Development of a multi-frequency system for medical applications of focused electrical impedance method (FIM) appropriate for developing countries

Abstract Background: Lead is a nonessential heavy metal, which can inhibit heme synthesis and has significant cytotoxic effects. Nevertheless, its effect on the electrical properties of red blood cells (RBCs) remains unclear. Consequently, this study aimed to investigate the electrical properties and the electrophysiological mechanism of lead exposure in mouse blood using Electrical Impedance Spectroscopy (EIS). Methods: AC impedance method was used to measure the electrical impedance of healthy and lead exposure blood of mice in 0.01-100 MHz frequency range. Data characteristic of the impedance spectrum, Bodes plot, Nyquist plot and Nichols plot, and three elements equivalent circuit model were used to explicitly analyze the differences in amplitude-frequency, phase-frequency, and the frequency characteristic of blood in electrical impedance properties. Results: Compared with the healthy blood in control mice, the changes in blood exposed to lead was as follows: (I) the hematocrit decreased; (II) the amplitude-frequency and phase-frequency characteristics of electrical impedance decreased; (III) the characteristic frequencies ( f 0 ) were significantly increased; (IV) the electrical impedance of plasma, erythrocyte membrane, and hemoglobin decreased, while the conductivity increased. Conclusion: Therefore, EIS can be used as an effective method to monitor blood and RBCs abnormalities caused by lead-exposure.

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High output resistance current drive circuits for medical applications

10.12681/eadd/50356 ◽

2006 ◽

Author(s):

Νικόλαος Τερζόπουλος

Keyword(s):

Electrical Impedance ◽

Current Drive ◽

Medical Applications ◽

Output Resistance ◽

High Output

Η έρευνα που περιγράφεται στην παρούσα διατριβή ασχολείται με την ανάλυση, σχεδιασμό και ανάπτυξη κυκλωμάτων πηγών ρεύματος πολύ υψηλής αντίστασης εξόδου για ιατρικές εφαρμογές. Αυτά τα κυκλώματα χρησιμοποιούνται σε ιατρικά μηχανήματα απεικόνισης, όπως ο τομογράφος ηλεκτρικής εμπέδησης (Electrical Impedance Tomograph,ΕΙΤ) . Η προδιαγραφή στόχος για ένα τέτοιο σύστημα ήταν μια σύνθετη αντίσταση εξόδου άνω του 1MΩ στο 1MHz. Διάφορα κυκλώματα πηγών ρεύματος έχουν μελετηθεί από κοινού με μια ποικιλία τεχνικών που αυξάνουν το επίπεδο της αντίστασης εξόδου για να επίτευξη του στόχου του διδακτορικού προγράμματος . Όλα τα κυκλώματα που αναφέρονται στη διατριβή αποτελούνται απο διπολικά τρανζίστορ και έχουν εξεταστεί στη βάση θεωρητικών αναλύσεων και κυκλωματικών προσομοιώσεων μέσω Η/Υ.Η πλειονότητα των αποτελεσμάτων των εργασιών αυτών, έχουν δημοσιευθεί από τον συγγραφέα στην τεχνική βιβλιογραφία.Η διατριβή ξεκινά με μια μελέτη και ορισμένες αρχικές μετρήσεις προκειμένου να διαπιστωθεί η δυνατότητα εφαρμογής και η καταλληλότητα των παραμέτρων του μοντέλου SPICE του τρανζίστορ. Αυτό ήταν αναγκαίο, διότι ο στόχος για υψηλή αντίσταση εξόδου σημαίνει ότι η δευτερογενής επιδράσης πρέπει να λαμβάνονται υπόψη . Τα αποτελέσματα αυτής της εργασίας οδήγησε σε καινοτόμες μεθόδους προσδιορισμού της αντίστασης βάσης συλλέκτη, rμ, σε ένα διπολικό τρανζίστορ , και στη συνέχεια δημοσιεύθηκε από τον συγγραφέα.Το επόμενο μέρος της διατριβής επικεντρώνεται στην αναθεώρηση των παραδοσιακών κυκλωμάτων πηγών ρεύματος και μια κριτική ανάλυση των επιδόσεών τους και την καταλληλότητά τους για τις ιατρικές εφαρμογές.Τέλος, σε επίπεδο τρανζίστορ σχεδιάστηκε μια πηγή ρεύματος με υψηλή αντίσταση εξόδου ιδανική για υλοποιήση ASIC(Ολοκληρωμένου Κυκλώματος)Η πηγή ρεύματος αποτελείται απο αρχιτεκτονική ρεύματος με τεχνική ανίχνευσης και χρησιμοποιήθηκε σε ένα βρόχο ανάδρασης με ένα τελεστικό ενισχυτή καθώς η έξοδος παρέχεται απο βελτιωμένες εκδόσεις βασιζόμενες σε ένα κύκλωμα B & S (Baxandall andSwallow)Η σύνθετη αντίσταση εξόδου υπερέβησε κατά πολύ τις προδιαγραφές του διδακτορικού προγράμματος που ήταν 1MΩ σε 1ΜΗz.

