Diffusive Mass Transport Research Articles

Insights from the geological record of deformation along the subduction interface at depths of seismogenesis

AbstractSubduction interfaces are loci of interdependent seismic slip behavior, fluid flow, and mineral redistribution. Mineral redistribution leads to coupling between fluid flow and slip behavior through decreases in porosity/permeability and increases in cohesion during the interseismic period. We investigate this system from the perspective of ancient accretionary complexes with regional zones of mélange that record noncoaxial strain during underthrusting adjacent to the subduction interface. Deformation of weak mudstones is accompanied by low-grade metamorphic reactions, dissolution along scaly microfaults, and the removal of fluid-mobile chemical components, whereas stronger sandstone blocks preserve veins that contain chemical components depleted in mudstones. These observations support local diffusive mass transport from scaly fabrics to veins during interseismic viscous coupling. Underthrusting sediments record a crack porosity that fluctuates due to the interplay of cracking and precipitation. Permanent interseismic deformation involves pressure solution slip, strain hardening, and the development of new shears in undeformed material. In contrast, coseismic slip may be accommodated within observed narrow zones of cataclastic deformation at the top of many mélange terranes. A kinetic model implies interseismic changes in physical properties in less than hundreds of years, and a numerical model that couples an earthquake simulator with a fluid flow system depicts a subduction zone interface governed by feedbacks between fluid production, permeability, hydrofracturing, and aging via mineral precipitation. During an earthquake, interseismic permeability reduction is followed by coseismic rupture of low permeability seals and fluid pressure drop in the seismogenic zone. Updip of the seismogenic zone, there is a post-seismic wave of higher fluid pressure that propagates trenchward.

Diffusive Mass Transfer and Gaussian Pressure Transient Solutions for Porous Media

This study revisits the mathematical equations for diffusive mass transport in 1D, 2D and 3D space and highlights a widespread misconception about the meaning of the regular and cumulative probability of random-walk solutions for diffusive mass transport. Next, the regular probability solution for molecular diffusion is applied to pressure diffusion in porous media. The pressure drop (by fluid extraction) or increase (by fluid injection) due to the production system may start with a simple pressure step function. The pressure perturbation imposed by the step function (representing the engineering intervention) will instantaneously diffuse into the reservoir at a rate that is controlled by the hydraulic diffusivity. Traditionally, the advance of the pressure transient in porous media such as geological reservoirs is modeled by two distinct approaches: (1) scalar equations for well performance testing that do not attempt to solve for the spatial change or the position of the pressure transient without reference to a well rate; (2) advanced reservoir models based on numerical solution methods. The Gaussian pressure transient solution method presented in this study can compute the spatial pressure depletion in the reservoir at arbitrary times and is based on analytical expressions that give spatial resolution without gridding-meaning solutions that have infinite resolution. The Gaussian solution is efficient for quantifying the advance of the pressure transient and associated pressure depletion around single wells, multiple wells and hydraulic fractures. This work lays the basis for the development of advanced reservoir simulations based on the superposition of analytical pressure transient solutions.

Kinetic partitioning of major-minor cations between olivine and Hawaiian tholeiitic basalt under variable undercooling and cooling rate conditions

