Matrix Sandwich Research Articles

Microstructure, mechanical, and cutting performance properties of B4C and SiC reinforced sandwich composite segments

This study aims to extend the work-life of diamond-cutting segments and to economize the operating cost of diamond-cutting tools. In order to achieve this object, bronze matrix sandwich segments reinforced with SiC and B4C were produced utilizing the hot pressing technique. In the term of the cutting segments, it is favorable that the outer layers are wear-resistant and the middle layer is tough. SEM and XRD analysis were used to determine the microstructural properties. Mechanical properties were evaluated by conducting hardness, wear, cutting performance, and three-point bending tests. The cutting performance of the segments was determined by turning andesite marble. SEM examinations showed that SiC and B4C grains were homogeneously distributed in the bronze matrix. The highest hardness value was 113.9 HB in the B4C reinforced sandwich segment. The reciprocating wear test findings indicated that the matrix exhibited the lowest wear rate in the B4C reinforced sandwich composite segment, followed by the hybrid sandwich composite segment. The lowest amount of cutting loss after turning andesite stone was achieved in the SiC, and B4C reinforced hybrid sandwich composite segment. The cutting performance of the hybrid sandwich composite segment increased by 46.15 % compared to the conventional segment without additives. The highest value of the transverse rupture strength of the specimens was 380 MPa for the B4C reinforced sandwich composite segment and 352 MPa for the hybrid sandwich composite segment. Considering all the tests and analyses, the hybrid sandwich composite segment sample may be the most suitable for diamond-cutting tools.

Porcine dermal matrix sandwich graft for lower eyelid reconstruction

ABSTRACT Purpose: To report the clinical outcomes of porcine acellular dermal matrix implants sandwiched between skin and conjunctival flaps for lower eyelid reconstruction following Mohs surgery. Methods: A retrospective review was performed on patients with lower eyelid defects following Mohs surgery treated using a porcine acellular dermal matrix sandwich graft from 2013 to 2018. Patient demographics, defect size and characteristics, and collagen matrix implant dimensions were evaluated. Postoperative course and complications were also reviewed. Results: The dermal matrix sandwich graft was performed in 13 cases (12 patients). Average horizontal marginal defect width was 11.7 mm (range: 6–16 mm). Mean width of the implanted dermal matrix was 7.7 mm (range: 5–9 mm). There were no instances of infection or graft failure. The reconstructed lid had an excellent marginal contour in 11 cases (84.6%), while 2 had minimal irregularities. All patients had an excellent thickness of the reconstructed margin. One patient (7.7%) required cauterization of overgrown marginal conjunctiva after surgery. Two patients (15.4%) experienced symptomatic trichiasis, requiring electrolysis (n = 1) and epilation (n = 1). Conclusions: The dermal matrix sandwich graft is an effective method for marginal defect repair when the remaining conjunctiva and skin are sufficient to develop the necessary flaps. While the resolution of edema and erythema may take several months, an excellent final result is achieved in the majority of cases. Complications are mild, relatively uncommon, and similar to those encountered in other reconstructive procedures. This single-stage, tissue-sparing technique preserves the capability of performing future tarsoconjunctival flaps or lateral canthal procedures, should the need arise.

Effect of Curing Agent on the Plateau Burning Mechanism of Solid Propellant Sandwiches

This study focuses on further understanding of the plateau burning mechanism of sandwiches containing a matrix of fine ammonium perchlorate (AP) particles and low/high-melt binder as affected by the type of the curing agent. Pure binder sandwiches and matrix sandwiches of various fine AP/binder ratios with two different curatives, isophorone diisocyanate (IPDI) and toluene diisocyanate (TDI), are considered. The burning rate versus middle lamina thickness curves are obtained to examine the interaction between the leading-edge flames (LEFs) anchored over the lamina interface edges. Pressure variation on matrix sandwich burning rates is considered in 1–12 MPa range. High-magnification combustion images and quenched surface features and profiles of these sandwiches are also examined. The IPDI-cured binder causes larger LEF standoff and inter-LEF distances in both pure binder and matrix sandwiches than the TDI-cured one. Consequently, the disparity in the burning rates with middle lamina thickness of IPDI-cured matrix sandwiches is minimal. The binder melt-layer thickness and its melt viscosity determine the flammability limits and midpressure extinction regimes of matrices depending upon the curative. Plateau burning trends of matrix sandwiches with large middle lamina thickness (greater than ) are observed to coincide with midpressure extinction of their corresponding matrices.

