Three-Dimensional Pore-Scale Modeling of Fracture Evolution in Heterogeneous Carbonate Caprock Subjected to CO2-Enriched Brine.

Fractures in caprocks overlying CO2 storage reservoirs can adversely affect the sealing capacity of the rocks. Interactions between acidified fluid and minerals with different reactivities along a fracture pathway can affect the chemically induced changes in hydrodynamic properties of fractures. To study porosity and permeability evolution of small-scale (millimeter scale) fractures, a three-dimensional pore-scale reactive transport model based on the lattice Boltzmann method has been developed. The model simulates the evolution of two different fractured carbonate-rich caprock samples subjected to a flow of CO2-rich brine. The results show that the existence of nonreactive minerals along the flow path can restrict the increase in permeability and the cubic law used to relate porosity and permeability in monomineral fractured systems is therefore not valid in multimineral systems. Moreover, the injection of CO2-acidified brine at high rates resulted in a more permeable fractured media in comparison to the case with lower injection rates. The overall rate of calcite dissolution along the fracture decreased over time, confirming similar observations from previous continuum scale models. The presented 3D pore-scale model can be used to provide inputs for continuum scale models, such as improved porosity-permeability relationships for heterogeneous rocks, and also to investigate other reactive transport processes in the context of CO2 leakage in fractured seals.

Interaction between graphene oxide and Pluronic F127 at the air-water interface.

Triblock copolymer Pluronic F127 (PF127) has previously been demonstrated to disperse graphene oxide (GO) in electrolyte solution and block the hydrophobic interaction between GO and l-tryptophan and l-tyrosine. However, the nature of this interaction between PF127 and GO remains to be characterized and elucidated. In the present study, we aimed to characterize and understand the interaction between GO and PF127 using a 2-dimensional Langmuir monolayer methodology at the air-water interface by surface pressure-area isotherm measurement, stability, adsorption, and atomic force microscopy (AFM) imaging. Based on the observation of surface pressure-area isotherms, adsorption, and stability of PF127 and PF127/GO mixture at the air-water interface, GO is suggested to change the conformation of PF127 at the air-water interface and also drag PF127 from the interface to the bulk subphase. Atomic force microscopy (AFM) image supports this assumption, as GO and PF127 can be observed by spreading the subphase solution outside the compressing barriers, as shown in the TOC graphic.

Coupling of multiscale lattice Boltzmann discrete-element method for reactive particle fluid flows.

Reactive particulate systems are of prime importance in varieties of practical applications in process engineering. As an example this study considers extraction of phosphorous from waste water by calcium silicate hydrate particles in the P-RoC process. For such systems modeling has a large potential to help to optimize process conditions, e.g., particle-size distributions or volume flows. The goal of this study is to present a new generic modeling framework to capture relevant aspects of reactive particle fluid flows using combined lattice Boltzmann method and discrete-element method. The model developed is Euler-Lagrange scheme which consist of three-components viz., a fluid phase, a dissolved reactive substance, and suspended particles. The fluid flow and reactive mass transport are described in a continuum framework using volume-averaged Navier-Stokes and volume-averaged advection-diffusion-reaction equations, respectively, and solved using lattice Boltzmann methods. The volume-averaging procedure ensures correctness in coupling between fluid flow, reactive mass transport, and particle motion. The developed model is validated through series of well-defined benchmarks. The benchmarks include the validation of the model with experimental data for the settling of a single particle in a cavity filled with water. The benchmark to validate the multi-scale reactive transport involves comparing the results with a resolved numerical simulation. These benchmarks also prove that the proposed model is grid convergent which has previously not been established for such coupled models. Finally, we demonstrate the applicability of our model by simulating a suspension of multiple particles in fluid with a dissolved reactive substance. Comparison of this coupled model is made with a one-way coupled simulation where the influence of particles on the fluid flow and the reactive solution transport is not considered. This elucidates the need for the two-way coupled model.

Single-relaxation-time lattice Boltzmann scheme for advection-diffusion problems with large diffusion-coefficient heterogeneities and high-advection transport.

