Explaining trans-phase potential differences with membrane theory, association-induction hypothesis and murburn concept

The characteristics of the experimentally measured trans-membrane potential (TMP) generated across an artificial membrane intervening two KCl solutions were found to be explicable using simple principles of electrochemistry, as given within the context of Association Induction Hypothesis (AIH). AIH suggests that the heterogeneous ion distribution which is caused by the adsorption of a mobile ion onto an immobile phase (bearing charge opposite to that of the mobile ion) is responsible for the TMP generation. Therefore, this work proposes AIH could be an important foundation for explaining the origin of TMP. Our experimental observation of nonzero TMP across an electrically charged non-biological/synthetic membrane is found to be intriguing, as such outcomes are classically associated to ion-pumping activities of membrane proteins in a living matter. Another experimental observation of nonzero potential across a neutral membrane is even more intriguing. Such a potential behavior is more in harmony with murburn concept, a new proposal for explaining redox metabolic and physiological phenomena.

Solutal Convection in Layered Sorbing Porous Media

<p>We study convective instability in the vertically layered porous media saturated with mixture. The mixture consists of a carrier fluid and solid nanoparticles. The nanoparticles are considered as solute within the continuous approach. The porous media are two horizontal sublayers with different permeabilities. The solute concentration is maximal near the upper boundary and is zero near the lower boundary of the superposed sublayers. Thus, one has suitable conditions for the onset of solutal convection in the gravitational field.</p><p>The porous sublayers are reactive media, which can absorb nanoparticles. The mixture transport here is accompanied by immobilization. It is described by the mobile/immobile media model. The mobile phase is carried by fluid flow, while the immobile phase is absorbed by porous matrix. The linear kinetic equation for the mixture redistribution between the phases is applied. The Boussinesq approximation is used in the equations for convection in each of the sublayers. Numerical simulation is performed by the shooting method.</p><p>We apply a linear stability theory to find the threshold Rayleigh-Darcy number for the onset of solutal convection. This similarity criterion is determined through the average permeability and porosity of uncontaminated porous sublayers. For the first time, we introduce a solutal pore shrinkage coefficient, which is analogous to the thermal expansion coefficient for thermal natural convection. This coefficient shows that porosity decreases as the concentration of immobile phase grows in the presence of sorption. Particles in this case join the surface of pores and shrink the void space.</p><p>Firstly, we find the permeability ratios for bimodal marginal stability curves in the uncontaminated sublayers. Here, the sublayer permeabilities differ by approximately 100 times. The bimodal curves demonstrate the competition between two convective instabilities. One of them is for the local convective rolls that generate within the more permeable layer and the other is for the large-scale rolls penetrating both layers. The rolls are similar to thermal natural convection in the multi-layered porous media studied by McKibbin and O'Sullivan (1980). For sorbing porous media, the type of convective rolls strongly depends on the solutal pore shrinkage coefficient. Even a small change in its value can produce a large variation of flow streamlines from the convective rolls localized within the upper highly permeable sublayer to the rolls covering both the upper and lower sublayers. The observed sorption effect on the transition from local to large-scale convection is due to the fact that the permeability ratio depends on the solutal pore shrinkage coefficient. It is also found that sorption effect delays the onset of solutal convection.</p><p>The work was supported by the Russian Science Foundation (Grant No. 20-11-20125).</p>

Application of Phase Change Tracking Approach in Predicting Condensate Blockage in Tight, Low, and High Permeability Reservoirs

Prediction of the timing and location of condensate build-up around the wellbore in gas condensate reservoirs is essential for the selection of appropriate methods for condensate recovery from these challenging reservoirs. The present work focuses on the use of a novel phase change tracking approach in monitoring the formation of condensate blockage in a gas condensate reservoir. The procedure entails the simulation of tight, low and high permeability reservoirs using global and local grid analysis in determining the size and timing of three common regions (Region 1, near wellbore; Region 2, condensate build-up; and Region 3, single-phase gas) associated with single and two-phase gas and immobile and mobile gas condensate. The results show that permeability has a significant influence on the occurrence of the three regions around the well, which in turn affects the productivity of the gas condensate reservoir studied. Predictions of the timing and location of condensate in reservoirs with different permeability levels of 1 mD to 100 mD indicate that local damage enhances condensate formation by 60% and shortens the duration of the immobile phase by 45%. Meanwhile, the global change in permeability increases condensate formation by 80% and reduces the presence of the immobile phase by 60%. Finally, this predictive approach can help in mitigating condensate blockage around the wellbore during production.