In order to elucidate the kinetic partitioning of cations between olivine and basalt, we performed undercooling (−ΔT) and cooling rate (CR) experiments at atmospheric pressure and QFM-2 buffer. Starting from the superliquidus temperature of 1250 °C, a Hawaiian tholeiitic basalt was cooled at the rates of 4 (CR4), 20 (CR20), and 60 (CR60) °C/h to the final target temperatures of 1175 °C (−ΔT = 35 °C; −ΔT35) and 1125 °C (−ΔT = 85 °C; −ΔT85). Results show that polyhedral olivine morphologies are obtained at -ΔT35, whereas strong disequilibrium skeletal and/or dendritic textures form at -ΔT85. The amount of forsterite in olivine decreases from to 85% to 78% with increasing both -ΔT and CR. A diffusive boundary layer also develops in the melt next to the olivine surface and its composition becomes progressively enriched in Ca, owing to its incompatible behavior with the lattice site. Residual melts are progressively depleted in silica and enriched in alkali from CR4 to CR60, but silica-rich melts are observed with increasing -ΔT. In terms of Fe2+-Mg exchange, olivines obtained at -ΔT35 are always in equilibrium with the diffusive boundary layer, comprising both the interface melt next to the olivine surface and the far-field melt where all chemical gradients cease. At -ΔT85, however, the Fe2+-Mg exchange indicates two distinct equilibration stages between olivine core and far-field melt, and between olivine rim and interface melt. Partition coefficients (Kd) of Mg, Fe, Mn, Ca, and Cr calculated at the olivine-melt interface preferentially change as a function of -ΔT rather than CR. From -ΔT35 to -ΔT85, KdMg, KdFe, KdMn, and KdCr remarkably increase, whereas the opposite applies to KdCa. Through the application of equilibrium partitioning models, we found that Mg, Fe, Mn, and Ca are incorporated into the olivine lattice site at near-equilibrium proportions. This generally good agreement with modeling data demonstrates that diffusive mass transport of cations in our experiments occurred under the conditions of local equilibrium at the olivine surface. In contrast, marked deviations from the expected equilibrium are found for KCr in response to the major influence of crystal field stabilization energy on cation incorporation.

Modelado de la isomerización de glucosa en un reactor de lecho empacado utilizando un nuevo enfoque del mecanismo de Briggs-Haldane

Nowadays, immobilized enzymes are utilized in several food industry applications. Some researches use apparent kinetic parameters in immobilized enzyme reactor systems, which are limited to such case studies. To enhance productivity in a packed bed reactor (PBR), a clear description of all the mechanisms (kinetic, intra-particle diffusive mass transport, fluid-particle convective mass transport, and axial dispersion) affecting the process should be established. The objective of this study was to model the isomerization of glucose in a PBR with calcium alginate beads (CAB), using an approach where the kinetic and diffusional mechanisms are described independently. The convective mass transfer (kL) and axial dispersion (Dz) coefficients were calculated from correlations. Validation was performed comparing predictions against experimental data (R2 = 0.907) of glucose conversion at the reactor’s outlet once steady state was reached. Under the study conditions, in contrast to the effect exerted by diffusive mass transport on fructose specific productivity, the effect of axial dispersion and convective mass transport is negligible. Analyzing different operation parameters via simulation, the particle size had the highest impact on the glucose bioconversion. By reducing the CAB size, the surface area is increased and thus the conversion. It is recommended to test new immobilizing agents or decreasing the CAB size, monitoring that immobilizing support preserves its stability and functionality.

Monte Carlo simulation of a lattice model for the dynamics of randomly branching double-folded ring polymers.

Supercoiled DNA, crumpled interphase chromosomes, and topologically constrained ring polymers often adopt treelike, double-folded, randomly branching configurations. Here we study an elastic lattice model for tightly double-folded ring polymers, which allows for the spontaneous creation and deletion of side branches coupled to a diffusive mass transport, which is local both in space and on the connectivity graph of the tree. We use Monte Carlo simulations to study systems falling into three different universality classes: ideal double-folded rings without excluded volume interactions, self-avoiding double-folded rings, and double-folded rings in the melt state. The observed static properties are in good agreement with exact results, simulations, and predictions of Flory theory for randomly branching polymers. For example, in the melt state rings adopt compact configurations and exhibit territorial behavior. In particular, we show that the emergent dynamics is in excellent agreement with a recent scaling theory and illustrate the qualitative differences with the familiar reptation dynamics of linear chains.

