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At least 19 recordsLinked to original sources
PubMed2000

The Electrical Capacitance of Small Systems.

The electrical capacitance of several small systems is determined by using results given by the fluctuation-dissipation theorem in the classical limit. Estimating the electrical capacitance is important because it is the link to knowledge of the fluctuation of several physical quantities, voltage and field fluctuations, dipole moment, pH, and charge, and also to knowledge of the polarizability and the dielectric dispersion of colloidal and polyelectrolyte systems. For small systems appearing in nature approximately (10-1000) Å the electric capacitance varies in the range approximately (10-1000)x10(-18) F with the corresponding field and dipole moment fluctuations in the order of units of (10(4)-10(6)) V-m and (10(2)-10(4)) D, respectively. Copyright 2000 Academic Press.

Journal Article↗
PubMed1978

Effects of n-decylamine and toluidine blue on the electric capacitance of isolated rat mast cells.

The electric capacitance of isolated rat mast cells and its change under the influence of either n-decylamine or toluidine blue was investigated. Since the electric circuit employed in the detection unit is the one merely sensitive for the capacitance changes, output signals pertain to the capacitance of the tested cell alone. N-decylamine released histamine without accompanying degranulation; and it caused a marked swelling of mast cells and a striking decrease of capacitance, although electric capacitance is usually proportional to the size of the cell. Morphological changes induced by toluidine blue are seemingly correlated with the changes in capacitance. At the concentrations (25-50 microgram/ml) in which the mast cell became enlarged, electric capacitances exceeded the control value. However, at the concentrations higher than 100 microgram/ml in which the cell became shrunken, the capacitance values were less than control value. Pretreatment with DNP (0.1 mM) or oxyphenbutazone (0.05-0.2 mM) was of little effect in inhibiting the histamine release, morphological alterations and capacitance changes due to n-decylamine, but pretreatment with either prevented all of those changes produced by toluidine blue. The mechanism of the capacitance changes in mast cells induced under influence of those compounds is discussed.

Amines↗
PubMed1980

[Changes in electrical capacitance of silicone rubber impression materials during setting process (author's transl)].

Since the silicone rubber impression materials have the high dielectrics, the changes in electrical capacitance during its setting process were measured. The time coordinate of the point of inflexion in the curve of percent changes in its electrical capacitance V.S. time at the setting process were compared with setting time in mechanical measurement. The results were summerized as follows. 1) The degree of advancement of the setting reaction in silicone rubber impression materials were able to be observed by measuring its electrical capacitance. 2) Since the change of the electrical capacitance measured here is corresponding to the setting process of the silicone rubber impression material in this system, the point of inflexion of the curve of the reduced electrical capacitance is the indication of the setting process. 3) The time which demands to reach to this point of inflexion highly corresponds to the setting time of the same material by the mechanical measurements. 4) It is possible to determine the setting time of the silicone rubber impression material by means of measuring the changes in its electrical capacitance.

Dental Impression Materials↗
PubMed1991

The relationship between skin surface temperature, transepidermal water loss and electrical capacitance among workers in the fish processing industry: comparison with other occupations. A field study.

A field study among workers in the fish processing industry (n = 143) was performed to obtain information about skin surface temperature, transepidermal water loss (TEWL), and electrical capacitance and their relationships during work. The skin temperature, TEWL and electrical capacitance were measured on the fingers, hands and forearms. A linear positive relation was found between the temperature and TEWL (in all measured areas), a linear negative relation between the temperature and capacitance (fingers and palms), and a linear negative relation between the capacitance and TEWL (fingers). The results on the fingers among workers in the fish processing industry were compared with results among metal workers (n = 52), cleaners (n = 30), gut cleaners (n = 25), nurses (n = 16), office workers with indoor climate syndrome (n = 20) and normal controls (n = 29). A linear positive relation was found between the respective temperature-TEWL values and a linear negative relation between the respective temperature-capacitance values in the various groups. Furthermore the slope of the temperature-TEWL relations was identical in all groups. Therefore, differences in TEWL levels (comparison at the same temperature) between the respective groups and controls and between the various groups might indicate damage to the skin barrier caused by contact with different irritants and chemicals. However, differences in environment-related variables in the various occupations might also affect TEWL levels. This field study demonstrates, from a practical point of view, how the skin temperature affects TEWL in the various occupations and, as a new point, how sensitive capacitance is to changes in skin temperature. Seasonal variation in TEWL and capacitance was demonstrated among workers in the fish processing industry, with a low TEWL and a high capacitance during summer when the workload is lower.

Adolescent↗
PubMed2002

Electrical capacitance of lipid bilayer membranes of hydrogenated egg lecithin at the temperature phase transition.