Steps toward Maturation of Embryonic Stem Cell-Derived Cardiomyocytes by Defined Physical Signals.

SummaryCardiovascular disease remains a leading cause of mortality and morbidity worldwide. Embryonic stem cell-derived cardiomyocytes (ESC-CMs) may offer significant advances in creating in vitro cardiac tissues for disease modeling, drug testing, and elucidating developmental processes; however, the induction of ESCs to a more adult-like CM phenotype remains challenging. In this study, we developed a bioreactor system to employ pulsatile flow (1.48 mL/min), cyclic strain (5%), and extended culture time to improve the maturation of murine and human ESC-CMs. Dynamically-cultured ESC-CMs showed an increased expression of cardiac-associated proteins and genes, cardiac ion channel genes, as well as increased SERCA activity and a Raman fingerprint with the presence of maturation-associated peaks similar to primary CMs. We present a bioreactor platform that can serve as a foundation for the development of human-based cardiac in vitro models to verify drug candidates, and facilitates the study of cardiovascular development and disease.

Data characterizing flexural properties of Al/Al2O3 syntactic foam core metal matrix sandwich.

Microstructural observations and flexural property datasets are provided for aluminum alloy matrix syntactic foam core sandwich composites. The tests are conducted in three-point bending configuration. The data supplied includes methods used for conducting microscopy and mechanical testing. Raw load–displacement data, which is used to plot stress–strain graphs, obtained during the flexural test is also included. Images from a DSLR camera are stitched together to form a detailed failure sequencing video. Failure of specimens is captured in sequential images using a digital camera. These images are stitched together to develop a video for visualization of failure mechanisms. Calculations are also included for a theoretical model that is used to estimate the flexural properties of the syntactic foam core sandwich.

Data characterizing compressive properties of Al/Al2O3 syntactic foam core metal matrix sandwich.

Microstructural observations and compressive property datasets of metal matrix syntactic foam core sandwich composite at quasi-static and high strain rate (HSR) conditions (525–845 s−1) are provided. The data supplied in this article includes sample preparation procedure prior to scanning electron and optical microscopy as well as the micrographs. The data used to construct the stress–strain curves and the derived compressive properties of all specimens in both quasi-static and HSR regions are included. Videos of quasi-static compressive failure and that obtained by a high speed image acquisition system during deformation and failure of HSR specimen are also included.

Toward Personalized Medicine: Using Cardiomyocytes Differentiated From Urine-Derived Pluripotent Stem Cells to Recapitulate Electrophysiological Characteristics of Type 2 Long QT Syndrome.

BackgroundHuman genetically inherited cardiac diseases have been studied mainly in heterologous systems or animal models, independent of patients’ genetic backgrounds. Because sources of human cardiomyocytes (CMs) are extremely limited, the use of urine samples to generate induced pluripotent stem cell–derived CMs would be a noninvasive method to identify cardiac dysfunctions that lead to pathologies within patients’ specific genetic backgrounds. The objective was to validate the use of CMs differentiated from urine-derived human induced pluripotent stem (UhiPS) cells as a new cellular model for studying patients’ specific arrhythmia mechanisms.Methods and ResultsCells obtained from urine samples of a patient with long QT syndrome who harbored the HERG A561P gene mutation and his asymptomatic noncarrier mother were reprogrammed using the episomal-based method. UhiPS cells were then differentiated into CMs using the matrix sandwich method.UhiPS-CMs showed proper expression of atrial and ventricular myofilament proteins and ion channels. They were electrically functional, with nodal-, atrial- and ventricular-like action potentials recorded using high-throughput optical and patch-clamp techniques. Comparison of HERG expression from the patient’s UhiPS-CMs to the mother’s UhiPS-CMs showed that the mutation led to a trafficking defect that resulted in reduced delayed rectifier K+ current (IKr). This phenotype gave rise to action potential prolongation and arrhythmias.ConclusionsUhiPS cells from patients carrying ion channel mutations can be used as novel tools to differentiate functional CMs that recapitulate cardiac arrhythmia phenotypes.

