Matrix Domain Research Articles

A mechanically strong shape-memory organohydrogel based on dual hydrogen bonding and gelator-induced solidification effect

Shape-memory gel materials are widely used in smart drives and biological tissues due to their excellent flexibility and diverse stimuli responsiveness. In particular, shape-memory organohydrogel materials have rose intense interest recently owing to their sophisticated shape memory behavior. However, conventional mechanical enhancement strategies, either by introducing nanoparticles or double-network structure, employed in the preparation of organohydrogels require high energy input, leading to difficulties in emulsification for emulsion precursors of organohydrogels. These strategies are not suitable for large-scale production of high-strength organohydrogels. Herein，a high-strength shape-memory organohydrogel NL-H was prepared based on dual hydrogen bonding and gelator-induced solidification effect. The precursor was easily emulsified, as the aqueous phase involved no nanoparticles or highly viscous polymers. Moreover, the dual hydrogen bonds among the dual amide groups of N-acryloyl glycinamide (NAGA) monomers can endow the organohydrogel with high mechanical properties. Owing to the oil-solidification effect of gelator HSA, the mechanical properties could be greatly enhanced, showing a high Young's modulus of 188.04 kPa. Furthermore, by integrating a high elastic hydrogel matrix and reversible oil domains, the organohydrogel showed a thermo-softening and favorable shape-memory properties. Consequently, this work provides a new enhancement strategy for the preparation of organohydrogel with high mechanical properties and excellent shape memory capabilities. And the simple preparation process can also facilitate the large-scale fabrication.

Effects of dynamic changes of desiccation cracks on preferential flow: experimental investigation and numerical modeling

Abstract. Preferential flow induced by desiccation cracks (PF-DC) has been proven to be an important hydrological effect that could cause various geotechnical engineering and ecological environment problems. Investigation on the PF-DC remains a great challenge due to the soil shrinking–swelling behavior. This work presents an experimental and numerical study of the PF-DC considering the dynamic changes of desiccation cracks. A soil column test was conducted under wetting–drying cycles to investigate the dynamic changes of desiccation cracks and their hydrological response. The ratios between the crack area and soil matrix area (crack ratio), crack aperture and depth were measured. The soil water content, matrix suction and water drainage were monitored. A new dynamic dual-permeability preferential flow model (DPMDy) was developed, which includes physically consistent functions in describing the variation of both porosity and hydraulic conductivity in crack and matrix domains. Its performance was compared to the single-domain model (SDM) and rigid dual-permeability model (DPM) with fixed crack ratio and hydraulic conductivity. The experimental results showed that the maximum crack ratio and aperture decreased when the evaporation intensity was excessively raised. The self-closure phenomenon of cracks and increased surficial water content was observed during low-evaporation periods. The simulation results showed that the matrix evaporation modeled by the DPMDy is lower than that of the SDM and DPM, but its crack evaporation is the highest. Compared to the DPM, the DPMDy simulated a faster pressure head building-up process in the crack domain and higher water exchange rates from the crack to the matrix domain during rainfall. Using a fixed crack ratio in the DPM, whether it is the maximum or the average value from the experiment data, will overestimate the infiltration fluxes of PF-DC but underestimate its contribution to the matrix domain. In conclusion, the DPMDy better described the underlying physics involving crack evolution and hydrological response with respect to the SDM and DPM. Further improvement of the DPMDy should focus on the hysteresis effect of the soil water retention curve and soil deformation during wetting–drying cycles.

HIV-1 Gag Binds the Multi-Aminoacyl-tRNA Synthetase Complex via the EPRS Subunit.