Electrical capacitance of the planar bilayer lipid membrane (BLM) formed from hydrogenated egg lecithin (HEL) has been studied during many passages through the phase transition temperature. In contrast to the BLM from individual synthetic phospholipids, membranes from HEL did not demonstrate any capacitance change at the phase transition temperature maximum, as measured by differential scanning calorimeter at 52 degrees C. Instead, two temperatures have been discerned by capacitance records: thickening at 42-43 degrees C and thinning at 57-59 degrees C. The first temperature region is close to the transition temperature of dipalmitoyllecithin, whereas the second is close to that of distearoyllecithin, two main components of the HEL. It was suggested that capacitance measurements were able to reveal a phase separation in the BLM from HEL which was not detected by differential scanning calorimetry. The phase transition of the BLM from the liquid crystal state to the gel state is followed by thickening of the bilayer structure, partly due to a gauche- trans transition of lipid molecules but mainly due to redistribution of the solvent n-decane.

Animals↗
PubMedDate not supplied

[Effect of phase transition on electric capacitance of plane lipid membranes].

Effect of lipid phase transition on electric capacitance of plane lipid membranes was studied. For this purpose the capacitance of the membranes formed from solutions of saturated synthetic phospholipids in different solvent systems were measured at different temperatures. It was found that the capacitance of the membranes formed from phospholipid solution in dioxane having practically no solvent decreased at phase transition from liquid crystal state to gel. It can be explained by an increased membrane thickness during phase transition due to a change of conformation of phospholipid hydrocarbon chains. At the same time the capacitance of the membranes formed from phospholipid solution in normal hydrocarbons increased at the temperatures below the phase transition one. The latter results agree with the data of other authors. It is explained by the thinning of the membrane at the expense of solvent yield from the membrane phase to microlenses.

Electrochemistry↗
PubMed1999

[Effects of sodium salicylate on outward potassium current, resting potential and membrane electric capacitance of the outer hair cell isolated from guinea pig cochlea].

OBJECTIVES: To study effects of sodium salicylate on the outward potassium current (IK), resting potential (RP) and membrane electric capacitance (MEC) of outer hair cells isolated from guinea pig cochleas and the cytoelectrophysiological mechanisms of effects of sodium salicylate on functions of hair cells. METHODS: Using the patch-clamp whole cell recording technique, IK, RP and MEC were measured before and after the administration of sodium salicylate at concentration of 0.1 or 1.0 mmol/L. The effects of sodium salicylate on IK, RP and MEC were observed. RESULTS: The effects of sodium salicylate on IK had time- and dosage-effect relations, of which the former mean IK increasing and then decreasing after administration, the later meant that the effects of sodium salicylate being much more dominant during either increasing or decreasing IK in higher concentration than in lower concentration. The mean RP was approximately--60 mV and the mean MEC was approximately 39 pF. Sodium salicylate could decrease RP and MEC, which possessed a dosage-effect relation, that is, the effect was stronger in higher concentration than in lower concentration, and there was no clear evidence for time-effect relation. CONCLUSIONS: The sodium salicylate might affect the K+ conduction at the lateral membrane and internal and external distribution of K+ in the outer hair cell. Sodium salicylate might affect the excitability and mechanical activity of the outer hair cell by means of affecting IK, RP and MEC, which might be one of the cochlear mechanisms of the effects of sodium salicylate on the functions of hair cells.

Animals↗
PubMed2003

[Non invasive intracranial hyperthermia with Electric Capacitive Transference -ECT- Intratumoral and cerebral thermometry results].

The aim of this work is to present the results of thermic increase obtained at the brain and intratumoral levels through a non invasive technique -Electric Capacitive Transference- (ECT), developed in 1985 by Indiba. A review of the literature does not provide any reference of cerebral and intratumoral thermometry in real time with a non invasive technique of intracranial hyperthermia. In the 8 studied patients, the increases of temperature in the brain, ranged between 0.7 and 1.5 degrees C in relation to the depth of the thermometric probe and the incidence angle of the external electrode. Between tumoral and perilesional brain tissues, thermic increase was 0.3 to 0.7 degrees C greater at tumoral level. The observation that in no case the surrounding brain tissue registered a temperature over 39.2 degrees C supports the harmlessness of the technique regarding the potential damage to healthy brain tissue and seems to confirm previous data obtained in anatomopathological studies in animal experimentation performed in 1990, which showed an absence of lesions in tissues and organs. The greater and somewhat more prolonged thermic increase observed at tumoral level has been called the "greenhouse effect".

Brain Neoplasms↗
PubMed1995

Use of continuous electrical capacitance and transepidermal water loss measurements for assessing barrier function in neonatal rat skin.

