Generalized Theory of Steady-State Voltammetry without a Supporting Electrolyte. Effect of Product and Substrate Diffusion Coefficient Diversity

2002 ◽  
Vol 74 (18) ◽  
pp. 4805-4813 ◽  
Author(s):  
Wojciech Hyk ◽  
Zbigniew Stojek
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Supporting Electrolyte ◽  
Substrate Diffusion

Temperature dependence of oxygen diffusion and consumption in mammalian striated muscle

1993 ◽  
Vol 264 (6) ◽  
pp. H1825-H1830 ◽  
Author(s):  
T. B. Bentley ◽  
H. Meng ◽  
R. N. Pittman
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Oxygen Diffusion ◽  
Striated Muscle ◽  
Effect Of Temperature ◽  
Retractor Muscle ◽  
Oxygen Solubility ◽  
Order Of Magnitude

This study investigated the effect of temperature on the oxygen diffusion coefficient (DO2) of hamster retractor muscle from 11 to 37 degrees C. DO2 was measured using a non-steady-state technique, whereas muscle O2 consumption (VO2) was estimated after steady state was reached. DO2 was 0.84 +/- 0.04 x 10(-5) cm2/s at 11 degrees C and rose exponentially to 2.41 +/- 0.19 x 10(-5) cm2/s at 37 degrees C, producing a temperature coefficient for DO2 of 4.60%/degrees C for this temperature range. To measure DO2 directly at 37 degrees C, it was necessary to inhibit tissue VO2 with Amytal. The DO2 measurements made at 37 degrees C were significantly higher than previously reported values, which had been based on extrapolations from lower temperatures (6). Further analysis suggests a possible transition in the diffusion pathway between 23 and 30 degrees C, resulting in a DO2 higher than that previously expected. This larger DO2, together with a recently published value of oxygen solubility (alpha) (21), results in an in vitro Krogh's diffusion coefficient (KO2) that is 2.4 times larger than that previously reported (24) and therefore significantly reduces an order of magnitude discrepancy between in vitro and estimated in vivo KO2 values (24). Muscle VO2 was 0.35 ml O2.min-1.100 g-1 at 11 degrees C and increased with temperature, resulting in an activation energy of the rate-limiting reaction from the Arrhenius equation of -10.5 kcal/mol between 11 and 30 degrees C.

Steady state solutions of a bi-stable quasi-linear equation with saturating flux

2011 ◽  
Vol 22 (4) ◽  
pp. 317-331 ◽  
Author(s):  
M. BURNS ◽  
M. GRINFELD
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Linear Equation ◽  
Stationary Solutions ◽  
Classical Solutions ◽  
Bifurcation Problem ◽  
Cahn Equation ◽  
Steady State Solutions

In this paper, we consider the bi-stable equation proposed by Rosenau to replace the Allen–Cahn equation in the case of large gradients. We discuss the bifurcation problem for stationary solutions of this equation on an interval as the diffusion coefficient and the length of the interval are varied, concentrating on classical solutions.

scholarly journals The Steady-State Transport of Oxygen through Hemoglobin Solutions

1966 ◽  
Vol 49 (4) ◽  
pp. 663-679 ◽  
Author(s):  
K. H. Keller ◽  
S. K. Friedlander
Keyword(s):  
Diffusion Coefficient ◽  
Brownian Motion ◽  
Steady State ◽  
Effective Diffusion ◽  
Close Correlation ◽  
Oxygen Electrode ◽  
Low Oxygen ◽  
Diffusion Rates ◽  
Oxygen Tensions ◽  
Diffusion Coefficient Of Oxygen

The steady-state transport of oxygen through hemoglobin solutions was studied to identify the mechanism of the diffusion augmentation observed at low oxygen tensions. A novel technique employing a platinum-silver oxygen electrode was developed to measure the effective diffusion coefficient of oxygen in steady-state transport. The measurements were made over a wider range of hemoglobin and oxygen concentrations than previously reported. Values of the Brownian motion diffusion coefficient of oxygen in hemoglobin solution were obtained as well as measurements of facilitated transport at low oxygen tensions. Transport rates up to ten times greater than ordinary diffusion rates were found. Predictions of oxygen flux were made assuming that the oxyhemoglobin transport coefficient was equal to the Brownian motion diffusivity which was measured in a separate set of experiments. The close correlation between prediction and experiment indicates that the diffusion of oxyhemoglobin is the mechanism by which steady-state oxygen transport is facilitated.

scholarly journals Combined bound water and water vapour diffusion of Norway spruce and European beech in and between the principal anatomical directions

Holzforschung ◽  
2011 ◽  
Vol 65 (6) ◽  
pp. 819-828 ◽  
Author(s):  
Walter Sonderegger ◽  
Manuele Vecellio ◽  
Pascal Zwicker ◽  
Peter Niemz
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Water Vapour ◽  
Diffusion Coefficients ◽  
Bound Water ◽  
European Beech ◽  
Unsteady State ◽  
Water Vapour Diffusion ◽  
Vapour Diffusion ◽  
Water Vapour Resistance

Abstract The combined bound water and water vapour diffusion of wood is of great interest in the field of building physics. Due to swelling stresses, the steady-state-determined diffusion coefficient clearly differs from the unsteady-state-determined diffusion coefficient. In this study, both diffusion coefficients and the water vapour resistance factor of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) were investigated for the principal anatomical directions (radial, tangential and longitudinal) and in 15° steps between these directions. The values were determined with the cup method as the basic principle. The unsteady-state-determined diffusion coefficient is, independent of the direction, about half that of the steady-state-determined diffusion coefficient. Both diffusion coefficients are about two to three times higher for spruce than for beech. They are up to 12 times higher in the longitudinal direction than perpendicular to the grain for spruce, and up to 15 times higher for beech. With increasing moisture content, the diffusion coefficients exponentially increase. The water vapour resistance factor shows converse values to the diffusion coefficients.

scholarly journals Diffusivity Measurements of Human Methemoglobin

1966 ◽  
Vol 49 (4) ◽  
pp. 681-687 ◽  
Author(s):  
K. H. Keller ◽  
S. K. Friedlander
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Experimental Measurements ◽  
Diffusion Cell ◽  
Millipore Filter ◽  
Diffusivity Measurements

Experimental measurements of the diffusion coefficient of human methemoglobin were made at 25°C with a modified Stokes diaphragm diffusion cell. A Millipore filter was used in place of the ordinary fritted disc to facilitate rapid achievement of steady state in the diaphragm. Methemoglobin concentrations varied from approximately 5 g/100 ml to 30 g/100 ml. The diffusion coefficient in this range decreased from 7.5 x 10-7 cm2/sec to 1.6 x 10-7 cm2/sec.

Steady-state voltammetry of strong and weak acids with and without supporting electrolyte

1992 ◽  
Vol 64 (20) ◽  
pp. 2372-2377 ◽  
Author(s):  
Malgorzata. Ciszkowska ◽  
Zbigniew. Stojek ◽  
Susan E. Morris ◽  
Janet G. Osteryoung
Keyword(s):  
Steady State ◽  
Supporting Electrolyte ◽  
Weak Acids
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