1D Finite Volume Scheme for Simulating Gas–Solid Reactions in Porous Spherical Particles with Application to Biomass Pyrolysis

Models for gas–solid reactions in porous particles typically consist of a set of mass and energy balances in the form of conservation equations. For spherical or close to spherical particles, these equations are formulated in 1D spherical coordinates. In the case where accumulation of gas inside the particle is significant, the balance equations contain convective terms. The present work presents a simple numerical scheme based on flux limited finite volume methods for discretizing conservation equations for convective and diffusive transport of mass and energy in radial direction in a porous sphere. The velocity is governed by Darcy’s law coupled to an equation of state. The proposed scheme is applied to a series of test problems that admit full or partial analytical solutions. For the cases where only partial analytical solutions are available, a Comsol model is adopted for comparison. It is found that the scheme is able to resolve step gradients without generating oscillations and that it properly handles changes in the sign of the convective velocity. Applying the scheme for solving a common model for biomass pyrolysis reveals the importance of convective gas transport in the pyrolysis of thermally thick biomass particles.

Unpicking the interplay of turbulence, diffusion, and thermophysics in cryogenic jets at supercritical pressures

Cryogenic supercritical fluids represent an intriguing category of fluids that combine mechanical and thermophysical properties of both ultralow temperature conditions and phenomena taking place well above the critical point. Recent research has demonstrated that it is a common misconception to consider the supercritical state as one homogeneous state. Instead, these fluids consist of two to four liquid and gas like phases, each with their own unique characteristics. In our work, we investigate numerically single-specie cryogenic fluid jets—initially at subcritical temperatures—which are injected into a supercritical environment (both the pressure and temperature exceed the thermodynamic critical state). For the investigation, a new solver, namely, “CoolFoam,” has been developed, which is designed for compressible non-isothermal two-fluid simulations where diffusive transport of heat and/or mass is accounted for. Real fluid thermodynamics are modeled using a polynomial fitting approach developed in our previous work. We introduce also a new phase characterization framework based on the association of phases with specific temperature ranges (rather than using a single line like the Widom line), which allowed us to better identify the similarity effects between the various conditions. We analyze the inter-dependence of the underlying phenomena: density gradient and diffusive mass transport [molecular and thermo(Soret)-diffusion] and turbulence. We also compared supercritical N2 with subcritical liquid and gas jets to highlight potential differences with respect to how these jets behave. We find that the jet dynamics are largely dictated by the thermodynamic transition of the injected fluid and the associated variation in thermophysical properties.

A novel organ-chip system emulates three-dimensional architecture of the human epithelia and the mechanical forces acting on it

Successful translation of in vivo experimental data to human patients is an unmet need and a bottleneck in the development of effective therapeutics. Organ-on-Chip technology aims to address this need by leveraging recent significant advancements in microfabrication and biomaterials, which enable modeling of organs and their functionality. These microengineered chips offer researchers the possibility to recreate critical elements of native tissue architecture such as in vivo relevant tissue-tissue interface, air-liquid interface, and mechanical forces, including mechanical stretch and fluidic shear stress, which are crucial to recapitulate tissue level functions. Here, we present the development of a new, comprehensive 3D cell-culture system, where we combined our proprietary Organ-Chip technology with the advantages offered by three-dimensional organotypic culture. Leveraging microfabrication techniques, we engineered a flexible chip that consists of a chamber containing an organotypic epithelium, surrounded by two vacuum channels that can be actuated to stretch the hydrogel throughout its thickness. Furthermore, the ceiling of this chamber is a removable lid with a built-in microchannel that can be perfused with liquid or air and removed as needed for direct access to the tissue. The bottom part of this chamber is made from a porous flexible membrane which allows diffusive mass transport to and from the microfluidic channel positioned below the membrane. This additional microfluidic channel can be coated with endothelial cells to emulate a blood vessel and recapitulate endothelial interactions. Our results show that the Open-Top Chip design successfully addresses common challenges associated with the Organs-on-Chip technology, including the capability to incorporate a tissue-specific extracellular matrix gel seeded with primary stromal cells, to reproduce the architectural complexity of tissues by micropatterning the gel, and to extract the gel for H&E staining. We also provide proof-of-concept data on the feasibility of using the system with primary human skin and alveolar epithelial cells.