A vital function of the skin is to oppose the loss of water to the environment. In this study, two complementary methods, transepidermal water loss (TEWL) and continuous electrical capacitance under occlusion, were used to assess epidermal barrier function in a developmental animal model, the neonatal Sprague-Dawley rat. TEWL monitors barrier function directly while the increase in capacitance under occlusion is related to both the skin's barrier function and to its water holding capacity. Serial tape stripping of the stratum corneum on 1-day-old rat pups led to a significant increase in both TEWL and continuous capacitance measurements. Anatomic site heterogeneity and the effects of surface temperature were also studied. The ventral skin surface exhibited an increase in the continuous capacitance measurements, an effect possibly due to the thinner stratum corneum on the ventral side. Both TEWL and continuous capacitance values were directly correlated with ambient temperatures within the physiological range.

Animals↗
PubMed1994

A prospective, double-blind trial of electrical capacitive coupling in the treatment of non-union of long bones.

Twenty-three patients who had an established non-union of a long bone were entered into a prospective, double-blind trial in which electrical capacitive coupling was used for treatment. Twenty-one patients completed the study: ten who were actively managed and eleven who were managed with a placebo unit. The non-union healed in six of the ten patients who had been managed actively but in none of the patients who had been managed with the placebo unit. This difference in the rates of healing between the actively managed and the placebo groups is highly significant (p = 0.004).

Adolescent↗
PubMed1970

Studies of electric capacitance of membranes. I. A model membrane composed of a filter paper and a lipid analogue.

A hydrophobic filter paper of a given pore size containing a synthetic lipid, i.e. dioleyl phosphate, was interposed between aqueous electrolyte solutions having the same chemical composition and temperature. The electric capacitance and conductance of the membrane immersed in various concentrations of KCl were measured in the frequency range from 20 to 3 x 10(6) cycle/sec. The observed capacitance and conductance were found to be strongly dependent on the applied frequency. A theory is proposed to account for this dispersion of impedance observed in the present membrane-electrolyte system. The dispersion is attributed to the formation of bilayer membranes of the lipid inside the filter paper. The effects of the salt concentration, the adsorbed quantity of the lipid, and the pore size of the filter paper on the capacitance and conductance of the membrane are discussed in terms of the distribution function of bilayers formed within the filter paper.

Electric Conductivity↗
PubMed1996

Surface electrical capacitance as a noninvasive index of epidermal barrier in cultured skin substitutes in athymic mice.

Restoration of an epidermal barrier is a definitive requirement for wound closure. To determine formation of an epidermal barrier as a function of hydration of the stratum corneum, we measured surface electrical capacitance (SEC) of the epidermis in cultured skin substitutes (CSS) in vitro and after grafting to athymic mice. CSS were prepared from human keratinocytes and fibroblasts attached to collagen-glycosaminoglycan substrates. On culture days 3, 7, 14, 17, and 21, SEC was measured in situ. CSS (n = 18; mean +/- SEM) showed a time-dependent decrease of SEC (picoFarads, "pF") from 4721 +/- 28 pF on day 3 to 394 +/- 117 pF on day 14, and subsequent increase to 1677 +/- 325 pF on day 21. After 14-d incubation, parallel CSS samples (n = 5) or murine autografts (n = 5) were grafted orthotopically to athymic mice. After grafting, CSS showed decreases in SEC from 910 +/- 315 pF at 2 wk to 40 +/- 10 pF at 4 wk with no significant decreases thereafter. Control values for murine autograft were 870 +/- 245 pF at 2 wk, and 87 +/- 30 pF at 4 wk. SEC values for native murine skin (n = 10) were 91 +/- 18 pF, and for native human skin (n = 10) were 32 +/- 5 pF. The data demonstrate that SEC decreases with time in culture and that healed or intact skin has approximately 10- to 100-fold lower SEC than CSS in vitro. This noninvasive technique provides a quantitative index of epidermal barrier in CSS in vitro and demonstrates the development of functional epidermal barrier during healing of wounds treated with cultured skin substitutes.

Animals↗
PubMed1990

Effect of low mole fraction of trehalose dicorynomycolate from Corynebacterium diphtheriae on water permeability and electrical capacitance of lipid bilayer membranes.

The effect of incorporation of different proportions of trehalose dicorynomycolates (TDC) into lecithin bilayer membranes was studied. It was found that TDC, induces a 14% decrease of water osmotic permeability (42.6 +/- 3.9 to 36.8 +/- 2.7 microns/s) at 1.6 mole%, suggesting that this substance leads to an increase of the degree of packing of the constituent lipid molecules. A condensing effect of TDC was also apparent from membrane electrical capacitance (Cm) measurement. By incorporating TDC into bilayer membranes, the value of Cm experienced a decrease of 29% at 1.6% mole fraction. This finding was taken to reflect an increase in membrane thickness, known in many examples, to be related to the condensing effect.

