Since backflow was diverted away from the needle track into white matter regions, backflow distances along the needle track were relatively constant over the insertion speeds and flow rates tested Figure 14B. Thus, insertion rate-dependent damage and changes in pre-stress were found to directly contribute to the extent of backflow, with slower insertion resulting in less damage and improved targeting. Therefore, the combined experiment and modeling approach used in this study establishes a useful way of estimating pre-stresses variation surrounding needles and other brain implants. Animal preparation and surgical procedures All experiments were performed on male Sprague-Dawley rats — g using protocols and procedures approved by the University of Florida Institutional Animal Care and Use Committee. Saved pages Keep track of important pages Recently visited pages Easily find again pages you have been reading Pages you might like Have pages recommended to you. Local tissue damage was also assessed.
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First, who puts it on? Also, pre-stress was determined to be non-uniform along the needle track. Edema may also develop in response to cellular injury or vascular damage, and this abnormal accumulation of fluid can result in swelling and volumetric tissue changes . Regions of injury were also found to be coincident with backflow. How does it feel to have two vaginas? The tongue may also penetrate the anus during anilingus , which is a form of oral and anal sex.
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Larger deformations associated with greater tissue strength may be the cause of more damage in these regions. A nonlinear viscoelastic Kelvin model is then used to predict the relationship between the deformation of tissue and the rupture force at different velocities. In an Emergency On-campus Resources. The larger diameter holes observed in the white matter regions of this study may be due to in part to this tensile residual stress. All galleries and links are provided by 3rd parties. CPu and white matter regions where easily delineated on each slice as shown in Figure 4A. Using a single condom of either type correctly and consistently can provide adequate protection during sexual contact.
At the slower insertion speed, bleeding was only observed close to the hole, and tissue fracturing was not observed. The extent of tissue coring was evaluated by monitoring CED infusion pressures. By introducing a specific contact model, this nonincreasing trend in force can be related to a reduction in deformation, as is done in the following sections. Needle insertion experiment Experiments were conducted at three insertion speeds: Therefore, tissue damage was more sensitive to insertion speed than brain region over the range of parameters tested.