Thermal Effects on Chemical Diffusion in Multicomponent Ionic Systems

A theoretical formulation for diffusion of multiple ions is presented in this paper which considers the effects of electrochemical and thermal diffusion potentials. The work presented is of relevance to applications such as the geological disposal of high level radioactive waste, where limited experimental information is available on ionic transfer in compacted clay buffer under non-isothermal conditions. The proposed approach incorporates the overall charge conservation in the formulation of multicomponent chemical diffusion. Thermal diffusion, i.e. Soret effect is studied in more detail by considering an explicit approach to include this process in the formulation. A detailed description of the theoretical developments is provided. A series of simulations using the proposed formulation is presented which involves pure diffusion of multiple ions under thermal gradients. The results are compared with experimental data reported in literature

Thermal effects on chemical diffusion in multicomponent ionic systems

A theoretical formulation for diffusion of multiple ions is presented in this paper which considers the effects of electrochemical and thermal diffusion potentials. The work presented is of relevance to applications such as the geological disposal of high level radioactive waste, where limited experimental information is available on ionic transfer in compacted clay buffer under non-isothermal conditions. The proposed approach incorporates the overall charge conservation in the formulation of multicomponent chemical diffusion. Thermal diffusion, i.e. Soret effect is studied in more detail by considering an explicit approach to include this process in the formulation. A detailed description of the theoretical developments is provided. A series of simulations using the proposed formulation is presented which involves pure diffusion of multiple ions under thermal gradients. The results are compared with experimental data reported in literature

From microscopic compartmentalization to hydrodynamic patterns: New pathways for information transport

Can we exploit hydrodynamic instabilities to trigger an efficient, selective and spontaneous flow of encapsulated chemical information? One possible answer to this question is presented in this paper where cross-diffusion, which commonly characterizes compartmentalized dispersed systems, is shown to initiate buoyancy-driven hydrodynamic instabilities. A general theoretical framework allows us to predict and classify cross-diffusion-induced convection in two-layer stratifications under the action of the gravitational field. The related nonlinear dynamics is described by a cross-diffusion-convection (CDC) model where fickian diffusion is coupled to the Stokes equations. We identify two types of hydrodynamic modes (the negative cross-diffusion-driven convection, NCC, and the positive cross-diffusion-driven convection, PCC) corresponding to the sign of the cross-diffusion term dominating the system dynamics. We finally show how AOT water-in-oil reverse microemulsions are an ideal model system to confirm the general theory and to approach experimentally cross-diffusion-induced hydrodynamic scenarios

Temperature response in electrosensors and thermal voltages in electrolytes

Temperature sensation is increasingly well understood in several model organisms. One of the most sensitive organs to temperature changes is the functional electrosensor of sharks and their relatives; its extreme thermal responsiveness, in excised preparations, has not been mechanistically described. In recent years, conflicting reports have appeared concerning the properties of a hydrogel that fills the ampullae of Lorenzini. The appearance of a thermoelectric effect in the gel (or, using different methods, a reported lack thereof) suggested a link between the exquisite electrosense and the thermal response of the electroreceptors (or, alternately, denied that link). I review available electrophysiology evidence of the organ’s temperature response, calculate a theoretical gel signal prediction using physical chemistry, analyze the strengths and weaknesses of the existing gel measurements, and discuss broader implications for the ampullae and temperature sensation