Towards causally cohesive genotype–phenotype modelling for characterization of the soft-tissue mechanics of the heart in normal and pathological geometries

A scientific understanding of individual variation is key to personalized medicine, integrating genotypic and phenotypic information via computational physiology. Genetic effects are often context-dependent, differing between genetic backgrounds or physiological states such as disease. Here, we analyse in silico genotype–phenotype maps (GP map) for a soft-tissue mechanics model of the passive inflation phase of the heartbeat, contrasting the effects of microstructural and other low-level parameters assumed to be genetically influenced, under normal, concentrically hypertrophic and eccentrically hypertrophic geometries. For a large number of parameter scenarios, representing mock genetic variation in low-level parameters, we computed phenotypes describing the deformation of the heart during inflation. The GP map was characterized by variance decompositions for each phenotype with respect to each parameter. As hypothesized, the concentric geometry allowed more low-level parameters to contribute to variation in shape phenotypes. In addition, the relative importance of overall stiffness and fibre stiffness differed between geometries. Otherwise, the GP map was largely similar for the different heart geometries, with little genetic interaction between the parameters included in this study. We argue that personalized medicine can benefit from a combination of causally cohesive genotype–phenotype modelling, and strategic phenotyping that captures effect modifiers not explicitly included in the mechanistic model.     

Effect of hyaluronic acid incorporation method on the stability and biological properties of polyurethane–hyaluronic acid biomaterials

The high failure rate of small diameter vascular grafts continues to drive the development of new materials and modification strategies that address this clinical problem, with biomolecule incorporation typically achieved via surface-based modification of various biomaterials. In this work, we examined whether the method of biomolecule incorporation (i.e., bulk versus surface modification) into a polyurethane (PU) polymer impacted biomaterial performance in the context of vascular applications. Specifically, hyaluronic acid (HA) was incorporated into a poly(ether urethane) via bulk copolymerization or covalent surface tethering, and the resulting PU–HA materials characterized with respect to both physical and biological properties. Modification of PU with HA by either surface or bulk methods yielded materials that, when tested under static conditions, possessed no significant differences in their ability to resist protein adsorption, platelet adhesion, and bacterial adhesion, while supporting endothelial cell culture. However, only bulk-modified PU–HA materials were able to fully retain these characteristics following material exposure to flow, demonstrating a superior ability to retain the incorporated HA and minimize enzymatic degradation, protein adsorption, platelet adhesion, and bacterial adhesion. Thus, despite bulk methods rarely being implemented in the context of biomolecule attachment, these results demonstrate improved performance of PU–HA upon bulk, rather than surface, incorporation of HA. Although explored only in the context of PU–HA, the findings revealed by these experiments have broader implications for the design and evaluation of vascular graft modification strategies.     

The method of fundamental solutions with dual reciprocity for diffusion and diffusion–convection using subdomains

The method of fundamental solutions (MFS), first proposed in the 1960s, has recently reappeared in the literature and solutions of an extraordinary accuracy have been reported using relatively few data points. The method requires no mesh and therefore no integration, and has been recently combined with dual reciprocity method (DRM) for treating inhomogeneous terms. The objective of this paper is the combination of the two methods for treating convective terms which are derivatives of the problem variable. First the formulation of the methods for mixed Neumann–Dirichlet boundary conditions is considered, as both these types of boundary condition are necessary for this type of problem. Next a formulation for the usual Crank–Nickleson and Galerkin time-stepping procedures is obtained for both diffusion and diffusion–convection and the use of the subdomain technique with MFS is considered. Finally results obtained for some test problems are presented including a diffusion convection problem with variable velocity using both a single domain and a division into subregions, the convective terms being modeled using DRM. Results are compared with exact solutions and in some cases with DRBEM examples from the literature.     

