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Full-Text Articles in Physical Sciences and Mathematics

Reconstruction And Future Trends Of The Aids Epidemic In The United States, Ron Brookmeyer Nov 1991

Reconstruction And Future Trends Of The Aids Epidemic In The United States, Ron Brookmeyer

Ron Brookmeyer

There has been considerable uncertainty in estimates of past and current human immunodeficiency virus (HIV) infection rates in the United States. Statistical estimates of historical infection rates can be obtained from acquired immunodeficiency syndrome (AIDS) incidence data and the incubation period. However, this approach is subject to a number of sources of uncertainty and two other approaches, epidemic models of HIV transmission and surveys of HIV prevalence, are used to corroborate and refine the statistical estimates. Analyses suggest the HIV infection rate in the United States grew rapidly in the early 1980s, peaked in the mid-1980s, and subsequently declined markedly. …


Madagascar: Island Of Ghosts, Nat Quansah Sep 1991

Madagascar: Island Of Ghosts, Nat Quansah

Nat Quansah

No abstract provided.


Reproducibility And Responsiveness Of Health Status Measures. Statistics And Strategies For Evaluation, Paula Diehr, Richard Deyo Aug 1991

Reproducibility And Responsiveness Of Health Status Measures. Statistics And Strategies For Evaluation, Paula Diehr, Richard Deyo

Paula Diehr

Before being introduced to wide use, health status instruments should be evaluated for reliability and validity. Increasingly, they are also tested for responsiveness to important clinical changes. Although standards exist for assessing these properties, confusion and inconsistency arise because multiple statistics are used for the same property; controversy exists over how to measure responsiveness; many statistics are unavailable on common software programs; strategies for measuring these properties vary; and it is often unclear how to define a clinically important change in patient status. Using data from a clinical trial of therapy for back pain, we demonstrate the calculation of several …


Estimating County Percentages Of People Without Health Insurance, Paula Diehr Jan 1991

Estimating County Percentages Of People Without Health Insurance, Paula Diehr

Paula Diehr

County data on the percentage of people without health insurance are seldom available, although state program planning requires such information. As part of an evaluation of Washington's Basic Health Plan (BHP), we conducted a telephone survey in nine Washington counties to estimate the percentage of people under the age of 65 who were uninsured. We used regression analysis to estimate the percentage uninsured in a county as a function of the percentage unemployed. Two validation approaches yielded very good results, suggesting that the equation could be used to estimate the percentage uninsured in unsurveyed counties. The variation ranged from 15% …


Solving Ill-Posed Problems With Artificial Neural Networks, Arun D. Kulkarni Dec 1990

Solving Ill-Posed Problems With Artificial Neural Networks, Arun D. Kulkarni

Arun Kulkarni

With many physical problems, measurement of spectral distribution, cosmic radiation, aerial and satellite imaging indirect sensing/recording devices are used. In many of these cases, the recording systems can be modeled by a Fredholm integral equation of the first kind. An inversion of the kernel representing a system, in the presence of noise, is an ill-posed problem. The direct inversion often yields an unacceptable solution. In this paper, we suggest an artificial neural network (ANN) architecture to solve certain kinds of ill-posed problems. The weights in the model are initialized using eigen-vectors and eigen-values of the kernel matrix that characterize the …