scholarly journals ELECTRIC IMPEDANCE OF HIPPONOË EGGS

1935 ◽  
Vol 18 (6) ◽  
pp. 877-887 ◽  
Author(s):  
Kenneth S. Cole
Keyword(s):  
Volume Concentration ◽  
Marked Effect ◽  
Sea Water ◽  
Unit Area ◽  
Specific Resistance ◽  
Internal Resistance ◽  
Simple Method ◽  
Low Frequencies ◽  
Static Capacity ◽  
Current Resistance

Alternating current resistance and capacity measurements have been made from 1.08 103 to 2.32 106 cycles per second on suspensions of unfertilized, fertilized, and swollen unfertilized eggs of the echinoderm Hipponoë esculenta. A simple method has been developed for measuring the volume concentration of eggs in a suspension. The membrane of the unfertilized egg is practically non-conducting at low frequencies and shows a static capacity of 0.87 µf/cm.2 except perhaps at the highest frequencies. The equivalent specific resistance of the egg interior is 11 times that of sea water. The membrane of the fertilized egg is practically non-conducting at low frequencies and shows a static capacity 2.5 times that of the unfertilized egg except at the higher frequencies where another reactive element produces a marked effect. The internal resistance is apparently higher than that of the unfertilized egg. The static capacity per unit area of the membrane decreases as a linear function of the surface area when the eggs are swollen in dilute sea water. In 40 per cent sea water, the capacity falls to about 75 per cent of normal.

scholarly journals ELECTRIC IMPEDANCE OF ASTERIAS EGGS

1936 ◽  
Vol 19 (4) ◽  
pp. 609-623 ◽  
Author(s):  
Kenneth S. Cole ◽  
Robert H. Cole
Keyword(s):  
Plasma Membrane ◽  
Sea Water ◽  
Specific Resistance ◽  
Surface Conductance ◽  
Electric Impedance ◽  
High Concentration ◽  
Low Frequencies ◽  
Definite Evidence ◽  
Asterias Forbesi ◽  
Current Resistance

The alternating current resistance and capacity of suspensions of unfertilized eggs of Asterias forbesi have been measured at frequencies from one thousand to sixteen million cycles per second. The plasma membrane of the egg has a static capacity of 1.10µf/cm.2 which is practically independent of frequency. The suspensions show a capacity dependent on frequency at low frequencies which may be attributable to surface conductance. The specific resistance of the cytoplasm is between 136 and 225 ohm cm. (4 to 7 times sea water), indicating a relatively high concentration of non-electrolytes. At frequencies above one million cycles there is definite evidence of another element of which the nucleus is presumably a part.

scholarly journals TRANSVERSE ELECTRIC IMPEDANCE OF THE SQUID GIANT AXON

1938 ◽  
Vol 21 (6) ◽  
pp. 757-765 ◽  
Author(s):  
Howard J. Curtis ◽  
Kenneth S. Cole
Keyword(s):  
Current Flow ◽  
Transverse Electric ◽  
Sea Water ◽  
Specific Resistance ◽  
Giant Axon ◽  
Simple Analysis ◽  
Axon Membrane ◽  
Polarization Impedance ◽  
Direct Current Resistance ◽  
Current Resistance

The impedance of the excised giant axon from hindmost stellar nerve of Loligo pealii has been measured over the frequency range from 1 to 2500 kilocycles per second. The measurements have been made with the current flow perpendicular to the axis of the axon to permit a relatively simple analysis of the data. It has been found that the axon membrane has a polarization impedance with an average phase angle of 76° and an average capacity of 1.1µf./cm2 at 1 kilocycle. The direct current resistance of the membrane could not be measured, but was greater than 3 ohm cm.2 and the average internal specific resistance was four times that of sea water. There was no detectable change in the membrane impedance when the axon lost excitability, but some time later it decreased to zero.

