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Parallel, multi frequency EIT measurement, suitable for recording impedance changes during epilepsy

by the subject. The impedance change associated with the seizure has two components. For each individual spike, the cell depolarisation causes an impedance decrease of approximately 1% at DC. At measurement frequencies below ~10 kHz, the applied current will predominately flow through the extracellular space, but as ion channels open at the seizure onset, some current will flow through the intracellular space, reducing the magnitude of the impedance change to about 0.1% [ 23 ]. Following this initial decrease in impedance, there is an increase of impedance due to

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Marking 100 years since Rudolf Höber’s discovery of the insulating envelope surrounding cells and of the β-dispersion exhibited by tissue

Introduction In a series of electrical experiments, performed between 1910 and 1913, Rudolf Höber provided the first evidence that cells possess a resistive dielectric membrane that surrounds a conducting electrolytic interior [ 1 , 2 , 3 ]. He determined that the conductivities of compacted red blood cells and frog muscle tissue measured at MHz frequencies were significantly higher than that measured at ~150 Hz. At low frequencies the current was deduced to flow around the cells, but that at high frequencies the current was able to penetrate into the

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A novel method to obtain proximal plethysmographic information from distal measurements using the impedance plethysmogram

distal part of one limb of a subject, thus forcing the current to flow from one limb to another, and the local and limb-to-limb IPG were measured by using the same injected current. In order to evaluate the arrival times of the pressure pulse at different locations, the two electrodes to obtain the local IPG were sequentially placed onto different measurement sites. During the experiments, an additional ECG was simultaneously obtained from an IPG-compatible system [ 15 ] in order to provide a timing reference for the recorded waveforms. For the hand-to-hand IPG test

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Sources of error in AC measurement of skin conductance

often used for skin conductance measurements. The left part of figure 5 shows the three-electrode system with the three electrodes placed on the surface of the skin. For a frequency range where the SC typically dominates the measurements (i.e. typically below 1 kHz), only the impedance in the SC below the measuring (M) electrode is measured. Because of the feedback through the skin, the operational amplifier will generate the necessary voltage to drive the inverting input to the same voltage as the non-inverting input, i.e. v i . Since no current flows to the

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Electrical characterization of bolus material as phantom for use in electrical impedance and computed tomography fusion imaging

(generated by the impedance spectroscope) was applied to the sample through the reference and the measuring electrode. The current, I z , flowed through the sample was measured with the measuring electrode. The measuring electrode was virtually grounded. Thus the voltage that is applied to the sample was V z and the current passing through the sample was I z , hence impedance spectrum of the tissue is calculated as follows: (1) Z = V Z I Z $$\text Z=\frac{{{\text V}_{\text Z}}}{{{I}_{\text Z}}}$$ The experimental

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DC feedback for wide band frequency fixed current source

layer of non-conductive lipid material sandwiched between two layers of conductive protein molecules. Biologically, the cell membrane functions as a permeable barrier separating the intracellular (cytoplasm) and extracellular components. The lipid membrane is traversed by proteins, which are soluble in water thus making pores through which water, ions, and other chemicals can enter and exit the cell. Controlling the flow of these materials is essential to life. The cell membrane protects the interior of the cell while allowing passage of some materials to which it is

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A new system for measuring electrical conductivity of water as a function of admittance

all frequencies of distilled water. Distilled Water f / kHz Admittance (μS) 2-Outer Electrodes Admittance (μS) 2-Inner Electrodes Admittance (μS) 4-Electrodes 0.05 1.49 2.91 13.09 2 1.65 3.77 20.10 6 2.55 5.06 24.96 20 6.62 10.38 24.03 60 15.78 20.25 34.16 100 20.05 23.81 44.28 The configuration of the electrodes also contributes to the increase in the measured admittance. For the four electrode setup there is no current flow through the voltage measurement electrodes, thus there

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Impedance of tissue-mimicking phantom material under compression

investigation and the stress relaxation of that material – then there would be no way of relating the measured passive electrical properties to the physical deformation of a sample. On the one hand, it is a very likely assumption (that impedance measurements reflect and underlying physical nature) as it is thoroughly baked into all bioimpedance research and has been successful thus far. On the other hand, the function in this particular case involves the flow of fluid through a deforming, quasi-biological, porous structure and is beyond the scope of this presentation. This

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Extraction of cardiac and respiration signals in electrical impedance tomography based on independent component analysis

between these two methods with the ECG-gating alternative was reported considerably less. However, the correlations between each of these methods and a known standard method for perfusion imaging were not computed, rendering the results from their study inconclusive regarding as to which method is more reliable. Proposed Method Using ICA Impedance change of cardiac signal mixes with the impedance change of respiration signal and impedance change of blood flow. The EIT signal gets demodulated with the respiration signal of the human body and the cardiac signal gets

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Evaluation of sugar yeast consumption by measuring electrical medium resistance

a function of time obtained from the bubbling of CO2 into the cell suspension. The black arrow indicates the start of bubbling. As shown in Fig. 8 , the CO 2 was insufflated at 7 min. Unlike the gradual increase in the Rm% shown in fig 3 and 4 , the Rm% increased very rapidly from 0 to 19%. This difference is attributed to the fact that few CO 2 bubbles are released at the beginning of the fermentation and that this number increases as the fermentation progresses. In this CO 2 bubbling experiment, the bubble flow rate is more intensive that the

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