Plasma spray physical vapor deposition aims tosubstantially evaporate powders in order to produce coatingswith various microstructures. This is achieved bypowder vapor condensation onto the substrate and/or bydeposition of fine melted powder particles and nanoclusters.The deposition process typically operates at pressuresranging between 10 and 200 Pa. In addition to the experimentalworks, numerical simulations are performed tobetter understand the process and optimize the experimentalconditions. However, the combination of hightemperatures and low pressure with shock waves initiatedby supersonic expansion of the hot gas in the low-pressuremedium makes doubtful the applicability of the continuumapproach for the simulation of such a process. This workinvestigates (1) effects of the pressure dependence ofthermodynamic and transport properties on computationalfluid dynamics (CFD) predictions and (2) the validity of thecontinuum approach for thermal plasma flow simulationunder very low-pressure conditions. The study comparesthe flow fields predicted with a continuum approach usingCFD software with those obtained by a kinetic-basedapproach using a direct simulation Monte Carlo method(DSMC). It also shows how the presence of high gradientscan contribute to prediction errors for typical PS-PVDconditions.

International audiencePlasma spray physical vapor deposition aims to substantially evaporate powders in order to produce coatings with various microstructures. This is achieved by powder vapor condensation onto the substrate and/or by deposition of fine melted powder particles and nanoclusters. The deposition process typically operates at pressures ranging between 10 and 200 Pa. In addition to the experimental works, numerical simulations are performed to better understand the process and optimize the experimental conditions. However, the combination of high temperatures and low pressure with shock waves initiated by supersonic expansion of the hot gas in the low-pressure medium makes doubtful the applicability of the continuum approach for the simulation of such a process. This work investigates (1) effects of the pressure dependence of thermodynamic and transport properties on computational fluid dynamics (CFD) predictions and (2) the validity of the continuum approach for thermal plasma flow simulation under very low-pressure conditions. The study compares the flow fields predicted with a continuum approach using CFD software with those obtained by a kinetic-based approach using a direct simulation Monte Carlo method (DSMC). It also shows how the presence of high gradients can contribute to prediction errors for typical PS-PVD conditions

Self-organizing human cardiac microchambers mediated by geometric confinement

Tissue morphogenesis and organ formation are the consequences of biochemical and biophysical cues that lead to cellular spatial patterning in development. To model such events in vitro, we use PEG-patterned substrates to geometrically confine human pluripotent stem cell colonies and spatially present mechanical stress. Modulation of the WNT/b-catenin pathway promotes spatial patterning via geometric confinement of the cell condensation process during epithelial–mesenchymal transition, forcing cells at the perimeter to express an OCT4þ annulus, which is coincident with a region of higher cell density and E-cadherin expression. The biochemical and biophysical cues synergistically induce self-organizing lineage specification and creation of a beating human cardiac microchamber confined by the pattern geometry. These highly defined human cardiac microchambers can be used to study aspects of embryonic spatial patterning, early cardiac development and drug-induced developmental toxicity

Electroweak parameters of the z0 resonance and the standard model

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