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Sinc interpolation is a useful method for improving digital waveforms measured by A/D converters. This algorithm reconstructs the intermediate points between sampled data. I describe here a fast method for computing the sinc interpolation by the use of the Hilbert transform.
A compiled program for MS-DOS computers is described. The program computes four useful measures for the Wechsler Adult Intelligence Scale--Revised (WAIS-R). It will estimate the subject's premorbid Verbal, Performance, and Full-Scale IQs from demographic data. It will prorate the sum of the Verbal or Performance scaled scores when less than the full number of subtests are administered. It will compute the deviation of each age-scaled score from either the Verbal or Performance mean, indicating the reliability and abnormality of all differences. For those subtests which differ significantly from the appropriate mean score, the program briefly describes the subject's relative strengths and weaknesses. Finally, the program will compute the difference between the Verbal and Performance IQs, indicating the reliability and abnormality of the difference.
Early-phase clinical trials, conducted to determine the appropriate dose of an experimental drug to take forward to later trials, are considered. The objective is to find the dose associated with some low probability of an adverse event. A Bayesian model is presented, and a decision-theoretic procedure for finding the optimal doses for each of a series of cohorts of subjects is derived. The procedure is flexible and can easily be conducted using standard statistical software. The results of simulations investigating the properties of the procedure are presented.
Pharmacokinetic-pharmacodynamic (PK-PD) models play an important role in educational simulations. The parameters of PK-PD models described in the scientific literature are obtained from studies in which the drug concentrations and the drug-effect data are measured simultaneously. Simultaneous PK-PD studies cannot be expected to incorporate all possible combinations of drugs and patient physiology that are desired for educational simulations. To solve this problem, we elaborate on the traditional simultaneous PK-PD model, creating a new model that accepts parameter data from different, more readily available, nonsimultaneous pharmacologic studies. These data are incorporated in the model using a novel estimation procedure for the parameters kc0 and EC50. A sensitivity analysis of the parameter estimation procedure confirms that the time of peak effect following a bolus and the dose-response curve are accurately reflected by the new model. It also demonstrates how inconsistencies among the different parameter sets affect simulation of the recovery phase. The model is extended to incorporate any monotonic parametric or nonparametric dose-response curve. For the neuromuscular relaxant vecuronium, we demonstrate that data from different pharmacologic studies are available, and that the described estimation procedure leads to parameter estimates that are within the standard deviations of the parameters determined in a simultaneous PK-PD study.
Dispersive instability appears in time-domain solutions of classical cochlear models. In this letter, a derivation of optimal initial data is presented to minimize the effect of instability. A second-order accurate implicit boundary integral method is introduced. Numerical solutions of two-dimensional models show that the optimal initial conditions work successfully in time-domain steady-state computations for both the zero Neumann and zero Dirichlet fluid pressure boundary conditions at the helicotrema.
In the last years, worldwide scientific communities working in the area of computational biology and medicine have shown an increasing interest to the problem of computation of electromagnetic fields in the human body and safety aspects of human exposure to RF radiation. In this paper we investigate the influence of the frequency of mobile phones upon the electromagnetic energy absorption in tissues and express it as specific absorption rate (SAR) calculated with an algorithm based on Finite Integration Technique for a mobile phone excited with two different frequencies: 900 MHz and 1800 MHz. A three-dimensional human model based on anatomical data, which describes the conductivity distribution in the human body, is used in these simulations.
Traditionally, the finance department has assumed responsibility for assessing process costs in healthcare organizations. To enhance process-improvement efforts, however, many healthcare providers need to include clinical staff in process cost analysis. Although clinical staff often use electronic spreadsheets to model the cost of specific processes, PC-based animated-simulation tools offer two major advantages over spreadsheets: they allow clinicians to interact more easily with the costing model so that it more closely represents the process being modeled, and they represent cost output as a cost range rather than as a single cost estimate, thereby providing more useful information for decision making.
Computational methods to predict drug safety liabilities are reviewed. A special emphasis of this article is on the perceived strengths and weaknesses of the commercial turnkey predictive toxicology programs (TOPKAT, MULTICASE and DEREK). This article includes proposals for improvements of individual predictive programs, experiences with pharmaceutical datasets, evaluations incorporating multiple programs, and strategies of their use as a sentinel filter for liability assessment early in the drug discovery process.
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Routinely collected clinical data are a valuable source of information for clinical epidemiology, health services research, and outcomes research. To explore, graph, and analyze such a large amount of material easily, one needs three kind of tools: a database management system, graphic displays, and statistical software. Although commercial software packages with these three functions do exist, it may be difficult to find one that fulfills the multiple requirements of a large hospital, allowing researchers to use the hospital information system to study various hypotheses. To address this issue we have integrated new exploratory modules with ClinQuery, a user-friendly computer program for online searching of clinical data. In this paper we describe some of the newly implemented graphics and statistical functions, along with practical examples of the way they may be used.
A very simplified 2-dimensional simulation model of the skin and subcutaneous tissues is presented. The model is given in an annotated FORTRAN computer program with suggested numerical values for all the required constants. The model can be used to evaluate surface temperature gradients and subcutaneous thermal gradients which result from deviations of subcutaneous blood flow or heat production.
A BASIC computer program for calculating ED50 and LD50 values and their confidence limits by probit analysis and weighted linear regression is presented. It also includes the Chi square procedure for testing the mathematical model and allows on-screen high resolution graphic display. The portable program can easily be modified for use in different models of microcomputers.
The purpose of this investigation was to evaluate a conceptual model of relations between two kinds of mathematical knowledge (simple arithmetic and conceptual knowledge), two kinds of child characteristics (working memory and on-task related classroom behavior), and individual differences in three kinds of fraction outcomes (fraction computation, estimation, and word problems) in 105 fifth grade students. Structural equation modeling provided consistent evidence that conceptual knowledge independently contributes to individual differences in the three fraction outcomes. Simple arithmetic knowledge was uniquely related only to variability in fraction computation skills. Mathematical knowledge was found to mediate some of the contributions of both working memory and classroom behavior on variability in fraction outcomes. These supported mediating processes extend the current literature by explication of the pathways via which characteristics of children may affect individual differences in fraction outcomes.
The paper describes certain cases of using mathematical methods in the planning of biological experiments. The paper presents an algorithm of the distribution of the experimental data based on dynamic programming. The paper discusses an application of computer-aided calculations for the formation of homogeneous groups of experimental and control tests.
A menu-driven PC program for simultaneously testing the equality of means and variances for paired bivariate normal data is described, illustrated and made available. While the corresponding tests for independent samples are well-known and widely implemented, in the paired situation only the test for no change in mean values (the paired t-test) has been similarly covered. Tests for no change in variability, while important, are less well-known and not implemented in most commercial statistical computing programs.
Disease risk in a study cohort can be compared with that in a reference population using the method of indirect standardization, adjusting for a difference in age distribution between the cohort and reference population. The common epidemiological practice is to use categorical age, typically in the form of 5-year age strata, in the standardization. This article discusses problems that arise owing to the categorization of age, including biased estimation and incorrect statistical inference on relative risk parameters. The same problems further extend to more general analyses using Poisson regression. We illustrate the problems using a hypothetical example and propose a simple remedy using linear splines. A slightly more elaborate method and its computer program are given in the appendix.
Most computations in the field of in vitro/in vivo correlations can be handled directly by Excel worksheets, without the need for specialized software. Following a summary of Excel features, applications are illustrated for numerical computation of AUC and Mean, Wagner-Nelson and Loo-Riegelman absorption plots, and polyexponential curve fitting.