Magnetic Skyrmions in FePt Square-Based Nanoparticles Around Room-Temperature

Magnetic skyrmions formed around room-temperature in square-based parallelepiped magnetic nanoparticles with perpendicular magnetocrystalline anisotropy similar to that of partially chemically ordered FePt were studied during the magnetization reversal using micromagnetic simulations. Finite Differences (FD) discretizations were used for the solution of the Landau-Lifshitz-Gilbert equation. Magnetic configurations exhibiting N\'eel chiral stripe and N\'eel skyrmionic formations were detected. The magnetic skyrmions can be created in different systems generated by the variation of external field, side length and width of the squared-based parallelepiped magnetic nanoparticles. Micromagnetic configurations revealed a variety of states which include skyrmionic textures with one distinct skyrmion formed and being stable for a range of external fields around room-temperature. The size of the formed N\'eel skyrmion is calculated as a function of the external field, temperature, magnetocrystalline anisotropy and nanoparticle's geometrical characteristic lengths which can be adjusted to produce N\'eel type skyrmions on demand having diameters down to 12 nm. The micromagnetic simulations revealed that stable skyrmions at the temperature range 270K-330K can be created for FePt magnetic nanoparticle systems lacking of chiral interactions such as Dzyaloshinsky-Moriya, providing new perspectives in the new magnetic writing era.Comment: 11 pages,12 Figures, research articl

A Large-Scale Fifteen-Year Minimum Survivorship of a Cementless Triple Tapered Femoral Stem

© 2020 Elsevier Inc. Background: This study reports the long-term outcomes of a metaphyseal fit-and-fill cementless femoral component in total hip arthroplasty (THA) with a follow-up of 15-19 years. Methods: We conducted a retrospective review of 376 consecutive THAs (345 patients), using a triple tapered stem performed between 2000 and 2003 with a view to assessing survivorship and radiological and functional outcomes. Images were assessed for initial alignment, terminal osteolysis, or subsidence, while clinical outcomes were assessed using the St Michael\u27s Hip Score. Results: Forty-five (11.9%) hips were lost to follow-up, 20 (5.31%) had died before our 15-year cutoff follow-up, and 4 (1.06%) had declined follow-up early on, leaving 307 hips (81.64%, 276 patients) available for both clinical and radiological follow-up at a minimum of 15 years (range 15-19). The mean age at the time of operation was 49.6 years (range 19-71) and the cohort included 131 (42.67%) male and 145 (47.23%) female patients. Seven stems (2.28%) were revised: 4 due to periprosthetic fractures, 2 for periprosthetic joint infection, and 1 for adverse reaction to metal debris at the trunnion. The St Michael\u27s Hip Score improved from 14.2 (range 9-23) preoperatively to 22.3 (range 13 to 25) at the last documented follow-up (P = .000). Kaplan-Meier survivorship with stem revision for any reason as the end point was 97.70%. Worst-case scenario Kaplan-Meier survivorship, where all lost to follow-up are considered as failures, was 85.3%. No stem was revised for aseptic loosening. Conclusion: This triple tapered stem in THA shows excellent survivorship beyond a minimum of 15 years