Experiments on Substrate Selection by Corophium Species: Films and Bacteria on Sand Particles

1964 ◽  
Vol 41 (3) ◽  
pp. 499-511
Author(s):  
P. S. MEADOWS
Keyword(s):  
Ionic Strength ◽  
Sea Water ◽  
Distilled Water ◽  
Substrate Selection ◽  
Corophium Volutator ◽  
Simple Method ◽  
Substrate Preferences ◽  
Solutions Of Electrolytes ◽  
Sand Particles ◽  
Micro Organisms

1. A simple method is described for determining the substrate preferences of Corophium volutator (Pallas) and Corophium arenarium Crawford. 2. If offered a choice of its own substrate with that of the other species each prefers its own. 3. Level of illumination and colour of substrate have little effect on choice. An animal's size and hence its age has little effect on its substrate preferences. 4. C. volutator prefers a substrate previously maintained under anaerobic conditions, C. arenarium vice versa. 5. Treatments which kill, inactivate, or remove micro-organisms render sands unattractive to Corophium. These include boiling, acid-cleaning, drying, and soaking in fixatives or distilled water. Attempts to make these sands attractive again failed. 6. Distilled water, and solutions of the non-electrolytes sucrose and glycerol at the same osmotic pressure as sea water, induce many bacteria to desorb from sand particles; smaller numbers are desorbed in the presence of solutions of electrolytes at the same ionic strength as sea water (NaCl, Na2SO4, KC1, MgSO4, MgCl2, CaCl2). Of all these, only distilled water and solutions of MgCl2 and CaCl2 reduce the attractive properties of sands. Hence the loss of bacteria from the surface of sand grains, though related to the ionic strength and composition of the medium, is not necessarily associated with a substrate becoming unattractive.

scholarly journals Installation for measuring the dielectric anisotropy of liquid crystals at low frequencies by the bridge method with constant displacement

2021 ◽  
Vol 1198 (1) ◽  
pp. 012006
Author(s):  
S V Kalashnikov ◽  
N A Romanov ◽  
A V Nomoev
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Internal Resistance ◽  
Dielectric Anisotropy ◽  
Dielectric Parameters ◽  
Low Frequencies ◽  
Offset Voltage ◽  
Wide Range ◽  
Ac Current ◽  
Constant Displacement

Abstract Installation designed to measure the dielectric anisotropy in laboratory studies of liquid crystal polymer films is described. The installation operates on the principle of a balanced alternating current (AC) bridge, allowing the application of a direct external current (bias) to the liquid crystal cell. The internal resistance of the direct current (DC) source, which affects the equilibrium condition of the bridge, is compensated. The frequency of the AC current feeding the bridge and the offset voltage of the cell is regulated within a wide range, which makes it possible to study various functional dependences of the dielectric parameters of liquid crystals and their modifiers.Introduction

Spectra of quarry blasts and microearthquakes recorded at local distances in Israel

1993 ◽  
Vol 83 (6) ◽  
pp. 1799-1812
Author(s):  
Yefim Gitterman ◽  
Torild van Eck
Keyword(s):  
Time Delays ◽  
Spectral Characteristics ◽  
Open Pit ◽  
Frequency Range ◽  
Simple Method ◽  
Low Frequencies ◽  
Event Identification ◽  
Routine Basis ◽  
Seismograph Network ◽  
Discrimination Method

Abstract In northern Israel, quarry blasts and microearthquakes occur in a region with complicated tectonics. Therefore correct event identification, preferably based on a simple method that can be applied on a routine basis, is essential for accurate and detailed seismotectonic studies. Spectral analysis of quarry blasts and microearthquakes recorded at local distances (5 < Δ < 2000 km) by stations of the Israel Seismograph Network revealed spectral characteristics in the frequency range less than 12.5 Hz that can be used routinely for event identification. Most quarry blasts in northern Israel are ripple-fired, open pit blasts, consequently we chose an event discrimination method based on the recognition of ripple-firing patterns in the signal. A simple model for ripple firing parameters, based on interference theory of linear systems and including random effects, predicts spectral minima at low frequencies identical for different seismic phases. We compared the spectra of complete seismogram signals of 52 events recorded by the ISN at different distances and azimuths, including both microearthquakes and quarry blasts in a selected region of northern Israel. Consistent spectral modulation was found in a band from about 2 to 8 Hz for 18 of 21 reliably identified, i.e., reported, quarry blasts with time delays of 20 to 40 msec. The spectral minima frequencies correspond to those predicted by the theory.