Host factor tRNAs facilitate the replication of retroviruses such as human immunodeficiency virus type 1 (HIV-1). HIV-1 uses human tRNALys3 as the primer for reverse transcription, and the assembly of HIV-1 structural protein Gag at the plasma membrane (PM) is regulated by matrix (MA) domain-tRNA interactions. A large, dynamic multi-aminoacyl-tRNA synthetase complex (MSC) exists in the cytosol and consists of eight aminoacyl-tRNA synthetases (ARSs) and three other cellular proteins. Proteomic studies to identify HIV-host interactions have identified the MSC as part of the HIV-1 Gag and MA interactomes. Here, we confirmed that the MA domain of HIV-1 Gag forms a stable complex with the MSC, mapped the primary interaction site to the linker domain of bi-functional human glutamyl-prolyl-tRNA synthetase (EPRS), and showed that the MA-EPRS interaction was RNA dependent. MA mutations that significantly reduced the EPRS interaction reduced viral infectivity and mapped to MA residues that also interact with phosphatidylinositol-(4,5)-bisphosphate. Overexpression of EPRS or EPRS fragments did not affect susceptibility to HIV-1 infection, and knockdown of EPRS reduced both a control reporter gene and HIV-1 protein translation. EPRS knockdown resulted in decreased progeny virion production, but the decrease could not be attributed to selective effects on virus gene expression, and the specific infectivity of the virions remained unchanged. While the precise function of the Gag-EPRS interaction remains uncertain, we discuss possible effects of the interaction on either virus or host activities.

Role of gRNA binding in HIV-1 Gag assembly process.

Assembly of human immunodeficiency virus type 1 (HIV-1) is a multi-step process that occurs at the host cell plasma membrane and is driven by a viral structural protein, Gag. Newly synthesized cytosolic Gag particles are targeted to the inner leaflet of the plasma membrane and membrane-bound Gag polyproteins interact with each other to form higher order multimers. Gag polyprotein is composed of multiple structured domains connected by flexible linkers. N-myristoylated matrix (MA) domain mediates membrane binding process, capsid (CA) and nucleocapsid (NC) domains play vital roles in Gag multimerization process. Interactions of gRNA with the zinc finger motifs of the NC domain facilitate gRNA packaging into virions. To investigate the effect of Gag-gRNA binding on the different multimerization states, we have performed all-atom molecular dynamics simulations of full-length Gag multimers (hexamer and hexamer-of-trimers) bound to an asymmetric membrane. MA domain multimerizes as a hexamer of trimers whereas cryo-ET data shows that CA domains are organized as hexameric lattice. The multidomain correlation of Gag polyprotein as well as the effect of multimerization of one domain to the dynamics of others are still not clear. Here we aim to gain atomic-level characterization of the inter and intra-protein interactions between different structural domains of Gag polyprotein in the presence/absence of the effective rigidity of NC domain, associated with gRNA binding. In the hexamer-of-trimers, the rigidity of NC domain is observed to modify the structure and dynamics of Gag monomers, resulting in a different binding surface for cytosolic Gag protein. In case of membrane-bound Gag hexamer, gRNA binding alters the dynamics of MA-CA linker domains, and we observe a signature of PIP2 and cholesterol enrichment in the membrane that can modify membrane binding affinity for Gag hexamer and facilitate recruitment of cytosolic Gag protein.

Field-Scale Modeling of Interwell Tracer Flow Behavior to Characterize Complex Fracture Networks Based on the Embedded Discrete Fracture Model in a Naturally Fractured Reservoir

Summary In a naturally fractured reservoir, natural fractures can not only provide main paths for fluid flow and increase its permeability but also complicate flow behavior and production performance. Interwell tracer tests have been widely applied to estimate the petrophysical properties; however, limited attempts have been made to accurately identify the natural fracture networks. In this study, the newly proposed numerical models have been verified and used to characterize the fracture distributions in a naturally fractured reservoir conditioned to tracer transport behavior. The stochastic fracture modeling approach is implemented to generate the randomly distributed natural fractures which are dealt with the embedded discrete fracture model (EDFM) while ensuring its sufficient accuracy. To be specific, the matrix domain is discretized using the structured grids, within which each embedded fracture is divided into a series of segments. Subsequently, nonneighboring connections (NNCs) allow us to couple the flow of fluid and tracer between the nonneighboring grid cells, while the historical tracer profiles are matched to delineate the geometry and properties of the fractures by taking multiple tracer transport mechanisms into account. Furthermore, the influences of fracture number, fracture length, fracture orientation, and tracer dispersion on the tracer production concentration have been investigated through sensitivity analysis. The response of an interwell tracer model is sensitive to the fracture parameters rather than tracer properties. A fracture network with its orientation parallel to the mainstream direction will cause the earliest tracer breakthrough. The tracer breakthrough time with an average fracture length of 40 m is 110 days earlier than that with a mean fracture length value of 10 m, while the tracer production peak concentration for the former is nearly two times higher than for the latter. A larger fracture number results in an earlier tracer breakthrough, and an intermediate fracture number will lead to the highest tracer production concentration. Additionally, the newly developed model has been validated through its comparison with the commercial ECLIPSE simulator and then extended to field applications to identify the possible fracture distributions by simulating multiwell tracer tests in the Midale field. The flexible and pragmatic EDFM-based method developed in this study can model the interwell tracer flow behavior as well as characterize the properties and geometries of the natural fractures with better accuracy and calculation efficiency in comparison with other fracture simulation methods (e.g., local grid refinement method).

