) in 3 minutes. The test can also distinguish EV71 from CA16 and lysozyme. Diagnosis of enterovirus 71 by electrochemical impedance spectroscopy has the potential to apply in clinic.

  12. Energy resolved electrochemical impedance spectroscopy for electronic structure mapping in organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Nádaždy, V., E-mail: nadazdy@savba.sk; Gmucová, K. [Institute of Physics SAS, Dúbravská cesta 9, 845 11 Bratislava (Slovakia); Schauer, F. [Faculty of Education, Trnava University in Trnava, 918 43 Trnava (Slovakia); Faculty of Applied Informatics, Tomas Bata University in Zlin, 760 05 Zlin (Czech Republic)

    2014-10-06

    We introduce an energy resolved electrochemical impedance spectroscopy method to map the electronic density of states (DOS) in organic semiconductor materials. The method consists in measurement of the charge transfer resistance of a semiconductor/electrolyte interface at a frequency where the redox reactions determine the real component of the impedance. The charge transfer resistance value provides direct information about the electronic DOS at the energy given by the electrochemical potential of the electrolyte, which can be adjusted using an external voltage. A simple theory for experimental data evaluation is proposed, along with an explanation of the corresponding experimental conditions. The method allows mapping over unprecedentedly wide energy and DOS ranges. Also, important DOS parameters can be determined directly from the raw experimental data without the lengthy analysis required in other techniques. The potential of the proposed method is illustrated by tracing weak bond defect states induced by ultraviolet treatment above the highest occupied molecular orbital in a prototypical σ-conjugated polymer, poly[methyl(phenyl)silylene]. The results agree well with those of our previous DOS reconstruction by post-transient space-charge-limited-current spectroscopy, which was, however, limited to a narrow energy range. In addition, good agreement of the DOS values measured on two common π-conjugated organic polymer semiconductors, polyphenylene vinylene and poly(3-hexylthiophene), with the rather rare previously published data demonstrate the accuracy of the proposed method.

  13. Electrochemical impedance spectroscopy based MEMS sensors for phthalates detection in water and juices

    International Nuclear Information System (INIS)

    Zia, Asif I; Syaifudin, A R Mohd; Mukhopadhyay, S C; Yu, P L; Al-Bahadly, I H; Gooneratne, Chinthaka P; Kosel, Juergen; Liao, Tai-Shan

    2013-01-01

    Phthalate esters are ubiquitous environmental and food pollutants well known as endocrine disrupting compounds (EDCs). These developmental and reproductive toxicants pose a grave risk to the human health due to their unlimited use in consumer plastic industry. Detection of phthalates is strictly laboratory based time consuming and expensive process and requires expertise of highly qualified and skilled professionals. We present a real time, non-invasive, label free rapid detection technique to quantify phthalates' presence in deionized water and fruit juices. Electrochemical impedance spectroscopy (EIS) technique applied to a novel planar inter-digital (ID) capacitive sensor plays a vital role to explore the presence of phthalate esters in bulk fluid media. The ID sensor with multiple sensing gold electrodes was fabricated on silicon substrate using micro-electromechanical system (MEMS) device fabrication technology. A thin film of parylene C polymer was coated as a passivation layer to enhance the capacitive sensing capabilities of the sensor and to reduce the magnitude of Faradic current flowing through the sensor. Various concentrations, 0.002ppm through to 2ppm of di (2-ethylhexyl) phthalate (DEHP) in deionized water, were exposed to the sensing system by dip testing method. Impedance spectra obtained was analysed to determine sample conductance which led to consequent evaluation of its dielectric properties. Electro-chemical impedance spectrum analyser algorithm was employed to model the experimentally obtained impedance spectra. Curve fitting technique was applied to deduce constant phase element (CPE) equivalent circuit based on Randle's equivalent circuit model. The sensing system was tested to detect different concentrations of DEHP in orange juice as a real world application. The result analysis indicated that our rapid testing technique is able to detect the presence of DEHP in all test samples distinctively.

  14. Electrochemical impedance spectroscopy based MEMS sensors for phthalates detection in water and juices

    KAUST Repository

    Zia, Asif I

    2013-06-10

    Phthalate esters are ubiquitous environmental and food pollutants well known as endocrine disrupting compounds (EDCs). These developmental and reproductive toxicants pose a grave risk to the human health due to their unlimited use in consumer plastic industry. Detection of phthalates is strictly laboratory based time consuming and expensive process and requires expertise of highly qualified and skilled professionals. We present a real time, non-invasive, label free rapid detection technique to quantify phthalates\\' presence in deionized water and fruit juices. Electrochemical impedance spectroscopy (EIS) technique applied to a novel planar inter-digital (ID) capacitive sensor plays a vital role to explore the presence of phthalate esters in bulk fluid media. The ID sensor with multiple sensing gold electrodes was fabricated on silicon substrate using micro-electromechanical system (MEMS) device fabrication technology. A thin film of parylene C polymer was coated as a passivation layer to enhance the capacitive sensing capabilities of the sensor and to reduce the magnitude of Faradic current flowing through the sensor. Various concentrations, 0.002ppm through to 2ppm of di (2-ethylhexyl) phthalate (DEHP) in deionized water, were exposed to the sensing system by dip testing method. Impedance spectra obtained was analysed to determine sample conductance which led to consequent evaluation of its dielectric properties. Electro-chemical impedance spectrum analyser algorithm was employed to model the experimentally obtained impedance spectra. Curve fitting technique was applied to deduce constant phase element (CPE) equivalent circuit based on Randle\\'s equivalent circuit model. The sensing system was tested to detect different concentrations of DEHP in orange juice as a real world application. The result analysis indicated that our rapid testing technique is able to detect the presence of DEHP in all test samples distinctively.

  15. The measurement of water transport in porous materials using impedance spectroscopy

    International Nuclear Information System (INIS)

    Ball, R J; Allen, G C

    2010-01-01

    This paper describes the application of electrical measurements to monitor the extraction (movement of water from the mortar) of water from calcium lime, natural hydraulic lime and Portland cement mortars placed on an adsorbent brick substrate. Impedance measurements were used to identify the changes in bulk resistance of the mortar. A model has been developed combining sharp front theory and Boltzmann's distribution law of statistical thermodynamics to identify the point at which no further absorption of water into the brick occurs. A linear relationship was found between the exponential of bulk resistance and the square root of time during dewatering. A change in gradient was attributed to the end of dewatering.

  16. Hybrid Microfluidic Platform for Multifactorial Analysis Based on Electrical Impedance, Refractometry, Optical Absorption and Fluorescence

    Directory of Open Access Journals (Sweden)

    Fábio M. Pereira

    2016-10-01

    Full Text Available This paper describes the development of a novel microfluidic platform for multifactorial analysis integrating four label-free detection methods: electrical impedance, refractometry, optical absorption and fluorescence. We present the rationale for the design and the details of the microfabrication of this multifactorial hybrid microfluidic chip. The structure of the platform consists of a three-dimensionally patterned polydimethylsiloxane top part attached to a bottom SU-8 epoxy-based negative photoresist part, where microelectrodes and optical fibers are incorporated to enable impedance and optical analysis. As a proof of concept, the chip functions have been tested and explored, enabling a diversity of applications: (i impedance-based identification of the size of micro beads, as well as counting and distinguishing of erythrocytes by their volume or membrane properties; (ii simultaneous determination of the refractive index and optical absorption properties of solutions; and (iii fluorescence-based bead counting.

  17. Application of stochastic Galerkin FEM to the complete electrode model of electrical impedance tomography

    International Nuclear Information System (INIS)

    Leinonen, Matti; Hakula, Harri; Hyvönen, Nuutti

    2014-01-01

    The aim of electrical impedance tomography is to determine the internal conductivity distribution of some physical body from boundary measurements of current and voltage. The most accurate forward model for impedance tomography is the complete electrode model, which consists of the conductivity equation coupled with boundary conditions that take into account the electrode shapes and the contact resistances at the corresponding interfaces. If the reconstruction task of impedance tomography is recast as a Bayesian inference problem, it is essential to be able to solve the complete electrode model forward problem with the conductivity and the contact resistances treated as a random field and random variables, respectively. In this work, we apply a stochastic Galerkin finite element method to the ensuing elliptic stochastic boundary value problem and compare the results with Monte Carlo simulations

  18. Magnetic resonance electrical impedance tomography (MREIT): conductivity and current density imaging

    International Nuclear Information System (INIS)

    Seo, Jin Keun; Kwon, Ohin; Woo, Eung Je

    2005-01-01

    This paper reviews the latest impedance imaging technique called Magnetic Resonance Electrical Impedance Tomography (MREIT) providing information on electrical conductivity and current density distributions inside an electrically conducting domain such as the human body. The motivation for this research is explained by discussing conductivity changes related with physiological and pathological events, electromagnetic source imaging and electromagnetic stimulations. We briefly summarize the related technique of Electrical Impedance Tomography (EIT) that deals with cross-sectional image reconstructions of conductivity distributions from boundary measurements of current-voltage data. Noting that EIT suffers from the ill-posed nature of the corresponding inverse problem, we introduce MREIT as a new conductivity imaging modality providing images with better spatial resolution and accuracy. MREIT utilizes internal information on the induced magnetic field in addition to the boundary current-voltage measurements to produce three-dimensional images of conductivity and current density distributions. Mathematical theory, algorithms, and experimental methods of current MREIT research are described. With numerous potential applications in mind, future research directions in MREIT are proposed

  19. A bio-electromechanical imaging technique with combined electrical impedance and ultrasound tomography

    International Nuclear Information System (INIS)

    Steiner, G; Watzenig, D; Soleimani, M

    2008-01-01

    Electrical impedance tomography (EIT) seeks to image the electrical conductivity of an object using electrical impedance measurement data at its periphery. Ultrasound reflection tomography (URT) is an imaging modality that is able to generate images of mechanical properties of the object in terms of acoustic impedance changes. Both URT and EIT have the potential to be used in various medical applications. In this paper we focus on breast tumour detection. Both URT and EIT belong to soft field tomography and suffer from the small amounts of available data and the inherently ill-posed nature of the inverse problems. These facts result in limited achievable reconstruction accuracy and resolution. A dual bio-electromechanical tomography system using ultrasound and electrical tomography is proposed in this paper to improve the detection of the small-size tumour. Data fusion techniques are implemented to combine the EIT/URT data. Based on simulations, we demonstrate the improvement of detection of small size anomalies and improved depth detection compared to single modality soft field tomography

  20. Transcephalic electrical impedance in the study of cerebral circulation in a juvenile pig model.

    Science.gov (United States)

    Grönlund, J; Bartocci, M; Kääpä, P; Jahnukainen, T; Rautanen, M; Halkola, L; Välimäki, I

    1997-11-01

    Transcephalic electrical impedance offers a technique for non-invasive, cot-side monitoring of neonatal cerebral circulation but the exact nature of the signal is somewhat ambiguous. The impedance signal is examined in an animal project where the ventilator settings are adjusted (20 min-1-10 min-1-40 min-1 for 10 min periods each) to produce circulatory changes. Six juvenile pigs are intubated, and ECG, arterial blood pressure, carotid flow (CF) by electromagnetic flowmeter and impedance are continuously monitored and stored on analogue tape. Cardiac output by thermodilution, blood oxygen (pO2) and carbon dioxide (pCO2) tensions are measured. ECG is converted to heart rate, mean blood pressure is integrated, and the high-frequency (1.50-4.00 Hz) component of the impedance signal delta Z is computed using autoregressive spectral estimation. Stroke volume, peripheral vascular resistance (PVR) and cerebral vascular resistance (CVR) are calculated. pCO2 and CF increase and pO2 decreases during hypoventilation. CF correlates positively with cardiac output, stroke volume, delta Z and pCO2, and negatively with pO2 and CVR. delta Z correlates positively with heart rate and cardiac output, and negatively with PVR and CVR. It is concluded that the impedance signal is related to the amount of blood transmitted to the brain by every beat of the heart, depending on the changes in both the systemic circulation and the cerebral vascular compliance.

  1. Electric Propulsion Induced Secondary Mass Spectroscopy

    Science.gov (United States)

    Amini, Rashied; Landis, Geoffrey

    2012-01-01

    A document highlights a means to complement remote spectroscopy while also providing in situ surface samples without a landed system. Historically, most compositional analysis of small body surfaces has been done remotely by analyzing reflection or nuclear spectra. However, neither provides direct measurement that can unambiguously constrain the global surface composition and most importantly, the nature of trace composition and second-phase impurities. Recently, missions such as Deep Space 1 and Dawn have utilized electric propulsion (EP) accelerated, high-energy collimated beam of Xe+ ions to propel deep space missions to their target bodies. The energies of the Xe+ are sufficient to cause sputtering interactions, which eject material from the top microns of a targeted surface. Using a mass spectrometer, the sputtered material can be determined. The sputtering properties of EP exhaust can be used to determine detailed surface composition of atmosphereless bodies by electric propulsion induced secondary mass spectroscopy (EPI-SMS). EPI-SMS operation has three high-level requirements: EP system, mass spectrometer, and altitude of about 10 km. Approximately 1 keV Xe+ has been studied and proven to generate high sputtering yields in metallic substrates. Using these yields, first-order calculations predict that EPI-SMS will yield high signal-to-noise at altitudes greater than 10 km with both electrostatic and Hall thrusters.

  2. Linearity of electrical impedance tomography during maximum effort breathing and forced expiration maneuvers.

    Science.gov (United States)

    Ngo, Chuong; Leonhardt, Steffen; Zhang, Tony; Lüken, Markus; Misgeld, Berno; Vollmer, Thomas; Tenbrock, Klaus; Lehmann, Sylvia

    2017-01-01

    Electrical impedance tomography (EIT) provides global and regional information about ventilation by means of relative changes in electrical impedance measured with electrodes placed around the thorax. In combination with lung function tests, e.g. spirometry and body plethysmography, regional information about lung ventilation can be achieved. Impedance changes strictly correlate with lung volume during tidal breathing and mechanical ventilation. Initial studies presumed a correlation also during forced expiration maneuvers. To quantify the validity of this correlation in extreme lung volume changes during forced breathing, a measurement system was set up and applied on seven lung-healthy volunteers. Simultaneous measurements of changes in lung volume using EIT imaging and pneumotachography were obtained with different breathing patterns. Data was divided into a synchronizing phase (spontaneous breathing) and a test phase (maximum effort breathing and forced maneuvers). The EIT impedance changes correlate strictly with spirometric data during slow breathing with increasing and maximum effort ([Formula: see text]) and during forced expiration maneuvers ([Formula: see text]). Strong correlations in spirometric volume parameters [Formula: see text] ([Formula: see text]), [Formula: see text]/FVC ([Formula: see text]), and flow parameters PEF, [Formula: see text], [Formula: see text], [Formula: see text] ([Formula: see text]) were observed. According to the linearity during forced expiration maneuvers, EIT can be used during pulmonary function testing in combination with spirometry for visualisation of regional lung ventilation.

  3. A multichannel frequency response analyser for impedance spectroscopy on power sources

    Directory of Open Access Journals (Sweden)

    DANIEL J. L. BRETT

    2013-06-01

    Full Text Available A low-cost multi-channel frequency response analyser (FRA has been developed based on a DAQ (data acquisition/LabVIEW interface. The system has been tested for electric and electrochemical impedance measurements. This novel association of hardware and software demonstrated performance comparable to a commercial potentiostat / FRA for passive electric circuits. The software has multichannel capabilities with minimal phase shift for 5 channels when operated below 3 kHz. When applied in active (galvanostatic mode in conjunction with a commercial electronic load (by discharging a lead acid battery at 1.5 A the performance was fit for purpose, providing electrochemical information to characterize the performance of the power source.

  4. Temperature dependent dielectric relaxation and ac-conductivity of alkali niobate ceramics studied by impedance spectroscopy

    Science.gov (United States)

    Yadav, Abhinav; Mantry, Snigdha Paramita; Fahad, Mohd.; Sarun, P. M.

    2018-05-01

    Sodium niobate (NaNbO3) ceramics is prepared by conventional solid state reaction method at sintering temperature 1150 °C for 4 h. The structural information of the material has been investigated by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FE-SEM). The XRD analysis of NaNbO3 ceramics shows an orthorhombic structure. The FE-SEM micrograph of NaNbO3 ceramics exhibit grains with grain sizes ranging between 1 μm to 5 μm. The surface coverage and average grain size of NaNbO3 ceramics are found to be 97.6 % and 2.5 μm, respectively. Frequency dependent electrical properties of NaNbO3 is investigated from room temperature to 500 °C in wide frequency range (100 Hz-5 MHz). Dielectric constant, ac-conductivity, impedance, modulus and Nyquist analysis are performed. The observed dielectric constant (1 kHz) at transition temperature (400 °C) are 975. From conductivity analysis, the estimated activation energy of NaNbO3 ceramics is 0.58 eV at 10 kHz. The result of Nyquist plot shows that the electrical behavior of NaNbO3 ceramics is contributed by grain and grain boundary responses. The impedance and modulus spectrum asserts that the negative temperature coefficient of resistance (NTCR) behavior and non-Debye type relaxation in NaNbO3.

  5. Impedance spectroscopy of Li2CO3 doped (Ba,Sr)TiO3 ceramic

    Science.gov (United States)

    Ham, Yong-Su; Koh, Jung-Hyuk

    2013-02-01

    (BaxSr1-x)TiO3-based ceramic has been considered as one of the most important electronic materials widely employed in microwave passive device applications. Many researches have been performed to lower the high sintering temperature, by adding various dopants such as B2O3, La2O3, etc. In our previous study, by adding Li2CO3 to (Ba0.5,Sr0.5)TiO3 ceramics, the sintering temperature of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics decreased from 1350 to 900 °C. This study observed the crystalline structure and electrical properties of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics. In scanning the crystalline structure of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics, no pyro phase was observed by X-ray diffraction analysis. To investigate the electrical properties of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics, real and imaginary parts of the impedances were analyzed. Complex impedance data were measured from 100 Hz to 1 MHz at various temperature ranges.

  6. Design and development of electrical impedance tomography system with 32 electrodes and microcontroller

    Science.gov (United States)

    Ansory, Achmad; Prajitno, Prawito; Wijaya, Sastra Kusuma

    2018-02-01

    Electrical Impedance Tomography (EIT) is an imaging method that is able to estimate electrical impedance distribution inside an object. This EIT system is developed by using 32 electrodes and microcontroller based module. From a pair of electrodes, sinusoidal current of 3 mA is injected and the voltage differences between other pairs of electrodes are measured. Voltage measurement data are then sent to MATLAB and EIDORS software; the data are used to reconstruct two dimensions image. The system can detect and determine the position of a phantom in the tank. The object's position is accurately reconstructed and determined with the average shifting of 0.69 cm but object's area cannot be accurately reconstructed. The object's image is more accurately reconstructed when the object is located near to electrodes, has a larger size, and when the current injected to the system has a frequency of 100 kHz or 200kHz.

  7. Multi-channel electrical impedance tomography for regional tissue hydration monitoring

    International Nuclear Information System (INIS)

    Chen, Xiaohui; Kao, Tzu-Jen; Ashe, Jeffrey M; Boverman, Gregory; Sabatini, James E; Davenport, David M

    2014-01-01

    Poor assessment of hydration status during hemodialysis can lead to under- or over-hydration in patients with consequences of increased morbidity and mortality. In current practice, fluid management is largely based on clinical assessments to estimate dry weight (normal hydration body weight). However, hemodialysis patients usually have co-morbidities that can make the signs of fluid status ambiguous. Therefore, achieving normal hydration status remains a major challenge for hemodialysis therapy. Electrical impedance technology has emerged as a promising method for hydration monitoring due to its non-invasive nature, low cost and ease-of-use. Conventional electrical impedance-based hydration monitoring systems employ single-channel current excitation (either 2-electrode or 4-electrode methods) to perturb and extract averaged impedance from bulk tissue and use generalized models from large populations to derive hydration estimates. In the present study, a prototype, single-frequency electrical impedance tomography (EIT) system with simultaneous multi-channel current excitation was used to enable regional hydration change detection. We demonstrated the capability to detect a difference in daily impedance change between left leg and right leg in healthy human subjects, who wore a compression sock only on one leg to reduce daily gravitational fluid accumulation. The impedance difference corresponded well with the difference of lower leg volume change between left leg and right leg measured by volumetry, which on average is ∼35 ml, accounting for 0.7% of the lower leg volume. We have demonstrated the feasibility of using multi-channel EIT to extract hydration information in different tissue layers with minimal skin interference. Our simultaneous, multi-channel current excitation approach provides an effective method to separate electrode contact impedance and skin condition artifacts from hydration signals. The prototype system has the potential to be used in

  8. Hardware Design of Tuber Electrical Resistance Tomography System Based on the Soil Impedance Test and Analysis

    OpenAIRE

    Liu Shuyi; Deng Xiang; Jiang Zili; Tang Yu

    2016-01-01

    The hardware design of tuber electrical resistance tomography (TERT) system is one of the key research problems of TERT data acquisition system. The TERT system can be applied to the tuber growth process monitoring in agriculture, i.e., the TERT data acquisition system can realize the real imaging of tuber plants in soil. In TERT system, the imaging tuber and soil multiphase medium is quite complexity. So, the impedance test and analysis of soil multiphase medium is very important to the desi...

  9. Theoretical and experimental studies on the electric impedance of active piezoelectric sensors bonded on cracked beams

    International Nuclear Information System (INIS)

    Kuang, Y D; Chen, C Y; Shi, S Q; Chan, P K L; He, X Q

    2010-01-01

    The electric impedance of symmetrically surface-bonded piezoelectric sensors on a cracked beam is studied. To investigate the effect of the crack on the electric impedance in a convenient fashion, an analytical expression is derived that is correlated to the physical parameters of the crack and the host beam. The beam segment covered with piezoelectric patches and the cracked region are regarded as a bimorph segment and an equivalent spring, respectively, and the entire beam system is then represented by three elastic beam segments and a bimorph segment together with the spring. Electric impedance experiments are also conducted for uncracked beams and for cracked beams with single-edge or double-edge cracks. The experimental results agree with those generated by the analytical expression. The crack depth has little effect on the corresponding mode frequency for cracks located at the mode node of a beam. For cracks located away from the mode node, the corresponding mode frequency decreases as the crack depth increases. Moreover, the closer the crack to the anti-node of the mode, the greater the decrease in the corresponding mode frequency. The mechanism of these changes is discussed. The findings should prove helpful for structural health monitoring using active piezoelectric sensors

  10. Self-assembled monolayers-based immunosensor for detection of Escherichia coli using electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    Geng Ping; Zhang Xinai; Meng Weiwei; Wang Qingjiang; Zhang Wen; Jin Litong; Feng Zhen; Wu Zirong

    2008-01-01

    An electrochemical impedance immunosensor for the detection of Escherichia coli was developed by immobilizing anti-E. coli antibodies at an Au electrode. The immobilization of antibodies at the Au electrode was carried out through a stable acyl amino ester intermediate generated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydrosuccinimide (NHS), which could condense antibodies reproducibly and densely on the self-assembled monolayer (SAM). The surface characteristics of the immunosensor before and after the binding reaction of antibodies with E. coli were characterized by atomic force microscopy (AFM). The immobilization of antibodies and the binding of E. coli cells to the electrode could increase the electro-transfer resistance, which was directly detected by electrochemical impedance spectroscopy (EIS) in the presence of Fe(CN) 6 3- /Fe(CN) 6 4- as a redox probe. A linear relationship between the electron-transfer resistance and the logarithmic value of E. coli concentration was found in the range of E. coli cells from 3.0 x 10 3 to 3.0 x 10 7 cfu mL -1 with the detection limit of 1.0 x 10 3 cfu mL -1 . With preconcentration and pre-enrichment steps, it was possible to detect E. coli concentration as low as 50 cfu/mL in river water samples

  11. Hydrogen evolution reaction on electrodes with different PT/C loadings by electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Chavez, L. [Inst. Tecnologico de Chihuahua 2, Chihuahua, Chih (Mexico); Ortega-Chavez, L.; Herrera-Peraza, E. [Centro de Investigacion en Materiales Avanzados, Chiuahua, Chih (Mexico); Verde, Y. [Inst. Tecnologico de Cancun, Cancun, Quintana Roo (Mexico)

    2008-04-15

    One of the most widely studied reactions in electrochemistry is the hydrogen evolution reaction (HER). HER is important for the development of water hydrolysis and fuel cell technologies. Because hydrogen-substrate interaction determines oxygen reduction efficiency, an understanding of the chemical and electronic state of hydrogen adsorbed on the electrocatalyst surface is required. Electrochemical impedance spectroscopy (EIS) is a proven highly efficient technique for interface characterization and kinetic parameter determination for different reactions carried out on interfaces. This article presented a study that utilized EIS for characterizing electrodes under HER by implementing a rotating disc electrode with different carbon supported platinum nanoparticles loadings and different potentials in acidic solutions. The results collected by EIS were analyzed in terms of equivalent circuits to calculate different parameters which were compared by statistical analysis. The study also considered the Volmer, Heyrovsky and Tafel steps in the HER reaction as well as a single electro-absorbed intermediate species. The article discussed the experimental set-up with reference to measurements, simulation and fitting. Parameters analysis using ANOVA were reviewed. It was concluded that an increase in impedance occurs when platinum loading decreases in both high and low frequencies. 22 refs., 1 tab., 5 figs.

  12. Impedance spectroscopy of PZT ceramics--measuring diffusion coefficients, mixed conduction, and Pb loss.

    Science.gov (United States)

    Donnelly, Niall J; Randall, Clive A

    2012-09-01

    Sintering of lead zirconate titanate (PZT) at high temperatures results in loss of Pb unless an ambient Pb activity is maintained. The tell-tale sign of Pb loss is an increased conductivity, usually manifested in unacceptably high values of tanδ. The conductivity is caused by oxygen vacancies and/or electron holes which are a byproduct of Pb evaporation. In the first part of this paper, it is shown how impedance spectroscopy can be used to separate ionic and electronic conductivity in a properly designed sample by selection of appropriate boundary conditions. Subsequently, impedance is used to probe defect concentrations in PZT during prolonged annealing at 700°C. It is found that oxygen vacancies are generated during annealing in air but the rate of generation actually decreases upon lowering the ambient pO(2). These results are explained by a model of Pb evaporation which, in this case, leads predominantly to oxygen vacancy generation. In principle, this effect could be used to generate a specific vacancy concentration in similar Pb-based oxides.

  13. Passivation of laser-treated nickel aluminum bronze as measured by electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    Klassen, R.D.; Hyatt, C.V.; Roberge, P.R.

    2000-01-01

    Electrochemical impedance spectroscopy was used to assess the corrosion behavior of the weld zones and surface conditions of a laser-clad nickel aluminum bronze immersed in a 3.5% neutral saline solution. The zones and conditions examined included: (i) as-cast base material; (ii) laser-clad material with the high temperature oxide from welding intact; (iii) polished laser-clad material and (iv) specimens representative of just the as-deposited and reheated zones of the laser-clad surface. A pseudo steady-state level of passivation was reached in all the samples within 40 hours. The reheated zone passivated more slowly than the as-deposited region and both weld zones passivated more quickly than the base material. Electrochemical impedance data illustrated a transition during the passivation process of the polished specimens that is consistent with the development of a film layer that restricted mass transfer. The welding oxide from the laser treatment immediately behaved as a passivation film that was indistinguishable from that which eventually develops on polished specimens. (author)

  14. Use of electrical impedance tomography to monitor regional cerebral edema during clinical dehydration treatment.

    Directory of Open Access Journals (Sweden)

    Feng Fu

    Full Text Available OBJECTIVE: Variations of conductive fluid content in brain tissue (e.g. cerebral edema change tissue impedance and can potentially be measured by Electrical Impedance Tomography (EIT, an emerging medical imaging technique. The objective of this work is to establish the feasibility of using EIT as an imaging tool for monitoring brain fluid content. DESIGN: a prospective study. SETTING: In this study EIT was used, for the first time, to monitor variations in cerebral fluid content in a clinical model with patients undergoing clinical dehydration treatment. The EIT system was developed in house and its imaging sensitivity and spatial resolution were evaluated on a saline-filled tank. PATIENTS: 23 patients with brain edema. INTERVENTIONS: The patients were continuously imaged by EIT for two hours after initiation of dehydration treatment using 0.5 g/kg intravenous infusion of mannitol for 20 minutes. MEASUREMENT AND MAIN RESULTS: Overall impedance across the brain increased significantly before and after mannitol dehydration treatment (p = 0.0027. Of the all 23 patients, 14 showed high-level impedance increase and maintained this around 4 hours after the dehydration treatment whereas the other 9 also showed great impedance gain during the treatment but it gradually decreased after the treatment. Further analysis of the regions of interest in the EIT images revealed that diseased regions, identified on corresponding CT images, showed significantly less impedance changes than normal regions during the monitoring period, indicating variations in different patients' responses to such treatment. CONCLUSIONS: EIT shows potential promise as an imaging tool for real-time and non-invasive monitoring of brain edema patients.

  15. Interface Design for CMOS-Integrated Electrochemical Impedance Spectroscopy (EIS Biosensors

    Directory of Open Access Journals (Sweden)

    Arjang Hassibi

    2012-10-01

    Full Text Available Electrochemical Impedance Spectroscopy (EIS is a powerful electrochemical technique to detect biomolecules. EIS has the potential of carrying out label-free and real-time detection, and in addition, can be easily implemented using electronic integrated circuits (ICs that are built through standard semiconductor fabrication processes. This paper focuses on the various design and optimization aspects of EIS ICs, particularly the bio-to-semiconductor interface design. We discuss, in detail, considerations such as the choice of the electrode surface in view of IC manufacturing, surface linkers, and development of optimal bio-molecular detection protocols. We also report experimental results, using both macro- and micro-electrodes to demonstrate the design trade-offs and ultimately validate our optimization procedures.

  16. Estimation of Parameters Obtained by Electrochemical Impedance Spectroscopy on Systems Containing High Capacities

    Directory of Open Access Journals (Sweden)

    Mirjana Rajčić Vujasinović

    2009-09-01

    Full Text Available Electrochemical systems with high capacities demand devices for electrochemical impedance spectroscopy (EIS with ultra-low frequencies (in order of mHz, that are almost impossible to accomplish with analogue techniques, but this becomes possible by using a computer technique and accompanying digital equipment. Recently, an original software and hardware for electrochemical measurements, intended for electrochemical systems exhibiting high capacities, such as supercapacitors, has been developed. One of the included methods is EIS. In this paper, the method of calculation of circuit parameters from an EIS curve is described. The results of testing on a physical model of an electrochemical system, constructed of known elements (including a 1.6 F capacitor in a defined arrangement, proved the validity of the system and the method.

  17. Degradation of Bilayer Organic Light-Emitting Diodes Studied by Impedance Spectroscopy.

    Science.gov (United States)

    Sato, Shuri; Takata, Masashi; Takada, Makoto; Naito, Hiroyoshi

    2016-04-01

    The degradation of bilayer organic light-emitting diodes (OLEDs) with a device structure of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) (hole transport layer) and tris-(8-hydroxyquinolate)aluminum (Alq3) (emissive layer and electron transport layer) has been studied by impedance spectroscopy and device simulation. Two modulus peaks are found in the modulus spectra of the OLEDs below the electroluminescence threshold. After aging of the OLEDs, the intensity of electroluminescence is degraded and the modulus peak due to the Alq3 layer is shifted to lower frequency, indicating that the resistance of the Alq3 layer is increased. Device simulation reveals that the increase in the resistance of the Alq3 layer is due to the decrease in the electron mobility in the Alq3 layer.

  18. Interface design for CMOS-integrated Electrochemical Impedance Spectroscopy (EIS) biosensors.

    Science.gov (United States)

    Manickam, Arun; Johnson, Christopher Andrew; Kavusi, Sam; Hassibi, Arjang

    2012-10-29

    Electrochemical Impedance Spectroscopy (EIS) is a powerful electrochemical technique to detect biomolecules. EIS has the potential of carrying out label-free and real-time detection, and in addition, can be easily implemented using electronic integrated circuits (ICs) that are built through standard semiconductor fabrication processes. This paper focuses on the various design and optimization aspects of EIS ICs, particularly the bio-to-semiconductor interface design. We discuss, in detail, considerations such as the choice of the electrode surface in view of IC manufacturing, surface linkers, and development of optimal bio-molecular detection protocols. We also report experimental results, using both macro- and micro-electrodes to demonstrate the design trade-offs and ultimately validate our optimization procedures.

