AC Impedance Measurements on Chara corallina. III. Characterisation of the Plasma Membrane Coat Using a New Presentation of Impedance Spectra

1994 ◽  
Vol 21 (2) ◽  
pp. 147 ◽  
Author(s):  
TC Chilcott ◽  
HGL Coster
Keyword(s):  
Plasma Membrane ◽  
Electron Micrographs ◽  
Transfer Functions ◽  
Chara Corallina ◽  
Frequency Range ◽  
Invasive Approach ◽  
Impedance Measurements ◽  
Time Constants ◽  
Geometrical Properties ◽  
Two Peaks

It has been shown that the measurement of electrical impedence can provide a non-invasive approach to detect the presence of the plasma membrane coat (PMC). Further, the measurements provide an estimate of the geometrical properties of plasmalemmasomes (charasomes) which are similar to estimates determined from electron micrographs. Impedance measurements were made in the range of 1-104 Hz. A transfer (network) function with either four or five time constants was fitted to the spectra. We present transfer functions as spectra in which peaks are observed at the reciprocal of these time constants. We call the reciprocal time constants frequency constants. Our analysis suggests that two peaks in the frequency range of 1-102 Hz arise from the series combination of the plasmalemma and tonoplast and a peak at very high frequencies (>>104 Hz) arises from the static cytoplasm. The remaining two peaks in the frequency range of 102-103 Hz we attribute to the presence of the PMC. The peak at the higher frequency we ascribe to the PMC along smooth sections of plasmalemma and that at the lower frequency we ascribe to the PMC in plasmalemmasomes (charasomes). We found that this peak was not present in spectra obtained from cells without plasmalemmasomes. Our model for the ultrastructure of the PMC and plasmalemmasomes is in good agreement with electron micrographs of these regions. Additionally, our measurements give a physiological range for the electrical properties of the PMC. Conductance and capacitance ranges are 13.6-52 S m-2 and 6.7-17 mF m-2 respectively.

Cl - channels in Chara

1982 ◽  
Vol 299 (1097) ◽  
pp. 435-445 ◽  
Keyword(s):  
Mathematical Model ◽  
Action Potential ◽  
Voltage Dependence ◽  
Quantitative Description ◽  
Chara Corallina ◽  
Squid Axon ◽  
Impedance Measurements ◽  
Time Constants ◽  
Effects Of Ph ◽  
Cl Channels

The action potential in the cells of the freshwater alga Chara corallina is slower than that in the nerve by about 1000-fold. The depolarization phase is brought on by the outflow of the Cl - ions. Voltage-clamp studies show that this Cl - current can be described by the Hodgkin-Huxley equations for the Na+ transient in the squid axon. The only change necessary to the form of the Hodgkin-Huxley equations is an introduction of a time delay between the stimulus and the onset of excitation. This mathematical model of the Chara action potential facilitates a quantitative description of the effects of pH and temperature. While a pH shift alters various Hodgkin-Huxley parameters, temperature change influences mainly the activation and inactivation time constants but leaves the voltage-dependence of these parameters unaffected. The delays in excitation are both temperature and potential dependent. In future some corrections to the Hodgkin-Huxley picture of the Chara action potential may be necessary, as recent impedance measurements suggest a change in the membrane capacitance at the time of excitation.

AC Impedance Measurements on Chava corallina.II. Can the Presence of Plasmalemmasomes be Detected?

1991 ◽  
Vol 18 (2) ◽  
pp. 201 ◽  
Author(s):  
TC Chilcott ◽  
HGL Coster
Keyword(s):  
Cell Surface ◽  
Cylindrical Surface ◽  
Cell Membranes ◽  
Unit Area ◽  
Ac Impedance ◽  
Chara Corallina ◽  
Spatial Variations ◽  
Substantial Part ◽  
Impedance Measurements ◽  
Geometrical Properties

Impedance measurements on cells of Chara corallina at frequencies of 10-102 Hz were used to investigate dielectric and geometrical properties of the plasmalemma and tonoplast at different longitudinal positions along the cylindrical surface of the cells. Large (100%) spatial variations occurred in the measured capacitance of some individual cells. Further, for spatially uniform cells, a 100% variation (from cell to cell) in capacitance was observed. Variations in capacitance (at 10-102 Hz) could be partially attributed to variations in: (i) the conductance of the series conductance element, (ii) the dielectric/geometrical properties of the tonoplast and (iii) the conductance of the cell membranes. However, we attribute a substantial part of the variations in capacitance to variations in the area of the plasmalemma per unit area of cell surface arising from extensive folding of the plasmalemma such as that found in plasmalemmasomes (charasomes).

