Paul Allen Williams

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We transfer an optical frequency over 251 km of optical fiber with a residual instability of 6x10(-19) at 100 s. This instability and the associated timing jitter are limited fundamentally by the noise on the optical fiber and the link length. We give a simple expression for calculating the achievable instability and jitter over a fiber link. Transfer of(More)
With the increased clinical interest in metal-on-metal and ceramic-on-ceramic total-hip replacements (THRs), the objective of this hip simulator study was to identify the relative wear ranking of three bearing systems, namely CoCr-polyethylene (M-PE), CoCr-CoCr (M-M) and ceramic-on-ceramic (C-C). Volumetric wear rates were used as the method of comparison.(More)
To assess the suitability of bismuth germanate as an electro-optic material for high precision applications, we have confirmed and extended previous data on its refractive index, electro-optic tensor element r(41), and thermal expansion coefficient. In addition, we have measured the thermo-optic coefficient dn/dT, the temperature dependence of the(More)
The advantages of all-alumina bearings are superb wear resistance, stability, and inertness demonstrated over 3 decades. The disadvantage is a small risk for brittle fracture, as described in this paper. Surveying the latest ceramic hip series reported in recent journal articles or presented at the 6th World Biomaterials Congress, we found 11 studies(More)
In the study the effects of vanous storage environments on the dielectric properties of bone were evaluated. Fresh cortical bone specimens from canine femora and tibiae were prepared and divided into three groups, with one group maintained at room temperature (24°C), a second group stored in a refrigerator at 3°C, and a third group stored in a freezer at(More)
In this study the electrical and dielectric properties of wet human cancellous bone from distal tibiae were examined as a function of frequency and direction. The resistance and capacitance of the cancellous bone specimens were measured at near 100% relative humidity. The measurements were made in all three orthogonal directions at discrete frequencies(More)
Hip simulator studies have shown that wear in the polyethylene liners used for total hip replacements increased with the larger-diameter femoral balls and could also be exacerbated by third-body abrasion. However, they also indicated that the more highly cross-linked polyethylene (HXPE) bearings were more wear resistant than conventional polyethylene (CXPE)(More)
Three THAs with cementless monolithic alumina ceramic sockets and cementless Co-alloy stems were retrieved because of aseptic loosening after 17 and 24 years. At revision heads and cups were marked for orientation. Maps were drawn of wear patterns with the use of light microscopy and surveyed by SEM. In a simulator experiment 28-mm-diameter alumina heads(More)