Pre-existing Matrix Research Articles

Effects of Matrix Cracking-Induced Delamination on Thermal Buckling of Composite Laminate

Abstract Delamination and matrix cracking are common damage modes in composite laminates, significantly impacting their structural integrity and performance. Under elevated temperatures, the collision of anisotropic thermal expansion and nonlinear stiffness responses affect the onset of thermal buckling in flying vehicles. This study implements a multi-scale analysis framework, incorporating finite element modeling and analytical methods to obtain the reduction in mechanical properties of the composite laminate and its stiffness degradation based on an effective stiffness model due to pre-existing matrix cracking in plies. Based on non-linear equations, obtained from the principle of virtual work, in combination with first-order shear deformable theory and von Kármán strain-displacement relations, the thermal buckling temperature, post-buckling behavior of composite laminates are investigated. This work paves the way for developing a model to predict the influence of the laminate stiffness, delamination size, transverse crack location, stacking sequence, and plies thickness on the laminate.

Evaluating a polymicrobial biofilm model for structural components by co-culturing Komagataeibacter hansenii produced bacterial cellulose with Pseudomonas aeruginosa PAO1

A polymicrobial biofilm model of Komagataeibacter hansenii and Pseudomonas aeruginosa was developed to understand whether a pre-existing matrix affects the ability of another species to build a biofilm. P. aeruginosa was inoculated onto the preformed K. hansenii biofilm consisting of a cellulose matrix. P. aeruginosa PAO1 colonized and infiltrated the K. hansenii bacterial cellulose biofilm (BC), as indicated by the presence of cells at 19 μm depth in the translucent hydrogel matrix. Bacterial cell density increased along the imaged depth of the biofilm (17-19 μm). On day 5, the average bacterial count across sections was 67 ± 4 % P. aeruginosa PAO1 and 33 ± 6 % K. hansenii. Biophysical characterization of the biofilm indicated that colonization by P. aeruginosa modified the biophysical properties of the BC matrix, which inlcuded increased density, heterogeneity, degradation temperature and thermal stability, and reduced crystallinity, swelling ability and moisture content. This further indicates colonization of the biofilm by P. aeruginosa. While eDNA fibres - a key viscoelastic component of P. aeruginosa biofilm - were present on the surface of the co-cultured biofilm on day 1, their abundance decreased over time, and by day 5, no eDNA was observed, either on the surface or within the matrix. P. aeruginosa-colonized biofilm devoid of eDNA retained its mechanical properties. The observations demonstrate that a pre-existing biofilm scaffold of K. hansenii inhibits P. aeruginosa PAO1 eDNA production and suggest that eDNA production is a response by P. aeruginosa to the viscoelastic properties of its environment.

Autocrine IL-6 drives cell and extracellular matrix anisotropy in scar fibroblasts

Fibrosis is associated with dramatic changes in extracellular matrix (ECM) architecture of unknown etiology. Here we exploit keloid scars as a paradigm to understand fibrotic ECM organization. We reveal that keloid patient fibroblasts uniquely produce a globally aligned ECM network in 2-D culture as observed in scar tissue. ECM anisotropy develops after rapid initiation of a fibroblast supracellular actin network, suggesting that cell alignment initiates ECM patterning. Keloid fibroblasts produce elevated levels of IL-6, and autocrine IL-6 production is both necessary and sufficient to induce cell and ECM alignment, as evidenced by ligand stimulation of normal dermal fibroblasts and treatment of keloid fibroblasts with the function blocking IL-6 receptor monoclonal antibody, tocilizumab. Downstream of IL-6, supracellular organization of keloid fibroblasts is controlled by activation of cell-cell adhesion. Adhesion formation inhibits contact-induced cellular overlap leading to nematic organization of cells and an alignment of focal adhesions. Keloid fibroblasts placed on isotropic ECM align the pre-existing matrix, suggesting that focal adhesion alignment leads to active anisotropic remodeling. These results show that IL-6-induced fibroblast cooperativity can control the development of a nematic ECM, highlighting both IL-6 signaling and cell-cell adhesions as potential therapeutic targets to inhibit this common feature of fibrosis.

