Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Electric Capacitance”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
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↗
PubMed2004

Tumor capacitance: electrical measurements of renal neoplasia.

PURPOSE: Studies have demonstrated that biological tissues possess unique electrical properties. We evaluate the electrical properties of renal tumors using a specialized probe with the capability of measuring intra-tissue capacitance in an ex vivo model of fresh surgically excised tissue. MATERIALS AND METHODS: An electrical monitoring device was used to measure tissue capacitance at a frequency of 1 MHz on 34 ex vivo kidney specimens freshly obtained after surgical excision. Tissue capacitance was promptly measured in the excised tumor as well as surrounding normal parenchyma and fat. Dielectric permittivity in each tissue was calculated using the measured capacitance data. These data were compared and correlated to pathological findings. RESULTS: The final pathology on the 34 specimens revealed 28 renal cell carcinomas (RCC), 3 oncocytomas and 3 angiomyolipomas. In patients with RCC dielectric permittivity of tumor tissue was 1.43 +/- 0.39 times greater than that of surrounding normal parenchyma (p < 0.001). The average tumor-to-normal tissue dielectric permittivity ratio for RCC was significantly greater than that for angiomyolipoma (1.43 +/- 0.39 vs 0.73 +/- 0.77, p < 0.05) but similar to that for oncocytoma (1.43 +/- 0.39 vs 1.63 +/- 0.77, p = 0.39). CONCLUSIONS: Tissue capacitance measurements may be used to differentiate renal tumor from surrounding normal tissue. In vivo studies will ultimately determine the clinical use of this technology in localizing renal neoplasms and differentiating between malignant and benign tissues.

Adenoma, Oxyphilic↗
PubMed1975

Aldosterone-induced moulting in amphibian skin and its effect on electrical capacitance.

The resistance and capacitance of the isolated amphibian skin have been determined from measurements of the response of the voltage across the skin to small steps to current. Previous work indicates that the electrical impedance of frog skin, when the skin is bathed with Ringer's solution on both sides, is largely determined by the properties of the functional outward-facing membrane of the skin, the outer membrane of the stratum granulosum (P.G. Smith, 1971, Acta Physiol. Scand. 81:355). This membrane can be represented by a resistance and capacitance in parallel. Aldosterone, which induces conversion of the s. granulosum into a cornified cell layer and transformation of the cell layer below into a new s. granulosum, also causes a transient rise in resistance and a short-lived decrease in capacitance to about one-half its initial value. It is suggested that these electrical changes are caused by the transitory presence of two functional outward-facing membranes in series. The method of determining resistance and capacitance from the voltage response is discussed in the Appendix.

Aldosterone↗
PubMed1990

Epidermal hydration and skin mechanics. The relationship between electrical capacitance and the mechanical properties of human skin in vivo.

The possible relationship between skin capacitance and the mechanical properties of the skin was studied using non-invasive techniques. Skin hydration was changed by soaking skin with tap water. Hydration of the skin increased the capacitance significantly (p less than 0.01) and hysteresis (creeping phenomenon) (p less than 0.01). The elasticity of the skin was reduced by hydration (p less than 0.01). Capacitance was found to be a poor predictor of the mechanical properties of untreated skin; while increases in hysteresis (creeping phenomenon) and decreases in elasticity were significantly (p less than 0.0001) related to changes in the capacitance of hydrated skin.

Adult↗
PubMed1991

Cyclic AMP increases electrical capacitance of apical membrane of toad urinary bladder.

We have measured the effects of oxytocin and three other compounds (chlorophenyl-thio-cyclic AMP, forskolin and theophylline) that increase cytoplasmic cyclic AMP on the impedance of the toad urinary bladder. Membrane capacitance was calculated from transepithelial impedance measured by a computerized sine wave method. All four agents increased tissue capacitance. Since in these tissues this parameter is proportional to apical membrane area our results suggest that cAMP can be a second messenger involved in the action of agents that promote fusion of exocytotic vesicles with the apical membrane.

Animals↗
PubMed1969

The electrical capacitance of phospholipid membranes.

As one of the methods of finding out the structural change of lipid bilayers due to change of environmental solution, the capacitances of phosphatidyl choline (egg lecithin) and phosphatidyl serine (bovine brain) bilayer membranes in solutions of various pH and salt contents were measured. It was found that the capacitance of the bilayer depended upon pH and salt content. The capacitance had a minimum value around pH 4 for phosphatidyl choline and around pH 3-4 for phosphatidyl serine bilayers, respectively. The value of the capacitance increased as the pH of the solution became lower or higher. As the concentration of cholesterol in the phosphatidyl choline bilayer increased, the capacitance increased and reached a saturation value. A DC voltage across the phosphatidyl choline bilayer did not affect the value of the capacitance practically.

Animals↗
PubMed1988

Hydration of human stratum corneum studied in vivo by optothermal infrared spectrometry, electrical capacitance measurement, and evaporimetry.

Optothermal infrared spectrometry (OTIS) is a recently introduced method for specific measurement, in vivo, of water in the skin. In the present study the method proved well suited to register the increase in water content in stratum corneum following application of emollients. The results were compared with those obtained with a commercial instrument, the Corneometer, and the two methods were found to match very closely. Neither method indicated any difference in hydration of normal skin between young and elderly women. Evaporimetry was used to detect any influence on the water barrier function of the skin following application of emollients; even though the water content of the skin was significantly higher after emollient treatment, the transepidermal water loss remained unchanged.

Adolescent↗