  19. Investigation of the suppression effect of polyethylene glycol on copper electroplating by electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    Hung, C.-C.; Lee, W.-H.; Wang, Y.-L.; Chan, D.-Y.; Hwang, G.-J.

    2008-01-01

    Polyethylene glycol (PEG) is an additive that is commonly used as a suppressor in the semiconductor copper (Cu)-electroplating process. In this study, electrochemical impedance spectroscopy (EIS) was used to analyze the electrochemical behavior of PEG in the Cu-electroplating process. Polarization analysis, cyclic-voltammetry stripping, and cell voltage versus plating time were examined to clarify the suppression behavior of PEG. The equivalent circuit simulated from the EIS data shows that PEG inhibited the Cu-electroplating rate by increasing the charge-transfer resistance as well as the resistance of the adsorption layer. The presence of a large inductance demonstrated the strong adsorption of cuprous-PEG-chloride complexes on the Cu surface during the Cu-electroplating process. Increasing the PEG concentration appears to increase the resistances of charge transfer, the adsorption layer, and the inductance of the electroplating system

  20. Diagnosis of Lithium-Ion Batteries State-of-Health based on Electrochemical Impedance Spectroscopy Technique

    DEFF Research Database (Denmark)

    Stroe, Daniel Ioan; Swierczynski, Maciej Jozef; Stan, Ana-Irina

    2014-01-01

    Lithium-ion batteries have developed into a popular energy storage choice for a wide range of applications because of their superior characteristics in comparison to other energy storage technologies. Besides modelling the performance behavior of Lithium-ion batteries, it has become of huge...... interest to accurately diagnose their state-of-health (SOH). At present, Lithium-ion batteries are diagnosed by performing capacity or resistance (current pulse) measurements; however, in the majority of the cases, these measurements are time consuming and result in changing the state of the battery...... as well. This paper investigates the use of the electrochemical impedance spectroscopy (EIS) technique for SOH diagnosis of Lithium-ion battery cells, instead of using the aforementioned techniques, since this new method allows for online and direct measurement of the battery cell response in any working...

  1. Electrochemical impedance spectroscopy study of the metal hydride alloy/electrolyte junction

    International Nuclear Information System (INIS)

    Khaldi, Chokri; Mathlouthi, Hamadi; Lamloumi, Jilani

    2009-01-01

    The behaviour of the LaNi 3.55 Mn 0.4 Al 0.3 Co 0.75 alloy, used as a negative electrode in the Ni-MH batteries, was studied by the electrochemical impedance spectroscopy (EIS), measured at different potentials. The modeling of the EIS spectra allows us to model the interface electrolyte/Ni-MH electrode by a succession of interfaces electrolyte/corrosion film/alloy particles. The various processes and the physics parameters of each interface are discussed and evaluated. When the potential shifts to more negative values, two reactions are in competition: the hydrogen molecular evolution and the hydrogen atomic absorption. The hydrogen diffuses in the bulk of the alloy and the diffusion is not the limiting factor for the hydrogen absorption.

  2. Electrochemical Impedance Spectroscopy Studies of Magnesium-Based Polymethylmethacrylate Gel Polymer Electroytes

    International Nuclear Information System (INIS)

    Osman, Z.; Zainol, N.H.; Samin, S.M.; Chong, W.G.; Md Isa, K.B.; Othman, L.; Supa’at, I.; Sonsudin, F.

    2014-01-01

    Magnesium-based rechargeable batteries might be an interesting future alternative to lithium-based batteries since magnesium compounds are highly abundant in the earth and are environmental friendly. In this work, we have prepared polymethylmethacrylate (PMMA) based gel polymer electrolyte (GPE) films containing two different magnesium salts, which is magnesium triflate, Mg(CF 3 SO 3 ) 2 and magnesium perchlorate, Mg(ClO 4 ) 2 using solution casting technique . The ionic conductivity of both gel polymer electrolyte systems was evaluated using a.c impedance spectroscopy. Results show that at room temperature, GPE-Mg(CF 3 SO 3 ) 2 system exhibits the highest conductivity value at 1.27 × 10 −3 S cm −1 for the film containing 20 wt.% of Mg(CF 3 SO 3 ) 2 salt, while the highest conductivity value for the GPE-Mg(ClO 4 ) 2 system is 3.13 × 10 −3 S cm −1 for the film containing 15 wt.% of Mg(ClO 4 ) 2 salt. The conductivity-temperature studies of both GPE systems follow the Arrhenius behavior. The activation energies for ionic conduction were determined to be in the range of 0.18–0.26 eV. The transport numbers of magnesium ions in both GPE systems were evaluated using the combination of a.c impedance spectroscopy and d.c polarization techniques. The results obtained indicate that the charge carriers in the GPE films for both systems are predominantly due to ions

  3. Impedance spectroscopy of organic magnetoresistance devices—Effect of interface disorder

    International Nuclear Information System (INIS)

    Fayolle, M.; Yamaguchi, M.; Ohto, T.; Tada, H.

    2015-01-01

    Organic magnetoresistance (OMAR) can be caused by either single carrier (bipolaron) or double carriers (electron-hole)-based mechanisms. In order to consider applications for OMAR, it is important to control the mechanism present in the device. In this paper, we report the effect of traps on OMAR resulting of disorder at the interface between the organic active layer with the hole injection layer [poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate): PEDOT:PSS]. It has been found that while the single carriers OMAR is enhanced by the presence of traps, the double carriers OMAR is totally removed in a sample with a high interface trap density. The reasons for these results are discussed based on the impedance spectroscopy measurements. First, the mechanism (single or double carriers) responsible of the OMAR was determined with the support of the capacitance measurement. Then, the influence of traps was discussed with the Nyquist diagrams and phase angle-frequency plots of the samples. The results suggested that with a rough interface and thus high disorder, the presence of traps enhanced the bipolaron formation. Traps also acted as recombination centers for electron-hole pairs, which prevented the double carriers OMAR in devices with a rough interface. On the other hand, with a low trap density, i.e., with a smooth surface, the single carrier OMAR decreased, and double carriers OMAR appeared. The sign of the OMAR could then be controlled by simply sweeping the bias voltage. This work demonstrated that the roughness at the interface is important for controlling OMAR and its reproducibility, and that the combination of OMAR measurement and impedance spectroscopy is helpful for clarifying the processes at the interface

  4. Electrochemical impedance spectroscopy and corrosion behaviour of Al2O3-Ni nano composite coatings

    International Nuclear Information System (INIS)

    Ciubotariu, Alina-Crina; Benea, Lidia; Lakatos-Varsanyi, Magda; Dragan, Viorel

    2008-01-01

    In this paper, the results on the electrochemical impedance spectroscopy and corrosion properties of electrodeposited nanostructured Al 2 O 3 -Ni composite coatings are presented. The nanocomposite coatings were obtained by codeposition of alumina nanoparticles (13 nm) with nickel during plating process. The coating thickness was 50 μm on steel support and an average of nano Al 2 O 3 particles inside of coatings at 15 vol.% was present. The structure of the coatings was investigated by scanning electron microscopy (SEM). It has been found that the codeposition of Al 2 O 3 particles with nickel disturbs the nickel coating's regular surface structure. The electrochemical behavior of the coatings in the corrosive solutions was investigated by polarization potentiodynamic and electrochemical impedance spectroscopy methods. As electrochemical test solutions 0.5 M sodium chloride and 0.5 M potassium sulphate were used in a three electrode open cell. The corrosion potential is shifted to more negative values for nanostructured coatings in 0.5 M sodium chloride. The polarization resistance in 0.5 M sodium chloride decreases in 24 h, but after that increases slowly. In 0.5 M potassium sulphate solution the polarization resistance decreases after 2 h and after 30 h of immersion the polarization resistance is higher than that of the beginning value. The corrosion rate calculated by polarization potentiodynamic curves obtained after 30 min from immersion in solution is smaller for nanostructured coatings in 0.5 M potassium sulphate (4.74 μm/year) and a little bit bigger in 0.5 M sodium chloride (5.03 μm/year)

  5. Bubble boundary estimation in an annulus two-phase flow using electrical impedance tomography

    International Nuclear Information System (INIS)

    Lee, Jeong Seong

    2008-02-01

    For the visualization of the phase boundary in an annulus two-phase flows, the electrical impedance tomography (EIT) technique is introduced. In EIT, a set of predetermined electrical currents is injected trough the electrodes placed on the boundary of the flow passage and the induced electrical potentials are measured on the electrode. With the relationship between the injected currents and the induced voltages, the electrical conductivity distribution across the flow domain is estimated through the image reconstruction algorithm. In this, the conductivity distribution corresponds to the phase distribution. In the application of EIT to two-phase flows where there are only two conductivity values, the conductivity distribution estimation problem can be transformed into the boundary estimation problem. This paper considers a bubble boundary estimation with EIT in an annulus two-phase flows. And in many industrial cases there are a priori known internal structures inside the vessels which could be used as internal electrodes in tomographical imaging. In this paper internal electrodes were considered in electrical impedance tomography. As the image reconstruction algorithm, the unscented Kalman filter (UKF) is adopted since from the control theory it is reported that the UKF shows better performance than the extended Kalman filter (EKF) that has been commonly used. The UKF algorithm was formulated to be incorporate into the image reconstruction algorithm for the present problem. Also, phantom experiments have been conducted to evaluate the improvement by UKF

  6. Investigation of conduction and relaxation phenomena in BaZrxTi1-xO3 (x=0.05) by impedance spectroscopy

    Science.gov (United States)

    Mahajan, Sandeep; Haridas, Divya; Ali, S. T.; Munirathnam, N. R.; Sreenivas, K.; Thakur, O. P.; Prakash, Chandra

    2014-10-01

    In present study we have prepared ferroelectric BaZrxTi1-xO3 (x=0.05) ceramic by conventional solid state reaction route and studied its electrical properties as a function of temperature and frequency. X-ray diffraction (XRD) analysis shows single-phase formation of the compound with orthorhombic crystal structure at room temperature. Impedance and electric modulus spectroscopy analysis in the frequency range of 40 Hz-1 MHz at high temperature (200-600 °C) suggests two relaxation processes with different time constant are involved which are attributed to bulk and grain boundary effects. Frequency dependent dielectric plot at different temperature shows normal variation with frequency while dielectric loss (tanδ) peak was found to obey an Arrhenius law with activation energy of 1.02 eV. The frequency-dependent AC conductivity data were also analyzed in a wide temperature range. In present work we have studied the role of grain and grain boundaries on the electrical behaviour of Zr-doped BaTiO3 and their dependence on temperature and frequency by complex impedance and modulus spectroscopy (CIS) technique in a wide frequency (40 Hz-1 MHz) and high temperature range.

  7. Frequency-Division Multiplexing for Electrical Impedance Tomography in Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Yair Granot

    2007-01-01

    Full Text Available Electrical impedance tomography (EIT produces an image of the electrical impedance distribution of tissues in the body, using electrodes that are placed on the periphery of the imaged area. These electrodes inject currents and measure voltages and from these data, the impedance can be computed. Traditional EIT systems usually inject current patterns in a serial manner which means that the impedance is computed from data collected at slightly different times. It is usually also a time-consuming process. In this paper, we propose a method for collecting data concurrently from all of the current patterns in biomedical applications of EIT. This is achieved by injecting current through all of the current injecting electrodes simultaneously, and measuring all of the resulting voltages at once. The signals from various current injecting electrodes are separated by injecting different frequencies through each electrode. This is called frequency-division multiplexing (FDM. At the voltage measurement electrodes, the voltage related to each current injecting electrode is isolated by using Fourier decomposition. In biomedical applications, using different frequencies has important implications due to dispersions as the tissue's electrical properties change with frequency. Another significant issue arises when we are recording data in a dynamic environment where the properties change very fast. This method allows simultaneous measurements of all the current patterns, which may be important in applications where the tissue changes occur in the same time scale as the measurement. We discuss the FDM EIT method from the biomedical point of view and show results obtained with a simple experimental system.

  8. Bioelectrical impedance spectroscopy as a fluid management system in heart failure

    International Nuclear Information System (INIS)

    Weyer, Sören; Wartzek, Tobias; Leicht, Lennart; Leonhardt, Steffen; Zink, Matthias Daniel; Mischke, Karl; Vollmer, Thomas

    2014-01-01

    Episodes of hospitalization for heart failure patients are frequent and are often accompanied by fluid accumulations. The change of the body impedance, measured by bioimpendace spectroscopy, is an indicator of the water content. The hypothesis was that it is possible to detect edema from the impedance data. First, a finite integration technique was applied to test the feasibility and allowed a theoretical analysis of current flows through the body. Based on the results of the simulations, a clinical study was designed and conducted. The segmental impedances of 25 patients suffering from heart failure were monitored over their recompensation process. The mean age of the patients was 73.8 and their mean body mass index was 28.6. From these raw data the model parameters from the Cole model were deduced by an automatic fitting algorithm. These model data were used to classify the edema status of the patient. The baseline values of the regression lines of the extra- and intracellular resistance from the transthoracic measurement and the baseline value of the regression line of the extracellular resistance from the foot-to-foot measurement were identified as important parameters for the detection of peripheral edema. The rate of change of the imaginary impedance at the characteristic frequency and the mean intracellular resistance from the foot-to-foot measurement were identified as important parameters for the detection of pulmonary edema. To classify the data, two decision trees were considered: One should detect pulmonary edema (n pulmonary = 13, n none = 12) and the other peripheral edema (n peripheral = 12, n none = 13). Peripheral edema could be detected with a sensitivity of 100% and a specificity of 90%. The detection of pulmonary edema showed a sensitivity of 92.31% and a specificity of 100%. The leave-one-out cross-validation-error for the peripheral edema detection was 12% and 8% for the detection of pulmonary edema. This enables the application of BIS as an

  9. Lipid Bilayer Membrane in a Silicon Based Micron Sized Cavity Accessed by Atomic Force Microscopy and Electrochemical Impedance Spectroscopy.

    Science.gov (United States)

    Khan, Muhammad Shuja; Dosoky, Noura Sayed; Patel, Darayas; Weimer, Jeffrey; Williams, John Dalton

    2017-07-05

    Supported lipid bilayers (SLBs) are widely used in biophysical research to probe the functionality of biological membranes and to provide diagnoses in high throughput drug screening. Formation of SLBs at below phase transition temperature ( Tm ) has applications in nano-medicine research where low temperature profiles are required. Herein, we report the successful production of SLBs at above-as well as below-the Tm of the lipids in an anisotropically etched, silicon-based micro-cavity. The Si-based cavity walls exhibit controlled temperature which assist in the quick and stable formation of lipid bilayer membranes. Fusion of large unilamellar vesicles was monitored in real time in an aqueous environment inside the Si cavity using atomic force microscopy (AFM), and the lateral organization of the lipid molecules was characterized until the formation of the SLBs. The stability of SLBs produced was also characterized by recording the electrical resistance and the capacitance using electrochemical impedance spectroscopy (EIS). Analysis was done in the frequency regime of 10 -2 -10⁵ Hz at a signal voltage of 100 mV and giga-ohm sealed impedance was obtained continuously over four days. Finally, the cantilever tip in AFM was utilized to estimate the bilayer thickness and to calculate the rupture force at the interface of the tip and the SLB. We anticipate that a silicon-based, micron-sized cavity has the potential to produce highly-stable SLBs below their Tm . The membranes inside the Si cavity could last for several days and allow robust characterization using AFM or EIS. This could be an excellent platform for nanomedicine experiments that require low operating temperatures.

  10. Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems

    Science.gov (United States)

    Weigand, Maximilian; Kemna, Andreas

    2017-02-01

    A better understanding of root-soil interactions and associated processes is essential in achieving progress in crop breeding and management, prompting the need for high-resolution and non-destructive characterization methods. To date, such methods are still lacking or restricted by technical constraints, in particular the charactization and monitoring of root growth and function in the field. A promising technique in this respect is electrical impedance tomography (EIT), which utilizes low-frequency (response in alternating electric-current fields due to electrical double layers which form at cell membranes. This double layer is directly related to the electrical surface properties of the membrane, which in turn are influenced by nutrient dynamics (fluxes and concentrations on both sides of the membranes). Therefore, it can be assumed that the electrical polarization properties of roots are inherently related to ion uptake and translocation processes in the root systems. We hereby propose broadband (mHz to hundreds of Hz) multi-frequency EIT as a non-invasive methodological approach for the monitoring and physiological, i.e., functional, characterization of crop root systems. The approach combines the spatial-resolution capability of an imaging method with the diagnostic potential of electrical-impedance spectroscopy. The capability of multi-frequency EIT to characterize and monitor crop root systems was investigated in a rhizotron laboratory experiment, in which the root system of oilseed plants was monitored in a water-filled rhizotron, that is, in a nutrient-deprived environment. We found a low-frequency polarization response of the root system, which enabled the successful delineation of its spatial extension. The magnitude of the overall polarization response decreased along with the physiological decay of the root system due to the stress situation. Spectral polarization parameters, as derived from a pixel-based Debye decomposition analysis of the multi

  11. Faradaic Impedance Spectroscopy for Detection of Small Molecules Binding using the Avidin-Biotin Model

    International Nuclear Information System (INIS)

    Yoetz-Kopelman, Tal; Ram, Yaron; Freeman, Amihay; Shacham-Diamand, Yosi

    2015-01-01

    The changes in the Faradaic impedance of gold/biomolecules system due to specific binding of small molecule to a significantly larger binding protein molecule were investigated. The biotin (244.31 Da) - avidin (66000 Da) couple was used as a model for small ligand - binding protein biorecognition. The study was carried out under open circuit potential in the presence of [Fe(CN) 6 ] −3/−4 redox couple. An equivalent electrical circuit was proposed and used for the interpretation of the recorded impedance spectra. Adsorption of thiolated avidin increased the electron transfer resistance, R ct , by a factor of about 7.5 while subsequent addition of biotin within the concentration range of 4.1-40.9 nM reduced the value of R ct by amount proportional to the biotin concentration. The addition of biotin did not affect, however, the equivalent double layer capacitance or other equivalent circuit parameters. A simple model based on effective surface coverage by the avidin molecules and the effect of the added biotin on electron transfer through the coated surface is proposed. A model for the minimum detection limit based on the random distribution of the binding protein and its dimensions is proposed

  12. Electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes: FFT-impedance spectroscopy of the growth process and magnetic properties.

    Science.gov (United States)

    Gerngross, Mark-Daniel; Carstensen, Jürgen; Föll, Helmut

    2014-01-01

    The electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes has been investigated by fast Fourier transform-impedance spectroscopy (FFT-IS) in the frequency range from 75 Hz to 18.5 kHz. The impedance data could be fitted very well using an electric circuit equivalent model with a series resistance connected in series to a simple resistor-capacitor (RC) element and a Maxwell element. Based on the impedance data, the Co deposition in ultra-high aspect ratio InP membranes can be divided into two different Co deposition processes. The corresponding share of each process on the overall Co deposition can be determined directly from the transfer resistances of the two processes. The impedance data clearly show the beneficial impact of boric acid on the Co deposition and also indicate a diffusion limitation of boric acid in ultra-high aspect ratio InP membranes. The grown Co nanowires are polycrystalline with a very small grain size. They show a narrow hysteresis loop with a preferential orientation of the easy magnetization direction along the long nanowire axis due to the arising shape anisotropy of the Co nanowires.

  13. Studi Electrochemical Impedance Spectroscopy dari Lembaran Polyvinyl Alcohol dengan Penambahan Liclo4 sebagai Bahan Elektolit Baterai Li-ion

    OpenAIRE

    Gunawan, Indra; Wahyudianingsih, Wahyudianingsih; Sudaryanto, Sudaryanto

    2016-01-01

    ELECTROCHEMICALIMPEDANCE SPECTROSCOPY STUDY OF POLYVINYL ALCOHOL SHEETWITHADDITION OFLiClO4AS ELECTROLYTE MATERIAL OF Li-ION BATTERAY. Solid polymer electrolyte materials for Li ion battery have been prepared using polyvinyl alcohol (PVA) added by lithium perchlorate (LiClO4) salt with various concentration. Electrochemical Impedance Spectroscopy (EIS) study of the material was done by making a Nyquist plot of the measurement with a LCR meter. These electrolyte materials prepared by using PVA...

  14. Effects of polydeoxyribonucleotides (PDRN) on wound healing: Electric cell-substrate impedance sensing (ECIS)

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Youngmi; Yun, Yeoheung, E-mail: yyun@ncat.edu

    2016-12-01

    Polydeoxyribonucleotides (PDRN) have been explored as an effective treatment for tissue repair in peripheral artery occlusive disease, diabetic foot ulcers, and eye lotion. We report on the effect of polydeoxyribonucleotides (PDRN) on wound healing by using the electric cell-substrate impedance sensing (ECIS) system and viability testing. Human osteoblasts (U2OS) and primary human dermal fibroblasts (HDF) were used to study the effect of PDRN on migration and proliferation. ECIS allowed the creation of a wound by applying high current, and then monitoring the healing process by measuring impedance in real time. The traditional culture-insert gap-closure migration assay was performed and compared with the ECIS wound assay. PDRN-treated U2OS and HDF cells affected cell motilities to wounding site. Viability test results show that HDF and U2OS proliferation depended on PDRN concentration. Based on the results, a PDRN compound can be useful in wound healing associated with bone and skin. - Highlights: • Wound-healing study by the electric cell-substrate impedance sensing (ECIS). • Effect of polydeoxyribonucleotides (PDRN) on migration and proliferation of U2OS and HDF. • Effect of PDRN concentration on viability of U2OS and HDF.

  15. Effects of polydeoxyribonucleotides (PDRN) on wound healing: Electric cell-substrate impedance sensing (ECIS)

    International Nuclear Information System (INIS)

    Koo, Youngmi; Yun, Yeoheung

    2016-01-01

    Polydeoxyribonucleotides (PDRN) have been explored as an effective treatment for tissue repair in peripheral artery occlusive disease, diabetic foot ulcers, and eye lotion. We report on the effect of polydeoxyribonucleotides (PDRN) on wound healing by using the electric cell-substrate impedance sensing (ECIS) system and viability testing. Human osteoblasts (U2OS) and primary human dermal fibroblasts (HDF) were used to study the effect of PDRN on migration and proliferation. ECIS allowed the creation of a wound by applying high current, and then monitoring the healing process by measuring impedance in real time. The traditional culture-insert gap-closure migration assay was performed and compared with the ECIS wound assay. PDRN-treated U2OS and HDF cells affected cell motilities to wounding site. Viability test results show that HDF and U2OS proliferation depended on PDRN concentration. Based on the results, a PDRN compound can be useful in wound healing associated with bone and skin. - Highlights: • Wound-healing study by the electric cell-substrate impedance sensing (ECIS). • Effect of polydeoxyribonucleotides (PDRN) on migration and proliferation of U2OS and HDF. • Effect of PDRN concentration on viability of U2OS and HDF.

  16. Development of an electrical impedance computed tomographic two-phase flows analyzer. Annual technical report for program renewal

    Energy Technology Data Exchange (ETDEWEB)

    Jones, O.C.

    1993-05-01

    This progress report details the theoretical development, numerical results, experimental design (mechanical), experimental design (electronic), and experimental results for the research program for the development of an electrical impedance computed tomographic two-phase flow analyzer.

  17. Exploratory study on the methodology of fast imaging of unilateral stroke lesions by electrical impedance asymmetry in human heads.

    Science.gov (United States)

    Ma, Jieshi; Xu, Canhua; Dai, Meng; You, Fusheng; Shi, Xuetao; Dong, Xiuzhen; Fu, Feng

    2014-01-01

    Stroke has a high mortality and disability rate and should be rapidly diagnosed to improve prognosis. Diagnosing stroke is not a problem for hospitals with CT, MRI, and other imaging devices but is difficult for community hospitals without these devices. Based on the mechanism that the electrical impedance of the two hemispheres of a normal human head is basically symmetrical and a stroke can alter this symmetry, a fast electrical impedance imaging method called symmetrical electrical impedance tomography (SEIT) is proposed. In this technique, electrical impedance tomography (EIT) data measured from the undamaged craniocerebral hemisphere (CCH) is regarded as reference data for the remaining EIT data measured from the other CCH for difference imaging to identify the differences in resistivity distribution between the two CCHs. The results of SEIT imaging based on simulation data from the 2D human head finite element model and that from the physical phantom of human head verified this method in detection of unilateral stroke.

  18. Impedance spectroscopy of micro-Droplets reveals activation of Bacterial Mechanosensitive Channels in Hypotonic Solutions

    Science.gov (United States)

    Ebrahimi, Aida; Alam, Muhammad A.

    Rapid detection of bacterial pathogens is of great importance in healthcare, food safety, environmental monitoring, and homeland security. Most bacterial detection platforms rely on binary fission (i.e. cell growth) to reach a threshold cell population that can be resolved by the sensing method. Since cell division depends on the bacteria type, the detection time of such methods can vary from hours to days. In contrast, in this work, we show that bacteria cells can be detected within minutes by relying on activation of specific protein channels, i.e. mechanosensitive channels (MS channels). When cells are exposed to hypotonic solutions, MS channels allow efflux of solutes to the external solution which leads to release the excessive membrane tension. Release of the cytoplasmic solutes, in turn, results in increase of the electrical conductance measured by droplet-based impedance sensing. The approach can be an effective technique for fast, pre-screening of bacterial contamination at ultra-low concentration.

  19. Electrochemical impedance spectroscopy (EIS) as a tool for measuring corrosion of polymer-coated fasteners used in treated wood

    Science.gov (United States)

    Samuel L. Zelinka; Lorraine Ortiz-Candelaria; Donald S. Stone; Douglas R. Rammer

    2009-01-01

    Currently, many of the polymer-coated fasteners on the market are designed for improved corrosion performance in treated wood; yet, there is no way to evaluate their corrosion performance. In this study, a common technique for measuring the corrosion performance of polymer-coated metals, electrochemical impedance spectroscopy (EIS), was used to evaluate commercial...

  20. The use of odd random phase electrochemical impedance spectroscopy to study lithium-based corrosion inhibition by active protective coatings

    NARCIS (Netherlands)

    Meeusen, M.; Visser, P.; Fernández Macía, L.; Hubin, A.; Terryn, H.A.; Mol, J.M.C.

    2018-01-01

    In this work, the study of the time-dependent behaviour of lithium carbonate based inhibitor technology for the active corrosion protection of aluminium alloy 2024-T3 is presented. Odd random phase electrochemical impedance spectroscopy (ORP-EIS) is selected as the electrochemical tool to study

  1. a Study of the Electrical Impedance of Erythrocyte Membranes the Effects of Temperature and Radiation.

    Science.gov (United States)

    Gerig, Lee Harvey

    The purpose of this work was to investigate the electrical impedance properties of Human Erythrocytes suspended in normal saline and specifically how radiation and temperature affected these properties. The cells were obtained by venepuncture from normal adult volunteers, washed three times and resuspended in phosphate buffered saline. The cells were irradiated by ('60)Co gamma rays to doses varying from 500 to 20,000 rads. The electrical impedance was measured using a computerized measurement and data acquisition system developed in the Biophysics Laboratory, School of Physics, University of New South Wales. The measurements were performed employing a four terminal technique and a digitally synthesized sine wave. The measurements revealed that nonirradiated blood from any specific individual had reproducible electrical properties from day to day and that there were only small differences in the electrical properties of blood from the various individuals sampled. This data displayed complex structure in both the capacitance versus frequency and conductance versus frequency curves. Of great interest was the dependence on the time post venesection, indicating a continual change in the state of the cells after removal from their natural environment. The experiments also revealed a non linear temperature dependence and a significant change in the suspension impedance as a function of absorbed dose. A model of the system was introduced which was able to emulate most of the measured phenomena. Studies of how the model can be adapted to fit the measured data for various cases (eg. time, temperature, radiation dose) suggested various physiological processes occurring within the membrane. The results were indicative of effects such as radiation induced changes in the lipid hydrocarbon region, the presence of a complex protein structure, the dissociation of charge within the protein, the presence of electrogenic pumps, and the destruction of the lipid matrix by radiation

  2. Effect of the number of electrodes on the reconstructed lung shape in electrical impedance tomography

    Directory of Open Access Journals (Sweden)

    Schullcke Benjamin

    2016-09-01

    Full Text Available Electrical impedance tomography (EIT is used to monitor the regional distribution of ventilation in a transversal plane of the thorax. In this manuscript we evaluate the impact of different quantities of electrodes used for current injection and voltage measurement on the reconstructed shape of the lungs. Results indicate that the shape of reconstructed impedance changes in the body depends on the number of electrodes. In this manuscript, we demonstrate that a higher number of electrodes do not necessarily increase the image quality. For the used stimulation pattern, utilizing neighboring electrodes for current injection and voltage measurement, we conclude that the shape of the lungs is best reconstructed if 16 electrodes are used.

  3. Study of NiO cathode modified by rare earth oxide additive for MCFC by electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    Huang Bo; Chen Gang; Li Fei; Yu Qingchun; Hu Keao

    2004-01-01

    The preparation and subsequent oxidation of nickel cathodes modified by impregnation with rare earth oxide were evaluated by surface and bulk analysis. The electrochemical behaviors of rare earth oxide impregnated nickel oxide cathodes were also evaluated in a molten 62 mol% Li 2 CO 3 +38 mol% K 2 CO 3 eutectic at 650 deg. C by electrochemical impedance spectroscopy (EIS) as a function of rare earth oxide content and immersion time. The rare earth oxide-impregnated nickel cathodes show almost the similar porosity, pore size, and morphology to the reference nickel cathode. The stability tests of rare earth oxide-impregnated nickel oxide cathodes show that the rare earth oxide additive can dramatically reduce the solubility of nickel oxide in a eutectic carbonate mixture under the standard cathode gas condition. The impedance response of all cathode materials at different immersion time is characterized by the presence of depressed semicircles in the high frequency range changing over into the lines with the angles of which observed with the real axis differing 45 deg. or 90 deg. in the low frequency range. The experimental Nyquist plots can be well analyzed theoretically with a modified model based on the well-known Randles-Ershler equivalent circuit model. In the new model, the double layer capacity (C d ) is replaced by the parallel combination of C d and b/ω; therefore, this circuit is modified to be the parallel combination of (C d ), b/ω, and the charge transfer resistance (R ct ) based on the Randles-Ershler equivalent circuit, to take into consideration both the non-uniformity of electric field at the electrode/electrolyte interface owing to the roughness of electrode surface, and the variety of relaxation times with adsorbed species on the electrode surface. The impedance spectra for all cathode materials show important variations during the 200 h of immersion. The incorporation of lithium in its structure and the low dissolution of nickel oxide and rare

  4. Impedance spectroscopy studies on lead free (Ba0.85Ca0.15(Ti0.9Zr0.1O3 ceramics

    Directory of Open Access Journals (Sweden)

    Ahcène Chaouchi

    2012-12-01

    Full Text Available The AC complex impedance spectroscopy technique has been used to obtain the electrical parameters of polycrystalline sample of (Ba0.85Ca0.15(Ti0.9Zr0.1O3 in a wide frequency range at different temperatures. This sample was prepared by a high temperature solid-state reaction technique and single phase formation was confirmed by X-ray diffraction technique. This study was carried out by the means of simultaneous analysis of impedance, modulus, and electrical conductivity. The Cole-Cole (Nyquist plots suggest that the grains and grain boundaries are responsible in the conduction mechanism of the material at high temperature. The ColeCole (Nyquist plot studies revealed the presence of grain and grain boundary effect at 485 °C. On the other hand, it showed only the presence of grain boundary component of the resistivity at 535 °C. Complex impedance analysis indicated the presence of non-Debye type dielectric relaxation. The bulk resistance of the material decreases with rise in temperature similar to a semiconductor, and the Cole-Cole (Nyquist plot showed the negative temperature coefficient of resistance (NTCR character of (Ba0.85Ca0.15(Ti0.9Zr0.1O3. The value of activation energy is found to be 0.7433 eV, which suggests that the conduction may be the result of defect and charge carriers present in the materials.

