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Results for “Statistical Distributions”

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At least 55 records · Page 3Linked to original sources
PubMed1977

Gamma-glutamyltransferase activity in plasma: statistical distributions, individual variations, and reference intervals.

Measurement of gamma-glutamyltransferase activity in plasma provides a useful index to liver function. Using as our study population those persons coming to the Center for Preventive Medicine, we described and measured the significance and importance of physiological and environmental variations. We established a classification for the variation factors. The three most important factors affecting this activity were drug intake, alcohol consumption, and excessive weight, followed by sex and age. We suggest a preliminary group of reference intervals for healthy subjects to be used in interpreting a laboratory test.

Adolescent↗
PubMed1996

Antihypertensive effect of drugs: statistical distribution of the trough-to-peak ratio.

Explicit formulas for the distribution function, the expectation, and the variance of the ratio X/Y were calculated, where X and Y are dependent variables. We assumed that the pair (X, Log Y) has a bivariate normal distribution. The work was motivated by a recent draft from the American Food and Drug Administration (FDA) on the treatment of high blood pressure (FDA, 1990, Draft of the Proposed Guidelines for the Clinical Evaluation of Antihypertensive Drugs). The effect of antihypertensive drugs on blood pressure usually achieves a peak level and then decreases to a trough level before the next dose. The FDA recommended that the ratio of trough-to-peak effects should be at least 0.5. It is well known that trough and peak effects are correlated.

Analysis of Variance↗
PubMed1993

Defining the statistical distribution of vesicle diameters facilitates quantitative assessment of spectral narrowing from small vesicles in protein/lipid interaction studies by 2H-NMR.

The diameters of vesicles comprising complexes of an integral membrane protein and 1,2-dimyristoyl-sn-glycero-3-phosphocholine, deuterated in the choline gamma-methyl groups, exhibited a lognormal distribution defined by the geometric mean (GM) and the logarithmic standard deviation (LSD). The range of vesicle sizes within each complex was very large (e.g., 99% of vesicles measured between 60 nm and 4,000 nm in one complex). This complicated assessment of spectral narrowing artefacts from small vesicles in broad line 2H-NMR results. Artefacts (e.g., decreases in quadrupole splitting and generation of two component spectra) resembled results attributed to membrane proteins in other 2H-NMR studies for which spectral narrowing was dismissed by demonstration of some vesicles > 400 nm in diameter. This was inadequate since 2H-NMR spectra from complexes with GM < 350 nm exhibited spectral narrowing artefacts despite the presence of some vesicles 1,200 nm in diameter. The nature and degree of artefact were determined by both GM and LSD. Quantifying vesicle sizes by GM and LSD accommodated the large size variation within a complex and facilitated quantitative assessment of artefacts through comparison of different complexes.

Bacteriorhodopsins↗
PubMed1999

Infants' sensitivity to statistical distributions of motion direction and speed.

Adults combine different local motions to form a global percept of motion. This study explores the origins of this process by testing how perturbations of local motion influence infants' sensitivity to global motion. Infants at 6-, 12-, and 18-weeks of age viewed random dots moving with a gaussian distribution of dot directions defined by a mean of 0 degree (rightward) or 180 degrees (leftward) and a standard deviation (SD) of 0, 34, or 68 degrees. A well-practiced observer used infants' optokinetic responses to judge the direction of stimulus motion. Infants were studied both cross-sectionally and longitudinally. Direction discrimination was relatively high at all ages when the SD was 0 degree. When the SD was 34 or 68 degrees, performance declined with age. Adult performance was nearly perfect at these SDs. A similar developmental pattern was found with distributions of dot speed. The decline in infant performance is consistent with the development of both neural tuning and receptive field size. The subsequent improvement by adulthood suggests the development of additional processes such as long-range interactions.

Analysis of Variance↗
PubMed1988

Statistical distributions of nucleosomes: nonrandom locations by a stochastic mechanism.

Expressions are derived for distributions of nucleosomes in chromatin. Nucleosomes are placed on DNA at the densities found in bulk chromatin, and their locations are allowed to vary at random. No further assumptions are required to simulate the periodic patterns of digestion obtained with various nucleases. The introduction of a boundary constraint, due for example to sequence-specific protein binding, results in an array of regularly spaced nucleosomes at nonrandom locations, similar to the arrays reported for some genes and other chromosomal regions.

Animals↗