Neutrophils direct preexisting matrix to initiate repair in damaged tissues

Internal organs heal injuries with new connective tissue, but the cellular and molecular events of this process remain obscure. By tagging extracellular matrix around the mesothelium lining in mouse peritoneum, liver and cecum, here we show that preexisting matrix was transferred across organs into wounds in various injury models. Using proteomics, genetic lineage-tracing and selective injury in juxtaposed organs, we found that the tissue of origin for the transferred matrix likely dictated the scarring or regeneration of the healing tissue. Single-cell RNA sequencing and genetic and chemical screens indicated that the preexisting matrix was transferred by neutrophils dependent on the HSF–integrin AM/B2-kindlin3 cascade. Pharmacologic inhibition of this axis prevented matrix transfer and the formation of peritoneal adhesions. Matrix transfer was thus an early event of wound repair and provides a therapeutic window to dampen scaring across a range of conditions.

Neutrophils guide pre-existing matrix into injured organs to initiate tissue repair.

Neutrophils guide pre-existing matrix into injured organs to initiate tissue repair.

Topological aspects responsible for recrystallization evolution in an IF-steel sheet – Investigation with cellular-automaton simulations

A cellular automaton algorithm for curvature-driven coarsening is applied to a cold-rolled interstitial-free steel’s microstructure - obtained through electron backscatter diffraction (EBSD). Recrystallization nucleation occurs naturally during the simulation, due to the highly heterogeneous and hence competitive growth among pre-existing (sub) grains. The spatial inhomogeneity of the subgrain growth that takes place derives from the large local variations of subgrain sizes and misorientations that comprise the prior deformed state. The results show that capillary-driven selective growth takes place to the extent that the prior elongated and deformed grains are replaced by equiaxed grains with no interior small-angle boundaries. Additionally, during the simulation certain texture components intensify and others vanish, which indicates that preferential growth occurs in a fashion that relates to the crystal orientations’ topology. The study of the early stages of recrystallization (i.e. nucleation) shows that the pre-existing subgrains that eventually recrystallize, exhibit certain topological characteristics at the prior deformed state. Successful nucleation occurs mostly for pre-existing matrix subgrains abutting shear bands or narrow deformation bands and particularly at regions where the latter intersect.

Multi-stage Reactive Formation of Troctolites in Slow-spreading Oceanic Lithosphere (Erro–Tobbio, Italy): a Combined Field and Petrochemical Study

Abstract Many recent studies have investigated the replacive formation of troctolites from mantle protoliths and the compositional evolution of the percolating melt during melt–rock interaction processes. However, strong structural and geochemical constraints for a replacive origin have not yet been established. The Erro–Tobbio impregnated mantle peridotites are primarily associated with a hectometre-size troctolitic body and crosscutting gabbroic dykes, providing a good field control on melt–rock interaction processes and subsequent magmatic intrusions. The troctolitic body exhibits high inner complexity, with a host troctolite (Troctolite A) crosscut by a second generation of troctolitic metre-size pseudo-tabular bodies (Troctolite B). The host Troctolite A is characterized by two different textural types of olivine, corroded deformed millimetre- to centimetre-size olivine and fine-grained rounded undeformed olivine, both embedded in interstitial to poikilitic plagioclase and clinopyroxene. Troctolite A shows melt–rock reaction microstructures indicative of replacive formation after percolation and impregnation of mantle dunites by a reactive melt. The evolution of the texture and crystallographic preferred orientation (CPO) of olivine are correlated and depend on the melt/rock ratio involved in the impregnation process. A low melt/rock ratio allows the preservation of the protolith structure, whereas a high melt/rock ratio leads to the disaggregation of the pre-existing matrix. The mineral compositions in Troctolite A define reactive trends, indicative of the buffering of the melt composition by assimilation of olivine during impregnation. The magmatic Troctolite B bodies are intruded within the pre-existing Troctolite A and are characterized by extreme textural variations of olivine, from decimetre-size dendritic to fine-grained euhedral crystals embedded in poikilitic plagioclase. This textural variability is the result of olivine assimilation during melt–rock reaction and the correlated increase in the degree of undercooling of the percolating melt. In the late gabbroic intrusions, mineral compositions are consistent with the fractional crystallization of melts modified after the reactive crystallization of Troctolites A and B. The Erro–Tobbio troctolitic body has a multi-stage origin, marked by the transition from reactive to fractional crystallization and diffuse to focused melt percolation and intrusion, related to progressive exhumation. During the formation of the troctolitic body, the melt composition was modified and controlled by assimilation and concomitant crystallization reactions occurring at low melt supply. Similar processes have been described in ultraslow-spreading oceanic settings characterized by scarce magmatic activity.