Association-dissociation equations, distinct from Michaelis-Menten equation for the quantification of the net flux of reactants with or without immobiliser.

The formation of enzyme-substrate complex, often in connection with the adsorption of the enzyme leading to either partial immobilisation in which the enzymes are adsorbed on a colloid or total immobilisation in which the enzyme is adsorbed on a rigid immobile phase is the concern of some researchers. The interest in immobilised substrate common in biological system is not very common. The objectives of this theoretical research are the rederivation of the equations of association and dissociation of reactants in the presence of adsorbents, insoluble larger macro-or supra-molecule and elucidation of why such equations are important and generalisable. The derivations produced two different equations that describe mathematically the net flux of either the substrate where the enzyme is adsorbed or the net flux of the enzyme where the substrate is adsorbed. The derivation also produced equations of translational velocities, given the probabilities that reactions occur following complex formation or that an escape of bullet molecules or dissociation reactions occur. In conclusion two different equations need separate derivation for association and dissociation of reactants. The needs for the flux of reactants have both biological and industrial relevance, respectively due to importance of time-dependent digestive processes and for the optimisation of the production of desired products of enzymatic action. The equations describing net flux seem generalisable in that information about the physicochemical properties of both crowding agent and immobilisers may not be needed for calculations.

The effects of globotriaosylceramide tail saturation level on bilayer phases

The globotriaosylceramide acyl chains from one leaflet interdigitate into the opposing leaflet and lead to significant bilayer rigidification and immobilisation of the lipid tails. Globotriaosylceramide with saturated acyl chains can form a highly ordered, relatively immobile phase which is resistant to bending.

Impact of flow velocity on biochemical processes – a laboratory experiment

Understanding and predicting hydraulic and chemical properties of natural environments are current crucial challenges. It requires considering hydraulic, chemical and biological processes and evaluating how hydrodynamic properties impact on biochemical reactions. In this context, an original laboratory experiment to study the impact of flow velocity on biochemical reactions along a one-dimensional flow streamline has been developed. Based on the example of nitrate reduction, nitrate-rich water passes through plastic tubes at several flow velocities (from 6.2 to 35 mm min−1), while nitrate concentration at the tube outlet is monitored for more than 500 h. This experimental setup allows assessing the biologically controlled reaction between a mobile electron acceptor (nitrate) and an electron donor (carbon) coming from an immobile phase (tube) that produces carbon during its degradation by microorganisms. It results in observing a dynamic of the nitrate transformation associated with biofilm development which is flow-velocity dependent. It is proposed that the main behaviors of the reaction rates are related to phases of biofilm development through a simple analytical model including assimilation. Experiment results and their interpretation demonstrate a significant impact of flow velocity on reaction performance and stability and highlight the relevance of dynamic experiments over static experiments for understanding biogeochemical processes.

Modeling of flow and mass transport in granular porous media

The scope of this work is to estimate the effective mass-transfer coefficient in a two-phase system of oil and water fluid droplets, both being in a porous medium. To this end, a tracer is advected from the flowing aqueous phase to the immobile non-aqueous one. Partitioning at the fluid-fluid interface and surface diffusion are also taken into account. By using spatial/volume-averaging techniques, the appropriately simplified boundary-value problems are described and numerically solved for the flow velocity field and for the transport problem. The problem was found to be controlled by the Peclet number of the flowing phase, the dimensionless parameter Λ, containing both diffusion and partition in the two phases, as well as the geometrical properties of the porous structure. It is also verified that the usually involved unit cell-configurations underestimate the mass transport to the immobile phase.