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Biomedical subjects

M L Johnson

Publications and source records attributed to M L Johnson.

420 records · Page 24Linked to original sources
PubMedDate not supplied

Wrinkles induced by the use of smoothing procedures applied to serial growth data.

This paper elucidates the effects of moving average filters when applied to serial growth measurements. This is a question of interest because smoothing procedures are inherently part of a number of analytical methods presently employed in auxological analyses. Particular attention is paid to sequential growth data analysed to identify what has been described as pulsatile, saltation and stasis patterns or mini-growth spurts. When applied to pulsatile, or saltatory, time series data the process of smoothing itself creates artifactual temporal patterns in the time series data similar to previously described mini growth spurts while removing the actual pulsatile characteristics of the data. These observations illustrate that smoothing approaches add noise to time series data while removing meaningful patterns in the original data sequence. Analyses employing such approaches produce results that include waveforms or other fluctuations compatible with an underlying pulsatile driving mechanism, but do not necessarily reflect the temporal characteristics of the original biological process.

Biometry↗
PubMedDate not supplied

An example of variation and pattern in saltation and stasis growth dynamics.

The serial data from two siblings, aged 6.6 and 7.5 years of age at the initiation of the study, measured each evening for total standing height during 365 days, are analysed by two methods to investigate the nature of the underlying growth pattern. The saltation and stasis model, designed to identify the presence of statistically significant pulses in sequential data, is compared for goodness-of-fit to first to sixth degree polynomial functions, used to investigate the presence of a slowly varying smooth continuous function in the data, and high order polynomials of the same degree of flexibility as the individual's saltation and stasis results. The saltation and stasis model is found to better-fit the experimental data than the slowly varying smooth continuous functions (p < 0.01 to 0.001). The timing characteristics of the saltation and stasis patterns are investigated and the temporal patterns are suggestive of a non-random, aperiodical deterministic system.

Algorithms↗
PubMedDate not supplied

Sonographic identification of lung maturation in the fetal lamb.

Ultrasound evaluation of fetal lung development in utero could be a noninvasive method for frequent monitoring of the state of pulmonary maturity and predicting when parturition could occur with minimum or no risk of respiratory distress syndrome of the newborn. In cases of high-risk obstetric management in premature labor, this ability may be a particularly useful tool. To pursue this possibility, the lungs and livers of 13 living fetal lambs were successfully imaged with a modified clinical B-scanner under carefully controlled conditions; physiologic function tests on the excised lungs determined the state of pulmonary maturity. In eight cases, maturity or immaturity was correctly identified by sonographic criteria. The results wer ambiguous in four cases. One case of immature lung was incorrectly identified as mature. The trends established in these animal studies appear promising and with refinement may form the basis for sonographic assessment of fetal lung maturity in a clinical setting.

Animals↗
PubMedDate not supplied

Characteristics and attitudes of early contraceptive implant acceptors in Texas.

In 1991, shortly after Norplant became available in the United States, 678 women who had received the implant from 17 providers in Texas were surveyed. Forty-five percent of these women were under 21 years old. The majority (56%) had tried the implant because they were dissatisfied with their previous contraceptive method. Forty-four percent of the sample indicated that the implant was one of the first contraceptive methods they had used and that they had only recently decided to prevent unplanned pregnancy. The average number of children per woman was 1.2, and one-third of the sample had had at least one abortion. While 37% of the women said they wanted no more children, 63% said they were using the implant as a spacing method. The reasons for choosing the implant and concerns about it varied according to the user's age, educational level and race or ethnic group.

Adolescent↗