The synergic effects of Sc and Zr on the microstructure and mechanical properties of Al–Si–Mg alloy

In order to clarify the possibility of Zr substitution for Sc on the modification of Al-Si casting alloys, the microstructural evolution and tensile properties of Al-Si-Mg based alloys with different combinations of Sc and Zr contents (Sc + Zr = 0.5 wt.%) were systematically investigated. It was found that 0.5 wt.% Sc addition could refine the microstructure significantly and modify the eutectic Si from plate-like morphology to fiber, which promotes the spheroidization of eutectic Si during heat treatment. When Zr was added to partly replace Sc, the microstructure was first further refined, but was then slightly coarsened with increasing Zr content. Moreover, high Zr content was found to decrease its modification on eutectic Si. It was observed that Zr can also concomitantly improve strength and ductility compared with the alloy modified by Sc only. The improvement of mechanical properties was attributed to microstructural refinement, particularly the modification of eutectic Si and precipitation of secondary nano-scale Al₃(Sc_1 − xZr_x) dispersoids.     

Effect of MgO contents on the mechanical properties and biological performances of bioceramics in the MgO–CaO–SiO2 system

The aim of this research was to investigate the effect of the chemical composition on the mechanical properties, bioactivity, and cytocompatibility in vitro of bioceramics in the MgO–CaO–SiO₂ system. Three single-phase ceramics (merwinite, akermanite and monticellite ceramics) with different MgO contents were fabricated. The mechanical properties were tested by an electronic universal machine, while the bioactivity in vitro of the ceramics was detected by investigating the bone-like apatite-formation ability in simulated body fluid (SBF), and the cytocompatibility was evaluated through osteoblast proliferation and adhesion assay. The results showed that their mechanical properties were improved from merwinite to akermanite and monticellite ceramics with the increase of MgO contents, whereas the apatite-formation ability in SBF and cell proliferation decreased. Furthermore, osteoblasts could adhere, spread and proliferate on these ceramic wafers. Finally, the elongated appearance and minor filopodia of cells on merwinite ceramic were more obvious than the other two ceramics.     

The relationship between the electrical and mechanical properties of polymer–nanotube nanocomposites and their microstructure

A range of polymer–nanotube nanocomposites were produced using different processing routes. Both polymer-grafted and as-grown nanotubes were used and latex and polystyrene matrices investigated. The microstructures of the nanocomposites were studied, mainly by electron microscopy, in terms of the dispersion state of the nanotubes and the polymer–nanotube interface. The mechanical and electrical properties of the composites were also measured. The relationship between the microstructures observed and the resulting physical properties are discussed. It is found that composites with apparently similar microstructures can exhibit similar mechanical properties but very different electrical behaviours. Moreover, the nanocomposites produced using polymer-grafted nanotubes exhibit a clear improvement of the stress at large deformation. Thus, from our results, it appears that the mechanical and electrical properties do not necessarily depend on the same microstructural parameters. However it is still a challenge to simultaneously improve both physical properties.     

The microstructure and mechanical properties of Fe–Cu materials fabricated by pressure-less-shaping of nanocrystalline powders

The microstructure of Fe-40%_wtCu nanocrystalline powders, prepared by mechanical alloying, was studied before and after the consolidation process. Pressure-less-shaping (PS) was used to consolidate the powders. The PS technique, similar to metal injection moulding (MIM), does not require external pressure in order to fill up the mould. The key factor of the process of consolidation is the use as binder a hybrid inorganic–organic monomer, formed by the reaction of zirconium propoxide and 2-hydroxy ethyl methacrylate. This type of monomer, mixed with the metallic powders, formed slurry having low viscosity, which was easily poured into mould. The binder stiffened upon polymerization. Some pieces were produced through debinding and sintering, both performed under inert atmosphere in order to avoid metal oxidation. Different microstructure and density were observed depending on the maximum sintering temperatures, ranging from 904 to 1,120 °C. In the sample sintered at 1,120 °C, the crystalline domains of the copper phase were of about 40 nm.     

