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PubMed1999

The effect of gamma-irradiation on the temperature dependence of D.C. electrical conductivity of dry bone.

The effect of gamma-irradiation with doses from 10 to 500 kGy on the electrical conductivity (g) of dry bone was studied. Temperature measurement of electrical conductivity were made from 393 to 533 K. The dependence obtained indicates the increase in g with temperature. An increase in irradiation dose resulted in a decreased g value for each dose up to temperature 462 K. Temperature 462 K was interpreted as the temperature of collagen melting point in dry bone. Above 462 K, g values were dose independent. A dose of 500 kGy shifted the melting point to lower temperature. In addition, the activation energy for the charge conduction process was calculated. Obtained values for electrical conductivity and activation energy were typical for dielectrics and indicated degradation of the organic component of bone.

Animals↗
PubMed1991

Variation in somatic cell count, California mastitis test, and electrical conductivity among various fractions of ewe's milk.

Variation of three estimates of udder inflammation (SCC, California mastitis test, and electrical conductivity) among the foremilk, machine milk, and hand stripping samples were studied. Foremilk and hand stripping milks were taken from each individual teat; machine milk was taken from the entire udder. For this experiment a total of 30 Manchega ewes were subjected to machine milking during the 9th wk of lactation. Samples were taken in duplicate during two milkings on consecutive mornings. Significant differences were observed in the SCC and electrical conductivity, but not in California mastitis test, between foremilk and stripping milk. The stripping fraction had higher SCC (70 +/- 12%) and lower electrical conductivity (difference = .52 +/- .03 mS/cm) than did the foremilk fraction in both healthy and mastitic udders. Machine milk, foremilk, and stripping milk fractions in udders where both halves were healthy were compared. The electrical conductivity values for the machine milk were intermediate and significantly different from conductivity of foremilk and stripping fractions. The log SCC of the machine milk did not differ from that of the foremilk fraction but was significantly less than the stripping milk.

Animals↗
PubMedDate not supplied

[Correlation of the solar activity with water electrical conductivity].

A correlation between the solar activity (Wolf numbers) and electric conductivity of water was found. It was suggested that changes in the electric conductivity of water are the primary cause of the known correlations between the solar activity and various processes in the biosphere.

Electric Conductivity↗
PubMed2000

Experimental study of critical exponents of electrical conductivity in a two-dimensional continuum percolation system

In this paper an experimental study is presented for critical exponents of electrical conductivity in an inverse Swiss-cheese model. Filled circles are drawn on random positions of square paper in drawing ink with an X-Y plotter, and electrical resistance between both opposite sides is measured automatically by the use of general purpose interface bus system. Electrical conductivity is obtained from the inverse of the electrical resistance. Electrical conductivity in a bond process is also measured with the same system. It is confirmed that the critical exponent of electrical conductivity of a continuum two-dimensional inverse Swiss-cheese model is different from that of a discrete one.

Journal Article↗
PubMed2006

The effect of water on the electrical conductivity of olivine.

It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals--for example, plastic deformation and melting temperature--and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200 km depth). Geophysical observations such as electrical conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the electrical conductivity of olivine, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the electrical conductivity of olivine aggregates on water content at high temperature and pressure. The electrical conductivity of synthetic polycrystalline olivine was determined from a.c. impedance measurements at a pressure of 4 GPa for a temperature range of 873-1,273 K for water contents of 0.01-0.08 wt%. The results show that the electrical conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of conductivity is best explained by a model in which electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains approximately 10(-2) wt% water, whereas the water content in the continental upper mantle is less than approximately 10(-3) wt%.

Journal Article↗
PubMed2006

Effects of salinity and the use of shackle/leg sprays on the electrical conductivity of a commercial waterbath stunner for broilers.

The effect of salinity and temperature on the electrical conductivity of a waterbath stunner was assessed in a commercial broiler processing plant. During a break in production, the waterbath was emptied and filled with either cold water, cold water plus sodium chloride, warm water, or warm water plus sodium chloride. Different concentrations of sodium chloride in distilled water at different temperatures were prepared in the laboratory and their conductivities were compared with the results obtained in the processing plant. No significant increase in conductivity was achieved through an increase in water temperature in either the laboratory or the processing plant, but there was an increase in conductivity after the addition of sodium chloride. However, the increase in conductivity was lost after 20 to 30 minutes of birds passing through the waterbath. The effects of the use, the location and the water temperature of the shackle/leg sprays on electrical conductivity were also studied, but under the conditions of the experiment none of these factors increased the electrical conductivity.

