Cartilage compositional MRI-a narrative review of technical development and clinical applications over the past three decades.

Articular cartilage damage and degeneration are among hallmark manifestations of joint injuries and arthritis, classically osteoarthritis. Cartilage compositional MRI (Cart-C MRI), a quantitative technique, which aims to detect early-stage cartilage matrix changes that precede macroscopic alterations, began development in the 1990s. However, despite the significant advancements over the past three decades, Cart-C MRI remains predominantly a research tool, hindered by various technical and clinical hurdles. This paper will review the technical evolution of Cart-C MRI, delve into its clinical applications, and conclude by identifying the existing gaps and challenges that need to be addressed to enable even broader clinical application of Cart-C MRI

A phase-field study of elastic stress effects on phase separation in ternary alloys

Most of the commercially important alloys are multicomponent, producing multiphase microstructures as a result of processing. When the coexisting phases are elastically coherent, the elastic interactions between these phases play a major role in the development of microstructures. To elucidate the key effects of elastic stress on microstructural evolution when more than two misfitting phases are present in the microstructure, we have developed a microelastic phase-field model in two dimensions to study phase separation in ternary alloy system. Numerical solutions of a set of coupled Cahn-Hilliard equations for the composition fields govern the spatiotemporal evolution of the three-phase microstructure. The model incorporates coherency strain interactions between the phases using Khachaturyan's microelasticity theory. We systematically vary the misfit strains (magnitude and sign) between the phases along with the bulk alloy composition to study their effects on the morphological development of the phases and the resulting phase separation kinetics. We also vary the ratio of interfacial energies between the phases to understand the interplay between elastic and interfacial energies on morphological evolution. The sign and degree of misfit affect strain partitioning between the phases during spinodal decomposition, thereby affecting their compositional history and morphology. Moreover, strain partitioning affects solute partitioning and alters the kinetics of coarsening of the phases. The phases associated with higher misfit strain appear coarser and exhibit wider size distribution compared to those having lower misfit. When the interfacial energies satisfy complete wetting condition, phase separation leads to development of stable core-shell morphology depending on the misfit between the core (wetted) and the shell (wetting) phases

Investigation of Interfacial Effects in Ferromagnetic Thin-Films

The magnetic behaviour in thin-film structures has attracted considerable interest and also has importance for wide ranging technological applications. As the dimension of magnetic films reduce, they are able to exhibit different electrical and magnetic properties, where interfacial magnetism become more important. This thesis is centered on the interfacial effects in ferromagnetic thin-film structures with various adjacent materials. Within this framework, the ferromagnetic materials Co and CoFeB:Ta alloy have been investigated. A detailed investigation of the structural, magnetic and anisotropic magnetoresistance (AMR) properties of Co thin-films with Cu and Ir overlayers as a function of Co thickness was performed. Magnetic characterization of thin-films was performed to determine possible magnetic dead layer formations in these thin-films, where no magnetic dead layers were found to be present within these structures. Electrical resistivity measurements showed that the AMR is dependent upon on Co film thickness, where it decreases with decreasing of Co thickness, and it tends toward zero for Co thicknesses below 6 nm. The contribution to the AMR from a single Co/Ir interface is presented where the AMR is shown to vary inversely proportional to the Co film thickness with a Co/Ir interface. Interface magnetism and magnetic dead layers in amorphous CoFeB:Ta alloy thin-film multilayers were studied using polarized neutron reflectometry. Temperature dependent variations in the effective magnetic thickness of the film are found, and correlated with structural intermixing at interfaces. At the interface between ferromagnetic film and capping-layer the structurally graded interface appears to cause a concomitant grading of the local Curie temperature, and at the interface between ferromagnetic film and GaAs(001) substrate local interfacial alloying also creates a region where a magnetic dead-layer forms. The thickness of the magnetic dead layer at the ferromagnet-semiconductor interface is shown to be temperature dependent, which may have significant implications for room-temperature operation of hybrid ferromagnetic metal-semiconductor spintronic devices. Enhancement of Gilbert damping in Co thin-films of various thicknesses with Cu or Ir overlayers is studied under ferromagnetic resonance to understand the role of local interface structure in spin-pumping. Structural analysis indicates that Co films less than 6 nm have fcc(111)-dominated texture while thicker films are dominated by hcp(0001) structure. The intrinsic damping for Co thicknesses above 6 nm is weakly dependent on Co thickness for thin-films with both overlayers, and below 6 nm the Ir overlayers show higher intrinsic damping enhancement compared to Cu overlayers, as expected due to spin-pumping. The interfacial spin-mixing conductance is significantly enhanced in structures where both Co and Ir have fcc(111) structure in comparison to those where the Co layer has subtly different hcp(0001) texture at the interface