High fidelity visualization of cell-to-cell variation and temporal dynamics in nascent extracellular matrix formation.

Extracellular matrix dynamics are key to tissue morphogenesis, homeostasis, injury, and repair. The spatiotemporal organization of this matrix has profound biological implications, but is challenging to monitor using standard techniques. Here, we address these challenges by using noncanonical amino acid tagging to fluorescently label extracellular matrix synthesized in the presence of bio-orthogonal methionine analogs. This strategy labels matrix proteins with high resolution, without compromising their distribution or mechanical function. We demonstrate that the organization and temporal dynamics of the proteinaceous matrix depend on the biophysical features of the microenvironment, including the biomaterial scaffold and the niche constructed by cells themselves. Pulse labeling experiments reveal that, in immature constructs, nascent matrix is highly fibrous and interdigitates with pre-existing matrix, while in more developed constructs, nascent matrix lacks fibrous organization and is retained in the immediate pericellular space. Inhibition of collagen crosslinking increases matrix synthesis, but compromises matrix organization. Finally, these data demonstrate marked cell-to-cell heterogeneity amongst both chondrocytes and mesenchymal stem cells undergoing chondrogenesis. Collectively, these results introduce fluorescent noncanonical amino acid tagging as a strategy to investigate spatiotemporal matrix organization, and demonstrate its ability to identify differences in phenotype, microenvironment, and matrix assembly at the single cell level.

Effect of zirconia particle size on the properties of alumina-spinel castables

The industrial application of alumina-spinel refractory castables has crucial requirements on the service performance. Thus, the effects of different sized desilicated zirconia particles on the castables microstructure, thermal-mechanical properties and high temperature elastic modulus have been investigated. The zirconia particle sizes were varied from 1000µm to 2.5µm (d50). It was observed that the finer (below 88µm) zirconia particles were beneficial to improve the cold modulus of rupture (CMOR) and the hot modulus of rupture (HMOR), but could not effectively enhance the thermal shock resistance. Fine zirconia particles can homogeneously disperse in the matrix and significantly promote the sintering process. Accompanied with the phase transformation of zirconia, both the high density of matrix cracks and the strong ceramic bonding (between the coarse grains and the matrix) were found in the refractory castables, which was responsible for an increase of CMOR. However, the binding characteristic could also give rise to the high stored elastic energy that was adverse to the thermal shock resistance, and the excessive amount of preexisting matrix cracks could induce more microdamage during the thermal shock. Additionally, it was proposed that the second-phase dispersion reinforcement and the highly ceramics bonding resulted in the superior HMOR when introducing fine ZrO2 particles.

Morphologies and Crystallization Behaviors in Melt-Miscible Crystalline/Crystalline Blends with Close Melting Temperatures but Different Crystallization Kinetics

Poly(l-lactic acid) (PLLA) and poly(oxymethylene) (POM), with very close melting temperatures (Tm), can crystallize simultaneously or separately in their blends depending on composition and crystallization temperature (Tc), resulting in various types of morphology. It is mainly attributable to the greatly different crystallization kinetics of PLLA and POM. At a content of POM (φPOM), 3 wt % < φPOM < 20 wt %, PLLA crystallization kinetics are comparable to POM, and therefore two type spherulites exhibit “side-by-side” simultaneous growth with the penetration of PLLA spherulites into POM crystals. Although crystal growth rate (vc) of POM is still a bit faster than that of PLLA, for φPOM = 3 wt %, the nucleation of POM is restrained and POM spherulites can only develop on the propagating PLLA growth fronts with the generation of novel “core–shell” blended spherulites. For 20 wt % ≤ φPOM < 80 wt %, interspherulitic growth of PLLA inside the pre-existing matrix of POM spherulites causes the formation of interp...