  5. Frequency effects on charge ordering in Y{sub 0.5}Ca{sub 0.5}MnO{sub 3} by impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sarwar, Tuba, E-mail: sarwartuba@gmail.com [EMMG, Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); DPAM, PIEAS, P. O. Nilore, Islamabad (Pakistan); Qamar, Afzaal [Queensland Micro-Nanotechnology Centre, Griffith University, Nathan, QLD 4111 (Australia); Nadeem, Muhammad [EMMG, Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan)

    2015-02-01

    In this work, structural and electrical properties of Y{sub 0.5}Ca{sub 0.5}MnO{sub 3} are investigated by employing X-ray diffraction and impedance spectroscopy, respectively. Applied ac electric field showed the charge ordering transition temperature around 265 K and below this temperature the heteromorphic behavior of the sample is discussed in the proximity of T{sub CO}. With frequency effects the volume of robust charge orbital ordering (COO) domains diminishes due to different competing phases along with Jahn Teller distortions. Comprehensive melting and collapse of charge orbital ordering occurs below T{sub N}(125 K), where a colossal drop in the value of impedance is observed. The change in profile of modulus plane plots determines the spreading of relaxation time of intermingled phases. Hopping mechanism is elaborated in terms of strong electron phonon coupling. Variable range hopping model and Arrhenius model are used to discuss the short and long range hopping between Mn{sup 3+} and Mn{sup 4+} channels assessing the activation energy E{sub a}. - Highlights: • Present study contains a detailed investigation over the electrical and structural properties of Y{sub 0.5}Ca{sub 0.5}MnO{sub 3} especially its behavior across the charge ordering transition. • Impedance measurements illustrate the comprehensive melting and collapse of robust charge orbital ordering with colossal drop in impedance. • In T{sub N}

  6. Impedance spectroscopy of p-ZnGa{sub 2}Te{sub 4}/n-Si nano-HJD

    Energy Technology Data Exchange (ETDEWEB)

    Fouad, S.S. [Thin film Laboratory, Department of Physics, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Sakr, G.B. [Nano-Science Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Yahia, I.S., E-mail: dr_isyahia@yahoo.com [Nano-Science Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Semiconductor Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); Abdel-Basset, D.M. [Nano-Science Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Yakuphanoglu, F. [Department of Physics, Faculty of Science, Firat University, Elazig (Turkey)

    2013-04-15

    The dielectric relaxation and alternating current mechanisms of nano-crystalline p-ZnGa{sub 2}Te{sub 4}/n-Si heterojunction diode (HJD) were investigated by complex impedance spectroscopy over a wide range of temperature (297–473 K) and a frequency range (42 Hz–5 MHz). The bulk resistance R{sub b} as well as the bulk capacitance C{sub b} were found to increase with increasing temperature. The dc conductivity exhibits a typical Arrhenius behavior. The electrical activation energy ΔE{sub σ} was determined to be (0.28 eV). The ac conductivity spectrum was found to obey Jonscher's universal power law. The frequency exponent s decreases slightly with increasing temperature. The temperature dependence of ac conductivity can be reasonably interpreted in terms of the correlated barrier hopping (CBH) model. The dielectric constant ε{sub 1}(ω) and dielectric loss ε{sub 2}(ω) were found to decrease with increasing frequency and to increase with increasing temperature. The mean value of the exponent m decreases with increasing temperature. The dielectric analysis is described by non-Debye type behavior.

  7. Electrical characterization of bolus material as phantom for use in electrical impedance and computed tomography fusion imaging

    Directory of Open Access Journals (Sweden)

    Parvind Kaur Grewal

    2014-04-01

    Full Text Available Phantoms are widely used in medical imaging to predict image quality prior to clinical imaging. This paper discusses the possible use of bolus material, as a conductivity phantom, for validation and interpretation of electrical impedance tomography (EIT images. Bolus is commonly used in radiation therapy to mimic tissue. When irradiated, it has radiological characteristics similar to tissue. With increased research interest in CT/EIT fusion imaging there is a need to find a material which has both the absorption coefficient and electrical conductivity similar to biological tissues. In the present study the electrical properties, specifically resistivity, of various commercially available bolus materials were characterized by comparing their frequency response with that of in-vivo connective adipose tissue. It was determined that the resistivity of Gelatin Bolus is similar to in-vivo tissue in the frequency range 10 kHz to 1MHz and therefore has potential to be used in EIT/CT fusion imaging studies.

  8. Design and simulation of superconducting Lorentz Force Electrical Impedance Tomography (LFEIT)

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Boyang, E-mail: bs506@cam.ac.uk; Fu, Lin, E-mail: lf359@cam.ac.uk; Geng, Jianzhao, E-mail: jg717@cam.ac.uk; Zhang, Xiuchang, E-mail: xz326@cam.ac.uk; Zhang, Heng, E-mail: hz301@cam.ac.uk; Dong, Qihuan, E-mail: qd210@cam.ac.uk; Li, Chao, E-mail: cl644@cam.ac.uk; Li, Jing, E-mail: jl908@cam.ac.uk; Coombs, T.A., E-mail: tac1000@cam.ac.uk

    2016-05-15

    Highlights: • Design of superconducting magnets using Halbach Array configuration. • Combination of superconducting magnets together with Lorentz Force Electrical Impedance Tomography (LFEIT) system. • Simulation of superconducting LFEIT system based on the theory of magneto-acoustic effect. - Abstract: Lorentz Force Electrical Impedance Tomography (LFEIT) is a hybrid diagnostic scanner with strong capability for biological imaging, particularly in cancer and haemorrhages detection. This paper presents the design and simulation of a novel combination: a superconducting magnet together with LFEIT system. Superconducting magnets can generate magnetic field with high intensity and homogeneity, which could significantly enhance the imaging performance. The modelling of superconducting magnets was carried out using Finite Element Method (FEM) package, COMSOL Multiphysics, which was based on Partial Differential Equation (PDE) model with H-formulation coupling B-dependent critical current density and bulk approximation. The mathematical model for LFEIT system was built based on the theory of magneto-acoustic effect. The magnetic field properties from magnet design were imported into the LFEIT model. The basic imaging of electrical signal was developed using MATLAB codes. The LFEIT model simulated two samples located in three different magnetic fields with varying magnetic strength and homogeneity.

  9. Microstructure Evolution and Impedance Spectroscopy Characterization of Thermal Barrier Coating Exposed to Gas Thermal-shock Environment

    Directory of Open Access Journals (Sweden)

    CHEN Wen-long

    2017-10-01

    Full Text Available Gas thermal-shock experiment of thermal barrier coatings (TBCs was carried out in air up to 1250℃ in order to simulate the thermal cycling process of the engine blades during the start heating and shut down cooling. The growth of thermal growth oxide (TGO layer and microstructure evolution of YSZ layer during thermal cycling process were investigated systematically by electrochemical impedance spectroscopy testing and SEM. The results show that the thickness of TGO layer increases when increasing the frequency of thermal cycling, and the impedance response of middle frequencies is more and more remarkable. Meanwhile, initiation and growth of micro-cracks occur in YSZ layer during the gas thermal-shock experiment. The corresponding impedance characterization of YSZ layer after 100 cycles is similar to the as-sprayed sample, indicating that micro-cracks in short time could heal since the YSZ micro-cracks sinter at high temperature. But after 300 cycles, the impedance spectroscopy of YSZ layer is quite different to the as-sprayed sample, with the corresponding impedance of particle-gap of YSZ more and more remarkable with the increase of the thermal-shock times, indicating that non-healing micro-cracks form in the YSZ layer, which may be the main reason to induce the failure of YSZ layer.

  10. An analysis of electrical impedance tomography with applications to Tikhonov regularization

    KAUST Repository

    Jin, Bangti

    2012-01-16

    This paper analyzes the continuum model/complete electrode model in the electrical impedance tomography inverse problem of determining the conductivity parameter from boundary measurements. The continuity and differentiability of the forward operator with respect to the conductivity parameter in L p-norms are proved. These analytical results are applied to several popular regularization formulations, which incorporate a priori information of smoothness/sparsity on the inhomogeneity through Tikhonov regularization, for both linearized and nonlinear models. Some important properties, e.g., existence, stability, consistency and convergence rates, are established. This provides some theoretical justifications of their practical usage. © EDP Sciences, SMAI, 2012.

  11. Sensitivity analysis of magnetic field measurements for magnetic resonance electrical impedance tomography (MREIT)

    DEFF Research Database (Denmark)

    Göksu, Cihan; Scheffler, Klaus; Ehses, Philipp

    2017-01-01

    Purpose: Clinical use of magnetic resonance electrical impedance tomography (MREIT) still requires significant sensitivity improvements. Here, the measurement of the current-induced magnetic field (DBz,c) is improved using systematic efficiency analyses and optimization of multi-echo spin echo...... (MESE) and steady-state free precession free induction decay (SSFP-FID) sequences. Theory and Methods: Considering T1, T2, and T 2 relaxation in the signal-to-noise ratios (SNRs) of the MR magnitude images, the efficiency of MESE and SSFP-FID MREIT experiments, and its dependence on the sequence...

  12. Simultaneous reconstruction of outer boundary shape and conductivity distribution in electrical impedance tomography

    KAUST Repository

    Hyvönen, Nuutti

    2016-01-05

    The simultaneous retrieval of the exterior boundary shape and the interior admittivity distribution of an examined body in electrical impedance tomography is considered. The reconstruction method is built for the complete electrode model and it is based on the Frechet derivative of the corresponding current-to-voltage map with respect to the body shape. The reconstruction problem is cast into the Bayesian framework, and maximum a posteriori estimates for the admittivity and the boundary geometry are computed. The feasibility of the approach is evaluated by experimental data from water tank measurements.

  13. An analysis of electrical impedance tomography with applications to Tikhonov regularization

    KAUST Repository

    Jin, Bangti; Maass, Peter

    2012-01-01

    This paper analyzes the continuum model/complete electrode model in the electrical impedance tomography inverse problem of determining the conductivity parameter from boundary measurements. The continuity and differentiability of the forward operator with respect to the conductivity parameter in L p-norms are proved. These analytical results are applied to several popular regularization formulations, which incorporate a priori information of smoothness/sparsity on the inhomogeneity through Tikhonov regularization, for both linearized and nonlinear models. Some important properties, e.g., existence, stability, consistency and convergence rates, are established. This provides some theoretical justifications of their practical usage. © EDP Sciences, SMAI, 2012.

  14. Impedance Spectroscopy Study of the Effect of Environmental Conditions on the Microstructure Development of Sustainable Fly Ash Cement Mortars.

    Science.gov (United States)

    Ortega, José Marcos; Sánchez, Isidro; Climent, Miguel Ángel

    2017-09-25

    Today, the characterisation of the microstructure of cement-based materials using non-destructive techniques has become an important topic of study, and among them, the impedance spectroscopy has recently experienced great progress. In this research, mortars with two different contents of fly ash were exposed to four different constant temperature and relative humidity environments during a 180-day period. The evolution of their microstructure was studied using impedance spectroscopy, whose results were contrasted with mercury intrusion porosimetry. The hardening environment has an influence on the microstructure of fly ash cement mortars. On one hand, the impedance resistances R₁ and R₂ are more influenced by the drying of the materials than by microstructure development, so they are not suitable for following the evolution of the porous network under non-optimum conditions. On the other hand, the impedance spectroscopy capacitances C₁ and C₂ allow studying the microstructure development of fly ash cement mortars exposed to those conditions, and their results are in accordance with mercury intrusion porosimetry ones. Finally, it has been observed that the combined analysis of the abovementioned capacitances could be very useful for studying shrinkage processes in cement-based materials kept in low relative humidity environments.

  15. Gravity-dependent ventilation distribution in rats measured with electrical impedance tomography

    International Nuclear Information System (INIS)

    Rooney, Daniel; Fraser, John F; R Dunster, Kimble; Schibler, Andreas; Friese, Marlies

    2009-01-01

    Ventilation in larger animals and humans is gravity dependent and mainly distributed to the dependent lung. Little is known of the effect of gravity on ventilation distribution in small animals such as rodents. The aim of this study was to investigate gravity-dependent ventilation distribution and regional filling characteristics in rats. Ventilation distribution and regional lung filling were measured in six rats using electrical impedance tomography (EIT). Measurements were performed in four body positions (supine, prone, left and right lateral), and all animals were ventilated with increasing tidal volumes from 3 to 8 mL kg −1 . The effect of gravity on regional ventilation distribution was assessed with profiles of relative impedance change and calculation of the geometric centre. Regional filling was measured by calculating the slope of the plot of regional versus global relative impedance change on a breath-by-breath basis. Ventilation was significantly distributed to the non-dependent lung regardless of body position and tidal volume used. The geometric centre was located in the dependent lung in all but prone position. The regional filling characteristics followed an anatomical pattern with the posterior and the right lung generally filling faster. Gravity had little impact on regional filling. Ventilation distribution in rats is gravity dependent, whereas regional filling characteristics are dependent on anatomy

  16. Hardware Design of Tuber Electrical Resistance Tomography System Based on the Soil Impedance Test and Analysis

    Directory of Open Access Journals (Sweden)

    Liu Shuyi

    2016-01-01

    Full Text Available The hardware design of tuber electrical resistance tomography (TERT system is one of the key research problems of TERT data acquisition system. The TERT system can be applied to the tuber growth process monitoring in agriculture, i.e., the TERT data acquisition system can realize the real imaging of tuber plants in soil. In TERT system, the imaging tuber and soil multiphase medium is quite complexity. So, the impedance test and analysis of soil multiphase medium is very important to the design of sensitive array sensor subsystem and signals processing circuits. In the paper, the soil impedance test experimental is described and the results are analysed. The data acquisition hardware system is designed based on the result of soil medium impedance test and analysis. In the hardware design, the switch control chip ADG508, the instrumentation amplifier AD620 and programmable amplifier AD526 are employed. In the meantime, the phase locked loop technique for signal demodulation is introduced. The initial data collection is given and discussed under the conditions of existing plant tuber and no existing plant tuber. Conclusions of the hardware design of TERT system are presented.

  17. Real-time imaging of cerebral infarction in rabbits using electrical impedance tomography.

    Science.gov (United States)

    Yang, Bin; Shi, Xuetao; Dai, Meng; Xu, Canhua; You, Fushen; Fu, Feng; Liu, Ruigang; Dong, Xiuzhen

    2014-02-01

    To investigate the possible use of electrical impedance tomography (EIT) in monitoring focal cerebral infarction in a rabbit model. A model of focal cerebral infarction was established in eight New Zealand rabbits using a photochemical method without craniectomy. Focal cerebral infarction was confirmed by histopathological examination. Intracranial impedance variation was measured using 16 electrodes placed in a circle on the scalp. EIT images were obtained using a damped least-squares reconstruction algorithm. The average resistivity value (ARV) of the infarct region on EIT images was calculated to quantify relative resistivity changes. A symmetry index was calculated to evaluate the relative difference in resistivity between the two sides of the cerebrum. EIT images and ARV curves showed that impedance changes caused by cerebral infarction increased linearly with irradiation time. A difference in ARV was found between measurements taken before and after infarct induction. Focal cerebral infarction can be monitored by EIT in the proposed animal model. The results are sufficiently encouraging that the authors plan to extend this study to humans, after further technical improvements.

  18. Raman and impedance spectroscopy methods of P{sub 2}O{sub 5}–Li{sub 2}O–Al{sub 2}O{sub 3} glass system doped with MgO

    Energy Technology Data Exchange (ETDEWEB)

    Jlassi, I., E-mail: ifa.jlassi@fst.rnu.tn [Laboratoire Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Département de Physique, Faculté des Sciences de Tunis, Université de Tunis ElManar, Campus Universitaire Farhat Hachad, ElManar 2092 (Tunisia); Sdiri, N. [Laboratoire Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Elhouichet, H. [Laboratoire Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Département de Physique, Faculté des Sciences de Tunis, Université de Tunis ElManar, Campus Universitaire Farhat Hachad, ElManar 2092 (Tunisia); Ferid, M. [Laboratoire Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia)

    2015-10-05

    Highlights: • We have prepared a new lithium diphosphate glasses doped MgO. • Investigate structural and electrical properties at room temperature. • Investigate relation between structure and electrical conductivity of the glass. - Abstract: Lithium diphosphate glasses doped MgO was prepared via a melt quenching technique. The samples were characterized by X-ray diffraction (XRD), Raman and impedance spectroscopy. XRD spectra reflected the amorphous nature of the glasses Raman spectra show structural network modifications with the composition variations of the studied glasses. Raman spectra of the studied glasses contain also typical phosphate glasses bands. Thus the band at ∼698 cm{sup −1} assigned to symmetric stretching vibrations of P−O−P groups and that from ∼1168 cm{sup −1} is attributed to symmetric stretching motions of the non-bridging oxygen (NBO) atoms bonded to phosphorous atoms (PO{sub 2}) in phosphate tetrahedron. Electric properties were investigated using complex impedance spectroscopy in a frequency range from 40 Hz to 6 MHz at room temperature. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE). Constant-phase elements (CPE) are used in equivalent electrical circuits for the fitting of experimental impedance data. The AC conductivity exhibited a Jonscher’s universal power law according with the relation σ(ω) = σ(0) + Aω{sup s} and it is observed that as the MgO content increases, frequency exponent (s) decreases.

  19. Classification of breast tumour using electrical impedance and machine learning techniques

    International Nuclear Information System (INIS)

    Amin, Abdullah Al; Parvin, Shahnaj; Kadir, M A; Tahmid, Tasmia; Alam, S Kaisar; Siddique-e Rabbani, K

    2014-01-01

    When a breast lump is detected through palpation, mammography or ultrasonography, the final test for characterization of the tumour, whether it is malignant or benign, is biopsy. This is invasive and carries hazards associated with any surgical procedures. The present work was undertaken to study the feasibility for such characterization using non-invasive electrical impedance measurements and machine learning techniques. Because of changes in cell morphology of malignant and benign tumours, changes are expected in impedance at a fixed frequency, and versus frequency of measurement. Tetrapolar impedance measurement (TPIM) using four electrodes at the corners of a square region of sides 4 cm was used for zone localization. Data of impedance in two orthogonal directions, measured at 5 and 200 kHz from 19 subjects, and their respective slopes with frequency were subjected to machine learning procedures through the use of feature plots. These patients had single or multiple tumours of various types in one or both breasts, and four of them had malignant tumours, as diagnosed by core biopsy. Although size and depth of the tumours are expected to affect the measurements, this preliminary work ignored these effects. Selecting 12 features from the above measurements, feature plots were drawn for the 19 patients, which displayed considerable overlap between malignant and benign cases. However, based on observed qualitative trend of the measured values, when all the feature values were divided by respective ages, the two types of tumours separated out reasonably well. Using K-NN classification method the results obtained are, positive prediction value: 60%, negative prediction value: 93%, sensitivity: 75%, specificity: 87% and efficacy: 84%, which are very good for such a test on a small sample size. Study on a larger sample is expected to give confidence in this technique, and further improvement of the technique may have the ability to replace biopsy. (paper)

  20. Classification of breast tumour using electrical impedance and machine learning techniques.

    Science.gov (United States)

    Al Amin, Abdullah; Parvin, Shahnaj; Kadir, M A; Tahmid, Tasmia; Alam, S Kaisar; Siddique-e Rabbani, K

    2014-06-01

    When a breast lump is detected through palpation, mammography or ultrasonography, the final test for characterization of the tumour, whether it is malignant or benign, is biopsy. This is invasive and carries hazards associated with any surgical procedures. The present work was undertaken to study the feasibility for such characterization using non-invasive electrical impedance measurements and machine learning techniques. Because of changes in cell morphology of malignant and benign tumours, changes are expected in impedance at a fixed frequency, and versus frequency of measurement. Tetrapolar impedance measurement (TPIM) using four electrodes at the corners of a square region of sides 4 cm was used for zone localization. Data of impedance in two orthogonal directions, measured at 5 and 200 kHz from 19 subjects, and their respective slopes with frequency were subjected to machine learning procedures through the use of feature plots. These patients had single or multiple tumours of various types in one or both breasts, and four of them had malignant tumours, as diagnosed by core biopsy. Although size and depth of the tumours are expected to affect the measurements, this preliminary work ignored these effects. Selecting 12 features from the above measurements, feature plots were drawn for the 19 patients, which displayed considerable overlap between malignant and benign cases. However, based on observed qualitative trend of the measured values, when all the feature values were divided by respective ages, the two types of tumours separated out reasonably well. Using K-NN classification method the results obtained are, positive prediction value: 60%, negative prediction value: 93%, sensitivity: 75%, specificity: 87% and efficacy: 84%, which are very good for such a test on a small sample size. Study on a larger sample is expected to give confidence in this technique, and further improvement of the technique may have the ability to replace biopsy.

  1. Evaluation method for corrosion level of rebar in RC with electrical impedance measurement

    Science.gov (United States)

    Sasamoto, Akira

    2018-04-01

    The author reported that the impedance measurement using the 4-terminal method on the RC surface for diagnosing corrosion of internal rebar. The difference between the maximum value at 0.01 Hz and the minimum value around 10 Hz indicates the corrosion level of rebar in that report. This is successive report on a signal processing method for estimating the corrosion level by the measured impedance data to obtain more high accuracy. In the dielectric, a graph of frequency and dielectric constant (Cole-Cole plot diagram by KS Cole and RH Cole article of 1941) draws a shape of circle if the dielectric is independent of frequency but it draws a shape of ellipse in reality due to frequency dependency. Havriliak and Negami have also presented Havriliak-Negami model which introduced parameter into dielectric constant equation which deforms Cole-Cole plot diagram and showed that acquired dielectric data of polymer materials fit to this model with proper parameters. In this report, we first consider electric model connected with resistance and capacitance as a rough model of RC concrete. If the capacitance in this model circuit has some loss of dielectric, it is stated that graph in impedance plot is expected to take as similar deformation in the dielectric Cole-Cole plot. Then a numerical optimization computer code for obtaining parameters in the Cole-Cole plot diagram and Havriliak-Negami model is constructed, and the correlation between the deformation parameter of each model and corrosion is shown by this code. These results are feasibility study for diagnosis of corrosion level of rebar by associated parameters to a shape of impedance graph.

  2. Generation of Small Single Domain Nanobody Binders for Sensitive Detection of Testosterone by Electrochemical Impedance Spectroscopy.

    Science.gov (United States)

    Li, Guanghui; Zhu, Min; Ma, Lu; Yan, Junrong; Lu, Xiaoling; Shen, Yanfei; Wan, Yakun

    2016-06-08

    A phage display library of variable domain of the heavy chain only antibody or nanobody (Nb) was constructed after immunizing a bactrian camel with testosterone. With the smaller molecular size (15 kDa), improved solubility, good stability, high affinity, specificity, and lower immunogenicity, Nbs are a promising tool in the next generation of diagnosis and medical applications. Testosterone is a reproductive hormone, playing an important role in normal cardiac function and being the highly predictive marker for many diseases. Herein, a simple and sensitive immunosensor based on electrochemical impedance spectroscopy (EIS) and Nbs was successfully developed for the determination of testosterone. We successfully isolated the antitestosterone Nbs from an immune phage display library. Moreover, one of the Nbs was biotinylated according to in vivo BirA system, which showed the highest production yield and the most stable case. Further, the EIS immunosensor was set up for testosterone detection by applying the biotinylated antitestosterone Nb. As a result, the biosensor exhibited a linear working range from 0.05 to 5 ng mL(-1) with a detection limit of 0.045 ng mL(-1). In addition, the proposed immunosensor was successfully applied in determining testosterone in serum samples. In conclusion, the proposed immunosensor revealed high specificity of testosterone detection and showed as a potential approach for sensitive and accurate diagnosis of testosterone.

  3. Impedance spectroscopy on pH-sensors with lithium lanthanum titanate sensitive material

    International Nuclear Information System (INIS)

    Bohnke, Cl.; Fourquet, J.-L.

    2003-01-01

    The ceramic Li 3x La 2/3-x , 1/3-2x TiO 3 is used, in an all-solid-state configuration, as pH-sensor in aqueous buffer solution. This ceramic displays a pH sensitivity comparable to the one obtained with a commercial glass electrode and does not show any sensitivity to the redox potential of the solution. This is one of the remarkable properties of this ceramic pH-sensor. It is shown in this paper that the reproducibility and the behaviour of the pH-response depend on the morphology of the grain boundaries particularly on the size of the grains. A so-called 'good' pH-response is obtained with a ceramic showing big and homogeneous grains. Complex impedance spectroscopy reveals that such ceramic has a high grain boundary resistance. Furthermore, this electrochemical technique allows us to determine that the interface reaction involved in the pH detection has a time constant of the order of the second. Several assumptions such as ion exchange or acid-base reaction are proposed to explain the sensitivity of the ceramic material to the pH of the solution

  4. Rapid and highly sensitive detection of Enterovirus 71 by using nanogold-enhanced electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    Li, Hsing-Yuan; Tseng, Shing-Hua; Cheng, Tsai-Mu; Chu, Hsueh-Liang; Lu, Yu-Ning; Wang, Fang-Yu; Tu, Lung-Chen; Chang, Chia-Ching; Tsai, Li-Yun; Shieh, Juo-Yu; Yang, Jyh-Yuan; Juan, Chien-Chang

    2013-01-01

    Enterovirus 71 (EV71) infection is an emerging infectious disease causing neurological complications and/or death within two to three days after the development of fever and rash. A low viral titre in clinical specimens makes the detection of EV71 difficult. Conventional approaches for detecting EV71 are time consuming, poorly sensitive, or complicated, and cannot be used effectively for clinical diagnosis. Furthermore, EV71 and Coxsackie virus A16 (CA16) may cross react in conventional assays. Therefore, a rapid, highly sensitive, specific, and user-friendly test is needed. We developed an EV71-specific nanogold-modified working electrode for electrochemical impedance spectroscopy in the detection of EV71. Our results show that EV71 can be distinguished from CA16, Herpes simplex virus, and lysozyme, with the modified nanogold electrode being able to detect EV71 in concentrations as low as 1 copy number/50 μl reaction volume, and the duration between sample preparation and detection being 11 min. This detection platform may have the potential for use in point-of-care diagnostics. (paper)

  5. Rapid and highly sensitive detection of Enterovirus 71 by using nanogold-enhanced electrochemical impedance spectroscopy

    Science.gov (United States)

    Li, Hsing-Yuan; Tseng, Shing-Hua; Cheng, Tsai-Mu; Chu, Hsueh-Liang; Lu, Yu-Ning; Wang, Fang-Yu; Tsai, Li-Yun; Shieh, Juo-Yu; Yang, Jyh-Yuan; Juan, Chien-Chang; Tu, Lung-Chen; Chang, Chia-Ching

    2013-07-01

    Enterovirus 71 (EV71) infection is an emerging infectious disease causing neurological complications and/or death within two to three days after the development of fever and rash. A low viral titre in clinical specimens makes the detection of EV71 difficult. Conventional approaches for detecting EV71 are time consuming, poorly sensitive, or complicated, and cannot be used effectively for clinical diagnosis. Furthermore, EV71 and Coxsackie virus A16 (CA16) may cross react in conventional assays. Therefore, a rapid, highly sensitive, specific, and user-friendly test is needed. We developed an EV71-specific nanogold-modified working electrode for electrochemical impedance spectroscopy in the detection of EV71. Our results show that EV71 can be distinguished from CA16, Herpes simplex virus, and lysozyme, with the modified nanogold electrode being able to detect EV71 in concentrations as low as 1 copy number/50 μl reaction volume, and the duration between sample preparation and detection being 11 min. This detection platform may have the potential for use in point-of-care diagnostics.

  6. Porosimetry and packing morphology of vertically-aligned carbon nanotube arrays via impedance spectroscopy.

    Science.gov (United States)

    Mutha, Heena K; Lu, Yuan; Stein, Itai; Cho, H Jeremy; Suss, Matthew; Laoui, Tahar; Thompson, Carl; Wardle, Brian; Wang, Evelyn

    2016-12-13

    Vertically aligned one-dimensional nanostructure arrays are promising in many applications such as electrochemical systems, solar cells, and electronics, taking advantage of high surface area per unit volume, nanometer length scale packing, and alignment leading to high conductivity. However, many devices need to optimize arrays for device performance by selecting an appropriate morphology. Developing a simple, non-invasive tool for understanding the role of pore volume distribution and interspacing would aid in the optimization of nanostructure morphologies in electrodes. In this work, we combined electrochemical impedance spectroscopy (EIS) with capacitance measurements and porous electrode theory to conduct in situ porosimetry of vertically-aligned carbon nanotubes (VA-CNTs) non-destructively. We utilized the EIS measurements with a pore size distribution model to quantify the average and dispersion of inter-CNT spacing (Γ), stochastically, in carpets that were mechanically densified from 1.7 × 1010 tubes/cm2 to 4.5 × 1011 tubes/cm2. Our analysis predicts that the inter-CNT spacing ranges from over 100 ± 50 nm in sparse carpets to sub 10 ± 5 nm in packed carpets. Our results suggest that waviness of CNTs leads to variations in the inter-CNT spacing, which can be significant in sparse carpets. This methodology can be used to predict the performance of many nanostructured devices, including supercapacitors, batteries, solar cells, and semiconductor electronics. Copyright 2016 IOP Publishing Ltd.

  7. In situ electrochemical impedance spectroscopy of Zr-1%Nb under VVER primary circuit conditions

    International Nuclear Information System (INIS)

    Nagy, Gabor; Kerner, Zsolt; Pajkossy, Tamas

    2002-01-01

    Oxide layers were grown on tubular samples of Zr-1%Nb under conditions simulating those in VVER-type pressurised water reactors, viz. in near-neutral borate solutions in an autoclave at 290 deg. C. These samples were investigated using electrochemical impedance spectroscopy which was found to be suitable to follow in situ the corrosion process. A -CPE ox parallel R ox - element was used to characterise the oxide layer on Zr-1%Nb. Both the CPE ox coefficient, σ ox , and the parallel resistance, R ox , were found to be thickness dependent. The layer thickness, however, can only be calculated after a calibration procedure. The temperature dependence of the CPE ox element was also found to be anomalous while the temperature dependence of R ox indicates that the oxide layer has semiconductor properties. The relaxation time - defined as (R ox σ ox ) 1/α - was found to be quasi-independent of oxidation time and temperature; thus it is characteristic to the oxide layer on Zr-1%Nb

  8. In-situ electrochemical impedance spectroscopy measurements of zirconium alloy oxide conductivity: Relationship to hydrogen pickup

    International Nuclear Information System (INIS)

    Couet, Adrien; Motta, Arthur T.; Ambard, Antoine; Livigni, Didier

    2017-01-01

    Highlights: • In-situ electrochemistry on zirconium alloys in 360 °C pure water show oxide layer resistivity changes during corrosion. • A linear relationship is observed between oxide resistivity and instantaneous hydrogen pickup fraction. • The resistivity of the oxide layer formed on Zircaloy-4 (and thus its hydrogen pickup fraction) is higher than on Zr-2.5Nb. - Abstract: Hydrogen pickup during nuclear fuel cladding corrosion is a critical life-limiting degradation mechanism for nuclear fuel. Following a program dedicated to zirconium alloys, corrosion, it has been hypothesized that oxide electronic resistivity determines hydrogen pickup. In-situ electrochemical impedance spectroscopy experiments were performed on Zircaloy-4 and Zr-2.5Nb alloys in 360 °C water. The oxide resistivity was measured as function of time. The results show that as the oxide resistivity increases so does the hydrogen pickup fraction. The resistivity of the oxide layer formed on Zircaloy-4 is higher than on Zr-2.5Nb, resulting in a higher hydrogen pickup fraction of Zircaloy-4, compared to Zr-2.5Nb.