Syntactic foam core metal matrix sandwich composite under bending conditions

The present work aims at characterizing a metal matrix syntactic foam core sandwich composite under three-point bending conditions. The sandwich comprises alumina hollow particle reinforced A356 alloy syntactic foam with carbon fabric skins. Crack initiation in the tensile side of the specimen causing failure of the skin, followed by rapid failure of the core in the direction applied load, is observed as the failure mechanism. Crack propagation through the alumina particles is observed in the failed specimens instead of interfacial failure. The average maximum strength, flexural strain and stiffness were measured as 91.2 ± 5.6 MPa, 0.49 ± 0.06% and 20.6 ± 0.7 GPa respectively. The collapse load is theoretically predicted using mechanics of sandwich beams. Experimental values show good agreement with theoretical predictions. • Flexural properties of A356 matrix syntactic foam core sandwich are studied. • Alumina hollow particle filled syntactic foam is combined with carbon fabric skins. • Flexural strength of 91.2 MPa and flexural stiffness of 20.6 GPA are measured. • Failure mode is included as tensile skin fracture and crack propagation in the core. • Cracks pass through the particles instead of crack tip blunting or bowing.

Syntactic foam core metal matrix sandwich composite: Compressive properties and strain rate effects

The present work is the first attempt to study metal matrix syntactic foam core sandwich composites. The sandwich is studied for microstructure and compressive properties at quasi-static and high strain rates. Under quasi-static compressive conditions, specimens were tested in the flatwise and edgewise orientations. The compressive strength, yield strength and plateau stress were higher in the flatwise orientation. Furthermore, both orientations for the sandwich composites showed a higher specific compressive strength and specific yield strength than the foam core alone. Failure initiated in the particles in the flatwise orientation, but in the carbon fabrics in the edgewise orientation. The results show that the fabric had a reinforcing effect under quasi-static conditions. The high strain rate (HSR) characterization was conducted in the strain rate range 525–845s−1 using a split-Hopkinson pressure bar set-up equipped with a high speed image acquisition system. Within this strain rate range, the compressive strength of the sandwich is similar to that of the syntactic foam core alone. Upon review, the syntactic foam core metal matrix sandwich outperforms most of the syntactic foams in terms of energy absorption and compressive strength at comparable density levels.

0134 : Using cardiomyocytes differentiated from urine-derived hiPSCs to recapitulate electrophysiological characteristics of LQT2 syndrome

Human genetically inherited cardiac diseases have mainly been studied in heterologous systems or animal models, independently of the patients’ genetic background. Because sources for human cardiomyocytes are extremely limited, the use of urine samples to derive cardiomyocytes would be a non-invasive method to identify cardiac dysfunctions that lead to pathologies within the patients’ specific genetic background. Cardiomyocytes differentiated from urine-derived pluripotent stem cells (UhiPS-CMs) were obtained from a patient with long QT syndrome and a mutation in hERG KCNH2 gene (p. A561P), and were characterized. Cells obtained from urine samples from the A561P patient and his asymptomatic mother carrying no hERG mutation were reprogrammed using the episomal-based method. UhiPS cells were then differentiated into cardiomyocytes using a modified matrix sandwich method. UhiPS-CMs showed proper expression of ventricular cytoskeletal proteins and ion channels. They were electrically functional, with nodal-, atrial- and ventricular-like action potentials (APs) recorded using both high-throughput CellOptiq and patch-clamp techniques. Application of ajmaline, 4-aminopyridine, nifedipine, chromanol 293B or E-4031 to the UhiPS-CMs confirmed that I Na , I to , I Ca , I Ks and I Kr currents, respectively, contributed to the APs. Comparing hERG expression from the patient's UhiPS-CMs to the mother's UhiPS-CMs showed that the mutation led to a trafficking defect that resulted in a reduced I Kr current. This phenotype led to APs prolongation that sometimes resulted in arrhythmias (early afterdepolarizations). Urine-derived pluripotent stem cells from patients carrying ion channels mutations can be used as novel models to differentiate functional cardiomyocytes that recapitulate cardiac arrhythmia phenotypes.