Materializing Power through Practice in the Late Postclassic Naco Valley, Northwestern Honduras

We contend that political structures emerge in the course of interpersonal dealings conducted by people organized within overlapping social networks. It is through these webs that resources needed to define and achieve goals and exert control over others are mobilized. Elites seeking to construct hierarchies and concentrate power must restructure the preexisting matrix of networks to redirect the flow of assets to their benefit. In doing so, they seek to create an affiliation that transcends loyalties to extant social groups while securing for themselves positions of preeminence within the overarching affiliation. Such social engineering involves manipulating the material symbols by which interpersonal ties are made tangible and imbued with emotional significance. The resulting political structures are less nested sets of stable territorial groups than dynamic networks of networks through which assets are deployed in the practices by which power is exercised. This perspective is used to describe Late Postclassic (A.D. 1300-1532) political processes in the Naco Valley, northwestern Honduras, calling attention to how power of various sorts took shape through complex relations among diverse people and varied things orchestrated within overlapping social networks. The implications of a network approach for studying political processes generally are also considered.

Mechanical regulation of fibroblast migration and collagen remodelling in healing myocardial infarcts

Effective management of healing and remodelling after myocardial infarction is an important problem in modern cardiology practice. We have recently shown that the level of infarct anisotropy is a critical determinant of heart function following a large anterior infarction, which suggests that therapeutic gains may be realized by controlling infarct anisotropy. However, factors regulating infarct anisotropy are not well understood. Mechanical, structural and chemical guidance cues have all been shown to regulate alignment of fibroblasts and collagen in vitro, and prior studies have proposed that each of these cues could regulate anisotropy of infarct scar tissue, but understanding of fibroblast behaviour in the complex environment of a healing infarct is lacking. We developed an agent-based model of infarct healing that accounted for the combined influence of these cues on fibroblast alignment, collagen deposition and collagen remodelling. We pooled published experimental data from several sources in order to determine parameter values, then used the model to test the importance of each cue for predicting collagen alignment measurements from a set of recent cryoinfarction experiments. We found that although chemokine gradients and pre-existing matrix structures had important effects on collagen organization, a response of fibroblasts to mechanical cues was critical for correctly predicting collagen alignment in infarct scar. Many proposed therapies for myocardial infarction, such as injection of cells or polymers, alter the mechanics of the infarct region. Our modelling results suggest that such therapies could change the anisotropy of the healing infarct, which could have important functional consequences. This model is therefore a potentially important tool for predicting how such interventions change healing outcomes.

Film/ethics

This essay appraises recent writing on film and ethics, exploring how contemporary thinkers attend to both sides of the virgule. It focuses especially on Sarah Cooper's Selfless Cinema? Ethics and French Documentary, Jane Stadler's Pulling Focus: Intersubjective Experience, Narrative Film, and Ethics, and Catherine Wheatley's Michael Haneke's Cinema: The Ethic of the Image. On the one hand, it explores how these works consider ethics as ethics, rather than as a branch of philosophical or social thought under ontology or epistemology. On the other hand, it investigates how these works discuss film as film, rather than as a pre-determined illustration of a philosophical concept or as an example of a pre-existing philosophical matrix. The best contemporary thought on film and ethics engages with the full range of the complex relationship between the cinematic and the ethical without reducing either to the other or collapsing them both under a third term.

Absence of TGFβ signaling in embryonic vascular smooth muscle leads to reduced lysyl oxidase expression, impaired elastogenesis, and aneurysm

To address the requirement for TGFbeta signaling in the formation and maintenance of the vascular matrix, we employed lineage-specific mutation of the type II TGFbeta receptor gene (Tgfbr2) in vascular smooth muscle precursors in mice. In both neural crest- and mesoderm-derived smooth muscle, absence of TGFbeta receptor function resulted in a poorly organized vascular elastic matrix in late-stage embryos which was prone to dilation and aneurysm. This defect represents a failure to initiate formation of the elastic matrix, rather than a failure to maintain a preexisting matrix. In mutant tissue, lysyl oxidase expression was substantially reduced, which may contribute to the observed pathology.

