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It is now well known that smart fluids [electrorheological (ER) and magnetorheological (MR)] can form the basis of controllable vibration damping devices. With both types of fluid, however, the force/velocity characteristic of the resulting damper is significantly non-linear, possessing the general form associated with a Bingham plastic. In a previous paper the authors showed that by using a linear feedback control strategy it is possible to produce the equivalent of a viscous damper with a continuously variable damping coefficient. In the present paper the authors illustrate an extension of the technique, by showing how the shape of the force/velocity characteristic can be controlled through feedback control. This is achieved by using a polynomial function to generate a set point based upon the damper velocity. The response is investigated for polynomial functions of zero, 1st and 2nd order. It is shown how the damper can accurately track higher order polynomial shaping functions, while the zero-order function is particularly useful in illustrating the dynamics of the closed-loop system. [ABSTRACT FROM PUBLISHER]

Background: The incidence of hereditary nonpolyposis colon cancer (HNPCC) in the general population is not well defined because of the lack of large population-based studies. We characterized the incidence of HNPCC in a large, population-based cohort of colorectal cancer probands and analyzed the location of colorectal tumors.Methods: Of the participating 1134 probands from three counties in Southern California, 907 had a negative family history of colorectal cancer and 227 had a positive family history of colorectal cancer. In addition, 11 referral case subjects with HNPCC were used to study mutation frequencies in two mismatch repair genes (MSH2 and MLH1) and microsatellite instability. All statistical tests were two-sided.Results: Among the probands diagnosed in Orange County during 1994 (population-based sample, all ages), five were consistent with the Amsterdam criteria for HNPCC (0.9%; 95% confidence interval [CI] = 0. 3%-2.1%). Among probands diagnosed at less than 65 years of age-from the wider three-county area and a longer time span-16 (2.1%; 95% CI = 1.2%-3.4%) had a clinical history consistent with the Amsterdam criteria for HNPCC. Five (approximately 45%) of 11 of the referral HNPCC case subjects had a mutation in MSH2 or MLH1 and also showed microsatellite instability. The family members of case subjects with mutations tended to show an earlier age at diagnosis of HNPCC and more multiple primary cancers than those of case subjects without detectable mutations. Many of the known characteristics of HNPCC, including the presence of ureteral and endometrial cancers, were seen in both sets of families. The previously reported proximal location of colorectal tumors in HNPCC kindreds was not seen in the population-based dataset but was similar to the location reported in the referral cases.Conclusions: On the basis of our data, we believe that the prevalence of HNPCC in the general population is likely to be closer to 1% than to 5%. Furthermore, our study suggests that some previously reported characteristics of HNPCC, such as the proximal location of tumors in the syndrome, may not always hold true in a population-based sample. [ABSTRACT FROM AUTHOR]