  9. Evaluation of the corrosion resistance of anodized aluminum 6061 using electrochemical impedance spectroscopy (EIS)

    Energy Technology Data Exchange (ETDEWEB)

    Huang Yuelong [Corrosion and Environmental Effects Laboratory (CEEL), Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-0241 (United States); Shih Hong [Lam Research Corporation, 4400 Cushing Parkway, Fremont, CA 94538 (United States)], E-mail: hong.shih@lamrc.com; Huang, Huochuan; Daugherty, John; Wu Shun; Ramanathan, Sivakami; Chang, Chris [Lam Research Corporation, 4400 Cushing Parkway, Fremont, CA 94538 (United States); Mansfeld, Florian [Corrosion and Environmental Effects Laboratory (CEEL), Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-0241 (United States)], E-mail: mansfeld@usc.edu

    2008-12-15

    The corrosion resistance of anodized Al 6061 produced by two different anodizing and sealing processes was evaluated using electrochemical impedance spectroscopy (EIS). The scanning electron microscope (SEM) was employed to determine the surface structure and the thickness of the anodized layers. The EIS data revealed that there was very little change of the properties of the anodized layers for samples that were hard anodized in a mixed acid solution and sealed in hot water over a 365 day exposure period in a 3.5 wt% NaCl solution. The specific admittance A{sub s} and the breakpoint frequency f{sub b} remained constant with exposure time confirming that the hard anodizing process used in this study was very effective in providing excellent corrosion resistance of anodized Al 6061 over extended exposure periods. Some minor degradation of the protective properties of the anodized layers was observed for samples that were hard anodized in H{sub 2}SO{sub 4} and exposed to the NaCl solution for 14 days.

  10. Human haptoglobin phenotypes and concentration determination by nanogold-enhanced electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Tsai-Mu; Lee, Tzu-Cheng; Tseng, Shin-Hua; Chu, Hsueh-Liang; Chang, Chia-Ching [Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 30050, Taiwan (China); Pan, Ju-Pin, E-mail: ccchang01@faculty.nctu.edu.tw [Division of Cardiology, Department of Medicine, Taipei Veterans General Hospital, Taipei 11217, Taiwan (China)

    2011-06-17

    Haptoglobin (Hp) is an acute phase protein that binds free hemoglobin (Hb), preventing Hb-induced oxidative damage in the vascular system. There are three phenotypes in human Hp, whose heterogeneous polymorphic structures and varying concentrations in plasma have been attributed to the cause of diseases and outcome of clinical treatments. Different phenotypes of Hp may be composed of the same subunits but different copy numbers, rendering their determination difficult by a single procedure. In this study, we have developed a simple, fast, reliable and sensitive method, using label-free nanogold-modified bioprobes coupled with self-development electrochemical impedance spectroscopy (EIS). By this method, probe surface charge transfer resistance is detected. The relative charge transfer resistance ratios for Hp 1-1, Hp 2-1 and Hp 2-2 were characterized. We were able to determine protein size difference within 3 nm, and the linear region of the calibration curve for Hp levels in the range of 90 pg ml{sup -1} and 90 {mu}g ml{sup -1} ({approx}1 fM to 1 pM). We surmise that similar approaches can be used to investigate protein polymorphism and altered protein-protein interaction associated with diseases.

  11. Study of Rust Effect on the Corrosion Behavior of Reinforcement Steel Using Impedance Spectroscopy

    Science.gov (United States)

    Bensabra, Hakim; Azzouz, Noureddine

    2013-12-01

    Most studies on corrosion of steel reinforcement in concrete are conducted on steel samples with polished surface (free of all oxides) in order to reproduce the same experimental conditions. However, before embedding in concrete, the steel bars are often covered with natural oxides (rust), which are formed during exposure to the atmosphere. The presence of this rust may affect the electrochemical behavior of steel rebar in concrete. In order to understand the effect of rust on the corrosion behavior of reinforcement steel, potentiodynamic and electrochemical impedance spectroscopy (EIS) tests were carried out in a simulated concrete pore solution using steel samples with two different surface conditions: polished and rusted samples. The obtained results have shown that the presence of rust on the steel bar has a negative effect on its corrosion behavior, with or without the presence of chlorides. This detrimental effect can be explained by the fact that the rust provokes a decrease of the electrolyte resistance at the metal-concrete interface and reduces the repassivating ability. In addition, the rust layer acts as a barrier against the hydroxyl ion diffusion, which prevents the realkalinization phenomenon.

  12. Ni/YSZ electrode degradation studied by impedance spectroscopy: Effects of gas cleaning and current density

    DEFF Research Database (Denmark)

    Hauch, Anne; Mogensen, Mogens Bjerg

    2010-01-01

    Anode supported (Ni/YSZ–YSZ–LSM/YSZ) solid oxide fuel cells were tested and the degradation over time was monitored and analyzed by impedance spectroscopy. Test conditions were chosen to focus on the anode degradation and all tests were operated at 750 °C. O2 was supplied to the cathode...... and the anode inlet gas mixture had a high p(H2O)/p(H2) ratio of 0.4/0.6. Commercially available gasses were applied. Cells were tested over a few hundred hours applying varying current densities (OCV, 0.75 A/cm2 and 1 A/cm2). To investigate the effects of possible impurities in the inlet gas stream...... on the anode degradation, tests were set-up both with and without gas cleaning. Gas cleaning was done by passing the H2 over porous nickel at room temperature. It was found that cleaning of the inlet H2 gas more than halved the anode degradation under current load. For tests at OCV the increase in the Ni...

  13. Evaluation of the corrosion resistance of anodized aluminum 6061 using electrochemical impedance spectroscopy (EIS)

    International Nuclear Information System (INIS)

    Huang Yuelong; Shih Hong; Huang, Huochuan; Daugherty, John; Wu Shun; Ramanathan, Sivakami; Chang, Chris; Mansfeld, Florian

    2008-01-01

    The corrosion resistance of anodized Al 6061 produced by two different anodizing and sealing processes was evaluated using electrochemical impedance spectroscopy (EIS). The scanning electron microscope (SEM) was employed to determine the surface structure and the thickness of the anodized layers. The EIS data revealed that there was very little change of the properties of the anodized layers for samples that were hard anodized in a mixed acid solution and sealed in hot water over a 365 day exposure period in a 3.5 wt% NaCl solution. The specific admittance A s and the breakpoint frequency f b remained constant with exposure time confirming that the hard anodizing process used in this study was very effective in providing excellent corrosion resistance of anodized Al 6061 over extended exposure periods. Some minor degradation of the protective properties of the anodized layers was observed for samples that were hard anodized in H 2 SO 4 and exposed to the NaCl solution for 14 days

  14. Nanostructured platform for the detection of Neisseria gonorrhoeae using electrochemical impedance spectroscopy and differential pulse voltammetry

    International Nuclear Information System (INIS)

    Singh, R.; Matharu, Z.; Srivastava, A.K.; Sood, S.; Gupta, R.K.; Malhotra, B.D.

    2012-01-01

    We report on a nanocomposite based genosensor for the detection of Neisseria gonorrhoeae, a bacterium causing the sexually transmitted disease gonorrhoea. Amino-labeled probe DNA was covalently immobilized on electrochemically prepared polyaniline and iron oxide (PANI-Fe 3 O 4 ) nanocomposite film on an indium tin oxide (ITO) electrode. Scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) techniques have been employed to characterize surface of the modified electrode. The genosensor has detection limits of 1 x 10 -15 M and 1 x 10 -17 M, respectively, using the EIS and DPV techniques. This biosensor can discriminate a complementary sequence from a single-base mismatch and from non-complementary DNA, and has been utilized for detection of DNA extracted from N. gonorrhoeae culture, and from patient samples with N. gonorrhoeae. It is found to exhibit good specificity for N. gonorrhoeae species and shows no response towards non-gonorrhoeae type of Neisseria species (NgNs) and other gram-negative bacterias (GNBs). The affinity constant for hybridization calculated using the Langmuir adsorption isotherm model is found to be 3. 39 x 10 8 M -1 . (author)

  15. Measurement of Two-Phase Flow Fields by Application of Dynamic Electrical Impedance Imaging

    International Nuclear Information System (INIS)

    Kim, KyungYoun; Kang, Sook In; Kim, Ho Chan; Kim, Sin; Lee, Yoon Joon; Kim, Min Chan; Anghaie, Samim

    2002-01-01

    This study presents a visualization technique for the phase distribution in a two-phase flow field with an electrical impedance imaging technique, which reconstructs the resistivity distribution with electrical responses that are determined by corresponding excitations. Special emphasis is placed on the development of dynamic imaging technique for two-phase system undergoing a rapid transient, which could not be visualized with conventional static imaging techniques. The proposed algorithm treats the image reconstruction problem as a nonlinear state estimation problem and the unknown state (resistivity distribution, i.e. phase distribution) is estimated with the aid of a Kalman filter in a minimum mean square error sense. Several illustrative examples with computer simulations are successfully provided to verify the reconstruction performance of the proposed algorithm. (authors)

  16. Monitoring of lobectomy in cystic fibrosis with electrical impedance tomography - a new diagnostic tool.

    Science.gov (United States)

    Lehmann, Sylvia; Tenbrock, Klaus; Schrading, Simone; Pikkemaat, Robert; Antink, Christoph Hoog; Santos, Susana; Spillner, Jan Wilhelm; Wagner, Norbert; Leonhardt, Steffen

    2014-12-01

    Electrical impedance tomography (EIT) is a radiation-free technique generating cross-sectional images of the lung. EIT visualizes global and regional ventilation by illustrating the distribution of electrical bioimpedance. With an electrode belt around the patient's thorax, rotating injection-couples of a harmless alternating current allow voltage measurement of the remaining electrodes. This enables the reconstruction of a tomogram with highly dynamic changes within ventilation. We report on a female six-year-old patient with cystic fibrosis and complete destruction of the upper and middle lobe of the right lung. Lobectomy, a rare therapeutic option in patients with cystic fibrosis that needs to be considered in cases of severe localized destruction, was performed. We show a pre- and postoperative documentation of static (radiology) and dynamic investigation tools (spirometry) in correlation with EIT as a new non-invasive and radiation-free diagnostic tool for this patient group.

  17. Epigastric electrical impedance for the quantitative determination of the gastric acidity

    International Nuclear Information System (INIS)

    Giouvanoudi, A C; Spyrou, N M

    2008-01-01

    Electrical impedance measurements have been used by scientists since the 1980s to investigate the gastric function. In this work, these measurements were carried out using the epigastrograph, a device generating alternating current of 32 kHz and injecting it in the gastric area of the human body with surface electrodes, located around the abdominal area. Although the method has been used for about three decades the physiological interpretation of these measurements is still under research. This work states that the electrical impedance measurements from the gastric area depend on the conductivity of the gastric lumen, due mainly to gastric acid secretions and to the conductivity and chemical form of the ingested meal. By choosing the proper test meal the gastric acidity in the empty, healthy stomach was also estimated. The estimated value is in accordance with the literature. The method is non-invasive, relatively inexpensive, simple to medical technologists and subjects, and involves no radiation risk. The method may form the basis for the development of a non-invasive gastric pH meter

  18. Age- and gender-associated differences in electrical impedance values of skeletal muscle

    International Nuclear Information System (INIS)

    Kortman, Hans G J; Wilder, Sarah C; Geisbush, Tom R; Narayanaswami, Pushpa; Rutkove, Seward B

    2013-01-01

    Electrical impedance measurements of skeletal muscle may be sensitive to age-associated declines in muscle health. In an effort to evaluate this concept further, we performed electrical impedance myography (EIM) using a handheld array on 38 individuals aged 19–50 years and 41 individuals aged 60–85 years. Individuals either had seven upper extremity or seven lower extremity muscles measured. The 50 kHz reactance, resistance and phase were used as the major outcome variables. Although the phase values were similar in both groups, both reactance and resistance values were lower in the lower extremities of the older individuals as compared to the younger (−23 ± 6%, p = 0.001 for reactance and −27 ± 7%, p = 0.005 for resistance), whereas changes in upper extremity values were not significantly different (−9 ± 5%, p = 0.096 for reactance and +5 ± 9%, p = 0.55 for resistance). When analyzing the genders separately, it became clear that this reduction in lower extremity values was most pronounced in men and less consistently present in women. These findings suggest that age- and gender-associated differences in muscle condition are detectable using EIM. The relationship of these easily obtained parameters to standard functional, imaging, and pathological markers of sarcopenia deserves further study. (paper)

  19. Bias-dependent model of the electrical impedance of ionic polymer-metal composites.

    Science.gov (United States)

    Cha, Youngsu; Porfiri, Maurizio

    2013-02-01

    In this paper, we analyze the charge dynamics of ionic polymer-metal composites (IPMCs) in response to voltage inputs composed of a large dc bias and a small superimposed time-varying voltage. The IPMC chemoelectrical behavior is described through the modified Poisson-Nernst-Planck framework, in which steric effects are taken into consideration. The physics of charge build-up and mass transfer in the proximity of the high surface electrodes is modeled by schematizing the IPMC as the stacked sequence of five layers, in which the ionomeric membrane is separated from the metal electrodes by two composite layers. The method of matched asymptotic expansions is used to derive a semianalytical solution for the concentration of mobile counterions and the electric potential in the IPMC, which is, in turn, used to establish an equivalent circuit model for the IPMC electrical response. The circuit model consists of the series connection of a resistor and two complex elements, each constituted by the parallel connection of a capacitor and a Warburg impedance. The resistor is associated with ion transport in the ionomeric membrane and is independent of the dc bias. The capacitors and the Warburg impedance idealize charge build-up and mass transfer in the vicinity of the electrodes and their value is controlled by the dc bias. The proposed approach is validated against experimental results on in-house fabricated IPMCs and the accuracy of the equivalent circuit is assessed through comparison with finite element results.

  20. Electrical characterization and impedance response of lanthanum doped barium titanate ceramics

    Directory of Open Access Journals (Sweden)

    Mančić D.

    2008-01-01

    Full Text Available The dielectric permittivity and dissipation factor of La-doped and undoped BaTiO3 were investigated as a function of frequency and temperature. The impedance response was used to study the electrical properties of La-doped BaTiO3 over the temperature range from room temperature (RT to 350°C. La-doped and undoped BaTiO3, obtained by a modified Pechini method, were sintered in air at 1300°C for 2 and 16 hours. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE. The most suitable electrical circuit for the interpretation of experimental results is found to be the equivalent circuit consisting of resistors and CPE elements which replace the capacitor elements. The contribution of grain boundary resistance to the total resistance of a system is remarkable at low temperature. Dielectric permittivity of doped BaTiO3 was in the range of 8000 to 12000 at 1 kHz and the dissipation factor was less than 1%.

  1. Optimization of impedance spectroscopy techniques for measuring cutaneous micropore formation after microneedle treatment in an elderly population.

    Science.gov (United States)

    Kelchen, Megan N; Holdren, Grant O; Farley, Matthew J; Zimmerman, M Bridget; Fairley, Janet A; Brogden, Nicole K

    2014-12-01

    The objective of this study was to optimize a reproducible impedance spectroscopy method in elderly subjects as a means to evaluate the effects of microneedles on aging skin. Human volunteers were treated with microneedles at six sites on the upper arm. Repeated impedance measurements were taken pre- and post-microneedle insertion. Two electrode types were evaluated (dry vs. gel), using either light or direct pressure to maintain contact between the electrode and skin surface. Transepidermal water loss (TEWL) was measured as a complementary technique. Five control subjects and nine elderly subjects completed the study. Microneedle insertion produced a significant decrease in impedance from baseline in all subjects (p micropore formation. This was supported by a complementary significant increase in TEWL (p micropore formation in elderly subjects, which will be essential for future studies describing microneedle-assisted transdermal delivery in aging populations.

  2. Evolution of microstructure of epoxy coating during UV degradation progress studied by slow positron annihilation spectroscopy and electrochemical impedance spectroscopy

    International Nuclear Information System (INIS)

    Liu, Fuwei; Yin, Mingxi; Xiong, Bangyun; Zheng, Feng; Mao, Wenfeng; Chen, Zhe; He, Chunqing; Zhao, Xipo; Fang, Pengfei

    2014-01-01

    Graphical abstract: - Highlights: • Decrements in S value and water uptake coefficient confirm the post-cure process. • Molecular chain scission leads to the formation of microporous structure. • The formation of an aged layer with high density is verified by EIS. - Abstract: Evolution of chemical functional groups, microstructure and water barrier properties of a polyamide-cured epoxy (diglycidyl ether of bisphenol-A epoxy resin, DGEBA) coating during ultraviolet A (UV-A) photo-oxidative aging is systematically investigated. At the early stage of aging, decrements of S parameter and water uptake coefficient indicate the formation of a more compact structure induced by the post-curing process. After 208 hours (h) of UV irradiation, a novel time constant at relatively high frequency (3.5 × 10 2 Hz) appears in the electrochemical impedance spectroscopy (EIS) spectra suggesting that a microporous layer generates near the surface of DGEBA film. With the increase in irradiation time, overlap of two time constants at frequencies around 18 Hz and 3.7 × 10 3 Hz is observed after 1.33 h of immersion, indicating that the micropores grow towards the bulk and form more characteristic layers with microporous structures. After irradiation for 399 h, a low S parameter region near the sample surface is observed, which implies that a surface layer with low free volume may have formed. With longer exposure, EIS results also reveal that the water barrier property of the coating can be improved, which confirms the formation of the denser surface layer near the surface as a result of radical recombination during UV-A treatment

  3. In vivo bioimpedance measurement of healthy and ischaemic rat brain: implications for stroke imaging using electrical impedance tomography

    International Nuclear Information System (INIS)

    Dowrick, T; Blochet, C; Holder, D

    2015-01-01

    In order to facilitate the imaging of haemorrhagic and ischaemic stroke using frequency difference electrical impedance tomography (EIT), impedance measurements of normal and ischaemic brain, and clotted blood during haemorrhage, were gathered using a four-terminal technique in an in vivo animal model, a first for ischaemic measurements. Differences of 5–10% in impedance were seen between the frequency spectrums of healthy and ischaemic brain, over the frequency range 0–3 kHz, while the spectrum of blood was predominately uniform. The implications of imaging blood/ischaemia in the brain using electrical impedance tomography are discussed, supporting the notion that it will be possible to differentiate stroke from haemorrhage. (paper)

  4. Thickness-, Composition-, and Magnetic-Field-Dependent Complex Impedance Spectroscopy of Granular-Type-Barrier Co/Co-Al2O3/Co MTJs

    Science.gov (United States)

    Tuan, Nguyen Anh; Anh, Nguyen Tuan; Nga, Nguyen Tuyet; Tue, Nguyen Anh; Van Cuong, Giap

    2016-06-01

    The alternating-current (ac) electrical properties of granular-type-barrier magnetic tunnel junctions (GBMTJs) based on Co/Co x (Al2O3)1- x ( t)/Co trilayer structures have been studied using complex impedance spectroscopy (CIS). Their CIS characteristics were investigated in external magnetic fields varying from 0 kOe to 3 kOe as a function of Co composition x at 10 at.%, 25 at.%, and 35 at.%, with barrier layer thickness t of 20 nm to 90 nm. The influence of these factors on the behaviors of the ac impedance response of the GBMTJs was deeply investigated and attributed to the dielectric or conducting nature of the Co-Al2O3 barrier layer. The most remarkable typical phenomena observed in these behaviors, even appearing paradoxical, include lower impedance for thicker t for each given x, a declining trend of Z with increasing x, a clear decrease of Z with H, and especially a partition of Z into zones according to the H value. All these effects are analyzed and discussed to demonstrate that diffusion-type and mass-transfer-type phenomena can be inferred from processes such as spin tunneling and Coulomb or spin blockade in the Co-Al2O3 barrier layer.

  5. Improvements in the image quality of ventilatory tomograms by electrical impedance tomography

    International Nuclear Information System (INIS)

    Hahn, G; Dittmar, J; Just, A; Hellige, G

    2008-01-01

    We present an improved approach to image ventilation in functional electrical impedance tomography (f-EIT). It combines the advantages of the two established procedures of calculating standard deviation as a functional parameter of ventilation (SD method) and the so-called filling capacity (FC method). The SD method quantifies the local impedance variation over a series of tomograms for each pixel; the FC method is based on the slope of a linear fit of regional versus the global impedance change. Tidal volume V T is displayed linearly by the SD method in f-EIT; it is, however, sensitive to noisy data. The FC method is much more robust with respect to noise but does not display the tidal volume V T . We combined the advantages of both techniques in a new VT method which is based on raw data. It saves computing time and is suitable for both f-EIT and absolute EIT (a-EIT). We separated the raw data into two representative sets: end expiratory and end inspiratory. This was accomplished by calculating the global time course of the relative impedance changes from the raw data. In this time course, we determined all frame numbers (indices) of end expiration and end inspiration. These frame numbers were used to calculate one mean expiratory and one mean inspiratory raw data frame. Reconstruction by difference imaging directly reflects the mean tidal volume V T during the acquired frame series. The effect of the improvement by the VT method was investigated at different noise levels by adding artificial noise from 0 to 100 µV rms to a real raw dataset. The robustness with regard to noise of the VT method was similar to that of the FC method. The practical value of suppression of non-ventilatory impedance changes, artefacts and noise was tested by studying ten healthy subjects (four females, six males) during normal breathing. We found a highly significant improvement in the image quality (p < 0.001) of ventilation for this group of volunteers

  6. Electrochemical impedance spectroscopy analysis of a thin polymer film-based micro-direct methanol fuel cell

    Science.gov (United States)

    Schulz, Tobias; Weinmüller, Christian; Nabavi, Majid; Poulikakos, Dimos

    A single cell micro-direct methanol fuel cell (micro-DMFC) was investigated using electrochemical impedance spectroscopy. The electrodes consisted of thin, flexible polymer (SU8) film microchannel structures fabricated in-house using microfabrication techniques. AC impedance spectroscopy was used to separate contributions to the overall cell polarization from the anode, cathode and membrane. A clear distinction between the different electrochemical phenomena occurring in the micro-DMFC, especially the distinction between double layer charging and Faradaic reactions was shown. The effect of fuel flow rate, temperature, and anode flow channel structure on the impedance of the electrode reactions and membrane/electrode double layer charging were investigated. Analysis of impedance data revealed that the performance of the test cell was largely limited by the presence of intermediate carbon monoxide in the anode reaction. Higher temperatures increase cell performance by enabling intermediate CO to be oxidized at much higher rates. The results also revealed that serpentine anode flow microchannels show a lower tendency to intermediate CO coverage and a more stable cell behavior than parallel microchannels.

  7. Patterns of gas and liquid reflux during transient lower oesophageal sphincter relaxation: a study using intraluminal electrical impedance

    OpenAIRE

    Sifrim, D; Silny, J; Holloway, R; Janssens, J

    1999-01-01

    Background—Belching has been proposed as a major mechanism underlying acid gastro-oesophageal reflux in normal subjects. However, the presence of oesophageal gas has not been measured directly but only inferred from manometry. 
Aims—To investigate, using intraluminal electrical impedance, the patterns of gas and liquid reflux during transient lower oesophageal sphincter (LOS) relaxations, the main mechanism of acid reflux in normal subjects. 
Methods—Impedance changes ass...

  8. Dynamic imaging in electrical impedance tomography of the human chest with online transition matrix identification.

    Science.gov (United States)

    Moura, Fernando Silva; Aya, Julio Cesar Ceballos; Fleury, Agenor Toledo; Amato, Marcelo Britto Passos; Lima, Raul Gonzalez

    2010-02-01

    One of the electrical impedance tomography objectives is to estimate the electrical resistivity distribution in a domain based only on electrical potential measurements at its boundary generated by an imposed electrical current distribution into the boundary. One of the methods used in dynamic estimation is the Kalman filter. In biomedical applications, the random walk model is frequently used as evolution model and, under this conditions, poor tracking ability of the extended Kalman filter (EKF) is achieved. An analytically developed evolution model is not feasible at this moment. The paper investigates the identification of the evolution model in parallel to the EKF and updating the evolution model with certain periodicity. The evolution model transition matrix is identified using the history of the estimated resistivity distribution obtained by a sensitivity matrix based algorithm and a Newton-Raphson algorithm. To numerically identify the linear evolution model, the Ibrahim time-domain method is used. The investigation is performed by numerical simulations of a domain with time-varying resistivity and by experimental data collected from the boundary of a human chest during normal breathing. The obtained dynamic resistivity values lie within the expected values for the tissues of a human chest. The EKF results suggest that the tracking ability is significantly improved with this approach.

  9. Electrical impedance tomography-based sensing skin for quantitative imaging of damage in concrete

    International Nuclear Information System (INIS)

    Hallaji, Milad; Pour-Ghaz, Mohammad; Seppänen, Aku

    2014-01-01

    This paper outlines the development of a large-area sensing skin for damage detection in concrete structures. The developed sensing skin consists of a thin layer of electrically conductive copper paint that is applied to the surface of the concrete. Cracking of the concrete substrate results in the rupture of the sensing skin, decreasing its electrical conductivity locally. The decrease in conductivity is detected with electrical impedance tomography (EIT) imaging. In previous works, electrically based sensing skins have provided only qualitative information on the damage on the substrate surface. In this paper, we study whether quantitative imaging of the damage is possible. We utilize application-specific models and computational methods in the image reconstruction, including a total variation (TV) prior model for the damage and an approximate correction of the modeling errors caused by the inhomogeneity of the painted sensing skin. The developed damage detection method is tested experimentally by applying the sensing skin to polymeric substrates and a reinforced concrete beam under four-point bending. In all test cases, the EIT-based sensing skin provides quantitative information on cracks and/or other damages on the substrate surface: featuring a very low conductivity in the damage locations, and a reliable indication of the lengths and shapes of the cracks. The results strongly support the applicability of the painted EIT-based sensing skin for damage detection in reinforced concrete elements and other substrates. (paper)

  10. Dynamic Phase Boundary Estimation in Two-phase Flows Based on Electrical Impedance Tomography

    International Nuclear Information System (INIS)

    Lee, Jeong Seong; Muhammada, Nauman Malik; Kim, Kyung Youn; Kim, Sin

    2008-01-01

    For the dynamic visualization of the phase boundary in two-phase flows, the electrical impedance tomography (EIT) technique is introduced. In EIT, a set of predetermined electrical currents is injected through the electrodes placed on the boundary of the flow passage and the induced electrical potentials are measured on the electrodes. With the relationship between the injected currents and the induced voltages, the electrical conductivity distribution across the flow domain is estimated through the image reconstruction algorithm where the conductivity distribution corresponds to the phase distribution. In the application of EIT to two-phase flows where there are only two conductivity values, the conductivity distribution estimation problem can be transformed into the boundary estimation problem. This paper considers phase boundary estimation with EIT in annular two-phase flows. As the image reconstruction algorithm, the unscented Kalman filter (UKF) is adopted since from the control theory it is reported that the UKF shows better performance than the extended Kalman filter (EKF) that has been commonly used. For the present problem, the formulation of UKF algorithm involved its incorporation in the adopted image reconstruction algorithm. Also, phantom experiments have been conducted to evaluate the improvement reported by UKF

  11. Non-contact multi-frequency magnetic induction spectroscopy system for industrial-scale bio-impedance measurement

    International Nuclear Information System (INIS)

    O'Toole, M D; Marsh, L A; Davidson, J L; Tan, Y M; Armitage, D W; Peyton, A J

    2015-01-01

    Biological tissues have a complex impedance, or bio-impedance, profile which changes with respect to frequency. This is caused by dispersion mechanisms which govern how the electromagnetic field interacts with the tissue at the cellular and molecular level. Measuring the bio-impedance spectra of a biological sample can potentially provide insight into the sample’s properties and its cellular structure. This has obvious applications in the medical, pharmaceutical and food-based industrial domains. However, measuring the bio-impedance spectra non-destructively and in a way which is practical at an industrial scale presents substantial challenges. The low conductivity of the sample requires a highly sensitive instrument, while the demands of industrial-scale operation require a fast high-throughput sensor of rugged design. In this paper, we describe a multi-frequency magnetic induction spectroscopy (MIS) system suitable for industrial-scale, non-contact, spectroscopic bio-impedance measurement over a bandwidth of 156 kHz–2.5 MHz. The system sensitivity and performance are investigated using calibration and known reference samples. It is shown to yield rapid and consistently sensitive results with good long-term stability. The system is then used to obtain conductivity spectra of a number of biological test samples, including yeast suspensions of varying concentration and a range of agricultural produce, such as apples, pears, nectarines, kiwis, potatoes, oranges and tomatoes. (paper)

  12. Pseudomonas aeruginosa can be detected in a polymicrobial competition model using impedance spectroscopy with a novel biosensor.

    Directory of Open Access Journals (Sweden)

    Andrew C Ward

    Full Text Available Electrochemical Impedance Spectroscopy (EIS is a powerful technique that can be used to elicit information about an electrode interface. In this article, we highlight six principal processes by which the presence of microorganisms can affect impedance and show how one of these--the production of electroactive metabolites--changes the impedance signature of culture media containing Pseudomonas aeruginosa. EIS, was used in conjunction with a low cost screen printed carbon sensor to detect the presence of P. aeruginosa when grown in isolation or as part of a polymicrobial infection with Staphylococcus aureus. By comparing the electrode to a starting measurement, we were able to identify an impedance signature characteristic of P. aeruginosa. Furthermore, we are able to show that one of the changes in the impedance signature is due to pyocyanin and associated phenazine compounds. The findings of this study indicate that it might be possible to develop a low cost sensor for the detection of P. aeruginosa in important point of care diagnostic applications. In particular, we suggest that a development of the device described here could be used in a polymicrobial clinical sample such as sputum from a CF patient to detect P. aeruginosa.

  13. Calculation of Voltages in Electric Power Transmission Lines During Historic Geomagnetic Storms: An Investigation Using Realistic Earth Impedances

    Science.gov (United States)

    Lucas, Greg M.; Love, Jeffrey J.; Kelbert, Anna

    2018-02-01

    Commonly, one-dimensional (1-D) Earth impedances have been used to calculate the voltages induced across electric power transmission lines during geomagnetic storms under the assumption that much of the three-dimensional structure of the Earth gets smoothed when integrating along power transmission lines. We calculate the voltage across power transmission lines in the mid-Atlantic region with both regional 1-D impedances and 64 empirical 3-D impedances obtained from a magnetotelluric survey. The use of 3-D impedances produces substantially more spatial variance in the calculated voltages, with the voltages being more than an order of magnitude different, both higher and lower, than the voltages calculated utilizing regional 1-D impedances. During the March 1989 geomagnetic storm 62 transmission lines exceed 100 V when utilizing empirical 3-D impedances, whereas 16 transmission lines exceed 100 V when utilizing regional 1-D impedances. This demonstrates the importance of using realistic impedances to understand and quantify the impact that a geomagnetic storm has on power grids.

  14. Calculation of voltages in electric power transmission lines during historic geomagnetic storms: An investigation using realistic earth impedances

    Science.gov (United States)

    Lucas, Greg M.; Love, Jeffrey J.; Kelbert, Anna

    2018-01-01

    Commonly, one-dimensional (1-D) Earth impedances have been used to calculate the voltages induced across electric power transmission lines during geomagnetic storms under the assumption that much of the three-dimensional structure of the Earth gets smoothed when integrating along power transmission lines. We calculate the voltage across power transmission lines in the mid-Atlantic region with both regional 1-D impedances and 64 empirical 3-D impedances obtained from a magnetotelluric survey. The use of 3-D impedances produces substantially more spatial variance in the calculated voltages, with the voltages being more than an order of magnitude different, both higher and lower, than the voltages calculated utilizing regional 1-D impedances. During the March 1989 geomagnetic storm 62 transmission lines exceed 100 V when utilizing empirical 3-D impedances, whereas 16 transmission lines exceed 100 V when utilizing regional 1-D impedances. This demonstrates the importance of using realistic impedances to understand and quantify the impact that a geomagnetic storm has on power grids.

  15. Influence of heart motion on cardiac output estimation by means of electrical impedance tomography: a case study

    International Nuclear Information System (INIS)

    Proença, Martin; Braun, Fabian; Rapin, Michael; Solà, Josep; Lemay, Mathieu; Adler, Andy; Grychtol, Bartłomiej; Bohm, Stephan H; Thiran, Jean-Philippe

    2015-01-01

    Electrical impedance tomography (EIT) is a non-invasive imaging technique that can measure cardiac-related intra-thoracic impedance changes. EIT-based cardiac output estimation relies on the assumption that the amplitude of the impedance change in the ventricular region is representative of stroke volume (SV). However, other factors such as heart motion can significantly affect this ventricular impedance change. In the present case study, a magnetic resonance imaging-based dynamic bio-impedance model fitting the morphology of a single male subject was built. Simulations were performed to evaluate the contribution of heart motion and its influence on EIT-based SV estimation. Myocardial deformation was found to be the main contributor to the ventricular impedance change (56%). However, motion-induced impedance changes showed a strong correlation (r = 0.978) with left ventricular volume. We explained this by the quasi-incompressibility of blood and myocardium. As a result, EIT achieved excellent accuracy in estimating a wide range of simulated SV values (error distribution of 0.57 ± 2.19 ml (1.02 ± 2.62%) and correlation of r = 0.996 after a two-point calibration was applied to convert impedance values to millilitres). As the model was based on one single subject, the strong correlation found between motion-induced changes and ventricular volume remains to be verified in larger datasets. (paper)

  16. Investigation of in-pile formed corrosion films on zircaloy fuel-rod claddings by impedance spectroscopy and galvanostatic anodization

    International Nuclear Information System (INIS)

    Gebhardt, O.