scholarly journals ELECTRIC IMPEDANCE OF THE FROG EGG

1942 ◽  
Vol 25 (5) ◽  
pp. 765-775 ◽  
Author(s):  
Kenneth S. Cole ◽  
Rita M. Guttman
Keyword(s):  
Plasma Membrane ◽  
Electrical Impedance ◽  
Rana Pipiens ◽  
Specific Resistance ◽  
Membrane Resistance ◽  
Leopard Frog ◽  
Electric Impedance ◽  
Frequency Range ◽  
Impedance Measurements ◽  
Membrane Capacity

Electrical impedance measurements were made upon unfertilized and fertilized eggs of the leopard frog, Rana pipiens, over a frequency range of 0.05 to 10 kc. Average values of 170 ohm cm.2 were obtained for the plasma membrane resistance of the egg, 2.0 µf/cm.2 for the plasma membrane capacity, 86° for the phase angle of the membrane, and 570 ohm cm. for the specific resistance of the interior. These values did not change upon fertilization. No spontaneous rhythmical impedance changes such as have been found by Hubbard and Rothschild in the trout egg were found in frog eggs.

scholarly journals Подвижность ионных носителей заряда в пьезоэлектрических кристаллах Li-=SUB=-2-=/SUB=-B-=SUB=-4-=/SUB=-O-=SUB=-7-=/SUB=-

2020 ◽  
Vol 62 (3) ◽  
pp. 386
Author(s):  
Н.И. Сорокин ◽  
Ю.В. Писаревский ◽  
В.В. Гребенев ◽  
В.А. Ломонов
Keyword(s):  
Crystal Lattice ◽  
Carrier Mobility ◽  
Room Temperature ◽  
Lithium Ion ◽  
Structural Data ◽  
Crystallographic Axis ◽  
Frequency Range ◽  
Impedance Measurements ◽  
Structural Mechanism ◽  
Ag Electrodes

The impedance measurements of Li2B4O7 single crystal with Ag electrodes in the frequency range 1-3*107 Hz at room temperature have been made. The Li2B4O7 crystal (sp. gr. I41cd, Z = 8) was oriented along crystallographic axis c. Contributions from the bulk crystal and crystal / electrode boundaries in the impedance hodograph of the Ag | Li2B4O7 | Ag system were selected. The structural mechanism of lithium-ion transport in Li2B4O7 has been discussed. Based on electrophysical and structural data, the conductivity σdc = 2.3 × 10–9 S / cm, carrier mobility (vacancies VLi) μmob = 6 × 10−10 cm2 / sV and their concentration nmob = 2.4 × 1019 cm – 3 (0.14% of the amount of lithium in the crystal lattice) have been determined.

scholarly journals Analysis of nonstationarity in renal autoregulation mechanisms using time-varying transfer and coherence functions

2008 ◽  
Vol 295 (3) ◽  
pp. R821-R828 ◽  
Author(s):  
Ki H. Chon ◽  
Yuru Zhong ◽  
Leon C. Moore ◽  
Niels H. Holstein-Rathlou ◽  
William A. Cupples
Keyword(s):  
Transfer Functions ◽  
Low Frequency ◽  
Time Varying ◽  
Frequency Range ◽  
Sprague Dawley ◽  
Dynamic Complexity ◽  
Spontaneously Hypertensive ◽  
Renal Autoregulation ◽  
Blood Flow Dynamics ◽  
Frequency Coherence

The extent to which renal blood flow dynamics vary in time and whether such variation contributes substantively to dynamic complexity have emerged as important questions. Data from Sprague-Dawley rats (SDR) and spontaneously hypertensive rats (SHR) were analyzed by time-varying transfer functions (TVTF) and time-varying coherence functions (TVCF). Both TVTF and TVCF allow quantification of nonstationarity in the frequency ranges associated with the autoregulatory mechanisms. TVTF analysis shows that autoregulatory gain in SDR and SHR varies in time and that SHR exhibit significantly more nonstationarity than SDR. TVTF gain in the frequency range associated with the myogenic mechanism was significantly higher in SDR than in SHR, but no statistical difference was found with tubuloglomerular (TGF) gain. Furthermore, TVCF analysis revealed that the coherence in both strains is significantly nonstationary and that low-frequency coherence was negatively correlated with autoregulatory gain. TVCF in the frequency range from 0.1 to 0.3 Hz was significantly higher in SDR (7 out of 7, >0.5) than in SHR (5 out of 6, <0.5), and consistent for all time points. For TGF frequency range (0.03–0.05 Hz), coherence exhibited substantial nonstationarity in both strains. Five of six SHR had mean coherence (<0.5), while four of seven SDR exhibited coherence (<0.5). Together, these results demonstrate substantial nonstationarity in autoregulatory dynamics in both SHR and SDR. Furthermore, they indicate that the nonstationarity accounts for most of the dynamic complexity in SDR, but that it accounts for only a part of the dynamic complexity in SHR.