Characterization of tensile behavior of a two-dimensional woven carbon/silicon carbide composite fabricated by chemical vapor infiltration

The tensile behavior of a two-dimensional woven carbon/silicon carbide composite has been characterized both by monotonic and loading/unloading tests. The composite shows markedly non-linear behavior with evident hysteresis loops, appreciable residual strains and continuously decreasing moduli. Both the loop width and residual strain have a continuous acceleration with applied stress, implying the composite failure precedes matrix cracking saturation. The shape of hysteresis loops is characterized by an initial parabolic region followed by a linear region. The preexisting matrix microcracks in as-processed specimens and multiple microcracks accompanied by extensive fiber pull-out in the failed specimens were observed, indicating large thermal residual stresses and relatively weak interfacial bonding exist in the present composite, respectively. Then the interfacial sliding stress and residual stress were quantitatively derived from the hysteresis analysis, and further used to predict matrix cracking stress and stress–strain behavior. Excellent agreement between predictions and experimental results was obtained.

Diffusion of colloidal fluids in random porous media

The diffusive relaxation of a colloidal fluid adsorbed in a porous medium depends on many factors, including the concentration and composition of the adsorbed colloidal fluid, the average structure of the porous matrix, and the nature of the colloid-colloid and colloid-substrate interactions. A simple manner to describe these effects is to model the porous medium as a set of spherical particles fixed in space at random positions with prescribed statistical structural properties. Within this model one may describe the relaxation of concentration fluctuations of the adsorbed fluid by simply setting to zero the short-time mobility of one species (the porous matrix) in a theory of the dynamics of equilibrium colloidal mixtures, or by extending such dynamic theory to explicitly consider the porous matrix as a random external field, as recently done in the framework of mode coupling theory [V. Krakoviack, Phys. Rev. Lett. 94, 065703 (2005)]. Here we consider the first approach and employ the self-consistent generalized Langevin equation (SCGLE) theory of the dynamics of equilibrium colloidal mixtures, to describe the dynamics of the mobile component. We focus on the short- and intermediate-time regimes, which we compare with Brownian dynamics simulations involving a binary mixture with screened Coulomb interactions for two models of the average static structure of the matrix: a porous matrix constructed by quenching configurations of an equilibrium mixture in which both species were first equilibrated together, and a preexisting matrix with prescribed average structure, in which we later add the mobile species. We conclude that in both cases, if the correct static structure factors are provided as input, the SCGLE theory correctly predicts the main features of the dynamics of the permeating fluid.

On the origins of the extracellular matrix in vertebrates

Extracellular matrix (ECM) is a key metazoan characteristic. In addition to providing structure and orientation to tissues, it is involved in many cellular processes such as adhesion, migration, proliferation and differentiation. Here we provide a comprehensive analysis of ECM molecules focussing on when vertebrate specific matrices evolved. We identify 60 ECM genes and 20 associated processing enzymes in the genome of the urochordate Ciona intestinalis. A comparison with vertebrate and protostome genomes has permitted the identification of both a core set of metazoan matrix genes and vertebrate-specific innovations in the ECM. We have identified a few potential cases of de novo vertebrate ECM gene innovation, but the majority of ECM genes have resulted from duplication of pre-existing genes present in the ancestral vertebrate. In conclusion, the modern complexity we see in vertebrate ECM has come about largely by duplication and modification of pre-existing matrix molecules. Extracellular matrix genes and their processing enzymes appear to be over-represented in the vertebrate genome suggesting that these genes played an active role enabling and underpinning the evolution of vertebrates.