    1993-01-01

    Hot-cell investigations have been executed to study the corrosion behaviour of irradiated Zircaloy fuel-rod claddings by impedance spectroscopy and galvanostatic anodization. The thickness of the compact oxide at the metal/oxide interface and the thickness of the minimum barrier oxide have been determined at different positions along the claddings. As shown by analysis, both quantities first increase and then decrease with increasing thickness of the total oxide. (author) 6 figs., 33 refs

  17. Sintering and thermal ageing studies of zirconia - yttria ceramics by impedance spectroscopy; Estudos de sinterizacao e de envelhecimento termico de ceramicas de zirconia - itria por espectroscopia de impedancia

    Energy Technology Data Exchange (ETDEWEB)

    Florio, Daniel Zanetti de

    1998-07-01

    ZrO{sub 2}:8 mol %Y{sub 2}O{sub 3} solid electrolyte ceramic pellets have been prepared with powders of three different origins: a Nissan (Japan) commercial powder, a powder obtained by the coprecipitation technique at IPEN, and the mixing of powder oxides (ZrO{sub 2} produced at a Pilot Plant at IPEN and 99.9% pure Y{sub 2}O{sub 3} of USA origin). These starting powders have been analysed by the following techniques: X-ray fluorescence for yttrium content, X-ray diffraction for structural phase content, sedimentation for particle size distribution, gas adsorption (BET) for surface area determination, and transmission electron microscopy for average particle size determination. Pressed ceramic pellets have been analysed by dilatometry to evaluate the sintering stages. Sintered pellets have been characterized by X-ray diffraction for phase analysis and scanning electron microscopy for grain morphology analysis. Impedance spectroscopy analysis have been carried out to follow thermal ageing of zirconia-yttria solid electrolyte at 600 deg C, the working temperature of permanent oxygen sensor, and to study sintering kinetics. The main results show that ageing at 600 deg C decreases the emf sensor response in the first 100 h to a steady value. Moreover, sintering studies by impedance spectroscopy allowed for finding correlations between electrical parameters, sintering kinetics and grain growth mechanisms. (author)

  18. Validating Body Fat Assessment by Bioelectric Impedance Spectroscopy in Taiwanese Hemodialysis Patients.

    Science.gov (United States)

    Lim, Paik Seong; Chen, Chang Hsu; Zhu, Fansan; Kotanko, Peter; Jeng, Yachung; Hu, Chun Yu; Chiu, Li Shu; Chang, Hui-Chen

    2017-01-01

    Obesity is becoming increasingly common in hemodialysis (HD) patients and is associated with inflammation and increased mortality. The primary aim of the present study was to evaluate the accuracy and variability of the bioimpedance device in measuring body fat in Taiwanese dialysis patients. Cross-sectional study. One hundred twenty-two adult patients receiving HD in a single hospital in Taiwan. We compared the results of fat mass (FM) measured by dual-energy x-ray absorptiometry (DEXA) and bioelectrical impedance spectroscopy device (Body composition monitor, BCM). FM measured by BCM was calculated by subtracting fat-free mass (FFM) from body mass assuming fractional hydration of FFM of 0.73 or the proprietary prediction equations from the BCM model. Assessment of whole-body composition showed that percentage FM measured using the 2 techniques was highly correlated when using the BCM model or estimating from total body water using constant (0.73) hydration (r = 0.87, P < .001). There was no evident difference in measurement between patients gender. The Bland-Altman plot also showed good agreement of percentage of FM (t = 3.82; P < .001). In female patients, it was found that BCM significantly underestimated mean FM as compared to DEXA. However, the mean differences of the estimates between the methods were small (0.35 ± 3.00 kg) and with Bland-Altman plot the limits of agreements were -5.5 to 6.2 kg (P = .40) for FM in female patients. Using DEXA as the reference test, BCM is a valid tool for the assessment of total body fat in HD patients. Hence, it may provide a more accessible tool for early detection of changes in body composition in these high-risk patients. Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

  19. Electrochemical impedance spectroscopy for study of electronic structure in disordered organic semiconductors—Possibilities and limitations

    Science.gov (United States)

    Schauer, F.; Nádaždy, V.; Gmucová, K.

    2018-04-01

    There is potential in applying conjugated polymers in novel organic optoelectronic devices, where a comprehensive understanding of the fundamental processes and energetics involved during transport and recombination is still lacking, limiting further device optimization. The electronic transport modeling and its optimization need the energy distribution of transport and defect states, expressed by the energy distribution of the Density of States (DOS) function, as input/comparative parameters. We present the Energy Resolved-Electrochemical Impedance Spectroscopy (ER-EIS) method for the study of transport and defect electronic states in organic materials. The method allows mapping over unprecedentedly wide energy and DOS ranges. The ER-EIS spectroscopic method is based on the small signal interaction between the surface of the organic film and the liquid electrolyte containing reduction-oxidation (redox) species, which is similar to the extraction of an electron by an acceptor and capture of an electron by a donor at a semiconductor surface. The desired DOS of electronic transport and defect states can be derived directly from the measured redox response signal to the small voltage perturbation at the instantaneous position of the Fermi energy, given by the externally applied voltage. The theory of the ER-EIS method and conditions for its validity for solid polymers are presented in detail. We choose four case studies on poly(3-hexylthiophene-2,5-diyl) and poly[methyl(phenyl)silane] to show the possibilities of the method to investigate the electronic structure expressed by DOS of polymers with a high resolution of about 6 orders of magnitude and in a wide energy range of 6 eV.

  20. Unraveling surface and bulk trap states in lead halide perovskite solar cells using impedance spectroscopy

    Science.gov (United States)

    Han, Changfeng; Wang, Kai; Zhu, Xixiang; Yu, Haomiao; Sun, Xiaojuan; Yang, Qin; Hu, Bin

    2018-03-01

    Organic-inorganic hybrid perovskites (OIHPs) have been widely recognized as an excellent candidate for next-generation photovoltaic materials because of their highly efficient power conversion. Acquiring a complete understanding of trap states and dielectric properties in OIHP-based solar cells at the steady state is highly desirable in order to further explore and improve their optoelectronic functionalities and properties. We report CH3NH3PbI3-x Cl x -based planar solar cells with a power conversion efficiency (PCE) of 15.8%. The illumination intensity dependence of the current density-voltage (J-V) revealed the presence of trap-assisted recombination at low fluences. Non-destructive ac impedance spectroscopy (ac-IS) was applied to characterize the device at the steady state. The capacitance-voltage (C-V) spectra exhibited some distinct variations at a wide range of ac modulation frequencies with and without photo-excitations. Since the frequency-dependent chemical capacitance ({{C}μ }) is concerned with the surface and bulk related density of states (DOS) in CH3NH3PbI3-x Cl x , we verified this by fitting the corresponding DOS by a Gaussian distribution function. We ascertained that the electronic sub-gap trap states present in the solution processed CH3NH3PbI3-x Cl x and their distribution differs from the surface to the bulk. In fact, we demonstrated that both surfaces that were adjacent to the electron and hole transport layers featured analogous DOS. Despite this, photo- and bias-induced giant dielectric responses (i.e. both real and imaginary parts) were detected. A remarkable reduction of {{C}μ } at higher frequencies (i.e. more than 100 kHz) was ascribed to the effect of dielectric loss in CH3NH3PbI3-x Cl x .

  1. Patient examinations using electrical impedance tomography—sources of interference in the intensive care unit

    International Nuclear Information System (INIS)

    Frerichs, Inéz; Pulletz, Sven; Elke, Gunnar; Gawelczyk, Barbara; Frerichs, Alexander; Weiler, Norbert

    2011-01-01

    Electrical impedance tomography (EIT) is expected to become a valuable tool for monitoring mechanically ventilated patients due to its ability to continuously assess regional lung ventilation and aeration. Several sources of interference with EIT examinations exist in intensive care units (ICU). Our objectives are to demonstrate how some medical nursing and monitoring devices interfere with EIT measurements and modify the EIT scans and waveforms, which approaches can be applied to minimize these effects and how possible misinterpretation can be avoided. We present four cases of EIT examinations of adult ICU patients. Two of the patients were subjected to pulsation therapy using a pulsating air suspension mattress while being ventilated by high-frequency oscillatory or conventional pressure-controlled ventilation, respectively. The EIT signal modulation synchronous with the occurrence of the pulsating wave was 2.3 times larger than the periodic modulation synchronous with heart rate and high-frequency oscillations. During conventional ventilation, the pulsating mattress induced an EIT signal fluctuation with a magnitude corresponding to about 20% of the patient's tidal volume. In the third patient, interference with EIT examination was caused by continuous cardiac output monitoring. The last patient's examination was disturbed by impedance pneumography when excitation currents of similar frequency to EIT were used. In all subjects, the generation of functional EIT scans was compromised and interpretation of regional ventilation impossible. Discontinuation of pulsation therapy and of continuous cardiac output and impedance respiration monitoring immediately improved the EIT signal and scan quality. Offline processing of the disturbed data using frequency filtering enabled partial retrieval of relevant information. We conclude that thoracic EIT examinations in the ICU require cautious interpretation because of possible mechanical and electromagnetic

  2. Circuit modeling of the electrical impedance: part III. Disuse following bone fracture

    International Nuclear Information System (INIS)

    Shiffman, C A

    2013-01-01

    Multifrequency measurements of the electrical impedance of muscle have been extended to the study of disuse following bone fracture, and analyzed using the five-element circuit model used earlier in the study of the effects of disease. Eighteen subjects recovering from simple fractures on upper or lower limbs were examined (ten males, eight females, aged 18–66). Muscles on uninjured contralateral limbs were used as comparison standards, and results are presented in terms of the ratios p(injured)/p(uninjured), where p stands for the circuit parameter r 1 , r 2 , r 3 , 1/c 1 or 1/c 2 . These are strikingly similar to the diseased-to-healthy ratios for patients with neuromuscular disease, reported in part I of this series. In particular, r 1 is virtually unaffected and the ratios for r 2 , r 3 , 1/c 1 and 1/c 2 can be as large as in serious disease. Furthermore, the same pattern of relationships between the parameters is found, suggesting that there is a common underlying mechanism for the impedance changes. Atrophy and fibrosis are examined as candidates for that mechanism, but it is argued that their effects are too small to explain the observed changes. Fundamental considerations aside, the sensitivity, reproducibility and technical simplicity of the technique recommend its use for in-flight assessments of muscles during orbital or interplanetary missions. (paper)

  3. Visualized Multiprobe Electrical Impedance Measurements with STM Tips Using Shear Force Feedback Control

    Directory of Open Access Journals (Sweden)

    Luis Botaya

    2016-05-01

    Full Text Available Here we devise a multiprobe electrical measurement system based on quartz tuning forks (QTFs and metallic tips capable of having full 3D control over the position of the probes. The system is based on the use of bent tungsten tips that are placed in mechanical contact (glue-free solution with a QTF sensor. Shear forces acting in the probe are measured to control the tip-sample distance in the Z direction. Moreover, the tilting of the tip allows the visualization of the experiment under the optical microscope, allowing the coordination of the probes in X and Y directions. Meanwhile, the metallic tips are connected to a current–voltage amplifier circuit to measure the currents and thus the impedance of the studied samples. We discuss here the different aspects that must be addressed when conducting these multiprobe experiments, such as the amplitude of oscillation, shear force distance control, and wire tilting. Different results obtained in the measurement of calibration samples and microparticles are presented. They demonstrate the feasibility of the system to measure the impedance of the samples with a full 3D control on the position of the nanotips.

  4. Assessment of regional ventilation distribution: comparison of vibration response imaging (VRI) with electrical impedance tomography (EIT).

    Science.gov (United States)

    Shi, Chang; Boehme, Stefan; Bentley, Alexander H; Hartmann, Erik K; Klein, Klaus U; Bodenstein, Marc; Baumgardner, James E; David, Matthias; Ullrich, Roman; Markstaller, Klaus

    2014-01-01

    Vibration response imaging (VRI) is a bedside technology to monitor ventilation by detecting lung sound vibrations. It is currently unknown whether VRI is able to accurately monitor the local distribution of ventilation within the lungs. We therefore compared VRI to electrical impedance tomography (EIT), an established technique used for the assessment of regional ventilation. Simultaneous EIT and VRI measurements were performed in the healthy and injured lungs (ALI; induced by saline lavage) at different PEEP levels (0, 5, 10, 15 mbar) in nine piglets. Vibration energy amplitude (VEA) by VRI, and amplitudes of relative impedance changes (rel.ΔZ) by EIT, were evaluated in seven regions of interest (ROIs). To assess the distribution of tidal volume (VT) by VRI and EIT, absolute values were normalized to the VT obtained by simultaneous spirometry measurements. Redistribution of ventilation by ALI and PEEP was detected by VRI and EIT. The linear correlation between pooled VT by VEA and rel.ΔZ was R(2) = 0.96. Bland-Altman analysis showed a bias of -1.07±24.71 ml and limits of agreement of -49.05 to +47.36 ml. Within the different ROIs, correlations of VT-distribution by EIT and VRI ranged between R(2) values of 0.29 and 0.96. ALI and PEEP did not alter the agreement of VT between VRI and EIT. Measurements of regional ventilation distribution by VRI are comparable to those obtained by EIT.

  5. QUANTIFICATION OF RESPIRATORY SINUS ARRHYTHMIA WITH HIGH-FRAMERATE ELECTRICAL IMPEDANCE TOMOGRAPHY

    Directory of Open Access Journals (Sweden)

    Christoph Hoog Antink

    2013-12-01

    Full Text Available Respiratory Sinus Arrhythmia, the variation in the heart rate synchronized with the breathing cycle, forms an interconnection between cardiac-related and respiratory-related signals. It can be used by itself for diagnostic purposes, or by exploiting the redundancies it creates, for example by extracting respiratory rate from an electrocardiogram (ECG. To perform quantitative analysis and patient specific modeling, however, simultaneous information about ventilation as well as cardiac activity needs to be recorded and analyzed. The recent advent of medically approved Electrical Impedance Tomography (EIT devices capable of recording up to 50 frames per second facilitates the application of this technology. This paper presents the automated selection of a cardiac-related signal from EIT data and quantitative analysis of this signal. It is demonstrated that beat-to-beat intervals can be extracted with a median absolute error below 20 ms. A comparison between ECG and EIT data shows a variation in peak delay time that requires further analysis. Finally, the known coupling of heart rate variability and tidal volume can be shown and quantified using global impedance as a surrogate for tidal volume.

  6. Optical breast shape capture and finite-element mesh generation for electrical impedance tomography

    International Nuclear Information System (INIS)

    Forsyth, J; Borsic, A; Halter, R J; Hartov, A; Paulsen, K D

    2011-01-01

    X-ray mammography is the standard for breast cancer screening. The development of alternative imaging modalities is desirable because mammograms expose patients to ionizing radiation. Electrical impedance tomography (EIT) may be used to determine tissue conductivity, a property which is an indicator of cancer presence. EIT is also a low-cost imaging solution and does not involve ionizing radiation. In breast EIT, impedance measurements are made using electrodes placed on the surface of the patient's breast. The complex conductivity of the volume of the breast is estimated by a reconstruction algorithm. EIT reconstruction is a severely ill-posed inverse problem. As a result, noisy instrumentation and incorrect modelling of the electrodes and domain shape produce significant image artefacts. In this paper, we propose a method that has the potential to reduce these errors by accurately modelling the patient breast shape. A 3D hand-held optical scanner is used to acquire the breast geometry and electrode positions. We develop methods for processing the data from the scanner and producing volume meshes accurately matching the breast surface and electrode locations, which can be used for image reconstruction. We demonstrate this method for a plaster breast phantom and a human subject. Using this approach will allow patient-specific finite-element meshes to be generated which has the potential to improve the clinical value of EIT for breast cancer diagnosis

  7. A Versatile and Reproducible Multi-Frequency Electrical Impedance Tomography System

    Directory of Open Access Journals (Sweden)

    James Avery

    2017-01-01

    Full Text Available A highly versatile Electrical Impedance Tomography (EIT system, nicknamed the ScouseTom, has been developed. The system allows control over current amplitude, frequency, number of electrodes, injection protocol and data processing. Current is injected using a Keithley 6221 current source, and voltages are recorded with a 24-bit EEG system with minimum bandwidth of 3.2 kHz. Custom PCBs interface with a PC to control the measurement process, electrode addressing and triggering of external stimuli. The performance of the system was characterised using resistor phantoms to represent human scalp recordings, with an SNR of 77.5 dB, stable across a four hour recording and 20 Hz to 20 kHz. In studies of both haeomorrhage using scalp electrodes, and evoked activity using epicortical electrode mats in rats, it was possible to reconstruct images matching established literature at known areas of onset. Data collected using scalp electrode in humans matched known tissue impedance spectra and was stable over frequency. The experimental procedure is software controlled and is readily adaptable to new paradigms. Where possible, commercial or open-source components were used, to minimise the complexity in reproduction. The hardware designs and software for the system have been released under an open source licence, encouraging contributions and allowing for rapid replication.

  8. Temperature-dependent impedance spectroscopy of La0.8Sr0.2FeO3 nano-crystalline material

    Science.gov (United States)

    Kafa, C. A.; Triyono, D.; Laysandra, H.

    2017-04-01

    LaFeO3 is a material with perovskite structure which electrical properties frequently investigated. Research are done due to the exhibition of excellent gas sensing behavior through resistivity comparison from the p-type semiconductor. Sr doping on LaFeO3 or La1-xSrxFeO3 are able to improve the electrical conductivity through structural modification. Using Sr dopant concentration (x) of 0.2, La0.8Sr0.2FeO3 nano-crystal pellet was synthesized. The synthesis used sol-gel method, followed by gradual heat treatment and uniaxial compaction. XRD characterization shows that the structure of the sample is Orthorhombic Perovskite. Topography of the sample by SEM reveals grain and grain boundary existence with emerging agglomeration. The electrical properties of the material, as functions of temperature and frequency, were measured by Impedance Spectroscopy method using RLC meter, for temperatures of 303-373K. Through the Nyquist plot and Bode plot, the electrical conductivity of La0.8Sr0.2FeO3 is contributed by the grain and grain boundary. Finally, the electrical permittivities of La0.8Sr0.2FeO3 are increasing with temperature increase, with the highest achieved when measured at 1 kHz frequency.

  9. Frequency effects on charge ordering in Y0.5Ca0.5MnO3 by impedance spectroscopy

    Science.gov (United States)

    Sarwar, Tuba; Qamar, Afzaal; Nadeem, Muhammad

    2015-02-01

    In this work, structural and electrical properties of Y0.5Ca0.5MnO3 are investigated by employing X-ray diffraction and impedance spectroscopy, respectively. Applied ac electric field showed the charge ordering transition temperature around 265 K and below this temperature the heteromorphic behavior of the sample is discussed in the proximity of TCO. With frequency effects the volume of robust charge orbital ordering (COO) domains diminishes due to different competing phases along with Jahn Teller distortions. Comprehensive melting and collapse of charge orbital ordering occurs below TN(125 K), where a colossal drop in the value of impedance is observed. The change in profile of modulus plane plots determines the spreading of relaxation time of intermingled phases. Hopping mechanism is elaborated in terms of strong electron phonon coupling. Variable range hopping model and Arrhenius model are used to discuss the short and long range hopping between Mn3+ and Mn4+ channels assessing the activation energy Ea.

  10. A partially reflecting random walk on spheres algorithm for electrical impedance tomography

    Energy Technology Data Exchange (ETDEWEB)

    Maire, Sylvain, E-mail: maire@univ-tln.fr [Laboratoire LSIS Equipe Signal et Image, Université du Sud Toulon-Var, Av. Georges Pompidou, BP 56, 83162 La Valette du Var Cedex (France); Simon, Martin, E-mail: simon@math.uni-mainz.de [Institute of Mathematics, Johannes Gutenberg University, 55099 Mainz (Germany)

    2015-12-15

    In this work, we develop a probabilistic estimator for the voltage-to-current map arising in electrical impedance tomography. This novel so-called partially reflecting random walk on spheres estimator enables Monte Carlo methods to compute the voltage-to-current map in an embarrassingly parallel manner, which is an important issue with regard to the corresponding inverse problem. Our method uses the well-known random walk on spheres algorithm inside subdomains where the diffusion coefficient is constant and employs replacement techniques motivated by finite difference discretization to deal with both mixed boundary conditions and interface transmission conditions. We analyze the global bias and the variance of the new estimator both theoretically and experimentally. Subsequently, the variance of the new estimator is considerably reduced via a novel control variate conditional sampling technique which yields a highly efficient hybrid forward solver coupling probabilistic and deterministic algorithms.

  11. Ventilation inhomogeneity in obstructive lung diseases measured by electrical impedance tomography: a simulation study.

    Science.gov (United States)

    Schullcke, B; Krueger-Ziolek, S; Gong, B; Jörres, R A; Mueller-Lisse, U; Moeller, K

    2017-10-10

    Electrical impedance tomography (EIT) has mostly been used in the Intensive Care Unit (ICU) to monitor ventilation distribution but is also promising for the diagnosis in spontaneously breathing patients with obstructive lung diseases. Beside tomographic images, several numerical measures have been proposed to quantitatively assess the lung state. In this study two common measures, the 'Global Inhomogeneity Index' and the 'Coefficient of Variation' were compared regarding their capability to reflect the severity of lung obstruction. A three-dimensional simulation model was used to simulate obstructed lungs, whereby images were reconstructed on a two-dimensional domain. Simulations revealed that minor obstructions are not adequately recognized in the reconstructed images and that obstruction above and below the electrode plane may result in misleading values of inhomogeneity measures. EIT measurements on several electrode planes are necessary to apply these measures in patients with obstructive lung diseases in a promising manner.

  12. Basic setup for breast conductivity imaging using magnetic resonance electrical impedance tomography

    International Nuclear Information System (INIS)

    Lee, Byung Il; Oh, Suk Hoon; Kim, Tae-Seong; Woo, Eung Je; Lee, Soo Yeol; Kwon, Ohin; Seo, Jin Keun

    2006-01-01

    We present a new medical imaging technique for breast imaging, breast MREIT, in which magnetic resonance electrical impedance tomography (MREIT) is utilized to get high-resolution conductivity and current density images of the breast. In this work, we introduce the basic imaging setup of the breast MREIT technique with an investigation of four different imaging configurations of current-injection electrode positions and pathways through computer simulation studies. Utilizing the preliminary findings of a best breast MREIT configuration, additional numerical simulation studies have been carried out to validate breast MREIT at different levels of SNR. Finally, we have performed an experimental validation with a breast phantom on a 3.0 T MREIT system. The presented results strongly suggest that breast MREIT with careful imaging setups could be a potential imaging technique for human breast which may lead to early detection of breast cancer via improved differentiation of cancerous tissues in high-resolution conductivity images

  13. [Research on respiration course of human at different postures by electrical impedance tomography].

    Science.gov (United States)

    Chen, Xiaoyan; Wu, Jun; Wang, Huaxiang; Li, Da

    2010-10-01

    In this paper, the respiration courses of human at different postures are reconstructed by electrical impedance tomography (EIT). Conjugate gradient least squares (CGLS) algorithm is applied to reconstruct the resistivity distribution during respiration courses, and the EIT images taken from human at flat lying, left lying, right lying, sitting and prone postures are reconstructed and compared. The relative changes of the resistivity in region of interest (ROI) are analyzed to evidence the influences caused by different postures. Results show that the changes in postures are the most influential factors for the reconstructions, and the EIT images vary with the postures. In human at flat-lying posture, the left and right lungs have larger pulmonary ventilation volume simultaneously, and the EIT-measured data are of lower variability.

  14. Compensation for geometric modeling errors by positioning of electrodes in electrical impedance tomography

    International Nuclear Information System (INIS)

    Hyvönen, N; Majander, H; Staboulis, S

    2017-01-01

    Electrical impedance tomography aims at reconstructing the conductivity inside a physical body from boundary measurements of current and voltage at a finite number of contact electrodes. In many practical applications, the shape of the imaged object is subject to considerable uncertainties that render reconstructing the internal conductivity impossible if they are not taken into account. This work numerically demonstrates that one can compensate for inaccurate modeling of the object boundary in two spatial dimensions by finding compatible locations and sizes for the electrodes as a part of a reconstruction algorithm. The numerical studies, which are based on both simulated and experimental data, are complemented by proving that the employed complete electrode model is approximately conformally invariant, which suggests that the obtained reconstructions in mismodeled domains reflect conformal images of the true targets. The numerical experiments also confirm that a similar approach does not, in general, lead to a functional algorithm in three dimensions. (paper)

  15. A reconstruction algorithm for electrical impedance tomography based on sparsity regularization

    KAUST Repository

    Jin, Bangti

    2011-08-24

    This paper develops a novel sparse reconstruction algorithm for the electrical impedance tomography problem of determining a conductivity parameter from boundary measurements. The sparsity of the \\'inhomogeneity\\' with respect to a certain basis is a priori assumed. The proposed approach is motivated by a Tikhonov functional incorporating a sparsity-promoting ℓ 1-penalty term, and it allows us to obtain quantitative results when the assumption is valid. A novel iterative algorithm of soft shrinkage type was proposed. Numerical results for several two-dimensional problems with both single and multiple convex and nonconvex inclusions were presented to illustrate the features of the proposed algorithm and were compared with one conventional approach based on smoothness regularization. © 2011 John Wiley & Sons, Ltd.

  16. Sampling of finite elements for sparse recovery in large scale 3D electrical impedance tomography

    International Nuclear Information System (INIS)

    Javaherian, Ashkan; Moeller, Knut; Soleimani, Manuchehr

    2015-01-01

    This study proposes a method to improve performance of sparse recovery inverse solvers in 3D electrical impedance tomography (3D EIT), especially when the volume under study contains small-sized inclusions, e.g. 3D imaging of breast tumours. Initially, a quadratic regularized inverse solver is applied in a fast manner with a stopping threshold much greater than the optimum. Based on assuming a fixed level of sparsity for the conductivity field, finite elements are then sampled via applying a compressive sensing (CS) algorithm to the rough blurred estimation previously made by the quadratic solver. Finally, a sparse inverse solver is applied solely to the sampled finite elements, with the solution to the CS as its initial guess. The results show the great potential of the proposed CS-based sparse recovery in improving accuracy of sparse solution to the large-size 3D EIT. (paper)

  17. Image Reconstruction Based on Homotopy Perturbation Inversion Method for Electrical Impedance Tomography

    Directory of Open Access Journals (Sweden)

    Jing Wang

    2013-01-01

    Full Text Available The image reconstruction for electrical impedance tomography (EIT mathematically is a typed nonlinear ill-posed inverse problem. In this paper, a novel iteration regularization scheme based on the homotopy perturbation technique, namely, homotopy perturbation inversion method, is applied to investigate the EIT image reconstruction problem. To verify the feasibility and effectiveness, simulations of image reconstruction have been performed in terms of considering different locations, sizes, and numbers of the inclusions, as well as robustness to data noise. Numerical results indicate that this method can overcome the numerical instability and is robust to data noise in the EIT image reconstruction. Moreover, compared with the classical Landweber iteration method, our approach improves the convergence rate. The results are promising.

  18. Suitability of a PXI platform for an electrical impedance tomography system

    International Nuclear Information System (INIS)

    Kourunen, J; Savolainen, T; Lehikoinen, A; Vauhkonen, M; Heikkinen, L M

    2009-01-01

    There are many different electrical impedance tomography (EIT) systems which are either non-commercial (in-house products) or commercial products. However, these systems are usually designed for specific applications and therefore the functionality of the systems might be limited. Nowadays there are commercially available many low-cost, efficient and accurate multifunctional components for data acquisition and signal processing. Therefore, it should be possible to construct an EIT system which is mainly built from commercially available components. The main goal of this work was to study the performance of a PXI-based EIT system . In this work, a PXI-based EIT system with 16 independent current injection channels and 80 independent measurement channels was constructed and tested. The results indicate that an EIT system can be constructed using a PXI platform which decreases the construction time of the system. Moreover, the system is efficient, accurate, modular, and it is not limited to any predetermined measurement protocols

  19. Linearized image reconstruction method for ultrasound modulated electrical impedance tomography based on power density distribution

    International Nuclear Information System (INIS)

    Song, Xizi; Xu, Yanbin; Dong, Feng

    2017-01-01

    Electrical resistance tomography (ERT) is a promising measurement technique with important industrial and clinical applications. However, with limited effective measurements, it suffers from poor spatial resolution due to the ill-posedness of the inverse problem. Recently, there has been an increasing research interest in hybrid imaging techniques, utilizing couplings of physical modalities, because these techniques obtain much more effective measurement information and promise high resolution. Ultrasound modulated electrical impedance tomography (UMEIT) is one of the newly developed hybrid imaging techniques, which combines electric and acoustic modalities. A linearized image reconstruction method based on power density is proposed for UMEIT. The interior data, power density distribution, is adopted to reconstruct the conductivity distribution with the proposed image reconstruction method. At the same time, relating the power density change to the change in conductivity, the Jacobian matrix is employed to make the nonlinear problem into a linear one. The analytic formulation of this Jacobian matrix is derived and its effectiveness is also verified. In addition, different excitation patterns are tested and analyzed, and opposite excitation provides the best performance with the proposed method. Also, multiple power density distributions are combined to implement image reconstruction. Finally, image reconstruction is implemented with the linear back-projection (LBP) algorithm. Compared with ERT, with the proposed image reconstruction method, UMEIT can produce reconstructed images with higher quality and better quantitative evaluation results. (paper)

  20. Progress in electrical impedance imaging of binary media: 1: Analytical and numerical methods

    International Nuclear Information System (INIS)

    Ovacik, Levent; Lin Jentai; Jones, Owen C.

    1998-01-01

    This is the first of two papers summarizing the use of electrical impedance excitation/measurement for producing cross sectional images of the distribution of insulating media imbedded in conducting media. This computed tomographic approach finds the distribution of electrical properties of an electric field which minimizes in the least squares sense the difference between measured and computed boundary response to excitation. In this paper we briefly review the basic analytical methods developed for this system. We then extend these methods to three dimensions, add a method for preconditioning voltages for error correction, describe methods for optimizing the resolution of a target by providing optimal excitation patterns and then describe the overall numerical sensitivity. The second paper then demonstrates the ability of this system to image multiple, separate, differently-sized two-dimensional or three-dimensional targets with demonstrated linear sensitivity of over 30:1 with maximum possible linear sensitivity of one part in 1300 based on our ability to distinguish variations from a homogeneous background. (author)

  1. Determination of the distribution of air and water in porous media by electrical impedance tomography and magneto-electrical imaging

    Energy Technology Data Exchange (ETDEWEB)

    Haegel, Franz-Hubert, E-mail: f.h.haegel@fz-juelich.de [Forschungszentrum Juelich GmbH, Institut fuer Chemie und Dynamik der Geosphaere, ICG-4 Agrosphaere, 52425 Juelich (Germany); Zimmermann, Egon [Forschungszentrum Juelich GmbH, Zentralinstitut fuer Elektronik, 52425 Juelich (Germany); Esser, Odilia; Breede, Katrin; Huisman, Johan Alexander [Forschungszentrum Juelich GmbH, Institut fuer Chemie und Dynamik der Geosphaere, ICG-4 Agrosphaere, 52425 Juelich (Germany); Glaas, Walter; Berwix, Joachim [Forschungszentrum Juelich GmbH, Zentralinstitut fuer Elektronik, 52425 Juelich (Germany); Vereecken, Harry [Forschungszentrum Juelich GmbH, Institut fuer Chemie und Dynamik der Geosphaere, ICG-4 Agrosphaere, 52425 Juelich (Germany)

    2011-06-15

    Monitoring the distribution of water content is essential for understanding hydrological processes in the lithosphere and the pedosphere. The movement of water in unsaturated rock formations and in the vadose zone is influenced by different processes (mainly infiltration, evaporation, percolation and capillary flow) which may be rate determining depending on the actual conditions. The interdependence of these processes also strongly influences the transport and distribution of solutes in the pore space. In order to gain a better understanding of the movement and distribution of water in unsaturated media, systematic investigations with non-invasive or minimal invasive methods appear to be most suitable. Studies on the distribution of electrical conductivity can improve risk analysis concerning waste disposals in general and nuclear waste repositories in particular. Induced polarization and magnetic flux density determined with two highly sensitive accessories yield additional information and may allow for better discrimination of coupled flow processes. Electrical impedance tomography (EIT) with 20 current injection and 48 voltage electrodes was used here to monitor the evaporation of tap water from a container filled with sand under laboratory conditions at 20 deg. C. The results are compared with data obtained by determining spectral induced polarization (SIP) of sand during desaturation in a multi-step outflow equipment. Infiltration processes and evaporation from sand saturated with 0.01 M CaCl{sub 2} were determined by magneto-electrical resistivity imaging technique (MERIT). The results were obtained from a long-term experiment under controlled conditions.

