P. Klein | Searcharxiv

arXiv2024

In vivo and in vitro study of resorbable magnesium wires for medical implants: Mg purity, surface quality, Zn alloying and polymer coating

Magnesium is an excellent material in terms of biocompatibility and its corrosion products can serve as an active source for new bone formation. However, localized corrosion and H2 generation limit the potential of Mg-based implants. Utilizing low-alloyed Mg-Zn wires can strongly reduce problems with large H2 bubbles and improve the mechanical properties considerably while maintaining excellent long-term biocompatibility. Acidic pickling and a polymer coating can be effectively used to lower the rate of in vivo degradation. In this work, microstructural, mechanical, and in vitro characterization of 250 um and 300 um extruded wires made from ultra-pure Mg, commercially pure Mg, Mg-0.15Zn, Mg-0.4Zn and Mg-1Zn was performed. Additionally, Mg-0.4Zn wires together with a variant coated with a copolymer of L-lactide and {\epsilon}-caprolactone were tested in vivo on artificially damaged Wistar rat femurs. Based on the observed Mg-induced osteogenesis, polymer-coated Mg wires with a small addition of Zn are a perspective material for bone-support applications, such as cerclage and fixation wires.

physics.med-ph↗

arXiv2017

Physics holo.lab learning experience: Using Smartglasses for Augmented Reality labwork to foster the concepts of heat conduction

Fundamental concepts of thermodynamics rely on abstract physical quantities such as energy, heat and entropy, which play an important role in the process of interpreting thermal phenomena and statistical mechanics. However, these quantities are not covered by human (visual) perception and thus, an intuitive understanding often is lacking. Today immersive technologies like head-mounted displays of the newest generation, especially HoloLens, allow for high quality augmented reality learning experiences, which can overcome this perception gap and simultaneously avoid a split attention effect. In a mixed reality (MR) scenario as presented in this paper---which we call a holo.lab---human perception can be extended to the thermal regime by presenting false-color representations of the temperature of objects as a virtual augmentation directly on the real object itself in real-time. Direct feedback to experimental actions of the users in form of different representations allows for immediate comparison to theoretical principles and predictions and therefore is supposed to intensify the theory-experiment interactions and to increase the conceptual understanding. We tested this technology for an experiment on thermal conduction of metals in the framework of undergraduate laboratories. A pilot study with treatment and control groups (N = 59) showed a small positive effect of MR on students' performance measured with a standardized concept test for thermodynamics, indicating an improvement of the understanding of the underlying physical concepts.

physics.ed-ph↗