Abstract 15972: Fibronectin is Essential for Mesendoderm Induction During Cardiac Differentiation of Human Pluripotent Stem Cells

Extracellular matrix (ECM) plays important roles in development, and we have previously demonstrated a matrix sandwich protocol for efficient cardiac differentiation of human pluripotent stem cells (hPSCs). The purpose of the present study was to identify the key ECM proteins required to initiate cardiogenic differentiation of hPSCs and define their mechanism of action. We tested purified ECM proteins including human laminin (LN111, LN521), fibronectin (FN) and collagen IV in the matrix sandwich protocol, and found FN promoted efficient cardiac differentiation. To determine if FN is essential for the early stages of cardiogenesis we tested three FN blockers: FUD peptide that binds the N-terminal 70-kDa fragment of FN, anti-human FN antibody clone10 which recognizes FN domain III2, and anti-human FN antibody clone 3E3 that binds on the cell attachment domain. All three blockers showed concentration-dependent inhibition of cardiac differentiation of hPSCs when added at day 0 for 24 hours, measured by flow cytometry for cTnT+ cells in the Matrigel/Matrigel (bottom/overlay) and FN/FN sandwich culture as well as in the small molecule GiWi protocol. Furthermore, clone10 showed significant inhibition of cardiac differentiation even in the absence of adding exogenous FN due to the robust endogenous expression of FN by the hPSCs. Gene expression analysis with qRT-PCR demonstrated that blocking FN by clone10 caused a significant suppression of gene expression related to: 1) epithelial to mesenchymal transition, e.g. SNAIL1, SNAIL2, GSC, VIM, CDH2 and FN1; 2) Mesendoderm e.g. T, MIXL1, SOX17 and precardiac mesoderm of MESP1; 3) Cardiac transcription factors ISL1 and NKX2.5. To investigate the cellular signaling activated by FN, we tested a blocking antibody (clone P5D2) to the major FN receptor, integrin β1, and found that P5D2 produced a concentration-dependent inhibition of cardiogenesis in multiple hPSC lines. Furthermore, the integrin-linked kinase (ILK) inhibitor, Cpd22, inhibited cardiac differentiation in a concentration-dependent fashion as well when added on day 0. We conclude that FN, acting via integrin β1-activated ILK signaling, is essential to mesendoderm formation enabling cardiogenesis of hPSCs.

A new human 3D-liver model unravels the role of galectins in liver infection by the parasite Entamoeba histolytica.

Investigations of human parasitic diseases depend on the availability of appropriate in vivo animal models and ex vivo experimental systems, and are particularly difficult for pathogens whose exclusive natural hosts are humans, such as Entamoeba histolytica, the protozoan parasite responsible for amoebiasis. This common infectious human disease affects the intestine and liver. In the liver sinusoids E. histolytica crosses the endothelium and penetrates into the parenchyma, with the concomitant initiation of inflammatory foci and subsequent abscess formation. Studying factors responsible for human liver infection is hampered by the complexity of the hepatic environment and by the restrictions inherent to the use of human samples. Therefore, we built a human 3D-liver in vitro model composed of cultured liver sinusoidal endothelial cells and hepatocytes in a 3D collagen-I matrix sandwich. We determined the presence of important hepatic markers and demonstrated that the cell layers function as a biological barrier. E. histolytica invasion was assessed using wild-type strains and amoebae with altered virulence or different adhesive properties. We showed for the first time the dependence of endothelium crossing upon amoebic Gal/GalNAc lectin. The 3D-liver model enabled the molecular analysis of human cell responses, suggesting for the first time a crucial role of human galectins in parasite adhesion to the endothelial cells, which was confirmed by siRNA knockdown of galectin-1. Levels of several pro-inflammatory cytokines, including galectin-1 and -3, were highly increased upon contact of E. histolytica with the 3D-liver model. The presence of galectin-1 and -3 in the extracellular medium stimulated pro-inflammatory cytokine release, suggesting a further role for human galectins in the onset of the hepatic inflammatory response. These new findings are relevant for a better understanding of human liver infection by E. histolytica.