Animals↗
PubMed2005

Electrical conduction in macroscopically oriented deoxyribonucleic and hyaluronic acid samples.

Measurements of the quasistatic and frequency dependent electrical conductivity below 1 MHz were carried out on wet-spun, macroscopically oriented, calf thymus deoxyribonucleic (DNA) and umbilical cord hyaluronic acid (HA) bulk samples. The frequency dependence of the electrical conductivity in the frequency range of approximately 10(-3) - 10(6) Hz of both materials is surprisingly rather similar. Temperature dependence of the quasistatic electrical conductivity above the low temperature saturation plateau can be well described by the activated Arrhenius law with the activation energy of approximately 0.8 eV for both DNA and HA. We discuss the meaning of these findings for the possible conduction mechanism in these particular charged polyelectrolytes.

Complex Mixtures↗
PubMed1990

Slotted resonator: principles and applications for high-frequency imaging and spectroscopy on electrically conducting samples.

The electric equivalent of an Alderman-Grant slotted resonator is analyzed in terms of two one-turn solenoids interconnected by a slotted cylinder resonator. The homogeneity of the magnetic RF field is probed using NMR imaging techniques and found to be comparable to that of a saddle-shaped coil. The dielectric losses of the slotted resonator are intrinsically low and much smaller than the inductive losses. Inductive losses are found to be proportional to the sample conductivity and to the fourth power of the sample diameter.

Electric Conductivity↗
PubMed1992

Electrical conductivity of milk: measurement, modifiers, and meta analysis of mastitis detection performance.

The physics, physiology, and pathology of electrical conductivity of milk are described. Based on a meta analysis, the use of electrical conductivity as a mastitis detection tool is discussed. Most reports were based on subclinical mastitis data. The gold standards of the different reports are discussed. With an overall sensitivity of 66% and an overall specificity of 94%, the predictive value of a positive electrical conductivity test remains low in a low prevalence population. The use of on-line systems for clinical mastitis detection is discussed. On-line systems that combine multiple data and perform multifactorial analyses will be of interest to the dairy industry.

Animals↗
PubMed2003

Electrical conduction in native deoxyribonucleic acid: hole hopping transfer mechanism?

Measurements of the quasistatic and frequency dependent electric conductivity below 1 MHz were carried out on wet-spun, macroscopically oriented, calf thymus DNA bulk samples, thus effectively extending previous radio frequency data down to quasistatic time scales. The frequency dependence of the electrical conductivity in the frequency range of approximately 10(-3)-10(15) Hz agrees well with predictions of the hopping hole mechanism. Temperature dependence of the quasistatic electrical conductivity can be rather well described by the activated Arrhenius law with the activation energy of approximately 0.9 eV; however, based on the quality of the fits, the hopping ansatz cannot be ruled out.

Animals↗
PubMed1995

Quantitative assessment of infant body fat by anthropometry and total-body electrical conductivity.

Measurement of total-body electrical conductivity (TOBEC) has emerged as a rapid, safe, and reproducible method for estimation of infant total body fat (TBF). Agreement of two anthropometric methods [by Dauncey et al (1977) and Weststrate et al (1989)] with TOBEC-TBF was assessed in 435 healthy infants aged 21-365 d. Dauncey-TBF correlated with TOBEC-TBF by r2 = 0.61 and exceeded TOBEC-TBF by 0.14 +/- 0.25 kg in infants < 4 mo of age. Thereafter, TOBEC-TBF exceeded Dauncey-TBF by 0.20 +/- 0.47 kg. We modified Dauncey's method, which significantly improved the correlation to r2 = 0.75. Weststrate-TBF correlated with TOBEC-TBF by r2 = 0.87, but exceeded TOBEC-TBF by 0.5 kg. Both methods showed poor agreement with TOBEC-TBF. We conclude that both methods, although suitable for comparison of TBF between groups, cannot be used to accurately assess TBF in an individual infant.

Adipose Tissue↗
PubMed1983

Lactation stage, parity, and infection affecting somatic cells, electrical conductivity, and serum albumin in milk.