The Tl–I phase diagram revisited and the thermodynamic properties of thallium iodides

The Tl–I system has been studied using differential thermal analysis, X-ray diffraction, and emf measurements on TlI concentration cells. A more accurate Tl–I phase diagram is presented, according to which the compounds existing in the Tl–I system are TlI, Tl₂I₃, and TlI₃. Thallium monoiodide melts congruently at 715 K and undergoes a polymorphic transformation at 440 K. The other iodides melt peritectically at 535 and 404 K, respectively. In contrast to what was reported previously, no compound of composition Tl₃I₄ has been obtained. Using experimental emf data, we evaluated relative partial molar thermodynamic functions of the TlI in alloys of the TlI–I system and the standard Gibbs free energy, enthalpy of formation, and standard entropies of TlI₃ (?ΔG ₂₉₈ ⁰ = 142.79 ± 0.73 kJ/mol, ?ΔH ₂₉₈ ⁰ = 135.37 ± 2.85 kJ/mol, and S ₂₉₈ ⁰ = 263.3 ± 7.4 J/(mol K)) and Tl₂I₃ (271.39 ± 1.47, 262.40 ± 5.34, and 322.8 ± 13.2).     

The effect of Ta on structure and magnetic properties in Fe–N films

Microstructure and magnetic properties of Fe–Ta–N alloy films near the eutatic composition were studied. The four systematic alloy films with different Ta content were prepared by reactive sputtering. The dependence of structures and magnetic properties on Ta and annealing were investigated by VSM and X-ray diffraction. It is found that Ta atoms replace Fe in α-Fe lattice and have strong affinity for nitrogen, which inhibits the formation of γ-Fe₄N phase in Fe–Ta–N films. The TaN phase precipitates in grain boundaries and suppresses the growth of α-Fe(N) crystalline during annealing. Coercivity varies with the change of microstructure.     

The effect of aging process on the microstructure and mechanical properties of a Cu–Be–Co–Ni alloy

The paper investigated the effect of two aging processes (i.e. normal aging and interrupted aging) on the microstructure and mechanical properties of a Cu–Be–Co–Ni alloy. The results of tensile and Kahn tear tests showed that the interrupted aging (IA) process could significantly improve the uniform elongation and plane stress fracture toughness with tiny decrease in ultimate tensile strength, when compared with the results from normal aging (NA) process. Under the scanning electron microscope, the fracture surface of samples treated by NA followed the intergranular fracture, while that of the samples treated by IA followed the transgranular fracture. The transmission electron microscope study revealed the differences between the microstructure of the alloy treated by NA and IA processes. After the NA process, the slender strip of γ′ precipitates aggregated at grain boundaries with a length of approximately 10 to 45 nm; the disk-shaped γ″ precipitates in the alloy treated by IA distributed homogenously throughout whole grains with a length of about 3 to 10 nm. The discussion of strengthening mechanisms demonstrated that the mechanism of precipitate shearing by dislocations made a contribution to the strengthening of the alloy treated by IA, while the Orowan mechanism was the dominant strengthening mechanism in the alloy treated by NA.     

The microstructure and mechanical properties of as-cast Mg–4Y/Nd–2Zn alloys

Optical microscopy, scanning electron microscopy, X-ray diffraction and tensile testing were performed to investigate the microstructure and mechanical properties of as-cast Mg–4Y/Nd–2Zn alloys. The results show that the secondary dendritic arm spacing for the Mg–4Y–2Zn alloy is smaller than that for the Mg–4Nd–2Zn alloy, and that X-Mg₁₂YZn or W-Mg₃Zn₃Nd₂ form in Mg–4Y/Nd–2Zn alloys. The lamellar X phase distributes at the grain boundary, pointing into the grains, whereas the rod-like W phase preferentially segregates at the triangle junction of the grain boundary. The greater grain boundary strengthening effect and the smaller fragmentation effect of the brittle eutectic phases leads to the as-cast Mg–4Y–2Zn alloy having better comprehensive mechanical properties. The fracture mechanism for as-cast Mg–4Y/Nd–2Zn alloys is quasi-cleavage fracture.     

The preparation and properties of CeO2–TiO2 film by sol–gel spin-coating process

Ultraviolet absorbing CeO₂–TiO₂ coatings were prepared by the sol–gel spin-coating process heat treated at 500 °C. The films obtained were brilliant yellow, adherent and had some pattern on the soda-lime glass substrate. The optical transmittance, thickness and hardness of the films as a function of the number of coatings, aging time (0, 24, 48, 96 h) or aging temperature (28, 35, 40, 50 °C) were determined, and surface microstructure of the films was observed by SEM. We found some pattern on the surface of films. This pattern was similar to that of the stage for fixing the substrate. The pattern on the surface of films would be caused by the difference of thermal conductivity to slide glass in the part of metal of the stage and hollow part of the stage.     