Mass Transport in Nanoporous Gold and Correlation with Surface Pores for EC1 Mechanism: Case of Ascorbic Acid

AbstractThe present work correlates the mass transport of ascorbic acid (AA), which undergoes an electrochemical reaction accompanied by a first‐order chemical reaction (EC1 mechanism), with the size of surface pores of nanoporous gold (NPG) films. NPG films were electrodeposited on gold microelectrodes, generating polycrystalline, and highly porous surfaces. Studies of AA electrooxidation reveal mainly diffusional mass transport driven by EC1 pathways on the NPG electrodes prepared by changing the deposition potential. Similar studies on the NPGs prepared by changing the deposition time exhibit mainly diffusional transport at shorter deposition times, and largely an adsorption process driven by EC1 at longer deposition times. Such transition in the reaction pathways from diffusion EC1 to adsorption EC1 is correlated with the evolution of micrometer large surface pores in NPG films prepared at longer deposition times, allowing the diffusion of AA from the bulk solution to the volume of NPG, which enhances the adsorption probability.

Effect of Mesopores in the Marimo nanocarbon anode material on the power generation performance of direct glucose fuel cell

In this study, the effect of mesopores in the Marimo nanocarbon (MNC) anode material on the power generation performance of a direct glucose fuel cell was investigated. Three types of MNC with different mesopore distributions were used for the catalyst support material; Pt was used as the loaded metal. In the glucose fuel cell performance test, MNC containing many pores of approximately 35 nm showed the highest maximum output density of 0.72 mW cm−2 at 5 wt% metal loading and 0.3 M Glucose aqueous solution. The pores of approximately 30 nm may promote ion diffusion and rapid mass transport of reactants and products. These results indicated that MNC was an effective anode material for the direct glucose fuel cell.

Diffusivities in Binary Mixtures of n-Hexane or 1-Hexanol with Dissolved CH4, Ne, Kr, R143a, SF6, or R236fa Close to Infinite Dilution

This work is a continuation of previous studies focusing on the influence of intermolecular interactions on the diffusive mass transport in mixtures consisting of liquids with dissolved gases by determining the Fick diffusion coefficient of the mixtures or self-diffusion coefficient of the gas solutes. Dynamic light scattering, Raman spectroscopy, and molecular dynamics simulations are applied to study the interplay between the liquid structure and diffusive mass transport in binary mixtures consisting of methane, neon, krypton, sulfur hexafluoride, and the two refrigerants R143a and R236fa dissolved in n-hexane or 1-hexanol. Experiments and simulations were performed at the macroscopic thermodynamic equilibrium close to infinite dilution of the solute at temperatures between 303 and 423 K. The obtained Fick diffusion coefficients increase with increasing temperature and are always smaller in mixtures based on 1-hexanol compared to those of n-hexane. For both solvents, a decreasing molar mass of the solutes leads to increasing Fick diffusion coefficients with the exception of methane and neon showing the opposite behavior. Next to a general discussion and comparison with the literature, the present diffusivity data are compared with values predicted by a semiempirical model, which was previously developed to predict mass diffusivities in binary mixtures consisting of n-alkanes or 1-alcohols with dissolved gases close to infinite dilution.

Carbon aerogels with integrated engineered macroporous architectures for improved mass transport

Carbon aerogels (CAs) combine unique properties including ultra-high surface area, high electrical conductivity, corrosion resistance, and robust mechanical properties making them ideal materials for electrochemical applications. Traditional CA synthesis results in isotropic, random nanoporous networks that work well for applications relying on diffusional mass transport. However, many applications would benefit from integration of engineered macroporous network structures that enable directed pressure-gradient-driven mass transport. Here, we report on using 3D-printed sacrificial polymeric templates to generate templated CAs (t-CAs) with integrated engineered nonrandom macroporous network structures. Specifically, we used projection micro-stereo-lithography (PμSL) and two-photon polymerization direct laser writing (2PP-DLW) to fabricate millimeter-to-centimeter-sized 3D sacrificial polymeric templates with features ranging from tens of microns (PμSL) to 100s of nanometers (2PP-DLW). T-CAs were fabricated by infiltrating the templates with resorcinol-formaldehyde (RF) precursor solution, followed by carbonization at 1050 °C to simultaneously convert the RF gel to a CA and decompose the 3D-printed template, leaving an embedded templated macroporous network structure behind. X-ray computer tomography confirms integration of the macroporous architecture defined by the template. The templated macroporous architecture improves mass transport in t-CAs compared to traditional bulk CA as demonstrated by more uniform activation and their response in electrochemical cyclic voltammetry and galvanostatic charge-discharge tests.