Effects of stage of lactation and parity on cell concentration, electrical conductivity, and serum albumin concentration of milk from quarters of known infection status were examined. For quarters free from infection, somatic cell concentration rose from 80 to 160 x 10(3) cells/ml between 35 and infected with Staphylococcus aureus the increase was from 250 to about 1000 x 10(3) cells/ml. As lactation number advanced, there was little change in cell concentration for quarters free from infection, whereas for quarters infected with Staphylococcus aureus, cell concentration rose from approximately 450 x 10(3) cells/ml for first lactation to about 1500 x 10(3) cells/ml for cows in their sixth or more lactations. Trends in electrical conductivity were similar to those for cell concentration, with the main influence on electrical conductivity being Staphylococcus aureus infection. For serum albumin concentration only the effect os stage of lactation was significant. Concentration of serum albumin rose from 150 mg/liter at the beginning of lactation to 280 mg/liter at 215 days postpartum. Effects of stage and number of lactation were minor compared with effects of infection by Staphylococcus aureus.

Animals↗
PubMed1986

In vivo total body electrical conductivity following perturbations of body fluid compartments in rats.

Total body electrical conductivity (TOBEC) provides a rapid and safe noninvasive technique for the assessment of total body water in animals and man. An instrument employing this principle has been shown to measure body water in healthy Sprague-Dawley rats. With the exception of adult obesity in humans, alterations in body fluid compartments that could theoretically affect the utility of conductivity measurements have not been studied. We, therefore, applied the total body electrical conductivity measurement in rats following perturbations of body fluid/electrolyte spaces including obesity, furosemide diuresis, severe burn, and low protein diet. Our findings confirm that total body water can be accurately measured by TOBEC in conditions of abnormal body fluid distribution. However, when the ratio of intracellular to extracellular fluid is significantly reduced, such as the severe burn or low protein intake, TOBEC does not reflect the intracellular (potassium) space but does predict total water and extracellular (sodium) space.

Animals↗
PubMed1963

CHANGES IN ELECTRICAL CONDUCTANCE OF RHODOPSIN ON PHOTOLYSIS.

The change in electrical conductance of rhodopsin solutions was studied with flash-photolysis techniques. The whole pattern of the conductance change on illumination consists of three different processes: (I) the initial decrease, (II) the increase, and (III) the slow decrease, which are in decreasing order of reaction rate. The processes I, II, and III can be most distinctly recognized on flash illumination of acid, slightly acid, and alkaline rhodopsins, respectively. On the other hand, the bleaching of rhodopsin also shows at least three successive phases of different rates, but none of them corresponds in reaction rate to any of the processes of the conductance change. The conductance change may be related to conformational changes of opsin following photoisomerization of retinene, being due to hydrogen or hydroxyl ions and some other inorganic electrolytes. The amount of the change, especially the initial decrease, is proportional to the amount of rhodopsin bleached, even when the photochemical back reaction towards rhodopsin and isorhodopsin occurs in the chromophore depending on the intensity of illumination. Of the three processes, the slow decrease is most severely affected by aging, but the initial decrease and increase are slightly affected. These two processes promptly caused by illumination are connected closely to the conformational changes during the conversion of rhodopsin to metarhodopsin, and perhaps to the initial stage of excitation of rod cells.

Chemical Phenomena↗
PubMed2003

Electrical conduction through nerve and DNA.

The aim of the present study was to analyse electric resistivity at different ambient temperatures between 300 to 20K in the frog sciatic nerve and salmon sperm DNA. When the electrical contacts were leaned just into the sciatic nerve, an increase of the sciatic nerve resistivity was observed for 240 K < T < 300 K and a rise of electrical conductivity was apparent below 240 K. This dependence is generally associated with a semiconductor behaviour. Once the sciatic nerve temperature was driven below 250K, the resistivity abruptly decreased and then at temperatures lower than 234 K, it remained constant and close to one tenth of its ambient temperature value. By contrast, when the electrical contacts were leaned into Salmon sperm DNA, the resistivity remained constant between 300K to 20K, showing a high electrical stability at low temperature. Thus, we report the existence of a new form of electric conductivity in the sciatic nerve at low ambient temperature, which in turn has many electric similarities with inorganic or organic superconductors, whereas temperature failed to alter DNA electrical properties until 20K.