A New Two-dimensional Dual-permeability Model of Preferential Water Flow in the Vadose Zone

LEAK2D (L2D) is a new, two-dimensional, dual-permeability model for the simulation of preferential water flow in the vadose zone, allowing for the continuous exchange of water between the matrix and the fracture domain. It is based on the two-dimensional Richards equation for the simulation of flow in the matrix domain and on the kinematic wave equation for the simulation of flow in the fracture domain. The Richards equation is solved by a combination of the Alternating Direction Implicit method and the Douglas-Jones predictor-corrector method. This combination leads to a very efficient, stable, and time-consuming method. A variable time step is used by which any instability of the numerical solution is avoided. The water transfer from the fracture to the matrix domain is estimated as a first-order approximation of the water diffusion equation. The model was used to satisfactorily simulate preferential flow under an extreme rainfall/irrigation event. The exchange of water between the two domains depends on parameters which have physical meaning; however, their exact values are difficult to be determined or measured. Based on the most common values of these parameters found in the literature, a sensitivity analysis was performed to define their effect on the output of the model.

Optimal estimates for the conductivity problem close to the boundary in dimension greater than two

<p style='text-indent:20px;'>In high-contrast composite materials, the electric field (or stress field) may blow up in the narrow region when a convex inclusion is closely to the boundary of the matrix domain. The gradient of solutions depends on the parameters–the distance between the inclusions and boundaries. An optimal upper bound was obtained for convex inclusions of arbitrary shape in dimension greater than two. Our results extend that in [<xref ref-type="bibr" rid="b3">3</xref>], where the disk inclusion case in 2D is considered.</p>

The membrane domain of respiratory complex I accumulates during muscle aging in Drosophila melanogaster

The boot-shaped respiratory complex I (CI) consists of a mitochondrial matrix and membrane domain organized into N-, Q- and P-modules. The N-module is the most distal part of the matrix domain, whereas the Q-module is situated between the N-module and the membrane domain. The proton-pumping P-module is situated in the membrane domain. We explored the effect of aging on the disintegration of CI and its constituent subcomplexes and modules in Drosophila flight muscles. We find that the fully-assembled complex remains largely intact in aged flies. And while the effect of aging on the stability of many Q- and N-module subunits in subcomplexes was stochastic, NDUFS3 was consistently down-regulated in subcomplexes with age. This was associated with an accumulation of many P-module subunits in subcomplexes. The potential significance of these studies is that genetic manipulations aimed at boosting, perhaps, a few CI subunits may suffice to restore the whole CI biosynthesis pathway during muscle aging.

Gradient discretization of a 3D-2D-1D mixed-dimensional diffusive model with resolved interface, application to the drying of a fractured porous medium

Abstract We consider a 3D-2D-1D mixed-dimensional diffusive model in a fractured porous medium coupling the 1D model along the centerline skeleton of a tubular network, the 2D model on a network of planar fractures and the 3D model in the surrounding matrix domain. The transmission conditions are based on a potential continuity assumption at matrix fracture interfaces, and on Robin type conditions at the resolved interfaces between the tubular network and the matrix and fracture network domains. The discretization of this mixed-dimensional model is formulated in the gradient discretization framework (Droniou, J., Eymard, R. & Herbin, R. (2016) Gradient schemes: generic tools for the numerical analysis of diffusion equations. ESAIM Math. Model. Numer. Anal., 50, 749–781), which covers a large class of conforming and nonconforming schemes and provides stability and error estimates based on general coercivity, consistency and limit-conformity properties. As an example of discretization fitting this framework, the mixed-dimensional version of the vertex approximate gradient (VAG) scheme is developed. It is designed to allow nonconforming meshes at the interface between the 1D and 3D-2D domains, to provide a conservative formulation with local flux expressions and to be asymptotic preserving in the limit of high transfer coefficients. Numerical experiments are provided on analytical solutions for simplified geometries, which confirm the theoretical results. Using its equivalent finite volume formulation, the VAG discretization is extended to a drying mixed-dimensional model coupling the Richards equation in a fractured porous medium and the convection diffusion of the vapor molar fraction along the 1D domain. It is applied to simulate the drying process between an operating tunnel and a radioactive waste storage rock with explicit representation of the fractures in the excavated damaged zone.