scholarly journals ELECTRIC IMPEDANCE OF ARBACIA EGGS

1936 ◽  
Vol 19 (4) ◽  
pp. 625-632 ◽  
Author(s):  
Kenneth S. Cole ◽  
Robert H. Cole
Keyword(s):  
Plasma Membrane ◽  
Sea Water ◽  
Low Frequency ◽  
Relaxation Dispersion ◽  
Surface Conductance ◽  
Low Frequencies ◽  
Membrane Capacity ◽  
A Value ◽  
Fertilization Membrane ◽  
Fertilized Egg

The alternating current resistance and capacity of suspensions of unfertilized and fertilized eggs of Arbacia punctulata have been measured at frequencies from 103 to 1.64 x 107 cycles per second. The unfertilized egg has a static plasma membrane capacity of 0.73 µf./cm.2 which is practically independent of frequency. The fertilized egg has a static membrane capacity of 3.1 µf./cm.2 at low frequencies which decreases to a value of 0.55 µf./cm.2 at high frequencies. The decrease follows closely the relaxation dispersion of the dielectric constant if the dissipation of such a system is ignored. It is considered more probable that the effect is due to a fertilization membrane of 3.1 µf./cm.2 capacity lifted 1.5 µ. from the plasma membrane, the interspace having the conductivity of sea water. The suspensions show a frequency-dependent capacity at low frequencies which may be attributable to surface conductance. The equivalent low frequency internal specific resistance of both the unfertilized and fertilized egg is about 186 ohm cm. or about 6 times that of sea water, while the high frequency data extrapolate to a value of about 4 times sea water. There is evidence at the highest frequencies that the current is penetrating the nucleus and other materials in the cytoplasm. If this effect were entirely due to the nucleus it would lead to a very approximate value of 0.1 µf./cm.2 for the capacity of the nuclear membrane. The measurements do not indicate any change in this effect on fertilization.

Decomposition of Atmospheric Disturbances into Standing and Traveling Components, with Application to Northern Hemisphere Planetary Waves and Stratosphere–Troposphere Coupling

2015 ◽  
Vol 72 (2) ◽  
pp. 787-802 ◽  
Author(s):  
Oliver Watt-Meyer ◽  
Paul J. Kushner
Keyword(s):  
Northern Hemisphere ◽  
Standing Waves ◽  
Real Space ◽  
Planetary Waves ◽  
Interference Effects ◽  
Simple Method ◽  
Low Frequencies ◽  
Spatial And Temporal Scales ◽  
Wave Interference ◽  
Atmospheric Disturbances

Abstract This study updates a body of literature that aims to separate atmospheric disturbances into standing and traveling zonal wave components. Classical wavenumber–frequency analysis decomposes longitude- and time-dependent signals into contributions from distinct spatial and temporal scales. Here, an additional decomposition of the spectrum into standing and traveling components is described. Previous methods decompose the power spectrum into standing and traveling parts with no explicit allowance for covariance between the two. This study provides a simple method to calculate the variance of each of these components and the covariance between them. It is shown that this covariance is typically a significant portion of the variance of the total signal. The approach also preserves phase information and allows for the reconstruction of the real-space standing and traveling components. The technique is applied to reanalysis wintertime geopotential height anomalies in the Northern Hemisphere in order to investigate planetary wave interference effects in stratosphere–troposphere coupling. The results show that for planetary waves 1–3, standing waves explain the largest portion of the variance at low frequencies. An exception is for wave 1 in the high-latitude troposphere, where there is a strong westward-traveling wave. Furthermore, the antinodes of the standing waves have preferred longitudes that tend to align with the extremes of the climatological wave, suggesting that standing waves contribute to a linear interference effect that has been shown to be an important part of stratosphere–troposphere interactions.

A fast and simple method of spectral enhancement

Geophysics ◽  
2014 ◽  
Vol 79 (3) ◽  
pp. V75-V80 ◽  
Author(s):  
Muhammad Sajid ◽  
Deva Ghosh
Keyword(s):  
Seismic Data ◽  
Real Data ◽  
Difference Operators ◽  
Frequency Noise ◽  
Simple Method ◽  
Low Frequencies ◽  
High Frequencies ◽  
Algorithm Comparison ◽  
Spectral Enhancement ◽  
Bed Thickness

