Methods of forming magnetically actuable tubular scaffolds for use in engineering smooth muscle tissues such as those of the intestines, blood vessels, and urethra are described. The scaffolds are ...fabricated from sheets of electrospun fibrils of biocompatible and biodegradable polymers containing spatially uniform dispersions of nanoscale magnetic Fe2O3 particles. The sheets are wound into tubes, which are designed to contain a uniform seeding of cells from inner to outer layer in the wound structure, as reported elsewhere. The tubes undergo a crimping deformation when exposed to a magnetic field, similar to the deformation of peristalsis. The deformation creates both strains in the tube walls and fluid pumping through the walls, which are desired to promote cell proliferation and differentiation. In this paper, the physical properties of the electrospun sheets and the wound tubes are reported, including the magnitude of the displacements and the flux through the walls induced by a given magnetic field. A model is presented that can be used to predict the deformation and fluid flow for given field strength and material and geometrical parameters. The model can be used to optimize tube design and interpret measurements from future experiments on cell culture.
An integral textile structure for 3-D CMC turbine airfoils includes top and bottom walls made from an angle-interlock weave, each of the walls comprising warp and weft fiber tows. The top and bottom ...walls are merged on a first side parallel to the warp fiber tows into a single wall along a portion of their widths, with the weft fiber tows making up the single wall interlocked through the wall's thickness such that delamination of the wall is inhibited. The single wall suitably forms the trailing edge of an airfoil; the top and bottom walls are preferably joined along a second side opposite the first side and parallel to the radial fiber tows by a continuously curved section in which the weave structure remains continuous with the weave structure in the top and bottom walls, the continuously curved section being the leading edge of the airfoil.
The effect of matrix grain growth kinetics on the densification behavior of a particulate composite has been investigated. Large alumina inclusions were added to two types of zirconia matrices having ...different grain growth kinetics, i.e., Zr(8Y)O2 and Zr(3Y)O2. Despite the evolution of different grain sizes, both matrices reached an end‐point relative density of 0.92 and 0.94, respectively, even though they contained 0.25 volume fraction of inclusions (based on total solid volume). However, the morphology and spatial distribution of the residual pores were distinct. The Zr(8Y)O2 matrix, which developed very large grains, had a dual microstructure with porous regions surrounded by a connective, denser region, as previously reported for an alumina matrix containing zirconia inclusions. Conversely, the Zr(3Y)O2 matrix was fully dense and uniform, but the composite contained large cracklike voids at inclusion/matrix interfaces. The large opening displacement of these cracklike voids locally relaxed the constraint to matrix shrinkage imposed by the inclusion network.
A phenomenological model is presented to describe the densification behavior of powder matrices containing dense reinforcements. Experimental studies emphasizing microstructural observations have ...established that the poor densification of the matrix originates either from the presence of large processing defects and/or from an inhomogeneous densification of the matrix caused by the presence of the inclusions. The large processing defects, apparently created during specimen consolidation and drying, open during sintering and relax any constraint produced by the inclusions. Alternatively, when green compacts are mostly free of these large defects, the densification of the matrix occurs inhomogeneously. Regions of the matrix located at the tip of elongated inclusions and between closely spaced inclusions densify rapidly whereas some interstitial regions remain porous. A numerical analysis of the strain gradients around isolated inclusions and between inclusion pairs has confirmed that regions of enhanced densification are sites of a compressive strain field. Once formed, these dense regions support rapid grain growth and constitute, with the inclusions, a creep resistant network percolating throughout the compact. The porous regions within the interstices of this network are constrained from further densification and develop into crack-like voids to minimize the total free energy of the system. The mechanism leading to pore enlargement is shown to result from the break-up of grain bridges linking polycrystalline clusters. Free energy calculations for two evolving grain-bridge configurations are presented. The instability of grain bridges is shown to be a function of the grain size to bridge length ratio. When this ratio exceeds a critical value, the bridge will break-up, e.g. desinter, to reduce the free energy of the system. This instability condition can be achieved either by grain coarsening at constant bridge length or by extending the bridge length under an applied tensile stress at constant grain size. In addition, grain growth kinetics of the matrix appeared as a critical parameter in this model. An additional experiment conducted with alumina inclusions in a matrix of either ZrO$\sb2$-3 mol%Y$\sb2$O$\sb3$ or ZrO$\sb2$-8 mol%Y$\sb2$O$\sb3$ showed that high end-point densities are achieved with both matrices despite their different grain growth kinetics and the presence of 25 vol.% inclusions. This result emphasized the effect of grain size on the mechanism producing damage.
Aims
The MITRA‐FR trial showed that among symptomatic patients with severe secondary mitral regurgitation, percutaneous repair did not reduce the risk of death or hospitalization for heart failure at ...12 months compared with guideline‐directed medical treatment alone. We report the 24‐month outcome from this trial.