The influence of multiscale fillers on the rheological and mechanical properties of carbon-nanotube–silica-reinforced epoxy composite

Multiscale fillers were fabricated through synthesis of carbon nanotubes (CNTs) on silica microparticles by the use of chemical vapor deposition. Three types of catalyst precursors with different concentrations and reaction times were investigated to find the optimal conditions for CNT synthesis. The produced multiscale fillers of CNT–silica were incorporated within epoxy resin to fabricate a multiscale composite. Rheological analysis and tensile and impact tests were performed to study the effect of fillers on the structural properties of composites. The rheological results demonstrated a similar viscous behavior between CNT–silica suspensions and epoxy, which implies that there was no critical increase of viscosity. Significant improvements in the elastic modulus and tensile and impact strength were achieved for epoxy matrix filled with the optimal fraction of multiscale fillers. The reinforcing efficiency of multiscale fillers was evaluated by comparing the results of micromechanical models with experimental data.     

The effect of Si and microstructure evolution on the thermal expansion properties of Fe–42Ni–Si alloy strips

An alloying element of 0–1.5 wt.% Si was added to an Fe–42%Ni system, and alloy strips were fabricated using a melt drag casting process. The effects of the Si and annealing treatments on the thermal expansion properties of Fe–42Ni alloy were investigated. The addition of Si enlarged the coexisting temperature region of the solid–liquid phase and reduced the melting point, which improved the formability of the alloy strip. An alloy containing 0.6 wt.% Si had a lower thermal expansion coefficient than any other alloy in the temperature range from 20 to 350 °C. The grain size increased with the rolling reduction ratio and annealing temperature, which caused an increase in magnetostriction and consequently a decrease in the thermal expansion coefficient of the strip. The alloy strip containing 1.5 wt.% Si had a higher thermal expansion coefficient than the alloy containing 0.6 wt.% Si because of grain refining caused by the precipitation of Ni₃Fe.     

The influences of rare earth content on the microstructure and mechanical properties of Mg–7Zn–5Al alloy

The influences of rare earth (RE) on the microstructure and mechanical properties of Mg–7Zn–5Al alloy were studied. The results indicate that both the dendrite and grain size of the alloy can be refined by low RE addition. The Al₂REZn₂ phase will be formed with increasing the RE content, however the high RE addition results in the grain coarsening in the alloy due to the decrease of the contribution of Al and Zn solutes on the grain refinement. The strengthening and weakening mechanisms caused by RE addition only lead to the obviously improve on the room temperature ultimate tensile strength. The mechanical properties of the studied alloys can be improved by aging treatment, and the aged Mg–7Zn–5Al–2RE alloy exhibits optimal mechanical properties at room temperature.     

The influence of pH and bath composition on the properties of Ni–Co coatings synthesized by electrodeposition

Ni–Co coatings were produced on Cu substrates by electrodeposition from electrolytes with different pH values and different Co²⁺ concentration. The current efficiency increases from 52.1% to 81.2% with the pH increasing from 2.0 to 5.4. It is clearly observed that the content of cobalt in the deposited coatings gradually increases from 9.4% to 19.6% as the pH value varies from 2.0 to 5.4. The Co content in the deposited coatings increases from 16.5% to 72.7% as the molar ratio of CoSO₄/NiSO₄ varying from 1:5 to 1:2 in electrolyte. XRD patterns reveal that the structure of the coatings strongly depends on the Co content in the binary coatings. Both granular and dendritic crystals were investigated by SEM and the different crystallization behaviors were illustrated. The saturation magnetization of the coatings goes up from 96.36 kAm⁻¹ to 136.08 kAm⁻¹ with the pH value increasing from 2.0 to 5.4. The saturation magnetization (M_s) and coercivity (H_c) move up from 144.84 kAm⁻¹ and 15.27 kAm⁻¹ to 175.13 kAm⁻¹ and 125.20 kAm⁻¹ with the increase of Co in the electrolyte, respectively.     