  2. Electric field measurements in a xenon discharge using Spark spectroscopy

    NARCIS (Netherlands)

    Wagenaars, E.; Bowden, M.D.; Kroesen, G.M.W.

    2005-01-01

    Measurements of electric field distributions in a low-pressure xenon discharge are presented. The measurement technique is based on Stark spectroscopy, using a 2 + 1 excitation scheme with fluorescence dip detection. Electric fields can be measured by detecting Stark shifts of high-lying Rydberg

  3. SU-E-I-52: Validation of Multi-Frequency Electrical Impedance Tomography Using Computed Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kohli, K; Liu, F; Krishnan, K [BC Cancer Agency, Surrey, BC (United Kingdom)

    2014-06-01

    Purpose: Multi-frequency EIT has been reported to be a potential tool in distinguishing a tissue anomaly from background. In this study, we investigate the feasibility of acquiring functional information by comparing multi-frequency EIT images in reference to the structural information from the CT image through fusion. Methods: EIT data was acquired from a slice of winter melon using sixteen electrodes around the phantom, injecting a current of 0.4mA at 100, 66, 24.8 and 9.9 kHz. Differential EIT images were generated by considering different combinations of pair frequencies, one serving as reference data and the other as test data. The experiment was repeated after creating an anomaly in the form of an off-centered cavity of diameter 4.5 cm inside the melon. All EIT images were reconstructed using Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software (EIDORS) package in 2-D differential imaging mode using one-step Gaussian Newton minimization solver. CT image of the melon was obtained using a Phillips CT Scanner. A segmented binary mask image was generated based on the reference electrode position and the CT image to define the regions of interest. The region selected by the user was fused with the CT image through logical indexing. Results: Differential images based on the reference and test signal frequencies were reconstructed from EIT data. Result illustrated distinct structural inhomogeneity in seeded region compared to fruit flesh. The seeded region was seen as a higherimpedance region if the test frequency was lower than the base frequency in the differential EIT reconstruction. When the test frequency was higher than the base frequency, the signal experienced less electrical impedance in the seeded region during the EIT data acquisition. Conclusion: Frequency-based differential EIT imaging can be explored to provide additional functional information along with structural information from CT for identifying different tissues.

  4. Electrical impedance tomography as possible guidance for individual positioning of patients with multiple lung injury.

    Science.gov (United States)

    Lehmann, Sylvia; Leonhardt, Steffen; Ngo, Chuong; Bergmann, Lukas; Schrading, Simone; Heimann, Konrad; Wagner, Norbert; Tenbrock, Klaus

    2018-01-01

    Electrical Impedance Tomography (EIT) is a tomographic, radiation-free technique based on the injection of a harmless alternating current. As electrical impedance strictly correlates with the variation of air content, EIT delivers highly dynamic information about global and regional ventilation. We want to demonstrate the potential of EIT individualizing ventilation by positioning. Gravity-dependent EIT findings were analyzed retrospectively in a critically ill mechanically ventilated pediatric patient with cystic fibrosis and coincident lung diseases. To further evaluate gravity-dependent changes in ventilation, six adult healthy and spontaneously breathing volunteers were investigated during simultaneous detection of EIT, breathing patterns, tidal volume (VT) and breathing frequency (BF). EIT findings in healthy lungs in five positions showed gravity-dependent effects of ventilation with overall ventilation of predominantly the right lung (except during left-side positioning) and with the ventral lung in supine, prone and upright position. These EIT-derived observations are in line with pathophysiological mechanisms and earlier EIT studies. Unexpectedly, the patient with cystic fibrosis and lobectomy of the right upper and middle lobe one year earlier, showed improvement of global and regional ventilation in the right position despite reduced lung volume and overinflation of this side. This resulted in individualized positioning and improvement of ventilation. Although therapeutic recommendations are available for gravitational influences of lung ventilation, they can be contradictory depending on the underlying lung disease. EIT has the potential to guide therapists in the positioning of patients according to their individual condition and disease, especially in case of multiple lung injury. © 2016 John Wiley & Sons Ltd.

  5. SU-E-I-52: Validation of Multi-Frequency Electrical Impedance Tomography Using Computed Tomography

    International Nuclear Information System (INIS)

    Kohli, K; Liu, F; Krishnan, K

    2014-01-01

    Purpose: Multi-frequency EIT has been reported to be a potential tool in distinguishing a tissue anomaly from background. In this study, we investigate the feasibility of acquiring functional information by comparing multi-frequency EIT images in reference to the structural information from the CT image through fusion. Methods: EIT data was acquired from a slice of winter melon using sixteen electrodes around the phantom, injecting a current of 0.4mA at 100, 66, 24.8 and 9.9 kHz. Differential EIT images were generated by considering different combinations of pair frequencies, one serving as reference data and the other as test data. The experiment was repeated after creating an anomaly in the form of an off-centered cavity of diameter 4.5 cm inside the melon. All EIT images were reconstructed using Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software (EIDORS) package in 2-D differential imaging mode using one-step Gaussian Newton minimization solver. CT image of the melon was obtained using a Phillips CT Scanner. A segmented binary mask image was generated based on the reference electrode position and the CT image to define the regions of interest. The region selected by the user was fused with the CT image through logical indexing. Results: Differential images based on the reference and test signal frequencies were reconstructed from EIT data. Result illustrated distinct structural inhomogeneity in seeded region compared to fruit flesh. The seeded region was seen as a higherimpedance region if the test frequency was lower than the base frequency in the differential EIT reconstruction. When the test frequency was higher than the base frequency, the signal experienced less electrical impedance in the seeded region during the EIT data acquisition. Conclusion: Frequency-based differential EIT imaging can be explored to provide additional functional information along with structural information from CT for identifying different tissues

  6. Assessment of Some Advanced Protective Schemes, Including Chromate and Non-Chromate Conversion Coatings for Mg Alloy ZE41A-T5 Using Electrochemical Impedance Spectroscopy

    National Research Council Canada - National Science Library

    Chang, Frank

    1994-01-01

    .... Electrochemical Impedance Spectroscopy (EIS) and salt spray tests have been employed to compare the corrosion behavior in chloride containing solutions of Mg alloy ZE41A-T5 which has been coated with various combinations of a conversion coating...

  7. Real-time imaging and detection of intracranial haemorrhage by electrical impedance tomography in a piglet model.

    Science.gov (United States)

    Xu, C H; Wang, L; Shi, X T; You, F S; Fu, F; Liu, R G; Dai, M; Zhao, Z W; Gao, G D; Dong, X Z

    2010-01-01

    The aim of this study was to use electrical impedance tomography (EIT) to detect and image acute intracranial haemorrhage (ICH) in an animal model. Blood was infused into the frontal lobe of the brains of anaesthetized piglets and impedance was measured using 16 electrodes placed in a circle on the scalp. The EIT images were constructed using a filtered back-projection algorithm. The mean of all the pixel intensities within a region of interest--the mean resistivity value (MRV)--was used to evaluate the relative impedance changes in the target region. A symmetrical index (SI), reflecting the relative impedance on both sides of the brain, was also calculated. Changes in MRV and SI were associated with the injection of blood, demonstrating that EIT can successfully detect ICH in this animal model. The unique features of EIT may be beneficial for diagnosing ICH early in patients after cranial surgery, thereby reducing the risk of complications and mortality.

  8. A high-speed bioelectrical impedance spectroscopy system based on the digital auto-balancing bridge method

    International Nuclear Information System (INIS)

    Li, Nan; Xu, Hui; Zhou, Zhou; Wang, Wei; Qiao, Guofeng; Li, David D-U

    2013-01-01

    A novel bioelectrical impedance spectroscopy system based on the digital auto-balancing bridge method improved from the conventional analogue auto-balancing method is presented for bioelectrical impedance measurements. The hardware of the proposed system consists of a reference source, a null detector, a variable source, a field programmable gate array, a clock generator, a flash and a USB controller. Software implemented in the field programmable gate array includes three major blocks: clock management, peripheral control and digital signal processing. The principle and realization of the least-mean-squares-based digital auto-balancing algorithm is introduced in detail. The performances of our system were examined by comparing with a commercial impedance analyzer. The results reveal that the proposed system has high speed (less than 3.5 ms per measurement) and high accuracy in the frequency range of 1 kHz–10 MHz. Compared with the commercial instrument based on the traditional analogue auto-balancing method, our system shows advantages in measurement speed, compactness and flexibility, making it suitable for various bioelectrical impedance measurement applications. (paper)

  9. The use of electrochemical impedance spectroscopy (EIS) in the evaluation of the electrochemical properties of a microbial fuel cell.

    Science.gov (United States)

    Manohar, Aswin K; Bretschger, Orianna; Nealson, Kenneth H; Mansfeld, Florian

    2008-04-01

    Electrochemical impedance spectroscopy (EIS) has been used to determine several electrochemical properties of the anode and cathode of a mediator-less microbial fuel cell (MFC) under different operational conditions. These operational conditions included a system with and without the bacterial catalyst and EIS measurements at the open-circuit potential of the anode and the cathode or at an applied cell voltage. In all cases the impedance spectra followed a simple one-time-constant model (OTCM) in which the solution resistance is in series with a parallel combination of the polarization resistance and the electrode capacitance. Analysis of the impedance spectra showed that addition of Shewanella oneidensis MR-1 to a solution of buffer and lactate greatly increased the rate of the lactate oxidation at the anode under open-circuit conditions. The large decrease of open-circuit potential of the anode increased the cell voltage of the MFC and its power output. Measurements of impedance spectra for the MFC at different cell voltages resulted in determining the internal resistance (R(int)) of the MFC and it was found that R(int) is a function of cell voltage. Additionally, R(int) was equal to R(ext) at the cell voltage corresponding to maximum power, where R(ext) is the external resistance that must be applied across the circuit to obtain the maximum power output.

  10. Analysis of specification of an electrode type sensor equivalent circuit on the base of impedance spectroscopy simulation

    International Nuclear Information System (INIS)

    Ogurtsov, V I; Mathewson, A; Sheehan, M M

    2005-01-01

    Simulation of electrochemical impedance spectroscopy (EIS) based on a LabVIEW model of a complex impedance measuring system in the frequency domain has been investigated to specify parameters of Randle's equivalent circuit, which is ordinarily used for electrode sensors. The model was based on a standard system for EIS instrumentation and consisted of a sensor modelled by Randle's equivalent circuit, a source of harmonic frequency sweep voltage applied to the sensor and a transimpedance amplifier, which transformed the sensor current to voltage. It provided impedance spectroscopy data for different levels of noise, modelled by current and voltage equivalent noise sources applied to the amplifier input. The noise influence on Randle's equivalent circuit specification was analysed by considering the behaviour of the approximation error. Different metrics including absolute, relative, semilogarithmic and logarithmic based distance between complex numbers on a complex plane were considered and compared to one another for evaluating this error. It was shown that the relative and logarithmic based metrics provide more reliable results for the determination of circuit parameters

  11. Analysis of specification of an electrode type sensor equivalent circuit on the base of impedance spectroscopy simulation

    Energy Technology Data Exchange (ETDEWEB)

    Ogurtsov, V I; Mathewson, A; Sheehan, M M [Tyndall National Institute, Lee Maltings, Prospect Row, Cork (Ireland)

    2005-01-01

    Simulation of electrochemical impedance spectroscopy (EIS) based on a LabVIEW model of a complex impedance measuring system in the frequency domain has been investigated to specify parameters of Randle's equivalent circuit, which is ordinarily used for electrode sensors. The model was based on a standard system for EIS instrumentation and consisted of a sensor modelled by Randle's equivalent circuit, a source of harmonic frequency sweep voltage applied to the sensor and a transimpedance amplifier, which transformed the sensor current to voltage. It provided impedance spectroscopy data for different levels of noise, modelled by current and voltage equivalent noise sources applied to the amplifier input. The noise influence on Randle's equivalent circuit specification was analysed by considering the behaviour of the approximation error. Different metrics including absolute, relative, semilogarithmic and logarithmic based distance between complex numbers on a complex plane were considered and compared to one another for evaluating this error. It was shown that the relative and logarithmic based metrics provide more reliable results for the determination of circuit parameters.

  12. Investigation of conduction and relaxation phenomena in BaZrxTi1−xO3 (x=0.05) by impedance spectroscopy

    International Nuclear Information System (INIS)

    Mahajan, Sandeep; Haridas, Divya; Ali, S.T.; Munirathnam, N.R.; Sreenivas, K.; Thakur, O.P.; Prakash, Chandra

    2014-01-01

    In present study we have prepared ferroelectric BaZr x Ti 1−x O 3 (x=0.05) ceramic by conventional solid state reaction route and studied its electrical properties as a function of temperature and frequency. X-ray diffraction (XRD) analysis shows single-phase formation of the compound with orthorhombic crystal structure at room temperature. Impedance and electric modulus spectroscopy analysis in the frequency range of 40 Hz–1 MHz at high temperature (200–600 °C) suggests two relaxation processes with different time constant are involved which are attributed to bulk and grain boundary effects. Frequency dependent dielectric plot at different temperature shows normal variation with frequency while dielectric loss (tanδ) peak was found to obey an Arrhenius law with activation energy of 1.02 eV. The frequency-dependent AC conductivity data were also analyzed in a wide temperature range. - Graphical abstract: The electrical properties which give electrical microstructure that correlates to its ceramic microstructure are less studied for BZT. Various parameters such as grain, grain boundary and electrode/interface that affect the electrical properties in ceramics. The charge transport can be attributed to the charge displacement, dipole reorientation and space charge formation. In present work we have studied the role of grain and grain boundaries on the electrical behaviour of Zr-doped BaTiO 3 and their dependence on temperature and frequency by complex impedance and modulus spectroscopy (CIS) technique in a wide frequency (40 Hz–1 MHz) and high temperature range. - Highlights: • BaZr x Ti 1−x O 3 (x=0.05) ceramic by conventional solid state reaction route. • CIS used to study the material behaviour in wide range of frequency and temperature. • tanδ peak was found to obey an Arrhenius law with activation energy of 1.02 eV. • A parallel combination of RC circuit found for grain and grain boundaries

  13. Automated criterion-based analysis for Cole parameters assessment from cerebral neonatal electrical bioimpedance spectroscopy measurements

    International Nuclear Information System (INIS)

    Seoane, F; Lindecrantz, Kaj; Ward, L C; Lingwood, B E

    2012-01-01

    Hypothermia has been proven as an effective rescue therapy for infants with moderate or severe neonatal hypoxic ischemic encephalopathy. Hypoxia-ischemia alters the electrical impedance characteristics of the brain in neonates; therefore, spectroscopic analysis of the cerebral bioimpedance of the neonate may be useful for the detection of candidate neonates eligible for hypothermia treatment. Currently, in addition to the lack of reference bioimpedance data obtained from healthy neonates, there is no standardized approach established for bioimpedance spectroscopy data analysis. In this work, cerebral bioimpedance measurements (12 h postpartum) in a cross-section of 84 term and near-term healthy neonates were performed at the bedside in the post-natal ward. To characterize the impedance spectra, Cole parameters (R 0 , R ∞ , f C and α) were extracted from the obtained measurements using an analysis process based on a best measurement and highest likelihood selection process. The results obtained in this study complement previously reported work and provide a standardized criterion-based method for data analysis. The availability of electrical bioimpedance spectroscopy reference data and the automatic criterion-based analysis method might support the development of a non-invasive method for prompt selection of neonates eligible for cerebral hypothermic rescue therapy. (paper)

  14. Biomass production and control of nutrient leaching of willows using different planting methods with special emphasis on an appraisal of the electrical impedance for roots

    Energy Technology Data Exchange (ETDEWEB)

    Yang Cao

    2011-07-01

    Willow reproduction can be achieved through vertically or horizontally planted cuttings. Conventionally, plantations are established by inserting cuttings vertically into the soil. There is, however, a lack of information about the biomass production and nutrient leaching of plantations established through horizontally planted cuttings. A greenhouse experiment and a field trial were carried out to investigate whether horizontally planted Salix schwerinii cuttings have a positive effect on stem yield, root distribution and nutrient leaching in comparison with vertically planted cuttings with different planting densities. The shoots' height of horizontally planted cuttings was significantly smaller than that of vertically planted cuttings during the first two weeks after planting in the pot experiment. Thereafter, no significant effect of planting orientation on the stem biomass was observed in the two conducted experiments. In both experiments the total stem biomass increased with the planting density. It was also found that the fine root biomass and the specific root length were not affected by the planting orientation or density, while the fine root surface area and the absorbing root surface area (ARSA) were affected only by the planting density. The planting orientation did not affect the nutrient concentrations in the soil leachate, apart from SO{sub 4}-S and PO{sub 4}-P in the pot experiment. The ARSA in the pot experiment was assessed by using the earth impedance method. The applicability of this method was evaluated in a hydroponic study of willow cuttings where root and stem were measured independently. Electrical resistance had a good correlation with the contact area of the roots with the solution. However, the resistance depended strongly on the contact area of the stem with the solution, which caused a bias in the evaluation of root surface area. A similar experimental set-up with electrical impedance spectroscopy was employed to study the

  15. A new method for electric impedance imaging using an eddy current with a tetrapolar circuit.

    Science.gov (United States)

    Ahsan-Ul-Ambia; Toda, Shogo; Takemae, Tadashi; Kosugi, Yukio; Hongo, Minoru

    2009-02-01

    A new contactless technique for electrical impedance imaging, using an eddy current managed along with the tetrapolar circuit method, is proposed. The eddy current produced by a magnetic field is superimposed on a constant current that is normally used in the tetrapolar circuit method, and thus is used to control the current distribution in the body. By changing the current distribution, a set of voltage differences is measured with a pair of electrodes. This set of voltage differences is used in the image reconstruction of the resistivity distribution. The least square error minimization method is used in the reconstruction algorithm. The principle of this method is explained theoretically. A backprojection algorithm was used to get 2-D images. Based on this principle, a measurement system was developed and model experiments were conducted with a saline-filled phantom. The estimated shape of each model in the reconstructed image was similar to that of the corresponding model. From the results of these experiments, it is confirmed that the proposed method is applicable to the realization of electrical conductivity imaging.

  16. Electrical impedance scanning - application of this new technique for lymph node evaluation in children

    Energy Technology Data Exchange (ETDEWEB)

    Mentzel, Hans-Joachim; Malich, Ansgar; Freesmeyer, Martin; Boettcher, Joachim; Vogt, Susanna; Kaiser, Werner A. [Institute of Diagnostic and Interventional Radiology, University of Jena, Bachstrasse 18, 07740 Jena (Germany); Kentouche, Karim; Gruhn, Bernd; Zintl, Felix [Department of Pediatrics, University of Jena, Jena (Germany); Schneider, Gerlind [Department of Otorhinolaryngology, University of Jena, Jena (Germany); Anderson, Roselle [Siemens-Elema, Elema (Sweden)

    2003-07-01

    Precise assessment of lymph nodes is crucial to the choice of therapy and prediction of outcome in cases of malignancy. Electrical impedance scanning (EIS) is being experimentally investigated for potential use as a diagnostic tool for differentiation of malignant lesions. Malignancies show different electrical properties with changes in conductivity and capacitance that can be analysed by EIS. Using a TransScan TS-2000 (TransScan Medical, Migdal Ha'Emek, Israel, distributed by Siemens-Elema AB, Solna, Sweden), EIS has been used in various studies for the identification of breast cancer as well as for characterisation of superficial lesions. To evaluate the reliability of EIS for classifying lymph nodes in a pediatric population with sonographically suspicious lesions and to prove its accuracy. The study population consisted of 77 children (42 boys, 35 girls) aged 1.1-17.1 years. All EIS results were compared to either histopathological findings or long-term follow-up investigations. Sensitivity for malignancies using EIS was 75% and specificity was 87%. The negative predictive value was 93% and the positive predictive value was 60%. This study suggests the potential usefulness of EIS as an additional imaging modality for the differentiation of lymph-node diseases in children. The histopatholgical spectrum of malignant lymph node transformation in children compared to studies in adults, and the characteristic meltdown in inflammatory or granulomatous transformed nodes, pose challenges to differentiation based on sonographic evaluation, and also to EIS classification. (orig.)

  17. A motion-compensated cone-beam CT using electrical impedance tomography imaging

    International Nuclear Information System (INIS)

    Pengpan, T; Smith, N D; Qiu, W; Yao, A; Mitchell, C N; Soleimani, M

    2011-01-01

    Cone-beam CT (CBCT) is an imaging technique used in conjunction with radiation therapy. For example CBCT is used to verify the position of lung cancer tumours just prior to radiation treatment. The accuracy of the radiation treatment of thoracic and upper abdominal structures is heavily affected by respiratory movement. Such movement typically blurs the CBCT reconstruction and ideally should be removed. Hence motion-compensated CBCT has recently been researched for correcting image artefacts due to breathing motion. This paper presents a new dual-modality approach where CBCT is aided by using electrical impedance tomography (EIT) for motion compensation. EIT can generate images of contrasts in electrical properties. The main advantage of using EIT is its high temporal resolution. In this paper motion information is extracted from EIT images and incorporated directly in the CBCT reconstruction. In this study synthetic moving data are generated using simulated and experimental phantoms. The paper demonstrates that image blur, created as a result of motion, can be reduced through motion compensation with EIT

  18. Reconstruction of electrical impedance tomography (EIT) images based on the expectation maximum (EM) method.

    Science.gov (United States)

    Wang, Qi; Wang, Huaxiang; Cui, Ziqiang; Yang, Chengyi

    2012-11-01

    Electrical impedance tomography (EIT) calculates the internal conductivity distribution within a body using electrical contact measurements. The image reconstruction for EIT is an inverse problem, which is both non-linear and ill-posed. The traditional regularization method cannot avoid introducing negative values in the solution. The negativity of the solution produces artifacts in reconstructed images in presence of noise. A statistical method, namely, the expectation maximization (EM) method, is used to solve the inverse problem for EIT in this paper. The mathematical model of EIT is transformed to the non-negatively constrained likelihood minimization problem. The solution is obtained by the gradient projection-reduced Newton (GPRN) iteration method. This paper also discusses the strategies of choosing parameters. Simulation and experimental results indicate that the reconstructed images with higher quality can be obtained by the EM method, compared with the traditional Tikhonov and conjugate gradient (CG) methods, even with non-negative processing. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

  19. Impedance spectroscopy of heterojunction solar cell a-SiC/c-Si with ITO antireflection film investigated at different temperatures

    International Nuclear Information System (INIS)

    Šály, V; Pern, M; Janíček, F; Mikolášek, M; Packa, J; Huran, J

    2017-01-01

    Progressive smart photovoltaic technologies including heterostructures a-SiC/c-Si with ITO antireflection film are one of the prospective replacements of conventional photovoltaic silicon technology. Our paper is focused on the investigation of heterostructures a-SiC/c-Si provided with a layer of ITO (indium oxide/tin oxide 90/10 wt.%) which acts as a passivating and antireflection coating. Prepared photovoltaic cell structure was investigated at various temperatures and the influence of temperature on its operation was searched. The investigation of the dynamic properties of heterojunction PV cells was carried out using impedance spectroscopy. The equivalent AC circuit which approximates the measured impedance data was proposed. Assessment of the influence of the temperature on the operation of prepared heterostructure was carried out by analysis of the temperature dependence of AC equivalent circuit elements. (paper)

  20. Impedance spectroscopy of heterojunction solar cell a-SiC/c-Si with ITO antireflection film investigated at different temperatures

    Science.gov (United States)

    Šály, V.; Perný, M.; Janíček, F.; Huran, J.; Mikolášek, M.; Packa, J.

    2017-04-01

    Progressive smart photovoltaic technologies including heterostructures a-SiC/c-Si with ITO antireflection film are one of the prospective replacements of conventional photovoltaic silicon technology. Our paper is focused on the investigation of heterostructures a-SiC/c-Si provided with a layer of ITO (indium oxide/tin oxide 90/10 wt.%) which acts as a passivating and antireflection coating. Prepared photovoltaic cell structure was investigated at various temperatures and the influence of temperature on its operation was searched. The investigation of the dynamic properties of heterojunction PV cells was carried out using impedance spectroscopy. The equivalent AC circuit which approximates the measured impedance data was proposed. Assessment of the influence of the temperature on the operation of prepared heterostructure was carried out by analysis of the temperature dependence of AC equivalent circuit elements.

  1. Exfoliation corrosion of Al-Zn-Mg-Cu-Zr alloy containing Sc examined by electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Y.P.; Liu, X.Y.; He, Y.B.; Li, C.L. [School of Materials Science and Engineering, Central South University, Changsha (China); Pan, Q.L. [School of Materials Science and Engineering, Central South University, Changsha (China); The Key Laboratory of Nonferrous Materials Science and Engineering of Ministry of Education, Changsha (China); Li, W.B. [School of Materials Science and Engineering, Central South University, Changsha (China); School of Civil Engineering, Hunan City University, Yiyang (China)

    2012-02-15

    The exfoliation corrosion behavior of an Al-Zn-Mg-Cu-Zr alloy containing Sc artificially aged at 120 C for 24 h is studied by macroscopic observation techniques and electrochemical impedance spectroscopy (EIS) measurements. After 48 h immersion, the blisters start bursting and delamination initiates, along with the appearance of two time constants in the impedance diagrams. According to the simulation by equivalent circuit, the corrosion rate decreases sharply and then reaches a steady state, which is due to the change of the solution pH and oxide layer thickness, as well as the accumulation of corrosion products. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Analysing impact of oxygen and water exposure on roll-coated organic solar cell performance using impedance spectroscopy

    DEFF Research Database (Denmark)

    Arredondo, B.; Romero, B.; Beliatis, M. J.

    2018-01-01

    In this work we study the degradation of roll-coated flexible inverted organic solar cells in different atmospheres. We demonstrate that impedance spectroscopy is a powerful tool for elucidating degradation mechanisms; it is used here to distinguish the different degradation mechanisms due to water...... and oxygen. Identical cells were exposed to different accelerated degradation environments using water only, oxygen only, and both water and oxygen simultaneously, all of them enhanced with UV light. The photocurrent is dramatically reduced in the oxygen-degraded samples. Impedance measurements indicate...... of degradation differs for the water and oxygen degraded samples. While oxygen + UV light decreases the conductivity of the PEDOT:PSS layer, water + UV light changes the PEDOT:PSS work function inducing a depletion region at the anode....

  3. Electrical stunning and exsanguination decrease the extracellular volume in the broiler brain as studied with brain impedance recordings

    NARCIS (Netherlands)

    Savenije, B; Lambooij, E; Pieterse, C; Korf, J

    Electrical stunning in the process of slaughtering poultry is used to induce unconsciousness and immobilize the animal for easier processing. Unconsciousness is a function of brain damage. Brain damage has been studied with brain impedance recordings under ischemic conditions. This experiment

  4. Textrode-enabled transthoracic electrical bioimpedance measurements - towards wearable applications of impedance cardiography

    Directory of Open Access Journals (Sweden)

    Juan Carlos Márquez Ruiz

    2013-10-01

    Full Text Available During the last decades the use of Electrical Bioimpedance (EBI in the medical field has been subject of extensive research, especially since it is an affordable, harmless and non-invasive technology. In some specific applications such as body composition assessment where EBI has proven a good degree of effectiveness and reliability, the use of textile electrodes and measurement garments have shown a good performance and reproducible results. Impedance Cardiography (ICG is another modality of EBI that can benefit from the implementation and use of wearable sensors. ICG technique is based on continuous impedance measurements of a longitudinal segment across the thorax taken at a single frequency. The need for specific electrode placement on the thorax and neck can be easily ensured with the use of a garment with embedded textile electrodes, textrodes. The first step towards the implementation of ICG technology into a garment is to find out if ICG measurements with textile sensors give a good enough quality of the signal to allow the estimation of the fundamental ICG parameters. In this work, the measurement performance of a 2-belt set with incorporated textrodes for thorax and neck was compared against ICG measurements obtained with Ag/AgCl electrodes. The analysis was based on the quality of the fundamental ICG signals (∆Z, dZ/dt and ECG, systolic time intervals and other ICG parameters. The obtained results indicate the feasibility of using textrodes for ICG measurements with consistent measurements and relatively low data dispersion. Thus, enabling the development of measuring garments for ICG measurements.

  5. Unilateral empyema impacts the assessment of regional lung ventilation by electrical impedance tomography

    International Nuclear Information System (INIS)

    Bläser, D; Becher, T; Schädler, D; Elke, G; Weiler, N; Frerichs, I; Pulletz, S

    2014-01-01

    Several studies have shown the ability of electrical impedance tomography (EIT) to assess regional ventilation distribution in human lungs. Fluid accumulation in the pleural space as in empyema, typically occurring on one chest side, may influence the distribution of ventilation and the corresponding EIT findings. The aim of our study was to examine this effect on the assessment of regional ventilation by EIT. Six patients suffering from unilateral empyema and intubated with a double-lumen endotracheal tube were studied. EIT data were acquired during volume-controlled ventilation with bilateral (tidal volume (V T ): 800 ml) and unilateral ventilation (V T : 400 ml) of the right and left lungs. Mean tidal amplitudes of the EIT signal were calculated in all image pixels. The sums of these values, expressed as relative impedance change (rel. ΔZ), were then determined in whole images and functionally defined regions-of-interest (ROI). The sums of rel. ΔZ calculated during the two cases of one-lung ventilation either on the affected or unaffected side were significantly smaller than during bilateral ventilation. However, in contrast to previous findings in patients with no pleural pathology, very low values of rel. ΔZ were found when the lung on the affected side was ventilated. ROI-based analysis rendered higher values than the whole-image analysis in this case, nonetheless, the values were significantly smaller than when the unaffected side was ventilated in spite of identical V T . In conclusion, our results indicate that the presence of empyema may affect the quantitative evaluation of regional lung ventilation by EIT. (paper)

  6. Electrochemical Impedance Spectroscopy Illuminating Performance Evolution of Porous Core–Shell Structured Nickel/Nickel Oxide Anode Materials

    International Nuclear Information System (INIS)

    Yan, Bo; Li, Minsi; Li, Xifei; Bai, Zhimin; Dong, Lei; Li, Dejun

    2015-01-01

    Highlights: • The electrochemical reaction kinetics of the Ni/NiO anode was studied for the first time. • Charge transfer resistance is main contribution to total resistance during discharge process. • The slow growth of the SEI film is responsible for the capacity fading upon cycling. • Some promising strategies to optimize NiO anode performance were summarized. - Abstract: The electrochemical reaction kinetics of the porous core–shell structured Ni/NiO anode for Li ion battery application is systematically investigated by monitoring the electrochemical impedance evolution for the first time. The electrochemical impedance under prescribed condition is measured by using impedance spectroscopy in equilibrium conditions at various depths of discharge (DOD) during charge–discharge cycles. The Nyquist plots of the binder-free porous Ni/NiO electrode are interpreted with a selective equivalent circuit composed of solution resistance, solid electrolyte interphase (SEI) film, charge transfer and solid state diffusion. The impedance analysis shows that the change of charge transfer resistance is the main contribution to the total resistance change during discharge, and the surface configuration of the obtained electrode may experience significant change during the first two cycles. Meanwhile, the increase of internal resistance reduced the utilization efficiency of the active material may be another convincing factor to increase the irreversible capacity. In addition, the impedance evolution of the as-prepared electrode during charge–discharge cycles reveals that the slow growth of the SEI film is responsible for the capacity fading after long term cycling. As a result, several strategies are summarized to optimize the electrochemical performances of transition metal oxide anodes for lithium ion batteries

  7. Methodology for Time-Domain Estimation of Storm-Time Electric Fields Using the 3D Earth Impedance

    Science.gov (United States)

    Kelbert, A.; Balch, C. C.; Pulkkinen, A. A.; Egbert, G. D.; Love, J. J.; Rigler, E. J.; Fujii, I.