scholarly journals ELECTRIC IMPEDANCE OF SINGLE MARINE EGGS

1938 ◽  
Vol 21 (5) ◽  
pp. 591-599 ◽  
Author(s):  
Kenneth S. Cole ◽  
Howard J. Curtis
Keyword(s):  
Preliminary Data ◽  
Sea Water ◽  
Membrane Conductance ◽  
Glass Tube ◽  
Alternating Current ◽  
Electric Impedance ◽  
Frequency Range ◽  
Impedance Measurements ◽  
Membrane Capacity ◽  
Thin Walled

Alternating current impedance measurements have been made on several single marine eggs over the frequency range from 1 to 2500 kilocycles per second. The eggs were placed in the center of a short capillary made by heating the end of a 2 mm. thin walled glass tube until it nearly closed, and electrodes were placed in the sea water on each side of the egg. When it is assumed that the membrane conductance is negligible, the membrane capacity and internal resistances of unfertilized and fertilized Arbacia eggs agree with the values obtained from suspensions. Preliminary data on centrifugally separated half Arbacia eggs, and whole Cumingia and Chaetopterus eggs are given.

Part Authentication Using Indirect Electromechanical Impedance Measurements

2020 ◽  
Author(s):  
Mohammad I. Albakri ◽  
Pablo A. Tarazaga
Keyword(s):  
Numerical Solutions ◽  
Numerical Models ◽  
Impedance Measurement ◽  
Piezoelectric Transducers ◽  
Frequency Range ◽  
Impedance Measurements ◽  
Manufacturing Defects ◽  
Electromechanical Impedance ◽  
Non Destructive Evaluation ◽  
Non Destructive

Abstract Motivated by its success as a structural health monitoring solution, electromechanical impedance measurements have been utilized as a means for non-destructive evaluation of conventionally and additively manufactured parts. In this process, piezoelectric transducers are either directly embedded in the part under test or bonded to its surface. While this approach has proven to be capable of detecting manufacturing anomalies, instrumentation requirements of the parts under test have hindered its wide adoption. To address this limitation, indirect electromechanical impedance measurement, through instrumented fixtures or testbeds, has recently been investigated for part authentication and non-destructive evaluation applications. In this work, electromechanical impedance signatures obtained with piezoelectric transducers indirectly attached to the part under test, via an instrumented fixture, are numerically investigated. This aims to better understand the coupling between the instrumented fixture and the part under test and its effects ON sensitivity to manufacturing defects. For this purpose, numerical models are developed for the instrumented fixture, the part under test, and the fixture/part assembly. The frequency-domain spectral element method is used to obtain numerical solutions and simulate the electromechanical impedance signatures over the frequency range of 10–50 kHz. Criteria for selecting the frequency range that is most sensitive to defects in the part under test are proposed and evaluated using standard damage metric definitions. It was found that optimal frequency ranges can be preselected based on the fixture design and its dynamic response.

scholarly journals Design of Cascaded and Shifted Fractional-Order Lead Compensators for Plants with Monotonically Increasing Lags

2020 ◽  
Vol 4 (3) ◽  
pp. 37
Author(s):  
Guido Maione
Keyword(s):  
Fractional Order ◽  
Transfer Functions ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Robust Controller ◽  
Simulation Experiments ◽  
Rational Transfer ◽  
Serial Connection ◽  
Efficiency Performance ◽  
Two Stages

This paper concerns cascaded, shifted, fractional-order, lead compensators made by the serial connection of two stages introducing their respective phase leads in shifted adjacent frequency ranges. Adding up leads in these intervals gives a flat phase in a wide frequency range. Moreover, the simple elements of the cascade can be easily realized by rational transfer functions. On this basis, a method is proposed in order to design a robust controller for a class of benchmark plants that are difficult to compensate due to monotonically increasing lags. The simulation experiments show the efficiency, performance and robustness of the approach.

Frequency-Importance and Transfer Functions for Recorded CID W-22 Word Lists

1991 ◽  
Vol 34 (2) ◽  
pp. 427-438 ◽  
Author(s):  
Gerald A. Studebaker ◽  
Robert L. Sherbecoe
Keyword(s):  
Transfer Function ◽  
Word Recognition ◽  
Transfer Functions ◽  
Normal Hearing ◽  
Frequency Range ◽  
Word Test ◽  
Word Lists ◽  
Articulation Index ◽  
Importance Function ◽  
The Right

Frequency-importance and transfer functions for the Technisonic Studios’ recordings of the CID W-22 word test are reported. These functions may be used to calculate Articulation Index (Al) values or to predict scores on the W-22 test. The functions were derived from the word recognition scores of 8 normal-hearing listeners who were tested under 308 conditions of filtering and masking. The importance function for the W-22 test has a broader frequency range and a different shape than the importance function used in the current ANSI standard on the Articulation Index (ANSI, 1969). The transfer function is similar in slope to to the ANSI transfer function for 256 PB-words, but is shifted to the right of that function by 0.05 Al.

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