Impurity Diffusion in a Chemical Potential Gradient (II): Iron Tracer Diffusion in Cobalt Oxide in an Oxygen Potential Gradient

1987 ◽  
Vol 91 (8) ◽  
pp. 779-785 ◽  
Author(s):  
M. Martin ◽  
S. Dorris
Keyword(s):  
Cobalt Oxide ◽  
Oxygen Potential ◽  
Chemical Potential ◽  
Potential Gradient ◽  
Tracer Diffusion ◽  
Impurity Diffusion ◽  
Chemical Potential Gradient

Thermodynamic Diffusion Coefficients

2008 ◽  
Vol 279 ◽  
pp. 39-52 ◽  
Author(s):  
G.B. Kale
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Driving Force ◽  
Chemical Potential ◽  
Potential Gradient ◽  
Ternary Systems ◽  
Tracer Diffusion ◽  
Chemical Potential Gradient ◽  
Concentration Difference ◽  
Phenomenological Coefficients

A new form of diffusion coefficient termed as thermodynamic diffusion coefficient is introduced in this paper. Conventionally, diffusion coefficients are evaluated using concentration gradient as driving force. But truly, chemical potential gradient is the actual driving force that determines the material flow in any part of the system. Thermodynamic diffusion coefficients are based on chemical potential gradient as driving force. The relation between thermodynamic diffusion coefficients and phenomenological coefficients has been established. The advantages of thermodynamic diffusion coefficients have been underlined, especially, in the cases of line compounds where concentration difference across the phase is zero or in case of intermetallic compounds with narrow homogeneity range. The intrinsic thermodynamic diffusion coefficients are equal to tracer diffusion coefficients. This helps in estimating tracer diffusivities in cases where tracers are not easily available. The advantages of thermodynamic diffusion coefficients are shown in binary and ternary systems by illustrating them in Ni-Al and Fe-Ni-Cr systems.

Active sodium transport in toad bladder despite removal of serosal potassium

1965 ◽  
Vol 208 (2) ◽  
pp. 401-406 ◽  
Author(s):  
Alvin Essig
Keyword(s):  
Sodium Transport ◽  
Chemical Potential ◽  
Potential Gradient ◽  
Ringer Solution ◽  
Active Sodium ◽  
Chemical Potential Gradient ◽  
Control Value ◽  
Active Sodium Transport ◽  
Solution Bathing ◽  
Determining Factor

Previous studies have demonstrated that removal of potassium from sodium-Ringer solution bathing the serosal surface of the toad badder depressed net sodium transport to some 5% of control value, whereas with choline-Ringer solution as serosal medium removal of serosal potassium depressed net sodium transport only to some 55% of control value. Although transport is down a chemical potential gradient in the latter situation, it appears to be an active process, for it is depressed by anaerobiosis, and persists against an electrochemical potential gradient. The data suggest that the concentration of potassium at the serosal aspect of the sodium pump is not in itself the rate-determining factor for active sodium transport following removal of serosal potassium.

scholarly journals Reverse cholesterol transport in the isolated perfused rat spleen

1990 ◽  
Vol 268 (2) ◽  
pp. 499-505 ◽  
Author(s):  
M A Mindham ◽  
P A Mayes ◽  
N E Miller
Keyword(s):  
Whole Blood ◽  
Chemical Potential ◽  
Specific Radioactivity ◽  
Density Lipoprotein ◽  
Potential Gradient ◽  
Cholesterol Transport ◽  
Unesterified Cholesterol ◽  
Chemical Potential Gradient ◽  
High Specific Radioactivity

1. A method has been developed which enables the rat spleen to be loaded in vivo with [3H]cholesterol to a high specific radioactivity using cholesterol-labelled erythrocytes. The erythrocytes were shown to be rapidly degraded by the spleen and not released intact during subsequent perfusion. 2. When labelled spleens were perfused with whole blood or serum, lipoproteins in the high-density lipoprotein (HDL) range were shown to be the principal lipoprotein vehicles for the removal of cholesterol, the specific radioactivity of cholesterol being much greater in the HDL fractions than in other lipoproteins, particularly in the d 1.175-1.210 fraction. 3. The formation of [3H]cholesteryl ester was restricted to the major HDL fractions. 4. Experiments utilizing individual HDL fractions added to a basal perfusate indicated that HDL1 (d 1.050-1.085) was of less importance in the removal of cholesterol from the spleen than HDL subfractions of higher density. Also, a decrease in density of the lipoproteins was observed during perfusion, concurrent with uptake of cholesterol, especially in the d 1.085-1.125 subfraction. 5. When [3H]cholesterol-labelled spleens were perfused with whole blood, about half of the radioactivity released was detected in erythrocytes, indicating a rapid exchange or transport of cholesterol. Thus erythrocytes could play an important role in the transfer of unesterified cholesterol when the chemical potential gradient is favourable.

scholarly journals Particle motion driven by solute gradients with application to autonomous motion: continuum and colloidal perspectives

2010 ◽  
Vol 667 ◽  
pp. 216-259 ◽  
Author(s):  
JOHN F. BRADY
Keyword(s):  
Chemical Potential ◽  
Particle Surface ◽  
Fluid Motion ◽  
Potential Gradient ◽  
Coarse Grained ◽  
Gradient Force ◽  
Total Force ◽  
Chemical Potential Gradient ◽  
Back Flow ◽  
Autonomous Motion