A Three-phase Circular Inclusion With A SlidingInterface And A Radial Matrix Crack

The solution for the elastic three-phase circular inclusion problem plays a fundamental role in many practical and theoretical applications. In particular, it offers the fundamental solution for the generalized self-consistent method in the mechanics of composites materials. In this paper, a general method is presented for evaluating the interaction between a pre-existing matrix crack and a threephase circular inclusion. The bonding at the inclusion-interphase interface is considered to be the sliding imperfect interface. Physically, this is important for modelling certain features of material behaviour (such as grain-boundary sliding and damage occurring in the circumferential direction at constituent interfaces). On the remaining boundary, that being the interphase-matrix interface, the bonding is considered to be perfect. Using complex variable techniques, we derive series representations for the corresponding stress functions inside the inclusion, in the interphase layer and in the surrounding matrix. The governing boundary value problem is then formulated in such a way that these stress distributions simultaneously satisfy the traction free condition along the crack face, the sliding imperfect interface condition and the prescribed asymptotic loading conditions. Stress intensity factor (SIF) calculations are performed at the crack tips for different material property combinations, interface imperfections and crack positions. The results illustrate convincingly the role of an interphase layer as well as the effects of a sliding interface on crack behaviour.

Amoeboid shape change and contact guidance: T-lymphocyte crawling through fibrillar collagen is independent of matrix remodeling by MMPs and other proteases

AbstractThe passage of leukocytes through basement membranes involves proteolytic degradation of extracellular matrix (ECM) components executed by focalized proteolysis. We have investigated whether the migration of leukocytes through 3-dimensional collagenous tissue scaffolds requires similar ECM breakdown. Human T blasts and SupT1 lymphoma cells expressed mRNA of MMP-9, MT1-MMP, MT4-MMP, cathepsin L, uPA, and uPAR as well as ADAM-9, -10, -11, -15, and -17. Upon long-term migration within 3-dimensional collagen matrices, however, no in situ collagenolysis was obtained by sensitive fluorescein isothiocyanate–collagen fragmentation analysis and confocal fluorescence/backscatter microscopy. Consistent with nonproteolytic migration, T-cell crawling and path generation were not impaired by protease inhibitor cocktail targeting MMPs, serine proteases, cysteine proteases, and cathepsins. Dynamic imaging of cell-ECM interactions showed T-cell migration as an amoeba-like process driven by adaptive morphology, crawling along collagen fibrils (contact guidance) and squeezing through pre-existing matrix gaps by vigorous shape change. The concept of nonproteolytic amoeboid migration was confirmed for multicomponent collagen lattices containing hyaluronan and chondroitin sulfate and for other migrating leukocytes including CD8+ T blasts, monocyte-derived dendritic cells, and U937 monocytic cells. Together, amoeboid shape change and contact guidance provide constitutive protease-independent mechanisms for leukocyte trafficking through interstitial tissues that are insensitive toward pharmacologic protease inhibitors.

The effect of spatio-temporal contraction force on various hyperelastic ventricle models

In an abandoned pasture in Brittany, we compared artificial small-scale disturbances to natural disturbances by wild boar and undisturbed vegetation. We developed a multivariate statistical approach which analyses how species biological attributes explain the response of community composition to disturbances. This technique, which reconciles the inductive and deductive approaches for functional classifications, identifies groups of species with similar responses to disturbance and characterizes their biological profiles. After 5 months of recolonization, artificial disturbances had a greater species richness than undisturbed vegetation as a result of recruitment of new species without the exclusion of pre-existing matrix species. Species morphology, described by canopy structure, canopy height and lateral spread, explained a large part (16 %) of community response to disturbance. Regeneration strategies, described by life history, seed mass, dispersal agent, dormancy and the existence of vegetative multiplication, explained a smaller part of community response to disturbance (8 %). Artificial disturbances were characterized by therophyte and compact rosettes with moderately dormant seeds, including a number of Asteraceae and other early successional species. Natural disturbances were colonized by leafy guerrilla species without seed dormancy. Few species were tightly related to undisturbed vegetation and were essentially grasses with a phalanx rosette morphology. The functional classification obtained is consistent with the classification of the community into fugitives, regenerators and persistors. These groups are structured according to Grubb's model for temperate grasslands, with regenerators and persistors in the matrix and fugitives taking advantage of gaps open by small-scale disturbances. The conjunction of functional diversity and species diversity within functional groups is the key to resilience to disturbance, an important ecosystem function.