Design and Analysis of Small-Scale Lift-Type Vertical-Axis Wind Turbine Using Composite Blade

This paper focuses on verifying the feasibility of applying fibre reinforced polymer matrix composite to vertical axis wind turbine. A small-scale lift-type vertical axis wind turbine using glass fibre reinforced epoxy matrix sandwich composite blade was proposed. An airfoil profile of blade was designed and a composite blade was fabricated. The structure parameters of the blade were optimized by means of the finite element modeling method. The mechanical and the resonant properties of the blade were investigated. Finally, a wind turbine with the designed blade was assembled, and its generating capacity was tested. It was demonstrated that the designed composite blade and the wind turbine had excellent performance, indicating a promising technology for utilizing wind power.

Proteome-Wide Analyses of Human Hepatocytes During Differentiation and Dedifferentiation

Failure to predict hepatotoxic drugs in preclinical testing makes it imperative to develop better liver models with a stable phenotype in culture. Stem cell-derived models offer promise, with differentiated hepatocyte-like cells currently considered to be “fetal-like” in their maturity. However, this judgment is based on limited biomarkers or transcripts and lacks the required proteomic datasets that directly compare fetal and adult hepatocytes. Here, we quantitatively compare the proteomes of human fetal liver, adult hepatocytes, and the HepG2 cell line. In addition, we investigate the proteome changes in human fetal and adult hepatocytes when cultured in a new air-liquid interface format compared to conventional submerged extracellular matrix sandwich culture. From albumin and urea secretion, and luciferase-based cytochrome P450 activity, adult hepatocytes were viable in either culture model over 2 weeks. The function of fetal cells was better maintained in the air-liquid interface system. Strikingly, the proteome was qualitatively similar across all samples but hierarchical clustering showed that each sample type had a distinct quantitative profile. HepG2 cells more closely resembled fetal than adult hepatocytes. Furthermore, clustering showed that primary adult hepatocytes cultured at the air-liquid interface retained a proteome that more closely mimicked their fresh counterparts than conventional culture, which acquired myofibroblast features. Principal component analysis extended these findings and identified a simple set of proteins, including cytochrome P450 2A6, glutathione S transferase P, and alcohol dehydrogenases as specialized indicators of hepatocyte differentiation. Conclusion: Our quantitative datasets are the first that directly compare multiple human liver cells, define a model for enhanced maintenance of the hepatocyte proteome in culture, and provide a new protein “toolkit” for determining human hepatocyte maturity in cultured cells. (Hepatology 2013;58:799–809)

Extracellular Matrix Promotes Highly Efficient Cardiac Differentiation of Human Pluripotent Stem Cells