A computational simulation of electromembrane extraction based on Poisson - Nernst - Planck equations

Electromembrane extraction (EME) has attracted a great deal of interest in researchers because of its advantages. For analysis, design and optimization purposes, understanding the ion transport mechanisms in the organic supported liquid membrane (SLM) is of prominent importance, where the interplay between the passive diffusion and electric-driven mass transport across SLM affects the mass transfer. In present work, a 2D numerical simulation is developed to examine the mass transfer behavior and the analyte recovery in EME devices. The presented model is capable of describing the effect of different parameters on the recovery of the EME setup. Initial analyte concentration in the sample solution, SLM thickness, applied potential, permittivity, diffusion coefficient, and the reservoir pH within both the sample and acceptor, can be considered as process variables. Predicted results revealed that the most important factors playing key role in EME, are the analyte diffusivity, distribution coefficient of the analyte as well as the level of protonation in both the donor and acceptor solutions. The proposed model is helpful in predicting the mass transfer behavior of the EME process in practical applications.

A Molecular Interpretation of the Dynamics of Diffusive Mass Transport of Water within a Glassy Polyetherimide.

The diffusion process of water molecules within a polyetherimide (PEI) glassy matrix has been analyzed by combining the experimental analysis of water sorption kinetics performed by FTIR spectroscopy with theoretical information gathered from Molecular Dynamics simulations and with the expression of water chemical potential provided by a non-equilibrium lattice fluid model able to describe the thermodynamics of glassy polymers. This approach allowed us to construct a convincing description of the diffusion mechanism of water in PEI providing molecular details of the process related to the effects of the cross- and self-hydrogen bonding established in the system on the dynamics of water mass transport.

Global–in–time existence for liquid mixtures subject to a generalised incompressibility constraint

We consider a system of partial differential equations describing diffusive and convective mass transport in a fluid mixture of N>1 chemical species. A weighted sum of the partial mass densities of the chemical species is assumed to be constant, which expresses the incompressibility of the fluid, while accounting for different reference sizes of the involved molecules. This condition is different from the usual assumption of a constant total mass density, and it leads in particular to a non-solenoidal velocity field in the Navier-Stokes equations. In turn, the pressure gradient occurs in the diffusion fluxes, so that the PDE–system of mass transport equations and momentum balance is fully coupled. Another striking feature of such incompressible mixtures is the algebraic formula connecting the pressure and the densities, which can be exploited to prove a pressure bound in L1. In this paper, we consider incompressible initial states with bounded energy and show the global existence of weak solutions with defect measure.

Particle Image Velocimetry Method for Prediction Hydrodynamic Conditions during Leaching Process on the Basis of Sn-NaOH System.

In leaching processes controlled by diffusion and convectional transport of mass, the hydrodynamic structure formed in the reactor’s working volume is an additional factor affecting the process. This research work presents results related to hydrodynamic structures developing in batch reactors, different in shape, recorded by means of the particle image velocimetry (PIV) method. The movement of the distilled water and leaching solution was analyzed during investigations. Next, the system hydrodynamics and the process of tin leaching were analyzed. Finally, the leaching is affected by the reactor geometry and the hydrodynamic structure developed in its working volume, especially when a convectional or diffusion mass transport decides the process efficiency.

