Characterization of electrical charge separation at the interface of two aqueous solutions in the presence of concentration gradients and cation/anion mobility ratio asymmetry

Open Physics ◽  
2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Adrian Cernescu ◽  
Tudor Luchian
Keyword(s):  
Diffusion Processes ◽  
Ionic Mobility ◽  
Electrical Charge ◽  
Diffusion Potential ◽  
Mobility Ratio ◽  
Ionic Diffusion ◽  
Measuring Instruments ◽  
Concentration Gradients ◽  
Diffusion Constants ◽  
Physical Consequences

AbstractPhysical consequences of ionic diffusion processes play a major role on the outcome of electrophysiology experiments due to both their contribution to the ionic transmembrane transport and phenomena taking place at the measuring instruments interface. As most of the time heterogenities in biological media with respect to ionic diffusion constants are disregarded, we intended to look upon the general case of ionic diffusion at the interface of two liquids on which gradients of these diffusion constants no longer can be neglected. We developed a theoretical model for the diffusion potential which emerges at an aqueous interface under gradients of concentration and diffusion constants. The experimental validation of our model was achieved through potential difference measurements of the diffusion potential between two solutions containing sodium chloride (NaCl) and glycerine solutions of various concentrations. Within the studied domain of the electrical charge mobility ratio, we noticed that experimental results are in agreement with the theoretically inferred diffusion potential values. This demonstrates that the resulting relationship for the diffusion potential inferred from our model could be applied for other cases, as well. When the ionic solutions contains an indefinite quantity of glycerine or an unknown substance able to modify diffusion constants of sodium and chloride, it was shown that through measurements of the diffusion potential one can infer the unknown concentration of glycerine and the modified ionic mobility ratio. This, in turn, builds up the foundation for a novel yet simple and efficient analitycal sensing device for quantitative determination in the field.

Influence of the Manufacturing Process on the Local Properties of Bronze-Bonded Grinding Tools

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Abdelhamid Bouabid ◽  
Berend Denkena ◽  
Bernd Breidenstein ◽  
Alexander Krödel
Keyword(s):  
Manufacturing Process ◽  
Diffusion Processes ◽  
Initial Mixture ◽  
Mechanical And Thermal Properties ◽  
Concentration Gradients ◽  
Workpiece Material ◽  
Bond Interface ◽  
Local Properties ◽  
Grinding Tool ◽  
Process Behavior

Abstract The process behavior of a grinding tool is defined by the sum of interactions between the active abrasive grains and the workpiece. These interactions depend on the workpiece material, the manipulated parameters of the grinding process, and the tool properties. The tool properties are defined within the tool manufacturing process. In this context, the effects of the abrasive, the bond, and the sinter process on the global properties such as hardness, porosity, and fracture strength of the grinding layer are content of several research works. In contrast to this, the effects on the local properties, which define the grain/bond interface and therefore the process behavior at microscopic scale, have not yet been identified. This paper deals with identifying the influence of the sintering process on the local properties of the grinding layer. This is achieved by investigating the densification as well as the bond microstructure depending on the sintering parameters and on the specification of the initial mixture. As a use case, the bronze bond is considered. The results show that the input parameters have a significant impact on the homogeneity of the grinding layer. Due to the diffusion processes during sintering, there are densification gradients as well as tin concentration gradients in the grinding layer. The local tin concentration gradients imply different local mechanical and thermal properties. For this reason, each abrasive grain has unique interface properties.

A network approach to analysis of nonsteady-state facilitated ionic diffusion processes

1997 ◽  
Vol 136 (1-2) ◽  
pp. 101-109 ◽  
Author(s):  
J. Castilla ◽  
M.T. García-Hernández ◽  
A. Hayas ◽  
J. Horno
Keyword(s):  
Diffusion Processes ◽  
Ionic Diffusion ◽  
Network Approach ◽  
Nonsteady State

scholarly journals Ionic Diffusion Processes in Polypyrrole

1994 ◽  
Vol 5 (3) ◽  
pp. 191-196 ◽  
Author(s):  
T. Matencio ◽  
M.-A. De Paoli ◽  
R.C.D. Peres ◽  
R. Torresi ◽  
S.I. Cordoba de Torresi
Keyword(s):  
Diffusion Processes ◽  
Ionic Diffusion

On the nature of the diffusion potential

1979 ◽  
Vol 57 (5) ◽  
pp. 717-721 ◽  
Author(s):  
J. S. Kirkaldy
Keyword(s):  
Steady State ◽  
Diffusion Processes ◽  
Potential Gradient ◽  
Diffusion Potential ◽  
Irreversible Processes ◽  
Minimum Entropy ◽  
Zero Current ◽  
State Diffusion ◽  
Dipole State ◽  
Improper Use