Methods and results
At 37 centres, we randomly assigned 304 symptomatic heart failure patients with severe secondary mitral regurgitation (effective regurgitant orifice area >20 mm2 or regurgitant volume >30 mL), and left ventricular ejection fraction between 15% and 40% to undergo percutaneous valve repair plus medical treatment (intervention group, n = 152) or medical treatment alone (control group, n = 152). The primary efficacy outcome was the composite of all‐cause death and unplanned hospitalization for heart failure at 12 months. At 24 months, all‐cause death and unplanned hospitalization for heart failure occurred in 63.8% of patients (97/152) in the intervention group and 67.1% (102/152) in the control group hazard ratio (HR) 1.01, 95% confidence interval (CI) 0.77–1.34. All‐cause
mortality occurred in 34.9% of patients (53/152) in the intervention group and 34.2% (52/152) in the control group (HR 1.02, 95% CI 0.70–1.50). Unplanned hospitalization for heart failure occurred in 55.9% of patients (85/152) in the intervention group and 61.8% (94/152) in the control group (HR 0.97, 95% CI 0.72–1.30).
Conclusions
In patients with severe secondary mitral regurgitation, percutaneous repair added to medical treatment did not significantly reduce the risk of death or hospitalization for heart failure at 2 years compared with medical treatment alone.
Although solar cells operate under illumination, most electrical characterization methods are carried out in darkness, which implies some bias. In this work, we study the influence of light on the ...contact resistivity of the electron and hole contacts of a silicon heterojunction (SHJ) cell using the transfer length method (TLM) method in order to determine them in conditions representative of an operating solar cell at maximum power point. A specific fabrication process has been developed to preserve the passivation level. Therefore, we first focus on the patterning approach used for processing, and show that we can fabricate TLM samples with good passivation properties. Using simulations, we also discuss on the influence of inhomogeneities in the excess minority carrier spatial concentration on the TLM analysis. These inhomogeneities, due to shading, local damages in the passivation or to carrier drift under bias voltage make the measurement complicated to carry out without significant error. Our results suggest that the measurement is more precise in darkness and at very high injection levels, under rear illumination and a low voltage bias.
•TLM samples for ρC(e-) and ρC(h+) measurement in SHJ cells can be fabricated while maintaining good passivation properties.•TLM measurements are carried out under illumination in order to probe ρC(e-) and ρC(h+) under operating conditions.•ρC is influenced by the excess minority carrier density: it should preferably be extracted under operating conditions.•A meaningful characterization requires a good and homogeneous passivation across the TLM sample, minimal shading and low voltage bias.•Our simulations suggest a moderate impact of light on ρC(e-) for standard c-Si doping levels.
Patients with acute STEMI undergoing PCI were assigned to cyclosporine or placebo. No significant between-group difference was seen in the rate of death, rehospitalization for heart failure, heart ...failure worsening during index hospitalization, or adverse left ventricular remodeling at 1 year.
Over the past three decades, major progress has been made in the treatment of patients with ST-segment elevation myocardial infarction (STEMI).
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Nevertheless, the rates of death, heart failure, and recurrent ischemic events occurring in the first year after infarction remain unacceptably elevated in this high-risk population. Although many advances have been made in the development of methods to reopen the culprit coronary artery and prevent reocclusion, there is currently no specific treatment that targets myocardial reperfusion injury, which is a paradoxical form of myocardial damage that occurs as a result of the restoration of vessel patency.
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Growing evidence from experimental . . .
Transcatheter aortic valve replacement (TAVR) has revolutionized management of high-risk patients with severe aortic stenosis. However, survival and the incidence of severe complications have been ...assessed in relatively small populations and/or with limited follow-up.
This report details late clinical outcome and its determinants in the FRANCE-2 (FRench Aortic National CoreValve and Edwards) registry.
The FRANCE-2 registry prospectively included all TAVRs performed in France. Follow-up was scheduled at 30 days, at 6 months, and annually from 1 to 5 years. Standardized VARC (Valve Academic Research Consortium) outcome definitions were used.
A total of 4,201 patients were enrolled between January 2010 and January 2012 in 34 centers. Approaches were transarterial (transfemoral 73%, transapical 18%, subclavian 6%, and transaortic or transcarotid 3%) or, in 18% of patients, transapical. Median follow-up was 3.8 years. Vital status was available for 97.2% of patients at 3 years. The 3-year all-cause mortality was 42.0% and cardiovascular mortality was 17.5%. In a multivariate model, predictors of 3-year all-cause mortality were male sex (p < 0.001), low body mass index, (p < 0.001), atrial fibrillation (p < 0.001), dialysis (p < 0.001), New York Heart Association functional class III or IV (p < 0.001), higher logistic EuroSCORE (p < 0.001), transapical or subclavian approach (p < 0.001 for both vs. transfemoral approach), need for permanent pacemaker implantation (p = 0.02), and post-implant periprosthetic aortic regurgitation grade ≥2 of 4 (p < 0.001). Severe events according to VARC criteria occurred mainly during the first month and subsequently in <2% of patients/year. Mean gradient, valve area, and residual aortic regurgitation were stable during follow-up.
The FRANCE-2 registry represents the largest database available on late results of TAVR. Late mortality is largely related to noncardiac causes. Incidence rates of severe events are low after the first month. Valve performance remains stable over time.
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