Insight into the adsorption mechanisms of ionizable imidazolinone herbicides in sediments: Kinetics, adsorption model, and influencing factors

To reveal the adsorption mechanisms of imazamox, imazapic, and imazethapyr on sediment and batch experiments were carried out in this study. The adsorption kinetics of three imidazolinone herbicides on sediment were accurately described by the pseudo-second-order kinetic model(R2 > 0.9004). The values of adsorption capacity (Qe.cal) were ranged from 0.0183 to 0.0859 mg kg−1 for three herbicides. Adsorption equilibrium was reached within 24 h for three herbicides on sediment, and well fitted by the Freundlich model(R2 > 0.9561). The KF of values for adsorption obtained sediment samples were ranged from 0.2501 to 1.322 L1/n mg1-1/n kg−1for three herbicides. These results indicated that intraparticle diffusion and external mass transport were the main rate controlling steps of the adsorption of herbicides on sediment and that the chemical adsorption was dominant during the adsorption processes. The calculated hysteresis coefficient H were 0.9422,0.7877 and 0.744 for imazmox, imazapic and imazethapyr in raw sediment, respectively, indicating that there is a hysteresis in desorption. The influences of solution pH and sediment organic carbon content on the imidazolinone herbicide adsorption behaviors were also examined. Which shown that the adsorption process for herbicides was highly pH-dependent and adsorption efficiency was closely related to the organic matter content of the sediment, suggesting that electrostatic interactions played crucial roles in the adsorption behavior between sediment and imidazolinone herbicides, and the herbicides were mostly absorbed by the amorphous materials of sediment. These research findings are important for assessing the fate and transport of imidazolinone herbicides in water–sediment systems.

Electric current dependence of plastic flow behavior with large tensile elongation in tetragonal zirconia polycrystal under a DC field

This study systematically investigated the electric direct current (DC) dependence of the plastic flow behavior in a densified tetragonal ZrO2 polycrystal (TZP). Consequently, we observed an optimal current density for tensile ductility. The maximum elongation of 135% was achieved under the current density of 250 mA∙mm−2 at a furnace temperature of 1000°C and an initial strain rate of 1 × 10−3 s−1. The diffusional mass transport in the TZP was accelerated by the combination of Joule heating and applied current effect, resulting in a reduced flow stress and an improved ductility.

Universal law for diffusive mass transport through mycelial networks.

Filamentous fungal cell factories play a pivotal role in biotechnology and circular economy. Hyphal growth and macroscopic morphology are critical for product titers; however, these are difficult to control and predict. Usually pellets, which are dense networks of branched hyphae, are formed during industrial cultivations. They are nutrient- and oxygen-depleted in their core due to limited diffusive mass transport, which compromises productivity of bioprocesses. Here, we demonstrate that a generalized law for diffusive mass transport exists for filamentous fungal pellets. Diffusion computations were conducted based on three-dimensional X-ray microtomography measurements of 66 pellets originating from four industrially exploited filamentous fungi and based on 3125 Monte Carlo simulated pellets. Our data show that the diffusion hindrance factor follows a scaling law with respect to the solid hyphal fraction. This law can be harnessed to predict diffusion of nutrients, oxygen, and secreted metabolites in any filamentous pellets and will thus advance the rational design of pellet morphologies on genetic and process levels.

Effect of Mesopores of Marimo Nano Carbon Anode Material on Power Generation Performance of Direct Glucose Fuel Cell

Direct Glucose Fuel Cell (DGFC) is attracting attention as a clean and sustainable energy source because glucose is the most organic substance in nature. In this study, the effect of the mesopores of marimo nano carbon (MNC) on power generation performance for anode material of direct glucose fuel cell was investigated. Three types of MNC with different mesopore distributions were used for the catalyst support material, Pt was used as the supported metal. Also, Vulcan XC-72 which is carbon black of microporous material was used as a comparative material. In the glucose fuel cell performance test, MNC having many pores of about 35 nm showed the highest maximum output density of 0.72 mW cm-2 at 5 wt% metal loading and 0.3 M Glucose. Vulcan XC-72, which was a microporous material had low power generation performance. MNC showed higher power generation performance than that of Vulcan XC-72. The pores of about 35 nm probably promoted ion diffusion and rapid mass transport of reactants and products. These results indicated that MNC was an effective material as anode material for DGFC. Figure 1