The growth and properties of (Sbx Bi1–x)2Te3 crystals

Abstract

Vertical Bridgman systems with programmable temperature control are used to grow (Sb_xBi_1:x)₂Te₃ crystals. High purity Bi, Sb and Te are used as sources and the diameter of 1.1 cm, little soft bulk crystals of (Sb_xBi_1–x)₂ Te₃ can be obtained. Scanning electron microscope (SEM) and electron probe microanalysis (EPMA) are used to analyze the micro‐structure and the compositions of the crystal. From the X‐ray diffraction patterns it appears that the grown crystal is single crystal or directive polycrystal. If the uniformity of the source solution and grown temperature are under control, then the high quality of single crystals can be obtained. The dependence of crystal structure and the thermoelectric characteristics on the changed compositions of grown crystals are discussed. The optimum composition for the thermoelectric properties is Sb_1.00 Bi_1.04Te_2.96. When the DC current, 3A, is applied to the Sb_1.00 Bi_1.04 Te_2.96 crystal with suitable electrodes, the temperature difference (△T) between two sides of the crystal can be as high as 60°C. It is 2 times larger than that ever obtained by Sb₂Te₃ crystal. It appeared that the grown (Sb_xBi_1‐x)₂Te₃ crystals have the potential on the fabrication of thermoelectric devices and electronic cooling system.     

The crystallization behavior and thermal expansion properties of β-eucryptite prepared by sol–gel route

Lithium–aluminosilicate glass–ceramics in the form of eucryptite were synthesized through sol–gel technique by mixing boehmite sol, silica sol and lithium salt and sintering at different temperatures for further analysis. Thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), IR analysis and dilatometry were done to study sintering characteristics, phase transformation and thermal expansion behavior on the sintered specimens. XRD and FTIR results confirmed that crystallization of β-eucryptite took place at about 600 °C, substantial increase of β-eucryptite was observed in the specimens sintered at temperatures from 800 to 1300 °C. Trace amount of cristobalite also emerged at 600 °C and disappeared at 1300 °C. The thermal expansion behavior characteristics were found to be strongly influenced by crystalline phases in the specimens which depended on the sintering temperatures.     

The effects of cell spacing and distribution of intermetallic fibers on the mechanical properties of hypoeutectic Al–Fe alloys

The aim of the present investigation was to contribute to provide a basis for understanding how to control solidification parameters, microstructure and mechanical strength of Al–Fe alloys. Upward directional solidification experiments have been carried-out with commercially pure Al and Al–0.5 wt.% Fe, Al–1.0 wt.% Fe and Al–1.5 wt.% Fe alloys. The tensile tests results have been correlated to cell spacing (λ₁), since cellular growth has prevailed along all obtained Al–Fe castings. The used casting assembly was designed in such way that the heat was extracted only through the water-cooled system at the bottom of the casting. In order to investigate the nature of Al–Fe intermetallic fibers, they were extracted from the aluminum-rich matrix by using a dissolution technique. These fibers were then investigated by SEM-EDAX microscopy. It was found that the ultimate tensile strength, yield tensile strength and elongation increase with decreasing cell spacing. The highest ultimate tensile strength was that obtained for the most refined microstructure, i.e. for the Al–1.5 wt.% Fe alloy sample, where a higher density of eutectic fibers was found distributed in a more homogeneous way along the casting section due to lower cell spacings. In contrast, the elongation was found to decrease with increasing solute content.     

The microstructure and mechanical properties of friction stir welded Al–Zn–Mg alloy in as welded and heat treated conditions

High strength aluminium alloys generally present low weldability because of the poor solidification microstructure, porosity in the fusion zone and loss in mechanical properties when welded by fusion welding processes which otherwise can be welded successfully by comparatively newly developed process called friction stir welding (FSW). This paper presents the effect of post weld heat treatment (T₆) on the microstructure and mechanical properties of friction stir welded 7039 aluminium alloy. It was observed that the thermo-mechanically affected zone (TMAZ) showed coarser grains than that of nugget zone but lower than that of heat affected zone (HAZ). The decrease in yield strength of welds is more serious than decrease in ultimate tensile strength. As welded joint has highest joint efficiency (92.1%). Post weld heat treatment lowers yield strength, ultimate tensile strength but improves percentage elongation.