Rationale: Cardiomyocytes (CMs) differentiated from human pluripotent stem cells (PSCs) are increasingly being used for cardiovascular research, including disease modeling, and hold promise for clinical applications. Current cardiac differentiation protocols exhibit variable success across different PSC lines and are primarily based on the application of growth factors. However, extracellular matrix is also fundamentally involved in cardiac development from the earliest morphogenetic events, such as gastrulation. Objective: We sought to develop a more effective protocol for cardiac differentiation of human PSCs by using extracellular matrix in combination with growth factors known to promote cardiogenesis. Methods and Results: PSCs were cultured as monolayers on Matrigel, an extracellular matrix preparation, and subsequently overlayed with Matrigel. The matrix sandwich promoted an epithelial-to-mesenchymal transition as in gastrulation with the generation of N-cadherin-positive mesenchymal cells. Combining the matrix sandwich with sequential application of growth factors (Activin A, bone morphogenetic protein 4, and basic fibroblast growth factor) generated CMs with high purity (up to 98%) and yield (up to 11 CMs/input PSC) from multiple PSC lines. The resulting CMs progressively matured over 30 days in culture based on myofilament expression pattern and mitotic activity. Action potentials typical of embryonic nodal, atrial, and ventricular CMs were observed, and monolayers of electrically coupled CMs modeled cardiac tissue and basic arrhythmia mechanisms. Conclusions: Dynamic extracellular matrix application promoted epithelial–mesenchymal transition of human PSCs and complemented growth factor signaling to enable robust cardiac differentiation.

Amniotic mesenchymal tissue cells inhibit tumor cell line proliferation

Amniotic mesenchymal tissue cells inhibit tumor cell line proliferation

Mapping ancestral genomes with massive gene loss: a matrix sandwich problem.

Motivation: Ancestral genomes provide a better way to understand the structural evolution of genomes than the simple comparison of extant genomes. Most ancestral genome reconstruction methods rely on universal markers, that is, homologous families of DNA segments present in exactly one exemplar in every considered species. Complex histories of genes or other markers, undergoing duplications and losses, are rarely taken into account. It follows that some ancestors are inaccessible by these methods, such as the proto–monocotyledon whose evolution involved massive gene loss following a whole genome duplication.Results: We propose a mapping approach based on the combinatorial notion of ‘sandwich consecutive ones matrix’, which explicitly takes gene losses into account. We introduce combinatorial optimization problems related to this concept, and propose a heuristic solver and a lower bound on the optimal solution. We use these results to propose a configuration for the proto-chromosomes of the monocot ancestor, and study the accuracy of this configuration. We also use our method to reconstruct the ancestral boreoeutherian genomes, which illustrates that the framework we propose is not specific to plant paleogenomics but is adapted to reconstruct any ancestral genome from extant genomes with heterogeneous marker content.Availability: Upon request to the authors.Contact: haris.gavranovic@gmail.com; eric.tannier@inria.fr

Thermo-mechanical damage modeling of polymer matrix sandwich composites in fire

The objective of this research is to develop a modeling and simulation approach for predicting the thermo-mechanical damage of composite materials subjected to fire environments. A 3D thermal damage model is developed for glass-reinforced polymer composite materials subject to high temperature and radiative environments. Homogenization methods are used to formulate the damaged material in terms of fiber, resin and char. The thermal damage model is implemented in Abaqus via an overlaid element approach. The solution of the mechanical response uses the existing functions in Abaqus for large-displacement analysis. Composite sandwich panels with balsa core are examined. Reasonable agreement in temperature is obtained between predictions and available experimental data. For the sandwich panels, delamination failure is predicted at the sandwich interface – consistent with the experiments. Comparisons of time-to-failure of the sandwich panel show the predictions are reasonable.

Quantitative NDE of cellular metallic materials and structures by using eddy current testing technique

The feasibility of Eddy Current Testing (ECT) for the nondestructive evaluation of cellular metallic materials is investigated. The inspection target is focused on the welding joints connecting the surface and inner layers of a typical cellular material - metallic sandwich plate. Through numerical simulations, it is found that the defects in the welding zone cause ECT signals of significant different phase property with those caused by welding bead. The multi-frequency signal processing algorithm (MFA) is used to process the signals in order to improve the S/N ratio, which enables the recognition of crack indication from the mixed signals of welding joint. In addition, through profile reconstruction of a crack in the welding zone by means of a deterministic inverse analysis and MFA, it is demonstrated that ECT is a suitable quantitative NDE technique for the matrix sandwich material.

371 Transplantation into gunn rats of rat hepatocyte-homologous acellular matrix (HAM) sandwich

371 Transplantation into gunn rats of rat hepatocyte-homologous acellular matrix (HAM) sandwich