The paper presents an approach that extends the flexibility of the standard lattice Boltzmann single relaxation time scheme in terms of spatial variation of dissipative terms (e.g., diffusion coefficient) and stability for high Péclet mass transfer problems. Spatial variability of diffusion coefficient in SRT is typically accommodated through the variation of relaxation time during the collision step. This method is effective but cannot deal with large diffusion coefficient variations, which can span over several orders of magnitude in some natural systems. The approach explores an alternative way of dealing with large diffusion coefficient variations in advection-diffusion transport systems by introducing so-called diffusion velocity. The diffusion velocity is essentially an additional convective term that replaces variations in diffusion coefficients vis-à-vis a chosen reference diffusion coefficient which defines the simulation time step. Special attention is paid to the main idea behind the diffusion velocity formulation and its implementation into the lattice Boltzmann framework. Finally, the performance, stability, and accuracy of the diffusion velocity formulation are discussed via several advection-diffusion transport benchmark examples. These examples demonstrate improved stability and flexibility of the proposed scheme with marginal consequences on the numerical performance.

Organophosphorus acid anhydrolase bio-template for the synthesis of CdS quantum dots.

A direct conjugation of organophosphorus acid anhydrolase (OPAA) with CdS quantum dots was prepared via arrested precipitation within the enzyme matrix. The bio-conjugate was found not only to retain enzyme conformational structure but also to retain enzyme activity and be effective at detecting diisopropyl fluorophosphate (DFP) at the micro molar level.

The gamma interferon (IFN-gamma) mimetic peptide IFN-gamma (95-133) prevents encephalomyocarditis virus infection both in tissue culture and in mice.

We have demonstrated previously that the C-terminal gamma interferon (IFN-gamma) mimetic peptide consisting of residues 95 to 133 [IFN-gamma(95-133)], which contains the crucial IFN-gamma nuclear localization sequence (NLS), has antiviral activity in tissue culture. Here we evaluate the efficacy of this peptide and its derivatives first in vitro and then in an animal model of lethal viral infection with the encephalomyocarditis (EMC) virus. Deletion of the NLS region from the IFN-gamma mimetic peptide IFN-gamma(95-133) resulted in loss of antiviral activity. However, the NLS region does not have antiviral activity in itself. Replacing the NLS region of IFN-gamma(95-133) with the NLS region of the simian virus 40 large T antigen retains the antiviral activity in tissue culture. IFN-gamma(95-133) prevented EMC virus-induced lethality in mice in a dose-dependent manner compared to controls. Mice treated with IFN-gamma(95-133) had no or low EMC virus titers in their internal organs, whereas control mice had consistently high viral titers, especially in the heart tissues. Injection of B8R protein, which is encoded by poxviruses as a defense mechanism to neutralize host IFN-gamma, did not inhibit IFN-gamma(95-133) protection against a lethal dose of EMC virus, whereas mice treated with rat IFN-gamma were not protected. The data presented here show that the IFN-gamma mimetic peptide IFN-gamma(95-133) prevents EMC virus infection in vivo and in vitro and may have potential against other lethal viruses, such as the smallpox virus, which encodes the B8R protein.

Treatment of mice with the suppressor of cytokine signaling-1 mimetic peptide, tyrosine kinase inhibitor peptide, prevents development of the acute form of experimental allergic encephalomyelitis and induces stable remission in the chronic relapsing/remitting form.

We have previously characterized a novel tyrosine kinase inhibitor peptide (Tkip) that is a mimetic of suppressor of cytokine signaling 1 (SOCS-1) and inhibits JAK2 phosphorylation of the transcription factor STAT1alpha. We show in this study that Tkip protects mice against experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis. Mice are immunized with myelin basic protein (MBP) for induction of disease. Tkip (63 mug) administered every other day suppressed the development of acute EAE in 75% of New Zealand White (NZW) mice. Furthermore, Tkip completely protected SJL/J mice, which where induced to get the relapsing/remitting form of EAE, against relapses compared with control groups in which >70% of the mice relapsed after primary incidence of disease. Protection of mice by Tkip was similar to that seen with the type I IFN, IFN-tau. Protection of mice correlated with lower MBP Ab titers in Tkip-treated groups as well as suppression of MBP-induced proliferation of splenocytes taken from EAE-afflicted mice. Cessation of Tkip and IFN-tau administration resulted in SJL/J mice relapsing back into disease. Prolonged treatment of mice with Tkip produced no evidence of cellular toxicity or weight loss. Consistent with its JAK2 inhibitory function, Tkip also inhibited the activity of the inflammatory cytokine TNF-alpha, which uses the STAT1alpha transcription factor. The data presented in this study show that Tkip, like the type I IFN, IFN-tau, inhibits both the autoreactive cellular and humoral responses in EAE and ameliorates both the acute and chronic relapsing/remitting forms of EAE.