Diffusiophoresis, the motion of a particle in response to an externally imposed concentration gradient of a solute species, is analysed from both the traditional coarse-grained macroscopic (i.e. continuum) perspective and from a fine-grained micromechanical level in which the particle and the solute are treated on the same footing as Brownian particles dispersed in a solvent. It is shown that although the two approaches agree when the solute is much smaller in size than the phoretic particle and is present at very dilute concentrations, the micromechanical colloidal perspective relaxes these restrictions and applies to any size ratio and any concentration of solute. The different descriptions also provide different mechanical analyses of phoretic motion. At the continuum level the macroscopic hydrodynamic stress and interactive force with the solute sum to give zero total force, a condition for phoretic motion. At the colloidal level, the particle's motion is shown to have two contributions: (i) a ‘back-flow’ contribution composed of the motion of the particle due to the solute chemical potential gradient force acting on it and a compensating fluid motion driven by the long-range hydrodynamic velocity disturbance caused by the chemical potential gradient force acting on all the solute particles and (ii) an indirect contribution arising from the mutual interparticle and Brownian forces on the solute and phoretic particle, that contribution being non-zero because the distribution of solute about the phoretic particle is driven out of equilibrium by the chemical potential gradient of the solute. At the colloidal level the forces acting on the phoretic particle – both the statistical or ‘thermodynamic’ chemical potential gradient and Brownian forces and the interparticle force – are balanced by the Stokes drag of the solvent to give the net phoretic velocity.For a particle undergoing self-phoresis or autonomous motion, as can result from chemical reactions occurring asymmetrically on a particle surface, e.g. catalytic nanomotors, there is no imposed chemical potential gradient and the back-flow contribution is absent. Only the indirect Brownian and interparticle forces contribution is responsible for the motion. The velocity of the particle resulting from this contribution can be written in terms of a mobility times the integral of the local ‘solute pressure’ – the solute concentration times the thermal energy – over the surface of contact between the particle and the solute. This was the approach taken by Córdova-Figueroa & Brady (Phys. Rev. Lett., vol. 100, 2008, 158303) in their analysis of self-propulsion. It is shown that full hydrodynamic interactions can be incorporated into their analysis by a simple scale factor.

Transport of adsorbates in microporous solids: arbitrary isotherm

1994 ◽  
Vol 446 (1926) ◽  
pp. 15-37 ◽  
Keyword(s):  
Driving Force ◽  
Chemical Potential ◽  
Transport Model ◽  
Potential Gradient ◽  
Isosteric Heat ◽  
Chemical Potential Gradient ◽  
Equilibrium Data ◽  
Random Walk Theory ◽  
Microporous Solids ◽  
Good Agreement

The transport of adsorbates in microporous random networks is examined in the presence of an arbitrary nonlinear local isotherm. The transport model is developed by means of a correlated random walk theory, assuming pore mouth equilibrium at an intersection in the network and a local chemical potential gradient driving force. The results demonstrate more rapid increase of the transport coefficient with adsorbed concentration than straightforward use of the classical Darken equation. Application of the theory to experimental data for diffusion of carbon dioxide in carbolac, with various local isotherm choices, shows good agreement when the activation energy associated with the mobility based on a chemical potential gradient driving force is taken as the Henry’s law region isosteric heat of adsorption. Furthermore, a combination of transport and equilibrium data can discriminate better among competing isotherms than the latter data alone.

Transfer of Ions against their Chemical Potential Gradient through Oil Membranes

Nature ◽  
1969 ◽  
Vol 222 (5192) ◽  
pp. 476-477 ◽  
Author(s):  
J. H. MOORE ◽  
R. S. SCHECHTER
Keyword(s):  
Chemical Potential ◽  
Potential Gradient ◽  
Chemical Potential Gradient

scholarly journals Thermodynamic Interpretation on the Rheology of Aqueous Bentonite Suspensions

2020 ◽  
Vol 71 (6) ◽  
pp. 51-58
Author(s):  
Ihsan Bozdogan ◽  
Muserref Onal ◽  
Abdullah Devrim Pekdemir ◽  
Yuksel Sarikaya
Keyword(s):  
Rheological Properties ◽  
Chemical Potential ◽  
Potential Gradient ◽  
Chemical Potential Gradient ◽  
Bingham Plastic ◽  
Aqueous Suspensions ◽  
Soda Content ◽  
Calcium Bentonite ◽  
Plastic Change ◽  
Thermodynamic Interpretation

Since their exceptional rheological behavior, bentonite suspensions are widely used in engineering, industrial, agricultural, and drilling applications. So, the aim of the present study is to investigate the rheological properties of three types aqueous suspensions prepared with calcium bentonite (CaB), sodium bentonite (NaB) obtained from that by Na2CO3 activation, and NaB with the excess soda. The CaB taken from Giresun/Turkey region contains calcium smectite (CaxS) as clay mineral and opal CT (SiO2.nH2O) as impurity which is paracrystalline silica. Soda content by the activation and bentonite content in the suspension were changed in the interval of 2.5-15.0% and 5-20% by mass, respectively. CaxS completely converted to sodium smectite (Na2xS) by the activation with the soda content of 2.5% and then Na2xS+Na2CO3 mixtures formed. Rheological properties of these aqueous suspensions were measured using a Fann Viscometer. These properties reached their maxima by the most thixotropic Na2xS suspensions and greatly increased with the increasing of smectite content. Rheological plots drawn of the shear rate vs. shear stress in the interval of 170-1020 s-1 showed that the suspensions flow as a Bingham Plastic. Change in rheological properties depending on the smectite type and content as well as excess soda content was explained thermodynamically based on the chemical potential gradient between interlayer and dispenser waters.

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