User:Eugene M. Izhikevich/Proposed/Diurnal
Diurnal (adj.; diurnally adv.; diurnality noun; from Latin diurnalis, referring to day: di from dies + urnalis from Latin adjective-forming suffix): relating to variations or events, biological and other, occurring between sunrise and sunset or during the illuminated fraction (photofraction) of a near-daily schedule of solar or artificially induced alternation of light and darkness. The added traditional transdisciplinary use of diurnal to refer to the time between two sunrises is discouraged. As a noun, diurnal is on occasion used for a diary, journal, newspaper, and in a chronobiological context for symptomology, activity or a drug recommended for use or occurring by daytime only, as in diurnality and diurnal (vs. nocturnal) epilepsy, asthma or filariasis.
IntroductionThe term diurnal has traditionally been used with two distinctly different meanings: for the time between sunrise and sunset, and for the time between two sunrises.
History of the term
Franz Halberg had originally proposed that the use in biology of "circadian", which he had just coined in 1950, be restricted to rhythms desynchronized from precisely 24 hours or from precisely 1 year, free-running from their schedule with which they are usually locked into sync. Hence he had also suggested the additional term dian for 24-hour synchronized rhythms. Committees of the International Society for the Study of Biological Rhythms (later the International Society for Chronobiology) and a committee of the International Union of Physiological Sciences voted for a single term for both kinds of rhythm, namely circadian, and advocated the use of diurnal for daylight hours (Figures 1-8), so as to avoid the double use of diurnal for both "24 hours" and for "part of the day", in a phrase like "a diurnal [24-hour] rhythm in diurnal [mostly daytime] epilepsy", where the same adjective stands for two different time spans; an elaboration, e.g., in figure headings by the words in the foregoing parentheses, would be cumbersome.
The examples of Figures 2-8 are all of circadian rhythms, not of diurnal ones, although many scholars unfamiliar with the history of the field or with medical practices (at this time not the majority) insist on the use of "diurnal" or "nycthemeral" to describe a 24-hour synchronized biological rhythm and restrict the use of "circadian" to desynchronized rhythms (as originally suggested by Halberg but rejected by committees on nomenclature). If the practice of the designation of a rhythm as synchronized or desynchronized from a given, e.g., 24-hour routine were generally followed, e.g., in health care, it would be cumbersome as yet insofar as it would require prior long-term monitoring in special environments and, in that case, perhaps more than one term, e.g., dian vs. circadian could be reconsidered (or diel vs. dieloid, also proposed by Halberg in 1955 but rejected by an international nomenclature committee). New technology for automatic monitoring of physiological functions and software for as-one-goes analysis may render such a dichotomy implementable, albeit not soon in general health care practice. At this time, in the majority of biomedical articles, circadian is used for both the synchronized and the desynchronized cases in biology and medicine and diurnal is mostly restricted to daytime, but the need to arrive at a consensus in all of science, including in particular physics, remains, unless one follows the practice of using a definition of terms in each report and allows these definitions to vary from one report to the next. The community of physicists has traditionally used diurnal to mean, "performed in or occupying one day; daily", notably in an astronomical context. But even in reference to physical matters such as environmental temperature, it seems awkward to say "a diurnal temperature rise during the day and diurnal fall at night". Usage of circadian or at least dian may also be more appropriate in this case and may also account for day-to-day variability.
Whereas it may be argued that the correct meaning of diurnal may be inferred by the context in which the term is used, ambiguity is more likely to occur with a term of multiple meanings such as diurnal that could easily be interpreted correctly or incorrectly even within a given context. In view of the critical requirement of exactitude in the scientific literature, repetitions being preferred to elegant variations whenever two terms do not have a fully equivalent meaning, reserving diurnal to relate to the lighted part of the day and using circadian to mean the about-24-hour frequency of events thus seems to be preferred to avoid any ambiguity while remaining succinct. In the examples of Figures 2-8, considering the broader meaning of the term, reference to the diurnality of epilepsy could equally be interpreted as a condition with an about-24-hour pattern (that could involve seizures by night) or as events occurring only during the illuminated part of the day, opposite implications by the use of the same term. Indeed, some patients with convulsive disorders have seizures restricted to daylight hours, others have convulsions only at other times, and yet others do not show a relation to any special part of the 24-hour scale. Hurdles remain with those who now echo earlier suggestions by restricting "diurnal" to 24-hour synchronized rhythms in biology and with a long-standing use in this context of "diurnal" in physics.
- Halberg, F. (1969). Chronobiology. Annu Rev Physiol 31: 675-725.
- Halberg, F., Cornélissen, G., Katinas, G., Syutkina, E., Sothern, R., Zaslavskaya, R., Halberg, F., Watanabe, Y., Schwartzkopff, O., Otsuka, K., Tarquini, R., Frederico, P., and Siggelova, J. (2003). Transdisciplinary unifying implications of circadian findings in the 1950s. J Circadian Rhythms 1(2). Page 61. online
- Halberg, F., Cornélissen, G., Bingham, C., Witte, H., Ribary, U., Hesse, W., Petsche, H., Engebretson, M., Geissler, H., Weiss, S., Klimesch, W., Rappelsberger, P., Katinas, G., & Schwartzkopff, O. (2003). Chronomics: Imaging in time by phase synchronization reveals wide spectral-biospheric resonances beyond short rhythms. Neuroendocrinol Lett 24: 355-380.