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Relating to or exhibiting periodic physiological activity that occurs more than once every 24 hours.

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
References in periodicals archive ?
Unlike the 24-hour circadian rhythm of sleep, alertness, body temperature and eating, the human brain is hard-wired to go through an ultradian cycle about every 90 minutes.
(9) TNG provides a peak-and-trough (ultradian) serum profile of testosterone, which, like the natural circadian rhythm of endogenous T production, is not steady state.
Some patients with bipolar disorder, however, exhibit ultradian (ultra-rapid) mood cycling, which may be confused with the diurnal mood variation seen in patients with unipolar depression.
CAP and arousals are involved in the homeostatic and ultradian sleep processes.
Effective strategies to mitigate these outcomes for employees include reducing interruptions from phones and emails by responding at designated times during the workday (i.e., ultradian sprints), being aware of their mental state when easily distracted, and setting aside time for tasks with the highest priority (Schwartz & McCarthy, 2007).
It also discusses stress transcriptomics of cyanobacteria, the proteomics of stress responses in cyanobacteria, changes in DNA supercoiling and transcription regulation, the biological membrane as a sensor of environmental changes, cyanobacterial far-red chlorophylls, metabolic regulation, circadian and ultradian regulation, and cyanobacterial biotechnology, including cyanofuels, bioactive compounds, and conventional approaches to optimize the yield of end products.
Chronobiological studies of chicken IgY: monitoring of infradian, circadian and ultradian rhythms of IgY in blood and yolk of chickens.
Second are ultradian rhythms, which have cycles shorter than a day.
Ultradian and circadian rhythmicity of behavioral activities in the young snail Helix aspersa maxima (Gastropoda, Helicidae).
McKenna et al., "Glucocorticoid ultradian rhythmicity directs cyclical gene pulsing of the clock gene period 1 in rat hippocampus," Journal of Neuroendocrinology, vol.