Cord Factors↗
PubMed1995

Surface electrical capacitance as a noninvasive bedside measure of epidermal barrier maturation in the newborn infant.

OBJECTIVE: The classical studies of epidermal barrier function in infants have relied on measurement of transepidermal water loss by evaporimetry. This technique, although valuable, is, in practice, slow, expensive, and susceptible to error because of convective air currents. In this prospective study, we evaluated gestation-dependent and postnatal age-dependent changes in epidermal barrier function by measurement of skin surface electrical capacitance (SEC) in 40 newborn infants ranging from 25 to 40 weeks' gestational age. SEC was measured in picofarads with a dermal phase meter. METHODOLOGY: The measurements were recorded continuously during a 12-second period from the forehead at 12 to 24 hours of life. The baseline (CBL) surface hydration at 1 second and the rate of change of SEC during probe occlusion (CSL) were used as measures of surface hydration and transepidermal water movement, respectively. In the most premature infants (< 30 weeks), these measurements were repeated daily for 5 days. Data were analyzed by analysis of variance after logarithmic (Ln) transformation. RESULTS: We found a significant difference in Ln(CBL) in infants born before and after 30 weeks' gestation (4.91 +/- 0.36 Ln[pF] vs 2.67 +/- 0.21 Ln[pF], respectively). Similarly, CSL was significantly different in infants born before and after 30 weeks' gestation (16.42 +/- 5.55 pF/s vs 1.59 + 0.22 pF/s, respectively). In infants born at less than 27 weeks, both Ln(CBL) and CSL decreased significantly by postnatal day 5. In the term group (n = 25), CSL was significantly greater in white than in black infants (1.96 +/- 1.32 pF/s vs. 0.95 +/- 0.55 pF/s, respectively). CONCLUSION: These results demonstrate impaired epidermal barrier properties in immature infants, less than 30 weeks' gestation, and reveal a remarkable rate of barrier maturation of this group in the first few days of postnatal life. Also, the finding of decreased CSL in black infants supports the hypothesis of differences in barrier function attributable to skin types. Overall, these findings demonstrate the feasibility of bedside SEC measurements in the evaluation of epidermal barrier properties in the newborn infant.

Black People↗
PubMed1989

Effects of single application of a moisturizer: evaporation of emulsion water, skin surface temperature, electrical conductance, electrical capacitance, and skin surface (emulsion) lipids.

Effects of single application of an oil in water emulsion were studied on the forearm skin of 12 healthy volunteers. Five different non-invasive methods were used. Values were followed for 360 min after application of the emulsion, with the contralateral forearm as untreated control. The evaporation of emulsion water from the skin surface immediately rose to high values, but within 15 min returned to the original level. A parallel initial increase in conductance was observed; however, this was followed by a slightly increased level throughout the 360 min study. Electrical capacitance was also slightly increased throughout the study. Skin surface lipids, dominated by emulsion lipids, were increased, with high values for at least 120 min, followed by a gradual decline toward normal. Single application of emulsion is characterized by an initial evaporation phase, with evaporation of emulsion water, which lasts less than 15 min, followed by a lipidization phase, which lasts at least 360 min, dominated by the oil-constituent of the emulsion undergoing epidermal absorption. During the lipidization phase, epidermal hydration parameters are slightly but consistently improved.

Aged↗
PubMedDate not supplied

[Electric capacitance of bilayer lipid membranes from hydrogenated egg lecithin during phase transition from liquid crystalline state to gel].

The electrical capacity of planar bilayer lipid membranes (BLM) from natural hydrogenated egg lecithin (HEL) in n-decane at a temperature of phase transition was measured. The temperature of phase transition was determined calorimetrically to be 51 degrees C. The data obtained revealed a phase separation of HEL in BLM into two fractions, one freezing at 42-44 degrees C and one that is converted to a liquid-crystal state at 51-59 degrees C. It was assumed that the first fraction is rich in dipalmitoyl lecithin, and the second fraction is rich in distearoyl lecithin. Freezing and the transition to the liquid-crystal state were accompanied by an increase and decrease in membrane thickness, respectively, in part due to a displacement of the solvent from the torus to the planar part of the bilayer. The displacement of the solvent is explained by changes in the disjoining pressure in BLM, which arises across the lipid bilayer due to van der Waals forces of attraction between water layers on both sides of the BLM.

Animals↗