    2016-12-01

    Magnetic storms can induce geoelectric fields in the Earth's electrically conducting interior, interfering with the operations of electric-power grid industry. The ability to estimate these electric fields at Earth's surface in close to real-time and to provide local short-term predictions would improve the ability of the industry to protect their operations. At any given time, the electric field at the Earth's surface is a function of the time-variant magnetic activity (driven by the solar wind), and the local electrical conductivity structure of the Earth's crust and mantle. For this reason, implementation of an operational electric field estimation service requires an interdisciplinary, collaborative effort between space science, real-time space weather operations, and solid Earth geophysics. We highlight in this talk an ongoing collaboration between USGS, NOAA, NASA, Oregon State University, and the Japan Meteorological Agency, to develop algorithms that can be used for scenario analyses and which might be implemented in a real-time, operational setting. We discuss the development of a time domain algorithm that employs discrete time domain representation of the impedance tensor for a realistic 3D Earth, known as the discrete time impulse response (DTIR), convolved with the local magnetic field time series, to estimate the local electric field disturbances. The algorithm is validated against measured storm-time electric field data collected in the United States and Japan. We also discuss our plans for operational real-time electric field estimation using 3D Earth impedances.

  8. Current distribution effects in AC impedance spectroscopy of electroceramic point contact and thin film model electrodes

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Jacobsen, Torben

    2010-01-01

    the primary current distribution to the DC current distribution restricted to the Three-Phase-Boundary (TPB) zone introduces an error in the determination of the reaction resistance, Rreac = Z(freq. → 0) − Z(freq. → ∞). The error is estimated for different width of the effective TPB zone and a rule of thumb...... regarding its significance is provided. The associated characteristic impedance spectrum shape change is simulated and its origin discussed. Furthermore, the characteristic shape of impedance spectra of thin electroceramic film electrodes with lateral ohmic resistance is studied as a function...

  9. Monitoring of peptide induced disruption of artificial lipid membrane constructed on boron-doped nanocrystalline diamond by electrochemical impedance spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Petrák, V.; Grieten, L.; Taylor, Andrew; Fendrych, František; Ledvina, Miroslav; Janssens, S. D.; Nesládek, M.; Haenen, K.; Wagner, P.

    2011-01-01

    Roč. 208, č. 9 (2011), s. 2099-2103 ISSN 1862-6300 R&D Projects : GA AV ČR KAN200100801; GA AV ČR(CZ) KAN400480701; GA MŠk(CZ) LD11076 Grant - others:European RD projects (XE) 238201-MATCON Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z10100520 Keywords : biosensor * boron-doped nanocrystalline diamond * electrochemical impedance spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.463, year: 2011

  10. Impedance spectroscopy of SrBi2Ta2O9 and SrBi2Nb2O9 ceramics correlation with fatigue behavior

    International Nuclear Information System (INIS)

    Chen, T.; Thio, C.; Desu, S.B.

    1997-01-01

    In this research, a fatigue model for ferroelectric materials is proposed. The reasons for the electrical fatigue resistance of SrBi 2 Ta 2 O 9 (SBT), SrBi 2 Nb 2 O 9 (SBN), and PbZr 1-x Ti x O 3 (PZT) are discussed in terms of the bulk ionic conductivities of the compounds. To obtain the bulk ionic conductivity of SBT and SBN, we have used impedance spectroscopy which provides an effective method that allows us to separate the individual contributions of bulk, grain boundaries, and electrode-ferroelectric interfaces from the total capacitor impedance. The bulk ionic conductivities of SBT and SBN (∼10 -7 S/cm) are much higher than those of the perovskite ferroelectrics, e.g., PZT (∼10 -11 -10 -10 S/cm). The high ionic conductivities led us to conclude that the good fatigue resistance of SrBi 2 Ta 2 O 9 and SrBi 2 Nb 2 O 9 is due to easy recovery of defects. Specifically, oxygen vacancies entrapped within the capacitors are easily released, resulting in limited space charge buildup and domain wall pinning during the polarization reversal process. However, the oxygen vacancies in PZT are trapped at trap sites to become space charges, resulting in capacitor fatigue. copyright 1997 Materials Research Society

  11. Use of cyclic voltammetry and electrochemical impedance spectroscopy for determination of active surface area of modified carbon-based electrodes

    International Nuclear Information System (INIS)

    Souza, Leticia Lopes de

    2011-01-01

    Carbon-based electrodes as well the ion exchange electrodes among others have been applied mainly in the treatment of industrial effluents and radioactive wastes. Carbon is also used in fuel cells as substrate for the electrocatalysts, having high surface area which surpasses its geometric area. The knowledge of the total active area is important for the determination of operating conditions of an electrochemical cell with respect to the currents to be applied (current density). In this study it was used two techniques to determine the electrochemical active surface area of glassy carbon, electrodes and ion exchange electrodes: cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The experiments were carried out with KNO 3 0.1 mol.L -1 solutions in a three-electrode electrochemical cell: carbon-based working electrode, platinum auxiliary electrode and Ag/AgCl reference electrode. The glassy carbon and porous carbon electrodes with geometric areas of 3.14 x 10 -2 and 2.83 X 10 -1 cm 2 , respectively, were used. The ion exchange electrode was prepared by mixing graphite, carbon, ion exchange resin and a binder, and this mixture was applied in three layers on carbon felt, using a geometric area of 1.0 cm 2 during the experiments. The capacitance (Cd) of the materials was determined by EIS using Bode diagrams. The value of 172 μF.cm -2 found for the glassy carbon is consistent with the literature data (∼ 200 μF.cm'- 2 ). By VC, varying the scan rate from 0.2 to 2.0 mV.s-1, the capacitance CdS (S = active surface area) in the region of the electric double layer (EDL) of each material was determined. By EIS, the values of C d , 3.0 x 10 -5 μF.cm'- 2 and 11 x 10 3 μF.cm-2, were found for the porous carbon and ion exchange electrodes, respectively, which allowed the determination of active surface areas as 3.73 x 106 cm 2 and 4.72 cm 2 . To sum up, the combined use of EIS and CV techniques is a valuable tool for the calculation of active surface

  12. A Simultaneous and Continuous Excitation Method for High-Speed Electrical Impedance Tomography with Reduced Transients and Noise Sensitivity

    Directory of Open Access Journals (Sweden)

    Antoine Dupré

    2018-03-01

    Full Text Available This paper presents a concept for soft field tomographic scan of all the projections of electromagnetic waves emanating from an array of electrodes. Instead of the sequential excitation of all pairs of electrodes in the list of all projections, the new method present here consists of a single and continuous excitation. This excitation signal is the linear combination of the excitation signals in the projection set at different AC frequencies. The response to a given projection is discriminated by selecting the corresponding AC frequency component in the signal spectra of the digitally demodulated signals. The main advantage of this method is the suppression of transients after each projection, which is particularly problematic in electrical impedance tomography due to contact impedance phenomena and skin effect. The second benefit over the sequential scan method is the increased number of samples for each measurement for reduced noise sensitivity with digital demodulation. The third benefit is the increased temporal resolution in high-speed applications. The main drawback is the increased number of signal sources required (one per electrode. This paper focuses on electrical impedance tomography, based on earlier work by the authors. An experimental proof-of-concept using a simple 4-electrodes electrical impedance tomographic system is presented using simulations and laboratory data. The method presented here may be extended to other modalities (ultrasonic, microwave, optical, etc..

  13. 基于直接寻找法的电阻抗断层成像%Electrical Impedance Tomography Based on Direct Search Method

    Institute of Scientific and Technical Information of China (English)

    蔡畅; 严壮志

    2005-01-01

    Solution to impedance distribution in electrical impedance tomography (EIT) is an ill-posed nonlinear inverse problem. It is especially difficult to reconstruct an EIT image in the center area of a measured object. Tikhonov regularization with some prior information is a sound regularization method for static electrical impedance tomography under the condition that some true impedance distribution information is known a priori. This paper presents a direct search method (DSM) as pretreatment of image reconstruction through which one not only can construct a regularization matrix which maylocate in areas of impedance change, but also can obtain an initial impedance distribution more similar to the true impedance distribution, as well as better current modes which can better distinguish the initial distribution and the true distribution. Simulation results indicate that, by using DSM, resolution in the center area of the measured object can be improved significantly.

  14. Characterisation and Modelling of a High Temperature PEM Fuel Cell Stack using Electrochemical Impedance Spectroscopy

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Jespersen, Jesper Lebæk; Schaltz, Erik

    2009-01-01

    temperature PEM (HTPEM) fuel cell stack. A Labview virtual instrument has been developed to perform the signal generation and data acquisition which is needed to perform EIS. The typical output of an EIS measurement on a fuel cell, is a Nyquist plot, which shows the imaginary and real part of the impedance...

  15. Modelling of passive films: complementarity and applicability to the electrochemical impedance spectroscopy analysis

    International Nuclear Information System (INIS)

    Boissy, Clement; Normand, Bernard

    2013-01-01

    A review of the published models to describe the passivation of metallic materials is proposed. The objective is to illustrate the importance of the selection of a model considering their complementarity. The discussion is based on an analysis to assess whether the mass transport in the film must be taken into account or not in the modelling of the electrochemical impedance. (authors)

  16. A comparison framework for temporal image reconstructions in electrical impedance tomography

    International Nuclear Information System (INIS)

    Gagnon, Hervé; Adler, Andy; Grychtol, Bartłomiej

    2015-01-01

    Electrical impedance tomography (EIT) provides low-resolution images of internal conductivity distributions, but is able to achieve relatively high temporal resolutions. Most EIT image reconstruction algorithms do not explicitly account for the temporal constraints on the measurements or physiological processes under investigation. Instead, algorithms typically assume both that the conductivity distribution does not change during the acquisition of each EIT data frame, and that frames can be reconstructed independently, without consideration of the correlation between images. A failure to account for these temporal effects will result in aliasing-related artefacts in images. Several methods have been proposed to compensate for these effects, including interpolation of raw data, and reconstruction algorithms using Kalman and temporal filtering. However, no systematic work has been performed to understand the severity of the temporal artefacts nor the extent to which algorithms can account for them. We seek to address this need by developing a temporal comparison framework and figures of merit to assess the ability of reconstruction algorithms to account for temporal effects. Using this approach, we compare combinations of three reconstruction algorithms using three EIT data frame types: perfect, realistic and interpolated. The results show that, without accounting for temporal effects, artefacts are present in images for dynamic conductivity contrasts at frequencies 10–20 times slower than the frame rate. The proposed methods show some improvements in reducing these artefacts. (paper)

  17. Electrical impedance myography for the assessment of children with muscular dystrophy: a preliminary study

    International Nuclear Information System (INIS)

    Rutkove, S B; Darras, B T

    2013-01-01

    Electrical impedance myography (EIM) provides a non-invasive approach for quantifying the severity of neuromuscular disease. Here we determine how well EIM data correlates to functional and ultrasound (US) measures of disease in children with Duchenne muscular dystrophy (DMD) and healthy subjects. Thirteen healthy boys, aged 2–12 years and 14 boys with DMD aged 4–12 years underwent both EIM and US measurements of deltoid, biceps, wrist flexors, quadriceps, tibialis anterior, and medial gastrocnemius. EIM measurements were performed with a custom-designed probe using a commercial multifrequency bioimpedance device. US luminosity data were quantified using a gray-scale analysis approach. Children also underwent the 6-minute walk test, timed tests and strength measurements. EIM and US data were combined across muscles. EIM 50 kHz phase was able to discriminate DMD children from healthy subjects with 98% accuracy. In the DMD patients, average EIM phase measurements also correlated well with standard functional measures. For example the 50 kHz phase correlated with the Northstar Ambulatory Assessment test (R = 0.83, p = 0.02). EIM 50 kHz phase and US correlated as well, with R = −0.79 (p < 0.001). These results show that EIM provides valuable objective measures Duchenne muscular dystrophy severity.

  18. Electrical impedance myography for the assessment of children with muscular dystrophy: a preliminary study

    Science.gov (United States)

    Rutkove, S. B.; Darras, B. T.

    2013-04-01

    Electrical impedance myography (EIM) provides a non-invasive approach for quantifying the severity of neuromuscular disease. Here we determine how well EIM data correlates to functional and ultrasound (US) measures of disease in children with Duchenne muscular dystrophy (DMD) and healthy subjects. Thirteen healthy boys, aged 2-12 years and 14 boys with DMD aged 4-12 years underwent both EIM and US measurements of deltoid, biceps, wrist flexors, quadriceps, tibialis anterior, and medial gastrocnemius. EIM measurements were performed with a custom-designed probe using a commercial multifrequency bioimpedance device. US luminosity data were quantified using a gray-scale analysis approach. Children also underwent the 6-minute walk test, timed tests and strength measurements. EIM and US data were combined across muscles. EIM 50 kHz phase was able to discriminate DMD children from healthy subjects with 98% accuracy. In the DMD patients, average EIM phase measurements also correlated well with standard functional measures. For example the 50 kHz phase correlated with the Northstar Ambulatory Assessment test (R = 0.83, p = 0.02). EIM 50 kHz phase and US correlated as well, with R = -0.79 (p Duchenne muscular dystrophy severity.

  19. Regional respiratory inflation and deflation pressure-volume curves determined by electrical impedance tomography.

    Science.gov (United States)

    Frerichs, I; Dargaville, P A; Rimensberger, P C

    2013-06-01

    Measurement of regional lung volume changes during a quasi-static pressure-volume (PV) manoeuvre using electrical impedance tomography (EIT) could be used to assess regional respiratory system mechanics and to determine optimal ventilator settings in individual patients. Using this approach, we studied regional respiratory system mechanics in healthy and lung-injured animals, before and after surfactant administration during inflation and deflation PV manoeuvres. The comparison of the EIT-derived regional PV curves in ventral, middle and dorsal regions of the right and left lungs showed not only different amounts of hysteresis in these regions but also marked differences among different landmark pressures calculated on the inflation and deflation limbs of the curves. Regional pressures at maximum compliance as well as the lower and upper pressures of maximum compliance change differed between the inflation and deflation and increased from ventral to dorsal regions in all lung conditions. All these pressure values increased in the injured and decreased in the surfactant treated lungs. Examination of regional respiratory system mechanics using EIT enables the assessment of spatial and temporal heterogeneities in the ventilation distribution. Characteristic landmarks on the inflation and especially on the deflation limb of regional PV curves may become useful measures for guiding mechanical ventilation.

  20. Regional respiratory inflation and deflation pressure–volume curves determined by electrical impedance tomography

    International Nuclear Information System (INIS)

    Frerichs, I; Dargaville, P A; Rimensberger, P C

    2013-01-01

    Measurement of regional lung volume changes during a quasi-static pressure–volume (PV) manoeuvre using electrical impedance tomography (EIT) could be used to assess regional respiratory system mechanics and to determine optimal ventilator settings in individual patients. Using this approach, we studied regional respiratory system mechanics in healthy and lung-injured animals, before and after surfactant administration during inflation and deflation PV manoeuvres. The comparison of the EIT-derived regional PV curves in ventral, middle and dorsal regions of the right and left lungs showed not only different amounts of hysteresis in these regions but also marked differences among different landmark pressures calculated on the inflation and deflation limbs of the curves. Regional pressures at maximum compliance as well as the lower and upper pressures of maximum compliance change differed between the inflation and deflation and increased from ventral to dorsal regions in all lung conditions. All these pressure values increased in the injured and decreased in the surfactant treated lungs. Examination of regional respiratory system mechanics using EIT enables the assessment of spatial and temporal heterogeneities in the ventilation distribution. Characteristic landmarks on the inflation and especially on the deflation limb of regional PV curves may become useful measures for guiding mechanical ventilation. (paper)

  1. Assessment of distribution of ventilation by electrical impedance tomography in standing horses

    International Nuclear Information System (INIS)

    Ambrisko, T D; Schramel, J P; Moens, Y P S; Adler, A; Kutasi, O; Makra, Z

    2016-01-01

    The aim was to evaluate the feasibility of using electrical impedance tomography (EIT) in horses. Thoracic EIT was used in nine horses. Thoracic and abdominal circumference changes were also measured with respiratory ultrasound plethysmography (RUP). Data were recorded during baseline, rebreathing of CO_2 and sedation. Three breaths were selected for analysis from each recording. During baseline breathing, horses regularly took single large breaths (sighs), which were also analysed. Functional EIT images were created using standard deviations (SD) of pixel signals and correlation coefficients (R) of each pixel signal with a reference respiratory signal. Left-to-right ratio, centre-of-ventilation and global-inhomogeneity-index were calculated. RM-ANOVA and Bonferroni tests were used (P  <  0.05). Distribution of ventilation shifted towards right during sighs and towards dependent regions during sighs, rebreathing and sedation. Global-inhomogeneity-index did not change for SD but increased for R images during sedation. The sum of SDs for the respiratory EIT signals correlated well with thoracic (r "2  =  0.78) and abdominal (r "2  =  0.82) tidal circumferential changes. Inverse respiratory signals were identified on the images at sternal location and based on reviewing CT images, seemed to correspond to location of gas filled intestines. Application of EIT in standing non-sedated horses is feasible. EIT images may provide physiologically useful information even in situations, such as sighs, that cannot easily be tested by other methods. (paper)

  2. Real-time imaging of subarachnoid hemorrhage in piglets with electrical impedance tomography.

    Science.gov (United States)

    Dai, Meng; Wang, Liang; Xu, Canhua; Li, Lianfeng; Gao, Guodong; Dong, Xiuzhen

    2010-09-01

    Subarachnoid hemorrhage (SAH) is one of the most severe medical emergencies in neurosurgery. Early detection or diagnosis would significantly reduce the rate of disability and mortality, and improve the prognosis of the patients. Although the present medical imaging techniques generally have high sensitivity to identify bleeding, the use of an additional, non-invasive imaging technique capable of continuously monitoring SAH is required to prevent contingent bleeding or re-bleeding. In this study, electrical impedance tomography (EIT) was applied to detect the onset of SAH modeled on eight piglets in real time, with the subsequent process being monitored continuously. The experimental SAH model was introduced by one-time injection of 5 ml fresh autologous arterial blood into the cisterna magna. Results showed that resistivity variations within the brain caused by the added blood could be detected using the EIT method and may be associated not only with the resistivity difference among brain tissues, but also with variations of cerebrospinal fluid dynamics. In conclusion, EIT has unique potential for use in clinical practice to provide invaluable real-time neuroimaging data for SAH after the improvement of electrode design, anisotropic realistic modeling and instrumentation.

  3. A shape-based quality evaluation and reconstruction method for electrical impedance tomography.

    Science.gov (United States)

    Antink, Christoph Hoog; Pikkemaat, Robert; Malmivuo, Jaakko; Leonhardt, Steffen

    2015-06-01

    Linear methods of reconstruction play an important role in medical electrical impedance tomography (EIT) and there is a wide variety of algorithms based on several assumptions. With the Graz consensus reconstruction algorithm for EIT (GREIT), a novel linear reconstruction algorithm as well as a standardized framework for evaluating and comparing methods of reconstruction were introduced that found widespread acceptance in the community. In this paper, we propose a two-sided extension of this concept by first introducing a novel method of evaluation. Instead of being based on point-shaped resistivity distributions, we use 2759 pairs of real lung shapes for evaluation that were automatically segmented from human CT data. Necessarily, the figures of merit defined in GREIT were adjusted. Second, a linear method of reconstruction that uses orthonormal eigenimages as training data and a tunable desired point spread function are proposed. Using our novel method of evaluation, this approach is compared to the classical point-shaped approach. Results show that most figures of merit improve with the use of eigenimages as training data. Moreover, the possibility of tuning the reconstruction by modifying the desired point spread function is shown. Finally, the reconstruction of real EIT data shows that higher contrasts and fewer artifacts can be achieved in ventilation- and perfusion-related images.

  4. A Deformable Smart Skin for Continuous Sensing Based on Electrical Impedance Tomography.

    Science.gov (United States)

    Visentin, Francesco; Fiorini, Paolo; Suzuki, Kenji

    2016-11-16

    In this paper, we present a low-cost, adaptable, and flexible pressure sensor that can be applied as a smart skin over both stiff and deformable media. The sensor can be easily adapted for use in applications related to the fields of robotics, rehabilitation, or costumer electronic devices. In order to remove most of the stiff components that block the flexibility of the sensor, we based the sensing capability on the use of a tomographic technique known as Electrical Impedance Tomography. The technique allows the internal structure of the domain under study to be inferred by reconstructing its conductivity map. By applying the technique to a material that changes its resistivity according to applied forces, it is possible to identify these changes and then localise the area where the force was applied. We tested the system when applied to flat and curved surfaces. For all configurations, we evaluate the artificial skin capabilities to detect forces applied over a single point, over multiple points, and changes in the underlying geometry. The results are all promising, and open the way for the application of such sensors in different robotic contexts where deformability is the key point.

  5. Pyramidal resistor networks for electrical impedance tomography with partial boundary measurements

    International Nuclear Information System (INIS)

    Borcea, L; Mamonov, A V; Druskin, V; Vasquez, F Guevara

    2010-01-01

    We introduce an inversion algorithm for electrical impedance tomography (EIT) with partial boundary measurements in two dimensions. It gives stable and fast reconstructions using sparse parameterizations of the unknown conductivity on optimal grids that are computed as part of the inversion. We follow the approach in Borcea et al (2008 Inverse Problems 24 035013) and Vasquez (2006 PhD thesis Rice University, Houston, TX, USA) that connects inverse discrete problems for resistor networks to continuum EIT problems, using optimal grids. The algorithm in Borcea et al (2008 Inverse Problems 24 035013) and Vasquez (2006 PhD Thesis Rice University, Houston, TX, USA) is based on circular resistor networks, and solves the EIT problem with full boundary measurements. It is extended in Borcea et al (2010 Inverse Problems 26 045010) to EIT with partial boundary measurements, using extremal quasi-conformal mappings that transform the problem to one with full boundary measurements. Here we introduce a different class of optimal grids, based on resistor networks with pyramidal topology, that is better suited for the partial measurements setup. We prove the unique solvability of the discrete inverse problem for these networks and develop an algorithm for finding them from the measurements of the Dirichlet to Neumann map. Then, we show how to use the networks to define the optimal grids and to approximate the unknown conductivity. We assess the performance of our approach with numerical simulations and compare the results with those in Borcea et al (2010)

  6. A shape-based quality evaluation and reconstruction method for electrical impedance tomography

    International Nuclear Information System (INIS)

    Antink, Christoph Hoog; Pikkemaat, Robert; Leonhardt, Steffen; Malmivuo, Jaakko

    2015-01-01

    Linear methods of reconstruction play an important role in medical electrical impedance tomography (EIT) and there is a wide variety of algorithms based on several assumptions. With the Graz consensus reconstruction algorithm for EIT (GREIT), a novel linear reconstruction algorithm as well as a standardized framework for evaluating and comparing methods of reconstruction were introduced that found widespread acceptance in the community.In this paper, we propose a two-sided extension of this concept by first introducing a novel method of evaluation. Instead of being based on point-shaped resistivity distributions, we use 2759 pairs of real lung shapes for evaluation that were automatically segmented from human CT data. Necessarily, the figures of merit defined in GREIT were adjusted. Second, a linear method of reconstruction that uses orthonormal eigenimages as training data and a tunable desired point spread function are proposed.Using our novel method of evaluation, this approach is compared to the classical point-shaped approach. Results show that most figures of merit improve with the use of eigenimages as training data. Moreover, the possibility of tuning the reconstruction by modifying the desired point spread function is shown. Finally, the reconstruction of real EIT data shows that higher contrasts and fewer artifacts can be achieved in ventilation- and perfusion-related images. (paper)

  7. Lung pathologies analyzed with multi-frequency electrical impedance tomography: Pilot animal study.

    Science.gov (United States)

    Aguiar Santos, Susana; Czaplik, Michael; Orschulik, Jakob; Hochhausen, Nadine; Leonhardt, Steffen

    2018-03-31

    In critically ill patients, correct diagnosis of lung disease is essential for successful therapy. Therefore, this study investigated whether new multi-frequency electrical impedance tomography (mfEIT) can detect, monitor and differentiate between pathologies associated with the acute respiratory distress syndrome (ARDS). For this pilot study, 12 pigs were randomized into an ARDS (bronchoalveolar lavage) group (n = 7) and a healthy control group (n = 5). Animals were monitored by means of mfEIT. In addition to functional images, a new impaired-ventilation (rImpVent) index was developed and frequency-difference images were computed and analyzed. Amplitude functional images revealed only small differences between the groups. However, phase functional images were of greater importance in distinguishing between lung pathologies. Correlation images showed substantial differences between the two groups. The new rImpVent index achieved high sensitivity (91%) and specificity (92%) in detecting PaO 2 /FiO 2  ≤ 200 mmHg. mfEIT was able to detect lung edema, differentiate this from atelectasis, and also monitor their progress over time in terms of global and regional differences. Copyright © 2018 Elsevier B.V. All rights reserved.

  8. Gamma-variate modeling of indicator dilution curves in electrical impedance tomography.

    Science.gov (United States)

    Hentze, Benjamin; Muders, Thomas; Luepschen, Henning; Leonhardt, Steffen; Putensen, Christian; Walter, Marian

    2017-07-01

    Electrical impedance tomography (EIT) is a non-invasive imaging technique, that can be used to monitor regional lung ventilation (V̇) in intensive care units (ICU) at bedside. This work introduces a method to extract regional lung perfusion (Q̇) from EIT image streams in order to quantify regional gas exchange in the lungs. EIT data from a single porcine animal trial, recorded during injection of a contrast agent (NaCl 10%) into a central venous catheter (CVC), are used for evaluation. Using semi-negative matrix factorization (Semi-NMF) a set of source signals is extracted from the data. A subsequent non-linear fit of a gamma-variate model to the source signals results in model signals, describing contrast agent flow through the cardio-pulmonary system. A linear fit of the model signals to the EIT image stream then yields functional images ofQ̇. Additionally, a pulmonary transit function (PTF) and parameters, such as mean transit time (MTT), time to peak (TTP) and area under curve (AUC) are derived. In result, EIT was used to track changes of regional lung ventilation to perfusion ratio (V̇/Q̇) during changes of positive end-expiratory pressure (PEEP). Furthermore, correlations of MTT and AUC with cardiac output (CO) indicate that CO measurement by EIT might be possible.

  9. Real-time management of faulty electrodes in electrical impedance tomography.

    Science.gov (United States)

    Hartinger, Alzbeta E; Guardo, Robert; Adler, Andy; Gagnon, Hervé

    2009-02-01

    Completely or partially disconnected electrodes are a fairly common occurrence in many electrical impedance tomography (EIT) clinical applications. Several factors can contribute to electrode disconnection: patient movement, perspiration, manipulations by clinical staff, and defective electrode leads or electronics. By corrupting several measurements, faulty electrodes introduce significant image artifacts. In order to properly manage faulty electrodes, it is necessary to: 1) account for invalid data in image reconstruction algorithms and 2) automatically detect faulty electrodes. This paper presents a two-part approach for real-time management of faulty electrodes based on the principle of voltage-current reciprocity. The first part allows accounting for faulty electrodes in EIT image reconstruction without a priori knowledge of which electrodes are at fault. The method properly weights each measurement according to its compliance with the principle of voltage-current reciprocity. Results show that the algorithm is able to automatically determine the valid portion of the data and use it to calculate high-quality images. The second part of the approach allows automatic real-time detection of at least one faulty electrode with 100% sensitivity and two faulty electrodes with 80% sensitivity enabling the clinical staff to fix the problem as soon as possible to minimize data loss.

  10. The Effect of Electrical Impedance Matching on the Electromechanical Characteristics of Sandwiched Piezoelectric Ultrasonic Transducers

    Directory of Open Access Journals (Sweden)

    Yuan Yang

    2017-12-01

    Full Text Available For achieving the power maximum transmission, the electrical impedance matching (EIM for piezoelectric ultrasonic transducers is highly required. In this paper, the effect of EIM networks on the electromechanical characteristics of sandwiched piezoelectric ultrasonic transducers is investigated in time and frequency domains, based on the PSpice model of single sandwiched piezoelectric ultrasonic transducer. The above-mentioned EIM networks include, series capacitance and parallel inductance (I type and series inductance and parallel capacitance (II type. It is shown that when I and II type EIM networks are used, the resonance and anti-resonance frequencies and the received signal tailing are decreased; II type makes the electro-acoustic power ratio and the signal tailing smaller whereas it makes the electro-acoustic gain ratio larger at resonance frequency. In addition, I type makes the effective electromechanical coupling coefficient increase and II type makes it decrease; II type make the power spectral density at resonance frequency more dramatically increased. Specially, the electro-acoustic power ratio has maximum value near anti-resonance frequency, while the electro-acoustic gain ratio has maximum value near resonance frequency. It can be found that the theoretically analyzed results have good consistency with the measured ones.

  11. Multi-phase flow monitoring with electrical impedance tomography using level set based method

    International Nuclear Information System (INIS)

    Liu, Dong; Khambampati, Anil Kumar; Kim, Sin; Kim, Kyung Youn

    2015-01-01

    Highlights: • LSM has been used for shape reconstruction to monitor multi-phase flow using EIT. • Multi-phase level set model for conductivity is represented by two level set functions. • LSM handles topological merging and breaking naturally during evolution process. • To reduce the computational time, a narrowband technique was applied. • Use of narrowband and optimization approach results in efficient and fast method. - Abstract: In this paper, a level set-based reconstruction scheme is applied to multi-phase flow monitoring using electrical impedance tomography (EIT). The proposed scheme involves applying a narrowband level set method to solve the inverse problem of finding the interface between the regions having different conductivity values. The multi-phase level set model for the conductivity distribution inside the domain is represented by two level set functions. The key principle of the level set-based method is to implicitly represent the shape of interface as the zero level set of higher dimensional function and then solve a set of partial differential equations. The level set-based scheme handles topological merging and breaking naturally during the evolution process. It also offers several advantages compared to traditional pixel-based approach. Level set-based method for multi-phase flow is tested with numerical and experimental data. It is found that level set-based method has better reconstruction performance when compared to pixel-based method

  12. Ventilation and perfusion imaging by electrical impedance tomography: a comparison with radionuclide scanning.

    Science.gov (United States)

    Kunst, P W; Vonk Noordegraaf, A; Hoekstra, O S; Postmus, P E; de Vries, P M

    1998-11-01

    Electrical impedance tomography (EIT) is a technique that makes it possible to measure ventilation and pulmonary perfusion in a volume that approximates to a 2D plane. The possibility of using EIT for measuring the left-right division of ventilation and perfusion was compared with that of radionuclide imaging. Following routine ventilation (81mKr) and perfusion scanning (99mTc-MAA), EIT measurements were performed at the third and the sixth intercostal level in 14 patients with lung cancer. A correlation (r = 0.98, p RC) was calculated for estimating the left-right division with EIT. The RC for the ventilation measurements was 94% and 96% for the perfusion measurements. The correlation analysis for reproducibility of the EIT measurements was 0.95 (p < 0.001) for the ventilation and 0.93 (p < 0.001) for the perfusion measurements. In conclusion, EIT can be regarded as a promising technique to estimate the left-right division of pulmonary perfusion and ventilation.

