Exponent

About: Exponent is a company organization based out in Menlo Park, California, United States. It is known for research contribution in the topics: Population & Risk assessment. The organization has 1589 authors who have published 2680 publications receiving 88140 citations.

Comparison of the properties of annealed crosslinked (Crossfire) and conventional polyethylene as hip bearing materials

Abstract: In 1998, orthopaedic manufacturers started to introduce highly crosslinked ultra-high molecular weight polyethylene (UHMWPE) for total hip replacement bearings. Today’s highly-crosslinked UHMWPEs materials are irradiation processed with a total dose ranging between 50 and 105 kGy, depending upon the manufacturer. Each manufacturer has adopted a different route for producing their highly crosslinked UHMWPE that includes a combination of three important processing steps: an irradiation step, an intra or post-irradiation thermal processing step, and a sterilization step. This paper reviews the choices available to an implant designer when developing a highly-crosslinked UHMWPE as an orthopaedic bearing material. We suggest that the application of annealing rather than re-melting in the thermal processing step allows the retention of important mechanical properties in the finished material. This approach will be illustrated with test data on Crossfire™ (Stryker Howmedica Osteonics, Mahwah, NJ), an annealed, highly-crosslinked UHMWPE developed specifically for total hip replacements. We compare the physical, mechanical, and wear properties of Crossfire™ with that of conventional (N2-Vac™) UHMWPE and with materials produced using published melt irradiation technology. At the short term (2 and 3 years) the results demonstrated through clinical follow-up, clinical results for Crossfire™, are encouraging. Longer follow-up is necessary to confirm the benefits to patients from reduction of debris released from the articulation.

Round-Robin Tests of Modulus and Strength of Polysilicou

Abstract: The Young’s modulus and strength of polysilicon specimens manufactured in the same production run were measured in four different laboratories. Specimens subjected to in-plane bending were tested at U. C. Berkeley and at Failure Analysis Associates, and tensile measurements were made at Caltech and Johns Hopkins. All specimens were produced at the Microelectronics Center of North Carolina (MCNC). In bending, the Young’s modulus for specimens nominally 2 µm thick was measured as 174 GPa and 137 GPa; whereas in tension, a value of 132 GPa was obtained. Modulus values of 136 GPa and 142 GPa were measured in tension on specimens nominally 1.5 µm and 3.5 µm thick. Strengths of the brittle polysilicon were 2.8 and 2.7 GPa in bending and 1.3 GPa for both thicknesses in tension. These preliminary results were presented at Symposium N - Microelectromechanical Structures for Materials Research at the Materials Research Society meeting in April 1998. This paper is a short overview of the test methods — each of which is described elsewhere — and a documentation of the results presented at that time.

Evaluation of costs for cystoid macular edema among patients after cataract surgery

Abstract: Purpose:Little is known about the costs of cystoid macular edema (CME), an important complication associated with cataract surgery. The purpose of this analysis was to estimate the cost of treatment for CME in the United States.Methods:Data were analyzed from the 1997 through 2001 Medicare 5% Benefi

World Health Organization estimates of the global and regional disease burden of four foodborne chemical toxins, 2010: a data synthesis.

Abstract: Background Chemical exposures have been associated with a variety of health effects; however, little is known about the global disease burden from foodborne chemicals. Food can be a major pathway for the general population's exposure to chemicals, and for some chemicals, it accounts for almost 100% of exposure. Methods and Findings Groups of foodborne chemicals, both natural and anthropogenic, were evaluated for their ability to contribute to the burden of disease. The results of the analyses on four chemicals are presented here - cyanide in cassava, peanut allergen, aflatoxin, and dioxin. Systematic reviews of the literature were conducted to develop age- and sex-specific disease incidence and mortality estimates due to these chemicals. From these estimates, the numbers of cases, deaths and disability adjusted life years (DALYs) were calculated. For these four chemicals combined, the total number of illnesses, deaths, and DALYs in 2010 is estimated to be 339,000 (95% uncertainty interval [UI]: 186,000-1,239,000); 20,000 (95% UI: 8,000-52,000); and 1,012,000 (95% UI: 562,000-2,822,000), respectively. Both cyanide in cassava and aflatoxin are associated with diseases with high case-fatality ratios. Virtually all human exposure to these four chemicals is through the food supply. Conclusion Chemicals in the food supply, as evidenced by the results for only four chemicals, can have a significant impact on the global burden of disease. The case-fatality rates for these four chemicals range from low (e.g., peanut allergen) to extremely high (aflatoxin and liver cancer). The effects associated with these four chemicals are neurologic (cyanide in cassava), cancer (aflatoxin), allergic response (peanut allergen), endocrine (dioxin), and reproductive (dioxin).