Evolution of microstructure and mechanical properties of a Ti80(CoFeNi)20 ultrafine eutectic composite during thermal processing

In this study, the influence of thermal processing on phase transformation and microstructural evolution of Ti80(CoFeNi)20 ultrafine eutectic composites was investigated. The as-cast alloy exhibited the typical hypoeutectic microstructure consisting of a number of β-Ti dendrites and the β-Ti + Ti2Ni-type ultrafine eutectic matrix. In comparison with the as-cast alloy, the alloy annealed at 1173 K for 1 h exhibited significant microstructural change from a hypoeutectic structure to a microscale dual-phase structure comprising the dispersed Ti2Ni-type phase and β-Ti matrix domain. The alloy aged at 873 K for 1 h exhibited a significant phase transformation from the β-Ti matrix to α-Ti and Ti2Ni-type phases by the eutectoid decomposition. These microstructural evolutions induced by heat treatment significantly influenced to the mechanical properties. Optimized mechanical properties (yield strength of 1530 MPa and plasticity of 5.7%) were achieved for the as-annealed alloy.

Realizations of Non-commutative Rational Functions Around a Matrix Centre, II: The Lost-Abbey Conditions

In a previous paper the authors generalized classical results on minimal realizations of non-commutative (nc) rational functions, using nc Fornasini–Marchesini realizations which are centred at an arbitrary matrix point. In particular, it was proved that the domain of regularity of a nc rational function is contained in the invertibility set of the corresponding pencil of any minimal realization of the function. In this paper we prove an equality between the domain of a nc rational function and the domain of any of its minimal realizations. As for evaluations over stably finite algebras, we show that the domain of the realization w.r.t any such algebra coincides with the so called matrix domain of the function w.r.t the algebra. As a corollary we show that the domain of regularity and the stable extended domain coincide. In contrary to both the classical case and the scalar case—where every matrix coefficients which satisfy the controllability and observability conditions can appear in a minimal realization of a nc rational function—the matrix coefficients in our case have to satisfy certain equations, called linearized lost-abbey conditions, which are related to Taylor–Taylor expansions in nc function theory.

The coupling effects of the matrix thickness and Peclet number on the late time transport tailing in the fracture-matrix systems

Solute transport process in fractured rocks is central to many engineering applications. However, how matrix diffusion affects non-Fickian transport behavior, which is typically characterized by the late time tailing in breakthrough curves and residence time distributions, remains underexplored, especially considering the coupling effects of the finite matrix thickness (h) and transport regimes quantified by Peclet number (Pe). In this work, the fluid flow and solute transport were simulated by directly solving the Navier-Stokes equations and advection-diffusion equation in a two-dimensional fracture-matrix system considering matrix diffusion. In total, eighty cases considering variations of h and Pe were conducted to investigate the impacts of h and Pe on the late time solute tailing characterized by the exponent (n) in the power law function. Numerical results demonstrate that n decreases with an increase of h and Pe, where n eventually reduces to 1.5 that is a theoretical value for an infinite matrix domain. Moreover, the relationship between n and (h, Pe) is established via a polynomial function, which is further validated by the three-dimensional heterogeneous fracture-matrix system. The newly-established function can be used to accurately assess the power law tailing process given the knowledge of measurable h and Pe.

