The frequency spectrum of the cerebrospinal fluid (CSF) pulse and the amplitude transfer function between arterial and CSF pressures were measured from the cisterna magna of anesthetized, artificially ventilated cats when the intracranial pressure (ICP) was raised by saline infusion. The spectrum of CSF pulsation was composed of a fundamental and three higher harmonic waves. The amplitude and the amplitude transfer function of each spectral component revealed significant positive correlation with ICP and negative correlation with cerebral perfusion pressure (CPP). Both the amplitude and the transfer function of the fundamental CSF pulse wave showed an exponential correlation with ICP and CPP. A distortion factor of the CSF pulse wave, a measure of its difference from a simple sine wave, was calculated from the spectral components. This showed that distortion of the CSF pulse wave was rapidly and progressively reduced as the ICP rose to 50 mm Hg and then was reduced less thereafter.
In this study, the fatigue properties of additively manufactured titanium clasps were compared with those of commercially pure titanium (CPTi) and Ti-6Al-4V (Ti64), manufactured using laser powder-bed fusion. Methods: Fourteen specimens of each material were tested under the cyclic condition at 1 Hz with applied maximum strokes ranging from 0.2 to 0.5 mm, using a small stroke fatigue testing machine. A numerical approach using finite element analysis (FEA) was also developed to predict the fatigue life of the clasps. Results: The results showed that although no significant differences were observed between the two materials when a stroke larger than 0.35 mm was applied, CPTi had a better fatigue life under a stroke smaller than 0.33 mm. The distributions of the maximum principal stress in the FEA and the fractured position in the experiment were in good agreement. Conclusions: Using a design of the clasp of the present study, the advantage of the CPTi clasp in its fatigue life under a stroke smaller than 0.33 mm was revealed experimentally. Furthermore, the numerical approach using FEA employing calibrated parameters for the Smith-Watson-Topper method are presented. Under the limitations of the aforementioned clasp design, the establishment of a numerical method enabled us to predict the fatigue life and ensure the quality of the design phase before manufacturing.
Blowout fractures most frequently involve the orbital floor. The contour of the orbit has been postulated as one of the factors responsible for this phenomenon, but only a few studies have been carried out. The present study was planned to determine the effect of the contour of the orbit when intraorbital pressure is raised to simulate the hydraulic mechanism of blowout fracture. The profile of the orbit was estimated from five dry human skulls, and the measurements were approximated to frame models. The deformation of these models by raised intraorbital pressure was calculated by computer simulation using the finite element method. In all of the orbital models, the deformation of the orbital floor was significantly greater than that of the roof. These findings verified that the orbital roof has a higher resistance than the floor against raised intraorbital pressure. We suspect that this resistance is due to the arched shape of the orbital roof, whereas the floor is rather flat.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.