Accurate chromosome segregation during meiosis depends on the assembly of a microtubule-based spindle of proper shape and size. Current models for spindle size control focus on reaction-diffusion based chemical regulation and balance in activities of motor proteins. While several molecular perturbations have been used to test these models, controlled mechanical perturbations have not been possible. Here we report a piezo-resistive dual-cantilever-based system to test models for spindle size control and, for the first time, examine the mechanical features, e.g., deformability and stiffness, of the vertebrate meiotic spindle. We found that meiotic spindles prepared in Xenopus egg extracts were viscoelastic and the shape was recovered to the original one in response to small compression. Larger compression resulted in plastic deformation, but surprisingly, the spindle adapted to it, establishing a stable mechanical architecture at different sizes. Our technique will also be useful for examining micro-mechanics of a variety of other cellular organelles.
Abstract. We present an augmented reality system for oral and maxillofacial surgery in this paper. Instead of being displayed on a separated screen, three-dimensional (3D) virtual presentations of osseous structures and soft tissues are projected onto the patient's body, providing surgeons with exact knowledge of depth information of high risk tissues inside the bone. We employ a 3D integral imaging technique which produce motion parallax in both horizontal and vertical direction over a wide viewing area in this study. In addition, surgeons are able to check the progress of the operation in real-time through an intuitive 3D based interface which is content-rich, hardware accelerated. These features prevent surgeons from penetrating into high risk areas and thus help improve the quality of the operation. Operational tasks such as hole drilling, screw fixation were performed using our system and showed an overall positional error of less than 1mm. Feasibility of our system was also verified with a human volunteer experiment.
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