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Measurement of Frost-hardiness in Douglas Fir at Three Nurseries by an Electrical Method

The Forestry Chronicle ◽

10.5558/tfc46065-1 ◽

1970 ◽

Vol 46 (1) ◽

pp. 65-66

Author(s):

R. van den Driessche

Keyword(s):

Electrical Impedance ◽

Douglas Fir ◽

Frost Hardiness ◽

Impedance Method ◽

Electrical Method

Frost-hardiness changes in three Douglas fir provenances at each of three nurseries were followed from September, 1968, to April, 1969, by measuring electrical impedance of stems. Nursery had a greater effect on hardiness than provenance, with seedlings at one nursery reaching the same level of hardiness two weeks earlier than those at another nursery. Detection of these hardiness differences shows the practical value of the impedance method for measuring frost-hardiness.

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Measurement of cardiac output by electrical impedance at rest and during exercise

Journal of Applied Physiology ◽

10.1152/jappl.1976.40.1.91 ◽

1976 ◽

Vol 40 (1) ◽

pp. 91-95 ◽

Cited By ~ 158

Author(s):

J. C. Denniston ◽

J. T. Maher ◽

J. T. Reeves ◽

J. C. Cruz ◽

A. Cymerman ◽

...

Keyword(s):

Cardiac Output ◽

Electrical Impedance ◽

Bicycle Ergometer ◽

Mean Value ◽

Impedance Method ◽

Wave Form ◽

Graded Exercise ◽

Movement Artifact ◽

Maximum Work ◽

Volume Equation

A comparison was made between cardiac output values determined by the dye dilution and electrical impedance methods in ten subjects at rest and during graded exercise on a bicycle ergometer. The cardiac output values determined by the two methods were linearly related and significantly (P less than 0.001) correlated (r = 0.90). Movement artifact associated with exercise at maximum or near-maximum work loads caused severe distortion of the dZ/dt wave form and prevented calculation of impedance cardiac output at these levels of work. Use of the lowest value of L (distance between mean value of L in the impedance stroke volume equation (SV = p(L2/ZO2) (dZ/dt)mt), resulted in nearly identical values for the least-squares line and equalvalue line of impedance and dye cardiac outputs. Although absolute values of cardiac output determined by the two methods were not identical in all subjects the changes in cardiac output were nearly identical during the different levels of exercise. The data support the validity of the impedance method as a noninvasive, atraumatic measure of cardiac output at rest and during graded exercise.

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Role of phase angle measurement in electrical impedance spectroscopy

International Agrophysics ◽

10.2478/intag-2013-0007 ◽

2013 ◽

Vol 27 (4) ◽

pp. 377-383 ◽

Cited By ~ 13

Author(s):

I. Cseresnyés ◽

K. Rajkai ◽

E. Vozáry

Keyword(s):

Energy Dissipation ◽

Impedance Spectroscopy ◽

Phase Angle ◽

Characteristic Frequency ◽

Electrical Impedance ◽

Angle Measurement ◽

Electrical Impedance Spectroscopy ◽

Impedance Method ◽

Soil System ◽

Current Frequency

Abstract Importance of phase angle measurement during the application of electrical impedance spectroscopy was studied by executing pot experiments with maize. Electrical impedance, phase angle (strength of capacitive character), and dissipation factor in the plant-soil system were scanned between 100 and 10 000 Hz current frequency. The frequency-dependent change in the phase angle could be described by optimum curves culminating within 920-3 650 Hz. Since the rate of energy dissipation is independent of root extent, the higher phase angle and lower energy dissipation were associated with the higher coefficient of determination achieved for the root electrical impedance - root system size (root dry mass and root surface area) regressions. The characteristic frequency selected on the basis of phase angle spectra provided a higher significance level at statistical comparison of plant groups subjected to stress conditions influencing root development. Due to the physicochemical changes observable in aging root tissue, the apex of phase angle spectra, thus the characteristic frequency, shifted continuously toward the higher frequencies over time. Consequently, the regularly repeated phase angle measurement is advisable in time-course studies for effective application of the electrical impedance method, and the systematic operation at the same frequency without determination of phase angle spectra should be avoided.

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