A computationally efficient model for fracture propagation and fluid flow in naturally fractured reservoirs

There is a need to develop computationally efficient models for oil and gas production from naturally fractured reservoirs. In this paper, we present an efficient, integrated fracturing-production simulator by combining a boundary element method (for fracture propagation) and a general Green's function solution (for fluid flow) that eliminates the need to discretize the matrix domain. First, the model is validated against analytical solutions and then compared with a fully numerical model. A comparison of results and computation time shows that our simulator significantly reduces the computation cost without any significant loss in accuracy. The simulator is then applied to investigate the effect of cluster spacing and pumping schedule on production from a hydraulically fractured horizontal well in a naturally fractured reservoir. The results show an optimal cluster spacing that can maximize the contact area between fractures and reservoirs while maintaining the highest production rate. Based on the chosen optimal cluster spacing, we observe that changes in the pumping schedule can have an impact on the production rate due to changes in the created fracture network.

Numerical modeling and analysis of the matrix acidizing process in fractured sandstone rocks with the Extended–FEM

Significant natural fractures develop in deep sandstone reservoirs. However, the previous numerical simulation for matrix acidizing in sandstone rocks always focused on the reactive flow in porous media. A series of responses between multiple types of acids and minerals in fracture and matrix pores have been a significant setback for seeking the mechanism of acid flow in fractured sandstone rocks. This paper, established a multistage reactive-transport model for fractured sandstone rocks based on the two-scale continuum model to explore the effects of fractures on the reactive flow. The weak forms of fluid flow and solute transport equations are derived using the Galerkin method to couple the matrix and fracture domains, and the extended finite element method was used to solve the discretization model. Additionally, we presented numerical simulations under 2D linear flow conditions with specific and sensitive analyses about fracture and matrix properties. Numerical cases showed that the wormhole-shaped structure generated by acid dissolution is hard to develop even in highly heterogeneous fractured sandstone rocks due to the low reaction rate between mud acid and minerals. However, fractures that are not parallel to the flow direction can accelerated acid flow in the formation and reduced Si(OH)4 precipitation. Increasing the injection rate can not change the dissolution patterns of sandstone, but expanded the acid diffusion range and decreased Si(OH)4 precipitation in fractured sandstone.

A specific eight-node hexahedral finite element for the analysis of 3D fibre-reinforced composites

This contribution deals with the development of an eight-node hexahedral finite element to estimate the effective elastic properties of fibre-reinforced composite materials and structures. This three-dimensional (3D) composite element is a combination of the standard eight-node hexahedral element, modelling a unit of the matrix domain, and 3D two-node truss elements that represent fibres crossing each matrix element. The so-called ‘Projected Fibre Approach’ is then considered to express the truss elements variables in terms of their corresponding matrix elements. Consequently, the obtained system of equations size is equivalent to that of a non-reinforced medium. In particular, we show that the proposed finite element formulation allows readily studying 3D composite structures with complex shape of the reinforcement like stitched sandwich panels.

Patterning of large area nanoscale domains in as-grown epitaxial ferroelectric PbTiO3 films

Effective tuning of nanoscale domain structures provides fundamental basis for controlling and engineering of various functionalities in ferroelectric materials. In this work, we demonstrate the precise patterning of nanoscopic domain structures in as-grown epitaxial PbTiO3 (PTO) films by merely introducing an ultrathin pre-patterned doping layer (e.g., Fe-doped PTO). The doping layer can effectively reverse the interfacial built-in bias, consequent to a reversed initial polarization reorientation in the as-grown film, which makes it possible to transfer the nano-patterns in the doping layer into the domain structure of ferroelectric films. For instance, we have successfully fabricated large area ordered array of nanoscale cylindrical domains (downward polarization) embedded in the matrix domain with opposite polarization (upward polarization) in PTO film. These nanoscale cylinder domains also allow deterministic and reversible erasure and creation induced by biased tip scanning. The results provide an effective pathway for on-demand patterning of large area nanoscale domains in the as-grown films, which may find applications in a wide range of nanoelectronic devices.

