Jupiterimages/Brand X Pictures/Getty Images. Panic is a natural reaction when you're served with a subpoena, but as far as legal documents are concerned, a subpoena duces tecum is one of the more innocuous ones you can encounter.
Circadian rhythms are biological oscillations that recur with a period of approximately one day. Health issues related to circadian rhythms include jet lag, shift work, seasonal depression, and time-of-day variations in response to medical treatments.
Circadian rhythms are produced by natural factors within the body, but they are also affected by signals from the environment. Light is the main cue influencing circadian rhythms, turning on or turning off genes that control an organism's internal clocks.