The ability to resolve seismic thin beds is a function of the bed thickness and the frequency content of the seismic data. To achieve high resolution, the seismic data must have broad frequency bandwidth. We developed an algorithm that improved the bandwidth of the seismic data without greatly boosting high-frequency noise. The algorithm employed a set of three cascaded difference operators to boost high frequencies and combined with a simple smoothing operator to boost low frequencies. The output of these operators was balanced and added to the original signal to produce whitened data. The four convolutional operators were quite short, so the algorithm was highly efficient. Synthetic and real data examples demonstrated the effectiveness of this algorithm. Comparison with a conventional whitening algorithm showed the algorithm to be competitive.

scholarly journals THE ELECTRIC CAPACITY OF SUSPENSIONS WITH SPECIAL REFERENCE TO BLOOD

1925 ◽  
Vol 9 (2) ◽  
pp. 137-152 ◽  
Author(s):  
Hugo Fricke
Keyword(s):  
Specific Resistance ◽  
Suspended Particle ◽  
Specific Capacity ◽  
Major Axis ◽  
Electrolytic Cell ◽  
Substitution Method ◽  
Static Capacity ◽  
Electric Capacity ◽  
Polarization Capacity ◽  
Made In

1. The specific capacity of a suspension is that capacity which) combined in parallel with a certain resistance, electrically balances 1 cm. cube of the suspension. 2. The following formula holds for the specific capacity of a suspension of spheroids, each of which is composed of a well conducting interior surrounded by a thin membrane of a comparatively high resistance: See PDF for Equation C, specific capacity of suspension; Co, static capacity of one sq. cm. of membrane; r, r1 specific resistances respectively of suspension and of suspending liquid; 2 q major axis of spheroid, α constant tabulated in Table I. 3. The following formula holds practically for any suspension whatever the form of the suspended particle. See PDF for Equation C = C100 being the specific capacity of a suspension with a concentration of 100 per cent. Formulæ (1a) and (1b) hold only for the case, when the frequency is so low, that the impedance of the static capacity of the membrane around a single particle is high as compared with the resistance of the interior of the particle. The formulae hold also for a suspension of homogeneous particles, when polarization takes place at the surface of each particle, provided the polarization resistance is low as compared with the impedance of the polarization capacity. 4. A description is given of a method for measuring the capacity of a suspension at frequencies between 800 and 4½ million cycles. By means of a specially designed bridge, a substitution method is employed, by which in the last analysis the suspension is compared with the suspending liquid which is so diluted as to have the same specific resistance as the suspension, consecutive measurements being made in the same electrolytic cell. 5. Formula (1b) is verified by measurements of the capacity of suspensions of varying volume concentrations of the red corpuscles of a dog. 6. By means of the above measurements, the value of Co is calculated by equation (1a). 7. It is found that Co is independent of the frequency up to 4½ million cycles and that it is also independent of the suspending liquid. These results furnish considerable evidence of the validity of the theory, that Co represents the static capacity of a corpuscle membrane. 8. On this assumption and using a probable value for the dielectric constant of the membrane, the thickness of the membrane is calculated to be 3.3·10–7 cm.

scholarly journals ELECTRIC TISSUE

1945 ◽  
Vol 28 (3) ◽  
pp. 187-212 ◽  
Author(s):  
R. T. Cox ◽  
C. W. Coates ◽  
M. Vertner Brown
Keyword(s):  
Unit Area ◽  
Electric Energy ◽  
Internal Resistance ◽  
Electrical Characteristics ◽  
Cross Sectional ◽  
Ohmic Resistance ◽  
Electric Organs ◽  
Maximum Current ◽  
Electric Eel ◽  
Simple Combination

In the main electric organs of the electric eel, the cross-sectional area, the thickness of the electroplaxes, and certain electrical characteristics of the tissue vary widely between the anterior and posterior ends. However, a transverse layer of the organs one electroplax thick has certain characteristics which are roughly uniform along the organs. These are its volume, its maximum voltage, its maximum current per unit area, and the resistance of unit area at the peak of the discharge. Measurements of the voltage developed by a segment of the organs across different external resistances at different instants during the discharge are all rather well described by representing the segment, with the adjacent non-electric tissue, as a simple combination of E.M.F. and ohmic resistance. The internal resistance of the tissue varies during the discharge. Its E.M.F. appears to be practically constant, at least during the greater part of the discharge. Estimates made of the total electric energy show it about equal to the energy supplied by the decrease of phosphocreatine and the formation of lactic acid.

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