Animals↗
PubMed1994

[Electric conductivity of erythrocyte sediments and red blood cell deformability].

BACKGROUND: To assess the deformability of erythrocytes several methods can be used. The latter investigate either the properties of single blood cell or the properties of a red cell suspension. The objective of the present study was to assess whether experimentally induced deterioration of the red cell deformability can be recorded by measurements of the electric conduction of red cell sediment. METHODS AND RESULTS: In ten patients with disorders of the circulation 10 ml blood samples were taken, mixed with a solution of sodium citrate and centrifuged at 1250 g for 10 minutes. The separated blood cells were repeatedly centrifuged and rinsed. Red cell deformability was experimentally enhanced by incubation of erythrocytes in a Ringer-albumin solution. The change of deformability was detected by viscosimetry and assessment of the electric conduction of the red cell sediment, using a conductometer Radelkis 101 OK, the temperature of the sediment being 10 degrees C. The viscosity values of red cell suspensions with a haematocrit of 0.45 were assessed at six shear rates and they were in all instances higher after incubation of red cell suspensions, as compared with the viscosity of suspensions of fresh erythrocytes. The mean value of electric conduction of the sediment with a haematocrit of 0.45 before incubation was 0.132 mS and after 24 hours incubation 0.218 mS; the difference was statistically significant (p < 0.0005). CONCLUSIONS: Deterioration of red cell deformability is associated with improved electric conduction of the red cell suspension of sediment. It is possible to use assessment of electric conduction of the red cell sediment to assess erythrocyte deformability. The method is simple and cheap, as compared with the viscosimetric method.

Blood Sedimentation↗
PubMed2004

On the flow dependency of the electrical conductivity of blood.

Experiments presented in the literature show that the electrical conductivity of flowing blood depends on flow velocity. The aim of this study is to extend the Maxwell-Fricke theory, developed for a dilute suspension of ellipsoidal particles in an electrolyte, to explain this flow dependency of the conductivity of blood for stationary laminar flow in a rigid cylindrical tube. Furthermore, these theoretical results are compared to earlier published measurement results. To develop the theory, we assumed that blood is a Newtonian fluid and that red blood cells can be represented by oblate ellipsoids. If blood flows through a cylindrical tube, shear stresses will deform and align the red blood cells with one of their long axes aligned parallel to the stream lines. The pathway of a low-frequency (< 1 MHz) alternating electrical current will be altered by this orientation and deformation of the red blood cells. Consequently, the electrical conductivity in the flow direction of blood increases. The theoretically predicted flow dependency of the conductivity of blood corresponds well with experimental results. This theoretical study shows that red blood cell orientation and deformation can explain quantitatively the flow dependency of blood conductivity.

Blood Flow Velocity↗
PubMed1999

Fat mass in infants and toddlers: comparability of total body water, total body potassium, total body electrical conductivity, and dual-energy X-ray absorptiometry.

BACKGROUND: Accurate assessment of body composition in infants and children is fundamental to understanding normal growth and development. Validation of methods applicable to pediatric populations is needed. In the absence of a gold standard, this study was conducted to compare methods using total body water, total body potassium, total body electrical conductivity, and dual-energy x-ray absorptiometry measurements for the estimation of body fat mass in infants and toddlers. METHODS: Repeated body composition measurements were performed on 76 healthy term infants at 0.5, 3, 6, 9, 12, 18, and 24 months of age. Total body water was determined by deuterium dilution and converted to fat-free mass. Total body electrical conductivity was used to measure fat mass. Total body potassium was estimated by whole-body counting and converted to fat-free mass. Dual-energy x-ray absorptiometry was used to estimate fat mass at 0.5, 12, and 24 months only. Data were analyzed by repeated measures analysis of variance, followed by Bonferroni multiple comparisons at 5%. RESULTS: Significant differences among methods were encountered at each age (p = 0.001-0.05). The rank order of the methods and the magnitude of the method differences were a function of age, not of gender or infant feeding mode. Wide limits of agreement imply that the methods are not interchangeable for group or individual measurements. CONCLUSIONS: Methods using total body water, total body potassium, total body electrical conductivity, and dual-energy x-ray absorptiometry to estimate body fat mass in infants and toddlers are not interchangeable and require further development and validation.

Absorptiometry, Photon↗