Noncutoff kinks in damped and parametrically driven nonlinear lattices.
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Journal Article↗
Biomedical subjects
H Quan
Publications and source records attributed to H Quan.
P-values after repeated significance testing: a simple approximation method.
The P-value after a repeated significance test is a useful measure of the strength of evidence against the null hypothesis. Its computation, however, requires a computer-intensive numerical integration method. The P-value is not conceptually straightforward, because it depends on how the sample space is ordered, which can be arbitrary. We look at two orderings of the sample space, one proposed by Tsiatis et al. and the other by Rosner and Tsiatis, and Chang. Although studies have shown that the latter ordering gives more reasonable confidence intervals than the former, the former gives a conservative and therefore more reasonable P-value. Both, however, should yield an identical P-value in most applications. In this paper we present a simple method of approximating P-values. We provide tables to implement the method for two to ten stages with alpha = 0.1, 0.05 and 0.01 for the Pocock and O'Brien-Fleming procedures. The proposed method can be applied to both orderings.
Data Interpretation, Statistical↗
Influence of age and gender on the plasma profiles of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitory activity following multiple doses of lovastatin and simvastatin.
The effects of age and of gender on the plasma profiles of HMG-CoA reductase inhibitors following separate once-a-day dosage regimens (17 days) of lovastatin (80 mg/day) and simvastatin (40 mg/day) were studied in hypercholesterolemic patients. In general, plasma concentrations of active and total HMG-CoA reductase inhibitors were higher in elderly individuals (age, 70 to 78 years) and in females for both drugs. However, the Tmax of these inhibitors was not significantly affected by either age or gender. Following the last dose of lovastatin, the mean steady-stage plasma concentrations of total and active HMG-CoA reductase inhibitors were 30-60% higher in the elderly than in young individuals (age, 19 to 30 years). Also, the mean plasma concentrations were 20-50% higher in female than in male patients. Similarly, following the last dose of simvastatin, the mean plasma concentrations of HMG-CoA reductase inhibitors were 40-60% higher in the elderly than in young patients and were 20-50% higher in female than in male patients. These age- and gender-related differences do not appear to be large enough to warrant modification of dosage regimens, because plasma concentrations of these inhibitors are not necessarily indicative of efficacy and the therapeutic windows for lovastatin and simvastatin are broad.
Adult↗
Confidence limits for low induced frequencies of oncogenic transformation in the presence of a background.
The problem is addressed of assessing realistic confidence limits for oncogenic transformation rates when the incidence of transformation is small, and there is a background present. It is shown that the commonly used approximations for assessing the confidence interval on the radiation-induced transformation rate (t1) and the control rate (t2) are inadequate when only a small number of transformants are observed. Accurate techniques are described for these cases for the estimation of confidence limits of t1, t2 and also t1-t2.
Cell Transformation, Neoplastic↗
Preparation and certification of human hair powder reference material.
Human hair powder reference material was prepared and certified for elemental composition. Human scalp hair (from Japanese men) was washed in a non-ionic detergent solution in an ultrasonic cleaner, dried, ground in an agate ball mill, sieved through a polyethylene net, blended, bottled (1100 vials, 2 g each), and finally sterilized by 60Co radiation. The prepared material satisfied the homogeneity criteria for a reference material. We determined trace elements by inductively coupled plasma atomic emission spectrometry and atomic absorption spectrometry and investigated matrix interference effects. The material was certified by using the data obtained by various analytical techniques; certified values are provided for Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Sr, and Zn. The elemental composition of this reference material is considered similar to normal values for the male Japanese population.
Analysis of Variance↗