Biologic Augmentation in Osteochondral Lesions of the Talus

Introduction Osteochondral lesions of the talus (OLT) are injuries involving damage to the cartilage and bone associated with the talar dome. They occur in up to 50% of ankle sprains and 73% of ankle fractures, varying in stability and severity.1 Standard weightbearing ankle radiographs may allow for visualization of the lesions if substantial bone fragmentation is involved but CT and MRI are more sensitive for subchondral bone damage and purely cartilaginous lesions, respectively (Figure 1). The majority of patients with OLT are active individuals in their 20s and 30s, and often present after sustaining an acute inversion injury.2 Trauma to the talar dome creates an ischemic environment in the joint, which ultimately leads to disintegration of the subchondral bone in addition to damage to the overlying cartilage. This may lead to generalized ankle pain, weakness, and swelling. In addition to acute trauma, these lesions may develop as a result of osteochondritis dissecans (OCD). OCD lesions commonly present in patients between 10-20 years of age and have a multifactorial etiology, including genetic predisposition and loss of blood supply to a region of the joint.3 Incidence of these lesions is higher in young athletes, suggesting that microtrauma also plays a role in OCD becoming symptomatic

Unsteady Forces on a Spherical Particle Accelerating or Decelerating in an Initially Stagnant Fluid

Flows with particles play an important role in a number of engineering applications. These include trajectories of droplets in sprays in fuel-injected-reciprocating-piston and gas-turbine engines, erosion of materials due to particle impact on a surface, and deposition of materials on surfaces by impinging droplets or particles that could solidify or bond on impact. For these applications, it is important to understand the forces that act on the particles so that their trajectories could be predicted. Considerable work has been done on understanding the forces acting on spherical particles, where the Reynolds numbers (Rep ) based on the particle diameter and the relative speed between the particle and the fluid is less than unity. When Rep is larger than unity and when the particle is accelerating or decelerating, the added-mass effect and the Basset forces are not well understood. In this study, time-accurate numerical simulations were performed to study laminar incompressible flow induced by a single non-rotating rigid spherical particle that is accelerated or decelerated at a constant rate in an initially stagnant fluid, where the unsteady flow about the spherical particle is resolved. The Rep studied range from 0.01 to 100, and the acceleration number (Ac ), where A c is the square of the relative velocity between the particle and the fluid divided by the acceleration times the particle diameter studied was in the range 2.13×-7 \u3c |Ac |\u3c 21337. Results obtained show the added mass effect for Rep up to 100 has the same functional form as those based on potential theory where the Rep is infinite and creeping flow where Rep is less than unity. The Basset force, however, differs considerably from those under creeping flow conditions and depends on Rep and the acceleration number (Ac ). A model was developed to provide the magnitude of the added-mass effect and the Basset force in the range of Rep and Ac studied. Results obtained also show the effect of unsteadiness to become negligible whenAc reaches 80

Inattentional Blindness for Redirected Walking Using Dynamic Foveated Rendering

Redirected walking is a Virtual Reality(VR) locomotion technique which enables users to navigate virtual environments (VEs) that are spatially larger than the available physical tracked space. In this work we present a novel technique for redirected walking in VR based on the psychological phenomenon of inattentional blindness. Based on the user's visual fixation points we divide the user's view into zones. Spatially-varying rotations are applied according to the zone's importance and are rendered using foveated rendering. Our technique is real-time and applicable to small and large physical spaces. Furthermore, the proposed technique does not require the use of stimulated saccades but rather takes advantage of naturally occurring saccades and blinks for a complete refresh of the framebuffer. We performed extensive testing and present the analysis of the results of three user studies conducted for the evaluation

Ion—modified optimization of smart scaffolds in bone tissue regeneration

Bioactive glasses and Calcium Phosphate bioceramics have emerged as promising scaffold biomaterials for bone tissue engineering. These materials possess inherent osteoinductive properties that work to create a more suitable environment for bone tissue formation. Additionally, these scaffolds exhibit dissolution properties when submerged in physiological fluids in vivo and therefore can release different ions. Incorporating therapeutic ion-modifiers that have independently demonstrated their osteogenic favorability to these scaffolds can further increase environmental suitability. This review discusses the favorable properties of bioactive glasses and Calcium Phosphate bioceramics in the context of Bone Tissue Engineering as well as potential incorporable metal ion-modifiers

Towards Understanding and Expanding Locomotion in Physical and Virtual Realities

Among many virtual reality interactions, the locomotion dilemma remains a significant impediment to achieving an ideal immersive experience. The physical limitations of tracked space make it impossible to naturally explore theoretically boundless virtual environments with a one-to-one mapping. Synthetic techniques like teleportation and flying often induce simulator sickness and break the sense of presence. Therefore, natural walking is the most favored form of locomotion. Redirected walking offers a more natural and intuitive way for users to navigate vast virtual spaces efficiently. However, existing techniques either lead to simulator sickness due to visual and vestibular mismatch or detract users from the immersive experience that virtual reality aims to provide. This research presents innovative techniques and applications to enhance the user experience by expanding walkable, physical space in Virtual Reality. The thesis includes three main contributions. The first contribution proposes a mobile application that uses markerless Augmented Reality to allow users to explore a life-sized virtual library through a divide-and-rule approach. The second contribution presents a subtle redirected walking technique based on inattentional blindness, using dynamic foveated rendering and natural visual suppressions like blinks and saccades. Finally, the third contribution introduces a novel redirected walking solution that leverages a deep neural network, to predict saccades in real-time and eliminate the hardware requirements for eye-tracking. Overall, this thesis offers valuable contributions to human-computer interaction, investigating novel approaches to solving the locomotion dilemma. The proposed solutions were evaluated through extensive user studies, demonstrating their effectiveness and applicability in real-world scenarios like training simulations and entertainment