The 'diffusion' potential concept is examined critically within the conditions imposed by Maxwell's equations and the Thermodynamics of Irreversible Processes. It is demonstrated that under the zero current condition during non-steady state diffusion the self-field associated with the diffusion potential gradient is due entirely to a diffusion-induced distribution of dipoles. The general failure to recognize that the charge associated with the field is due to dipoles has led to an improper use of Poisson's equation and to certain oft-remarked-upon paradoxes. The dipoles appear in systems where counter-current ion mobilities differ greatly. In seeking electroneutrality the ion trajectories become 'curved' in such a way as to generate an instantaneous dipole current and field. The magnitudes have nothing to do with the dielectric properties of the medium.It is demonstrated that the zero current condition represents a quasi-steady state of minimum entropy production. Such a state of stability can be sustained provided the process of relaxation of the field to the pure dipole state by real charge neutralization is fast compared with the relaxation process for the chemical potentials of the neutral salts in solution. The energetics of ionic solutions are usually such as to abet the neutrality condition during diffusion processes.

scholarly journals Superstatistical modelling of protein diffusion dynamics in bacteria

2021 ◽  
Vol 18 (176) ◽  
Author(s):  
Yuichi Itto ◽  
Christian Beck
Keyword(s):  
Anomalous Diffusion ◽  
Recent Experiment ◽  
Diffusion Processes ◽  
Diffusion Constant ◽  
Protein Diffusion ◽  
Gaussian Form ◽  
Diffusion Constants ◽  
Diffusion Dynamics ◽  
Associated Proteins ◽  
Good Agreement

A recent experiment (Sadoon AA, Wang Y. 2018 Phys. Rev. E 98 , 042411. ( doi:10.1103/PhysRevE.98.042411 )) has revealed that nucleoid-associated proteins (i.e. DNA-binding proteins) exhibit highly heterogeneous diffusion processes in bacteria where not only the diffusion constant but also the anomalous diffusion exponent fluctuates for the various proteins. The distribution of displacements of such proteins is observed to take a q -Gaussian form, which decays as a power law. Here, a statistical model is developed for the diffusive motion of the proteins within the bacterium, based on a superstatistics with two variables. This model hierarchically takes into account the joint fluctuations of both the anomalous diffusion exponents and the diffusion constants. A fractional Brownian motion is discussed as a possible local model. Good agreement with the experimental data is obtained.

scholarly journals Isothermal Dendritic Growth - A Low Gravity Experiment

1986 ◽  
Vol 87 ◽  
Author(s):  
M. E. Glicksman ◽  
E. Winsa ◽  
R. C. Hahn ◽  
T. A. Lograsso ◽  
E. R. Rubinstein ◽  
...  
Keyword(s):  
Dendritic Growth ◽  
Diffusion Processes ◽  
Free Fall ◽  
Current Approach ◽  
Low Earth Orbit ◽  
Length Scale ◽  
Concentration Gradients ◽  
Volumetric Expansion ◽  
Volumetric Expansion Coefficient ◽  
Orbital Free

AbstractThe growth of dendrites in pure melts and alloys is controlled by diffusion-limited transport of heat and/or solute. The presence of temperature or concentration gradients within a molten phase subject to gravitational forces generally promotes convection, which in turn, modifies the diffusion processes. The vigor of melt convection is controlled by several parameters often expressed as a lumped dimensionless group, the Grashof number Gr = gβΔTℓ3/ν2, where g is the acceleration due to gravity; is the volumetric expansion coefficient; ΔT is the undercooling; ν is the kinematic viscosity; and ℓ is the relevant length scale, e.g., the characteristic diffusion distance. Dendritic growth, by its nature, does not permit independent manipulation of the controlling length scale, ℓ, which is determined by materials properties (e.g. diffusion coefficient or thermal diffusivity) and the undercooling or supersaturation. The reduction of g through orbital free fall is often the only practical way to lower Gr sufficiently to permit careful observation of the morphological and kinetic characteristics of isothermal dendritic growth. Previously conducted ground-based studies and the current approach to performing these studies in low earth orbit will be described.

Non-Fickian Ionic Diffusion Across High-Concentration Gradients

1995 ◽  
Vol 31 (9) ◽  
pp. 2213-2218 ◽  
Author(s):  
Anne E. Carey ◽  
Stephen W. Wheatcraft ◽  
Robert J. Glass ◽  
John P. O'Rourke
Keyword(s):  
Ionic Diffusion ◽  
High Concentration ◽  
Concentration Gradients
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