  13. Data-driven classification of ventilated lung tissues using electrical impedance tomography

    International Nuclear Information System (INIS)

    Gómez-Laberge, Camille; Hogan, Matthew J; Elke, Gunnar; Weiler, Norbert; Frerichs, Inéz; Adler, Andy

    2011-01-01

    Current methods for identifying ventilated lung regions utilizing electrical impedance tomography images rely on dividing the image into arbitrary regions of interest (ROI), manually delineating ROI, or forming ROI with pixels whose signal properties surpass an arbitrary threshold. In this paper, we propose a novel application of a data-driven classification method to identify ventilated lung ROI based on forming k clusters from pixels with correlated signals. A standard first-order model for lung mechanics is then applied to determine which ROI correspond to ventilated lung tissue. We applied the method in an experimental study of 16 mechanically ventilated swine in the supine position, which underwent changes in positive end-expiratory pressure (PEEP) and fraction of inspired oxygen (F I O 2 ). In each stage of the experimental protocol, the method performed best with k = 4 and consistently identified 3 lung tissue ROI and 1 boundary tissue ROI in 15 of the 16 subjects. When testing for changes from baseline in lung position, tidal volume, and respiratory system compliance, we found that PEEP displaced the ventilated lung region dorsally by 2 cm, decreased tidal volume by 1.3%, and increased the respiratory system compliance time constant by 0.3 s. F I O 2 decreased tidal volume by 0.7%. All effects were tested at p < 0.05 with n = 16. These findings suggest that the proposed ROI detection method is robust and sensitive to ventilation dynamics in the experimental setting

  14. Rotational electrical impedance tomography using electrodes with limited surface coverage provides window for multimodal sensing

    Science.gov (United States)

    Lehti-Polojärvi, Mari; Koskela, Olli; Seppänen, Aku; Figueiras, Edite; Hyttinen, Jari

    2018-02-01

    Electrical impedance tomography (EIT) is an imaging method that could become a valuable tool in multimodal applications. One challenge in simultaneous multimodal imaging is that typically the EIT electrodes cover a large portion of the object surface. This paper investigates the feasibility of rotational EIT (rEIT) in applications where electrodes cover only a limited angle of the surface of the object. In the studied rEIT, the object is rotated a full 360° during a set of measurements to increase the information content of the data. We call this approach limited angle full revolution rEIT (LAFR-rEIT). We test LAFR-rEIT setups in two-dimensional geometries with computational and experimental data. We use up to 256 rotational measurement positions, which requires a new way to solve the forward and inverse problem of rEIT. For this, we provide a modification, available for EIDORS, in the supplementary material. The computational results demonstrate that LAFR-rEIT with eight electrodes produce the same image quality as conventional 16-electrode rEIT, when data from an adequate number of rotational measurement positions are used. Both computational and experimental results indicate that the novel LAFR-rEIT provides good EIT with setups with limited surface coverage and a small number of electrodes.

  15. The Effect of Subcutaneous Fat on Electrical Impedance Myography: Electrode Configuration and Multi-Frequency Analyses.

    Directory of Open Access Journals (Sweden)

    Le Li

    Full Text Available This study investigates the impact of the subcutaneous fat layer (SFL thickness on localized electrical impedance myography (EIM, as well as the effects of different current electrodes, varying in distance and direction, on EIM output. Twenty-three healthy subjects underwent localized multi-frequency EIM on their biceps brachii muscles with a hand-held electrode array. The EIM measurements were recorded under three different configurations: wide (or outer longitudinal configuration 6.8 cm, narrow (or inner longitudinal configuration 4.5 cm, and narrow transverse configuration 4.5 cm. Ultrasound was applied to measure the SFL thickness. Coefficients of determination (R2 of three EIM variables (resistance, reactance, and phase and SFL thickness were calculated. For the longitudinal configuration, the wide distance could reduce the effects of the subcutaneous fat when compared with the narrow distance, but a significant correlation still remained for all three EIM parameters. However, there was no significant correlation between SFL thickness and reactance in the transverse configuration (R2 = 0.0294, p = 0.434. Utilizing a ratio of 50kHz/100kHz phase was found to be able to help reduce the correlation with SFL thickness for all the three configurations. The findings indicate that the appropriate selection of the current electrode distance, direction and the multi-frequency phase ratio can reduce the impact of subcutaneous fat on EIM. These settings should be evaluated for future clinical studies using hand-held localized arrays to perform EIM.

  16. A two-layered forward model of tissue for electrical impedance tomography

    International Nuclear Information System (INIS)

    Kulkarni, Rujuta; Saulnier, Gary J; Kao, Tzu-Jen; Newell, Jonathan C; Boverman, Gregory; Isaacson, David

    2009-01-01

    Electrical impedance tomography is being explored as a technique to detect breast cancer, exploiting the differences in admittivity between normal tissue and tumors. In this paper, the geometry is modeled as an infinite half space under a hand-held probe. A forward solution and a reconstruction algorithm for this geometry were developed previously by Mueller et al (1999 IEEE Trans. Biomed. Eng. 46 1379). In this paper, we present a different approach which uses the decomposition of the forward solution into its Fourier components to obtain the forward solution and the reconstructions. The two approaches are compared in terms of the forward solutions and the reconstructions of experimental tank data. We also introduce a two-layered model to incorporate the presence of the skin that surrounds the body area being imaged. We demonstrate an improvement in the reconstruction of a target in a layered medium using this layered model with finite difference simulated data. We then extend the application of our layered model to human subject data and estimate the skin and the tissue admittivities for data collected on the human abdomen using an ultrasound-like hand-held EIT probe. Lastly, we show that for this set of human subject data, the layered model yields an improvement in predicting the measured voltages of around 81% for the lowest temporal frequency (3 kHz) and around 61% for the highest temporal frequency (1 MHz) applied when compared to the homogeneous model

  17. The effect of serial data collection on the accuracy of electrical impedance tomography images

    International Nuclear Information System (INIS)

    Yerworth, Rebecca; Bayford, Richard

    2013-01-01

    There has been a surge of interest in using electrical impedance tomography (EIT) for monitoring regional lung ventilation, however, EIT is an ill-conditioned problem, and errors/noise in the boundary voltages can have an undesirable effect on the quality of the final image. Most EIT systems in clinical usage use serial data collection hence data used to create a single image will have been collected at different times. This paper presents a study of the resulting image distortion, and proposes a method for correcting this lag in situations where the frame rate is insufficient to prevent significant image degradation. Significant correlation between the standard deviation of the time dependent reciprocity error and time delay dL e between the reciprocal electrode combinations was found for both adult and neonate data. This was reduced when the data was corrected for dL e . Original and corrected data was reconstructed with the GREIT algorithm and visible differences were found for the neonate data. Ideally EIT systems should be run at a frame rate of at least 50 times the frequency of the dominant and interesting physiological signals. Where this is not practical, the intra-frame system timings should be determined and lag corrected for. (paper)

  18. A Local Region of Interest Imaging Method for Electrical Impedance Tomography with Internal Electrodes

    Directory of Open Access Journals (Sweden)

    Hyeuknam Kwon

    2013-01-01

    Full Text Available Electrical Impedance Tomography (EIT is a very attractive functional imaging method despite the low sensitivity and resolution. The use of internal electrodes with the conventional reconstruction algorithms was not enough to enhance image resolution and accuracy in the region of interest (ROI. We propose a local ROI imaging method with internal electrodes developed from careful analysis of the sensitivity matrix that is designed to reduce the sensitivity of the voxels outside the local region and optimize the sensitivity of the voxel inside the local region. We perform numerical simulations and physical measurements to demonstrate the localized EIT imaging method. In preliminary results with multiple objects we show the benefits of using an internal electrode and the improved resolution due to the local ROI image reconstruction method. The sensitivity is further increased by allowing the surface electrodes to be unevenly spaced with a higher density of surface electrodes near the ROI. Also, we analyse how much the image quality is improved using several performance parameters for comparison. While these have not yet been studied in depth, it convincingly shows an improvement in local sensitivity in images obtained with an internal electrode in comparison to a standard reconstruction method.

  19. Ultrasound guided electrical impedance tomography for 2D free-interface reconstruction

    Science.gov (United States)

    Liang, Guanghui; Ren, Shangjie; Dong, Feng

    2017-07-01

    The free-interface detection problem is normally seen in industrial or biological processes. Electrical impedance tomography (EIT) is a non-invasive technique with advantages of high-speed and low cost, and is a promising solution for free-interface detection problems. However, due to the ill-posed and nonlinear characteristics, the spatial resolution of EIT is low. To deal with the issue, an ultrasound guided EIT is proposed to directly reconstruct the geometric configuration of the target free-interface. In the method, the position of the central point of the target interface is measured by a pair of ultrasound transducers mounted at the opposite side of the objective domain, and then the position measurement is used as the prior information for guiding the EIT-based free-interface reconstruction. During the process, a constrained least squares framework is used to fuse the information from different measurement modalities, and the Lagrange multiplier-based Levenberg-Marquardt method is adopted to provide the iterative solution of the constraint optimization problem. The numerical results show that the proposed ultrasound guided EIT method for the free-interface reconstruction is more accurate than the single modality method, especially when the number of valid electrodes is limited.

  20. An optimized strategy for real-time hemorrhage monitoring with electrical impedance tomography

    International Nuclear Information System (INIS)

    Xu, Canhua; Dai, Meng; You, Fusheng; Shi, Xuetao; Fu, Feng; Liu, Ruigang; Dong, Xiuzhen

    2011-01-01

    Delayed detection of an internal hemorrhage may result in serious disabilities and possibly death for a patient. Currently, there are no portable medical imaging instruments that are suitable for long-term monitoring of patients at risk of internal hemorrhage. Electrical impedance tomography (EIT) has the potential to monitor patients continuously as a novel functional image modality and instantly detect the occurrence of an internal hemorrhage. However, the low spatial resolution and high sensitivity to noise of this technique have limited its application in clinics. In addition, due to the circular boundary display mode used in current EIT images, it is difficult for clinicians to identify precisely which organ is bleeding using this technique. The aim of this study was to propose an optimized strategy for EIT reconstruction to promote the use of EIT for clinical studies, which mainly includes the use of anatomically accurate boundary shapes, rapid selection of optimal regularization parameters and image fusion of EIT and computed tomography images. The method was evaluated on retroperitoneal and intraperitoneal bleeding piglet data. Both traditional backprojection images and optimized images among different boundary shapes were reconstructed and compared. The experimental results demonstrated that EIT images with precise anatomical information can be reconstructed in which the image resolution and resistance to noise can be improved effectively

  1. Circular resistor networks for electrical impedance tomography with partial boundary measurements

    International Nuclear Information System (INIS)

    Borcea, L; Mamonov, A V; Druskin, V

    2010-01-01

    We introduce an algorithm for the numerical solution of electrical impedance tomography (EIT) in two dimensions, with partial boundary measurements. The algorithm is an extension of the one in Borcea et al (2008 Inverse Problems 24 035013 (31pp)) and Vasquez (2006 PhD Thesis Rice University, Houston, TX, USA) for EIT with full boundary measurements. It is based on resistor networks that arise in finite volume discretizations of the elliptic partial differential equation for the potential on so-called optimal grids that are computed as part of the problem. The grids are adaptively refined near the boundary, where we measure and expect better resolution of the images. They can be used very efficiently in inversion, by defining a reconstruction mapping that is an approximate inverse of the forward map, and acts therefore as a preconditioner in any iterative scheme that solves the inverse problem via optimization. The main result in this paper is the construction of optimal grids for EIT with partial measurements by extremal quasiconformal (Teichmüller) transformations of the optimal grids for EIT with full boundary measurements. We present the algorithm for computing the reconstruction mapping on such grids, and we illustrate its performance with numerical simulations. The results show an interesting trade-off between the resolution of the reconstruction in the domain of the solution and distortions due to artificial anisotropy induced by the distribution of the measurement points on the accessible boundary

  2. NUMERICAL SIMULATION OF ELECTRICAL IMPEDANCE TOMOGRAPHY PROBLEM AND STUDY OF APPROACH BASED ON FINITE VOLUME METHOD

    Directory of Open Access Journals (Sweden)

    Ye. S. Sherina

    2014-01-01

    Full Text Available This research has been aimed to carry out a study of peculiarities that arise in a numerical simulation of the electrical impedance tomography (EIT problem. Static EIT image reconstruction is sensitive to a measurement noise and approximation error. A special consideration has been given to reducing of the approximation error, which originates from numerical implementation drawbacks. This paper presents in detail two numerical approaches for solving EIT forward problem. The finite volume method (FVM on unstructured triangular mesh is introduced. In order to compare this approach, the finite element (FEM based forward solver was implemented, which has gained the most popularity among researchers. The calculated potential distribution with the assumed initial conductivity distribution has been compared to the analytical solution of a test Neumann boundary problem and to the results of problem simulation by means of ANSYS FLUENT commercial software. Two approaches to linearized EIT image reconstruction are discussed. Reconstruction of the conductivity distribution is an ill-posed problem, typically requiring a large amount of computation and resolved by minimization techniques. The objective function to be minimized is constructed of measured voltage and calculated boundary voltage on the electrodes. A classical modified Newton type iterative method and the stochastic differential evolution method are employed. A software package has been developed for the problem under investigation. Numerical tests were conducted on simulated data. The obtained results could be helpful to researches tackling the hardware and software issues for medical applications of EIT.

  3. Compressed sampling for boundary measurements in three-dimensional electrical impedance tomography

    International Nuclear Information System (INIS)

    Javaherian, Ashkan; Soleimani, Manuchehr

    2013-01-01

    Electrical impedance tomography (EIT) utilizes electrodes on a medium's surface to produce measured data from which the conductivity distribution inside the medium is estimated. For the cases that relocation of electrodes is impractical or no a priori assumptions can be made to optimize the electrodes placement, a large number of electrodes may be needed to cover all possible imaging volume. This may occur in dynamically varying conductivity distribution in 3D EIT. Three-dimensional EIT then requires inverting very large linear systems to calculate the conductivity field, which causes significant problems regarding storage space and reconstruction time in addition to that data acquisition for a large number of electrodes will reduce the achievable frame rate, which is considered as major advantage of EIT imaging. This study proposes an idea to reduce the reconstruction complexity based on the well-known compressed sampling theory. By applying the so-called model-based CoSaMP algorithm to large size data collected by a 256 channel system, the size of forward operator and data acquisition time is reduced to those of a 32 channel system, while accuracy of reconstruction is significantly improved. The results demonstrate great capability of compressed sampling for overriding the challenges arising in 3D EIT. (paper)

  4. A Novel Method for Monitoring Data Quality in Electrical Impedance Tomography

    International Nuclear Information System (INIS)

    Adler, Andy; Mamatjan, Yasin; Grychtol, Bartłomiej; Gaggero, Pascal; Justiz, Jörn; Koch, Volker

    2013-01-01

    Electrical impedance tomography (EIT) has the promise to help improve care for patients undergoing ventilation therapy by providing real-time bed-side information on the distribution of ventilation in their lungs. To realise this potential, it is important for an EIT system to provide a reliable and meaningful signal at all times, or alert clinicians when this is not possible. Because the reconstructed images in EIT are sensitive to system instabilities (including electrode connection problems) and artifacts caused by e.g. movement or sweat, there is a need for EIT systems to continuously monitor, recognize and, if possible, correct for such errors. Motivated by this requirement, our paper describes a novel approach to quantitatively measure EIT data quality suitable for online and offline applications. We used a publicly available data set of ventilation data from two pediatric patients with lung disease to evaluate the data quality on clinical data. Results suggest that the developed data quality could be a useful tool for real-time assessment of the quality of EIT data and, hence, to indicate the reliability of any derived physiological information.

  5. Ultrasound guided electrical impedance tomography for 2D free-interface reconstruction

    International Nuclear Information System (INIS)

    Liang, Guanghui; Ren, Shangjie; Dong, Feng

    2017-01-01

    The free-interface detection problem is normally seen in industrial or biological processes. Electrical impedance tomography (EIT) is a non-invasive technique with advantages of high-speed and low cost, and is a promising solution for free-interface detection problems. However, due to the ill-posed and nonlinear characteristics, the spatial resolution of EIT is low. To deal with the issue, an ultrasound guided EIT is proposed to directly reconstruct the geometric configuration of the target free-interface. In the method, the position of the central point of the target interface is measured by a pair of ultrasound transducers mounted at the opposite side of the objective domain, and then the position measurement is used as the prior information for guiding the EIT-based free-interface reconstruction. During the process, a constrained least squares framework is used to fuse the information from different measurement modalities, and the Lagrange multiplier-based Levenberg–Marquardt method is adopted to provide the iterative solution of the constraint optimization problem. The numerical results show that the proposed ultrasound guided EIT method for the free-interface reconstruction is more accurate than the single modality method, especially when the number of valid electrodes is limited. (paper)

  6. Evaluation of reconstruction parameters of electrical impedance tomography on aorta detection during saline bolus injection

    Directory of Open Access Journals (Sweden)

    Thürk Florian

    2016-09-01

    Full Text Available An accurate detection of anatomical structures in electrical impedance tomography (EIT is still at an early stage. Aorta detection in EIT is of special interest, since it would favor non-invasive assessment of hemodynamic processes in the body. Here, diverse EIT reconstruction parameters of the GREIT algorithm were systematically evaluated to detect the aorta after saline bolus injection in apnea. True aorta position and size were taken from computed tomography (CT. A comparison with CT showed that the smallest error for aorta displacement was attained for noise figure nf = 0.7, weighting radius rw = 0.15, and target size ts = 0.01. The spatial extension of the aorta was most precise for nf = 0.7, rw = 0.25, and ts = 0.07. Detection accuracy (F1-score was highest with nf = 0.6, rw = 0.15, and ts = 0.04. This work provides algorithm-related evidence for potentially accurate aorta detection in EIT after injection of a saline bolus.

  7. A feasibility study of magnetic resonance electrical impedance tomography for prostate cancer detection

    International Nuclear Information System (INIS)

    Liu, Yang; Zhang, Yingchun

    2014-01-01

    Magnetic resonance electrical impedance tomography (MREIT) is an imaging technique that reconstructs the conductivity distribution inside the subject using magnetic flux density or current density measurements acquired by a magnetic resonance imaging system. Since the primary prostate cancer diagnostic method, prostate biopsy, has limited accuracy in cancer diagnosis and malignant tissues have shown significantly different electrical properties from normal or benign tissues, MREIT has potential application in prostate cancer detection. The feasibility of utilizing MREIT in detecting prostate cancer was evaluated via a series of well-designed computer simulations in the present study. MREIT techniques with three different electrode configurations (external, trans-rectal, and trans-urethral electrode arrays) and two different reconstruction algorithms (J-substitution algorithm and harmonic B z  algorithm) were successfully developed. The performance of different MREIT techniques were evaluated and compared based on the imaging accuracy of the reconstructed conductivity distribution in the prostate. Without the presence of noise, the external MREIT achieves a better imaging accuracy than the two endo-MREIT (trans-rectal and trans-urethral) techniques, while the trans-urethral MREIT achieves the best imaging accuracy in noisy environments. We also found that the J-substitution reconstruction algorithm consistently offered better imaging accuracy than the harmonic B z  algorithm. When Gaussian distributed random noise with a standard deviation of 0.25 nT was added, the relative errors (RE) between the reconstructed and target conductivity distributions inside the prostate were observed to be 14.18% and 17.35% by the trans-urethral MREIT with the J-substitution and harmonic B z  algorithms respectively. The lower REs of 9.64% and 11.17% were achieved respectively when the standard deviation of noise was reduced to 0.05 nT. The simulation results demonstrate the

  8. Non-invasive determination of absolute lung resistivity in adults using electrical impedance tomography

    International Nuclear Information System (INIS)

    Zhang, Jie; Patterson, Robert

    2010-01-01

    Lung resistivity is a physiological parameter that describes the electrical characteristics of the lungs. Lung composition changes due to changes in the lung tissues, fluid and air volume. Various diseases that can cause a change in lung composition may be monitored by measuring lung resistivity. Currently, there is no accepted non-invasive method to measure lung resistivity. In this study, we presented a method and framework to non-invasively determine lung resistivity using electrical impedance tomography (EIT). By comparing actual measurements from subjects with data from a 3D human thorax model, an EIT image can be reconstructed to show a resistivity difference between the model and the subject. By adjusting the lung resistivity in the model, the resistivity difference in the lung regions can be reduced to near zero. This resistivity value then is the estimation of the lung resistivity of the subject. Using the proposed method, the lung resistivities of four normal adult males (43 ± 13 years, 78 ± 10 kg) in the supine position at air volumes starting at functional residual capacity (FRC—end expiration) and increasing in 0.5 l steps to 1.5 l were studied. The averaged lung resistivity changes 12.59%, from 1406 Ω cm to 1583 Ω cm, following the inspiration of 1.5 l air from FRC. The coefficients of variation (CV) of precision for the four subjects are less than 10%. The experiment was repeated five times at each air volume on a subject to test the reproducibility. The CVs are less than 3%. The results show that it is feasible to determine absolute lung resistivity using an EIT-based method

  9. Non-invasive determination of absolute lung resistivity in adults using electrical impedance tomography.

    Science.gov (United States)

    Zhang, Jie; Patterson, Robert

    2010-08-01

    Lung resistivity is a physiological parameter that describes the electrical characteristics of the lungs. Lung composition changes due to changes in the lung tissues, fluid and air volume. Various diseases that can cause a change in lung composition may be monitored by measuring lung resistivity. Currently, there is no accepted non-invasive method to measure lung resistivity. In this study, we presented a method and framework to non-invasively determine lung resistivity using electrical impedance tomography (EIT). By comparing actual measurements from subjects with data from a 3D human thorax model, an EIT image can be reconstructed to show a resistivity difference between the model and the subject. By adjusting the lung resistivity in the model, the resistivity difference in the lung regions can be reduced to near zero. This resistivity value then is the estimation of the lung resistivity of the subject. Using the proposed method, the lung resistivities of four normal adult males (43 +/- 13 years, 78 +/- 10 kg) in the supine position at air volumes starting at functional residual capacity (FRC--end expiration) and increasing in 0.5 l steps to 1.5 l were studied. The averaged lung resistivity changes 12.59%, from 1406 Omega cm to 1583 Omega cm, following the inspiration of 1.5 l air from FRC. The coefficients of variation (CV) of precision for the four subjects are less than 10%. The experiment was repeated five times at each air volume on a subject to test the reproducibility. The CVs are less than 3%. The results show that it is feasible to determine absolute lung resistivity using an EIT-based method.

  10. Electrical Impedance Tomography: a new study method for neonatal Respiratory Distress Syndrome?

    Science.gov (United States)

    Chatziioannidis, I; Samaras, T; Nikolaidis, N

    2011-01-01

    Treatment of cardiorespiratory system diseases is a procedure that usually demands data collection on terms of the anatomy and the operation of the organs that are under study. Electrical Impedance Tomography (EIT) is an alternative approach, in comparison to existing techniques. With EIT electrodes are placed in the perimeter of the human body and images of the estimated organ are reconstructed, using the measurement of its impendence (or resistance) distribution and determining its alteration through time, while at the same time the patient is not exposed to ionizing radiation. Its clinical use presupposes the correct placement of the electrodes over the perimeter of the human body, the rapid data collection and electrical safety. It is a low cost technique and it is implemented near the patient. It is able to determine the distribution of ventilation, blood supply, diffused or localized lung defects, but it can also estimate therapeutic interventions or alteration to assisted ventilation of the neonate. EIT was developed at the beginning of the 1980s, but it has only recently begun to be implemented on neonates, and especially in the study of their respiratory system function. The low rate of image analysis is considered to be a drawback, but it is offset by the potential offered for the estimation of lungs' function (both under normal and pathological conditions), since ventilation and resistance are two quite similar concepts. In this review the most important studies about EIT are mentioned as a method of estimating respiratory distress syndrome in neonates. In terms of the above mentioned development, it is supposed that this technique will offer a great amount of help to the doctor in his / her estimations of the cardiorespiratory system and to his / her selection of the best intervening strategies. PMID:22435017

  11. Indirect measurement of lung density and air volume from electrical impedance tomography (EIT) data.

    Science.gov (United States)

    Nebuya, Satoru; Mills, Gary H; Milnes, Peter; Brown, Brian H

    2011-12-01

    This paper describes a method for estimating lung density, air volume and changes in fluid content from a non-invasive measurement of the electrical resistivity of the lungs. Resistivity in Ω m was found by fitting measured electrical impedance tomography (EIT) data to a finite difference model of the thorax. Lung density was determined by comparing the resistivity of the lungs, measured at a relatively high frequency, with values predicted from a published model of lung structure. Lung air volume can then be calculated if total lung weight is also known. Temporal changes in lung fluid content will produce proportional changes in lung density. The method was implemented on EIT data, collected using eight electrodes placed in a single plane around the thorax, from 46 adult male subjects and 36 adult female subjects. Mean lung densities (±SD) of 246 ± 67 and 239 ± 64 kg m(-3), respectively, were obtained. In seven adult male subjects estimates of 1.68 ± 0.30, 3.42 ± 0.49 and 4.40 ± 0.53 l in residual volume, functional residual capacity and vital capacity, respectively, were obtained. Sources of error are discussed. It is concluded that absolute differences in lung density of about 30% and changes over time of less than 30% should be detected using the current technology in normal subjects. These changes would result from approximately 300 ml increase in lung fluid. The method proposed could be used for non-invasive monitoring of total lung air and fluid content in normal subjects but needs to be assessed in patients with lung disease.

  12. Electrical impedance tomography in 3D using two electrode planes: characterization and evaluation.

    Science.gov (United States)

    Wagenaar, Justin; Adler, Andy

    2016-06-01

    Electrical impedance tomography (EIT) uses body surface electrical stimulation and measurements to create conductivity images; it shows promise as a non-invasive technology to monitor the distribution of lung ventilation. Most applications of EIT have placed electrodes in a 2D ring around the thorax, and thus produced 2D cross-sectional images. These images are unable to distinguish out-of-plane contributions, or to image volumetric effects. Volumetric EIT can be calculated using multiple electrode planes and a 3D reconstruction algorithm. However, while 3D reconstruction algorithms are available, little has been done to understand the performance of 3D EIT in terms of the measurement configurations available. The goal of this paper is to characterize the phantom and in vivo performance of 3D EIT with two electrode planes. First, phantom measurements are used to measure the reconstruction characteristics of seven stimulation and measurement configurations. Measurements were then performed on eight healthy volunteers as a function of body posture, postures, and with various electrode configurations. Phantom results indicate that 3D EIT using two rings of electrodes provides reasonable resolution in the electrode plane but low vertical resolution. For volunteers, functional EIT images are created from inhalation curve features to analyze the effect of posture (standing, sitting, supine and decline) on regional lung behaviour. An ability to detect vertical changes in lung volume distribution was shown for two electrode configurations. Based on tank and volunteer results, we recommend the use of the 'square' stimulation and measurement pattern for two electrode plane EIT.

  13. Optimal distance of multi-plane sensor in three-dimensional electrical impedance tomography.

    Science.gov (United States)

    Hao, Zhenhua; Yue, Shihong; Sun, Benyuan; Wang, Huaxiang

    2017-12-01

    Electrical impedance tomography (EIT) is a visual imaging technique for obtaining the conductivity and permittivity distributions in the domain of interest. As an advanced technique, EIT has the potential to be a valuable tool for continuously bedside monitoring of pulmonary function. The EIT applications in any three-dimensional (3 D) field are very limited to the 3 D effects, i.e. the distribution of electric field spreads far beyond the electrode plane. The 3 D effects can result in measurement errors and image distortion. An important way to overcome the 3 D effect is to use the multiple groups of sensors. The aim of this paper is to find the best space resolution of EIT image over various electrode planes and select an optimal plane spacing in a 3 D EIT sensor, and provide guidance for 3 D EIT electrodes placement in monitoring lung function. In simulation and experiment, several typical conductivity distribution models, such as one rod (central, midway and edge), two rods and three rods, are set at different plane spacings between the two electrode planes. A Tikhonov regularization algorithm is utilized for reconstructing the images; the relative error and the correlation coefficient are utilized for evaluating the image quality. Based on numerical simulation and experimental results, the image performance at different spacing conditions is evaluated. The results demonstrate that there exists an optimal plane spacing between the two electrode planes for 3 D EIT sensor. And then the selection of the optimal plane spacing between the electrode planes is suggested for the electrodes placement of multi-plane EIT sensor.

  14. Modelling carbon steels corrosion during a long period in soils: Contribution of A.C. impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pons, E.; Lemaitre, C.; Crusset, D.; David, D. [Laboratoire Roberval de Mecanique, UMR 6066 du CNRS, Universite de Technologie de Compiegne, BP 20529, F - 60205 Compiegne cedex (France)

    2004-07-01

    The corrosion of historical objects from World War I fields were studied by using two methods: characterization of the corrosion products by Raman Laser Spectroscopy, and behaviour of the corrosion layers by using electrochemical studies. The first technique, previously used, had shown that two layers are present on these objects, containing both different oxides and oxy-hydroxides of iron. In the present part of the work, the A.C. Impedance Spectroscopy was used to show the differences between the two layers concerning the corrosion of these objects. In order to observe the different behaviours, the specimens were studied in three surface states: with the two layers, with the internal layer only, and without oxide. The results have shown that the internal layer limits the corrosion kinetics. Then this layer was especially studied, particularly its porosity, by a comparison of the impedance results in two media with very different conductivity, and the evolution of these results with different immersion times. The buried objects had the behaviour of a porous electrode, due to the presence of the internal layer. Thus, this behaviour can be modelled with the simplified De Levie's theory, considering that each porosity is a semi-infinite hole. It appeared that the corrosion process at the oxidized interface corresponds to the transport in the electrolyte in the pores completed by a part of transport in the solid phase. These properties can be used to predict the long term corrosion behaviour of carbon steels in soils for long periods. (authors)

  15. Modelling carbon steels corrosion during a long period in soils: Contribution of A.C. impedance spectroscopy

    International Nuclear Information System (INIS)

    Pons, E.; Lemaitre, C.; Crusset, D.; David, D.

    2004-01-01

    The corrosion of historical objects from World War I fields were studied by using two methods: characterization of the corrosion products by Raman Laser Spectroscopy, and behaviour of the corrosion layers by using electrochemical studies. The first technique, previously used, had shown that two layers are present on these objects, containing both different oxides and oxy-hydroxides of iron. In the present part of the work, the A.C. Impedance Spectroscopy was used to show the differences between the two layers concerning the corrosion of these objects. In order to observe the different behaviours, the specimens were studied in three surface states: with the two layers, with the internal layer only, and without oxide. The results have shown that the internal layer limits the corrosion kinetics. Then this layer was especially studied, particularly its porosity, by a comparison of the impedance results in two media with very different conductivity, and the evolution of these results with different immersion times. The buried objects had the behaviour of a porous electrode, due to the presence of the internal layer. Thus, this behaviour can be modelled with the simplified De Levie's theory, considering that each porosity is a semi-infinite hole. It appeared that the corrosion process at the oxidized interface corresponds to the transport in the electrolyte in the pores completed by a part of transport in the solid phase. These properties can be used to predict the long term corrosion behaviour of carbon steels in soils for long periods. (authors)

  16. SOFC LSM:YSZ cathode degradation induced by moisture: An impedance spectroscopy study

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Mogensen, Mogens Bjerg

    2011-01-01

    The cause of the degradation effect of moisture during operation of LSM cathode based SOFCs has been investigated by means of a detailed impedance characterization on LSM:YSZ composite cathode based SOFCs. Further the role of YSZ as cathode composite material was studied by measurements on SOFCs...... with a LSM:CGO composite cathode on a CGO interdiffusion barrier layer. It was found that both types of cathodes showed similar electrochemical characteristics towards the presence of moisture during operation. Upon addition and removal of moisture in the fed air the impedance study showed a change...... in the high frequency cathode arc, which is associated with the charge transport/transfer at the LSM/YSZ interface. On prolonged operation with the presence of moisture an ongoing increase in the high frequency cathode arc resulted in a permanent loss of cathode/electrolyte contact and thus increase...

  17. Dielectric Sensing of Toxic and Explosive Chemicals via Impedance Spectroscopy and Plasmonic Resonance

    Science.gov (United States)

    2017-05-07

    who thoroughly characterized the rapid decontamination of chemical warfare agents VX, soman (GD) and distilled mustard gas (HD)18. The work shows...Joshua J. Phillips, Jennifer R. Soliz, and Adam J. Hauser, “XMCD and Impedance Analysis of Fe2O3 Nanoparticles for Explosive and Chemical Warfare ...Virender K Sharma,"Treatment of chemical warfare agents by zero-valent iron nanoparticles and ferrate (VI)/(III) composite" Journal of hazardous

  18. Analytical solutions of electric potential and impedance for a multilayered spherical volume conductor excited by time-harmonic electric current source: application in brain EIT

    International Nuclear Information System (INIS)

    Xiao Chunyan; Lei Yinzhao

    2005-01-01

    A model of a multilayered spherical volume conductor with four electrodes is built. In this m