Dual-interface model for twinning in the coupled crystal plasticity finite element – Phase field method

Crystallographic shear transformation banding such as deformation twinning and martensitic transformation accommodates plastic deformation and generates new domain with different orientation or phase in matrix. The evolution of a new domain is described by the migration of interfaces separating the domain from the matrix. A coupled crystal plasticity finite element (CPFE) – phase field (PF) method is thus developed to simulate the migration of interfaces and plastic deformation. We propose a dual-interface model that integrates the constrained-sharp interface in FE method to solve the deformation fields, and the refined-diffuse interface in PF method to solve the domain evolution. The constrained-sharp interface in FE consists of one transition element between matrix and new domain. The refined-diffuse interface is locally extracted from the constrained-sharp interface by multi-classifier neural network fitting. Such a smoothing technique rubs off the jaggies of the constrained-sharp interface by a smooth function and thus diminishes mesh sensitivity of interface. Finally, we implemented the dual-interface model into the coupled CPFE-PF method and demonstrated the capability of diminishing mesh sensitivity in modelling deformation twinning.

Numerical upscaling of nonlinear flow in low-permeability sandstone matrix system

The matrix system's apparent permeability model based on nano- and micro-scale mechanism modeling is limited in its role in low-permeability reservoir numerical simulation due to the lack of suitable up-scaling methods. This paper developed a numerical simulation method to evaluate the microporous structure's apparent permeability contribution to total permeability of the heterogeneous representative elementary volume (REV)-scale matrix under macroscopic pressure gradients. First, a local apparent liquid permeability (LALP) model considering the heterogeneous microporous structure and multiple water-transport mechanisms was established to describe the nonlinear seepage behavior of fluid in microscopic computational domain. Then, a multiresolution-image-based REV-scale domain reconstruction method was proposed, in which the microporous structural characteristics were quantified by fractal heterogeneous-porous-media model, and the REV-scale matrix was subsequently stochastic reconstructed based on the porosity distribution characteristics of microporous structures. Finally, the microscopic LALP model and macroscopic continuum model were fully coupled to numerical simulate the nonlinear seepage progress in REV-scale matrix domain. The comparisons between simulation results and experimental results demonstrated that the developed numerical simulation method can effectively predict the nonlinear flow velocity curve of REV-scale sandstone matrix. The influences of internal factors (microporous structural characteristics and seepage fluid properties) and external factors (temperature and pressure) on absolute permeability and apparent permeability of REV-scale matrix were investigated. The results demonstrated that (1) microporous structural characteristics determines the approximate level of intrinsic reservoir permeability, especially the average maximum pore size of discrete domain; (2) with microporous structure's permeability distribution heterogeneity increasing, the macroscopic intrinsic permeability decreases and the differences between apparent permeability and intrinsic permeability increase.

Factorization of Hilbert operators

In this research, we introduce some factorization for Hilbert operators of order n based on two important classes of Hausdorff operators, Cesàro and gamma. These factorizations lead us to some new inequalities, one is a generalized version of Hilbert’s inequality. Moreover, as an application of our factorization, we compute the norm of Hilbert operators on some matrix domains.

Unsaturated Hydraulic Conductivity in Composite Porous Media

Determining the constitutive properties that describe the incipient hydraulic behavior of the materials, including the matrix domains and the distribution of macro and micropores, is crucial to analyzing the preferential water flow in saturated soils, ks, and unsaturated, ku. This study focused on determining the hydraulic conductivity in porous media under total and partial saturation conditions. The infiltration characteristics of three reconstituted soils were evaluated using five suction ranges employing conventional permeameters, an automated dual system, and mini-disk infiltrometers. The experimental cycles were carried out in granular soils with mixtures of diatomaceous soils, iron oxide (Fe2O3), and calcium carbonate (CaCO3) in 5–40% proportions. The differences between the granular microstructures of each material and the different hydraulic interaction mechanisms (suctione levels) significantly affected the values of ks and ku and the coupling between the pore domains and the defined water regime. Additionally, a lower impact was observed in the data set exposed to higher percentages of Fe2O3 and CaCO3 in different suction ranges, mainly due to a tension effect (meniscus) generated by suction in the granular skeleton. Since both parameters are mutually correlated and have a similar impact between methods and soil cores, ks and ku must be optimized simultaneously in each mechanism analyzed. The main findings of this work result in the confirmation that the unsaturated permeability decreases as suction is imposed on the sample. As well as the addition of different materials with Particle Size Distribution finer than the base sample, it also reveals a reduction in hydraulic conductivity, both saturated and unsaturated.