Bayesian model checking: A comparison of tests

Two procedures for checking Bayesian models are compared using a simple test problem based on the local Hubble expansion. Over four orders of magnitude, p-values derived from a global goodness-of-fit criterion for posterior probability density functions (Lucy 2017) agree closely with posterior predictive p-values. The former can therefore serve as an effective proxy for the difficult-to-calculate posterior predictive p-values.Comment: 4 pages, 3 figures. Submitted to Astronomy & Astrophysic

Optical conductivity and Raman scattering of iron superconductors

We discuss how to analyze the optical conductivity and Raman spectra of multi-orbital systems using the velocity and the Raman vertices in a similar way Raman vertices were used to disentangle nodal and antinodal regions in cuprates. We apply this method to iron superconductors in the magnetic and non-magnetic states, studied at the mean field level. We find that the anisotropy in the optical conductivity at low frequencies reflects the difference between the magnetic gaps at the X and Y electron pockets. Both gaps are sampled by Raman spectroscopy. We also show that the Drude weight anisotropy in the magnetic state is sensitive to small changes in the lattice structure.Comment: 14 pages, 10 figures, as accepted in Phys. Rev. B, explanations/discussion added in Secs. II, III and V

Crystal field effects on spin pumping

"Spin pumping" is the injection of spin angular momentum by a time-dependent magnetization into an adjacent normal metal proportional to the spin mixing conductance. We study the role of electrostatic interactions in the form of crystal fields on the pumped spin currents generated by insulators with exchange-coupled local moments at the interface to a metal. The crystal field is shown to render the spin currents anisotropic, which implies that the spin mixing conductance of insulator|normal metal bilayers depends on crystal cut and orientation. We interpret the interface "effective field" (imaginary part of the spin mixing conductance) in terms of the coherent motion of the equilibrium spin density induced by proximity in the normal metal.Comment: 8 pages+, 7 figure

First-order ferromagnetic transitions of lanthanide local moments in divalent compounds: An itinerant electron positive feedback mechanism and Fermi surface topological change

Around discontinuous (first-order) magnetic phase transitions the strong caloric response of materials to the application of small fields is widely studied for the development of solid-state refrigeration. Typically strong magnetostructural coupling drives such transitions and the attendant substantial hysteresis dramatically reduces the cooling performance. In this context we describe a purely electronic mechanism which pilots a first-order paramagnetic-ferromagnetic transition in divalent lanthanide compounds and which explains the giant non-hysteretic magnetocaloric effect recently discovered in a Eu$_2$In compound. There is positive feedback between the magnetism of itinerant valence electrons and the ferromagnetic ordering of local $f$-electron moments, which appears as a topological change to the Fermi surface. The origin of this electronic mechanism stems directly from Eu's divalency, which explains the absence of a similar discontinuous transition in Gd$_2$In.Comment: 8 pages, 7 figure

Voltage control of interface rare-earth magnetic moments

The large spin orbit interaction in rare earth atoms implies a strong coupling between their charge and spin degrees of freedom. We formulate the coupling between voltage and the local magnetic moments of rare earth atoms with partially filled 4f shell at the interface between an insulator and a metal. The rare earth-mediated torques allow power-efficient control of spintronic devices by electric field-induced ferromagnetic resonance and magnetization switching

Solid Freeform Fabrication of Artificial Human Teeth

In this paper, we describe a solid freeform fabrication procedure for human dental restoration via porcelain slurry micro-extrusion. Based on submicron-sized dental porcelain powder obtained via ball milling process, a porcelain slurry formulation has been developed. The formulation developed allows the porcelain slurry to show a pseudoplastic behavior and moderate viscosity, which permits the slurry to re-shape to form a near rectangular cross section. A well-controlled cross-section geometry of the extrudate is important for micro-extrusion to obtain uniform 2-D planes and for the addition of the sequential layers to form a 3-D object. Human teeth are restored by this method directly from CAD digital models. After sintering, shrinkage of the artificial teeth is uniform in all directions. Microstructure of the sintered teeth is identical to that made via traditional dental restoration processes.Mechanical Engineerin

Laser Densification of Extruded Dental Porcelain Bodies in Multi-Material Laser Densification (MMLD) Process

In this study commercial dental porcelain powder was deposited via slurry extrusion and laser densified to fabricate dental restorations in a Multi-Material Laser Densification (MMLD) process. The processing conditions for laser densification of single lines and closed rings were investigated in order to avoid warping and cracking. Multi-layer rings were also investigated to study the dependence of bonding between layers on the laser densification conditions. The laser densified rings showed no warping, and good bonding between layers could be achieved when the laser densification condition was selected properly. The mechanism to achieve porcelain rings without warping and cracking is discussed. The understanding developed will pave the way for fabricating a physical dental restoration unit.Mechanical Engineerin