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At least 91 records · Page 5Linked to original sources
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↗
PubMed1975

Aspartate aminotransferase and alanine aminotransferase activities in plasma: statistical distributions, individual variations, and reference values.

The determination of frequency value (percentile limits) and the classification of the different variation factors allow us to define more and more homogeneous subpopulations as we use these factors for sorting. Using as our study population those persons coming to the Centre for Preventive Medicine, we were able to: (a) Describe and measure the significance and importance of physiological variations or of variations attributed to age--the latter largely related only to excessive weight, which it seems to us is often the case. (b) Establish a classification for variation factors; the recapitulatory table should be useful to clinical chemists in helping physicians interpret a laboratory test result that falls within the zone of incertitude. (c) Suggest a preliminary group of reference values for healthy subjects, to be used in interpreting a laboratory test in this way.

Adolescent↗
PubMed2001

Impulse noise in industrial plants: statistical distribution of levels.

Impulse noise generated by industrial machines and occurring at a workplace is a cause of substantial hearing loss in workers. The paper presents data on workplace impulse noise, recorded in three plants of the machine industry. The data were collected in drop-forge, punch-press and machinery shops. The results of the measurements are shown as cumulative relative frequency distributions of the C-weighted peak sound pressure level, L(Cpeak), the A-weighted maximum RMS sound pressure level (SPL), L(Amax), and the A-weighted sound exposure level, L(EA) of isolated acoustic impulse noises. The survey shows that in the drop-forge shop over 90% of acoustic impulses generated by hammer strikes exceed permissible levels of L(Cpeak) = 135 dB and L(Amax) = 115 dB. In the stamp-press shop, only 10-20% of impulses generated during the technological process exceed maximum permissible levels.

Humans↗