Crossword clues for rarefaction
rarefaction
The Collaborative International Dictionary
Rarefaction \Rar`e*fac"tion\ (r[a^]r`[-e]*f[a^]k"sh[u^]n), n. The act or process of rarefying; the state of being rarefied; -- opposed to condensation; as, the rarefaction of air.
Douglas Harper's Etymology Dictionary
c.1600, from Middle French raréfaction or directly from Medieval Latin rarefactionem (nominative rarefactio), noun of action from past participle stem of Latin rarefacere (see rarefy). Used chiefly in reference to gases.
Wiktionary
n. a reduction in the density of a material, especially that of a fluid
WordNet
n. a decrease in the density of something; "a sound wave causes periodic rarefactions in its medium"
Wikipedia
Rarefaction is the reduction of an item's density, the opposite of compression. Like compression, which can travel in waves ( sound waves, for instance), rarefaction waves also exist in nature. A common rarefaction wave is the area of low relative pressure following a shock wave (see picture).
Rarefaction waves expand with time (much like sea waves spread out as they reach a beach); in most gases rarefaction waves keep the same overall profile ('shape') at all times throughout the wave's movement: it is a self-similar expansion. Each part of the wave travels at the local speed of sound, in the local medium. This expansion behaviour is in contrast to the behaviour of pressure increases, which get narrower with time, until they steepen into shock waves.
In ecology, rarefaction is a technique to assess species richness from the results of sampling. Rarefaction allows the calculation of species richness for a given number of individual samples, based on the construction of so-called rarefaction curves. This curve is a plot of the number of species as a function of the number of samples. On the left, the steep slope indicates that a large fraction of the species diversity remains to be discovered. If the curve becomes flatter to the right, a reasonable number of individual samples have been taken: more intensive sampling is likely to yield only few additional species.
The issue that occurs when sampling various species in a community is that the larger the number of individuals sampled, the more species that will be found. Rarefaction curves are created by randomly re-sampling the pool of N samples multiple times and then plotting the average number of species found in each sample (1,2, ... N). "Thus rarefaction generates the expected number of species in a small collection of n individuals (or n samples) drawn at random from the large pool of N samples.". Rarefaction curves generally grow rapidly at first, as the most common species are found, but the curves plateau as only the rarest species remain to be sampled.
Usage examples of "rarefaction".
Diffuse spotty rarefaction, cortical thinning, penciling of at least one phalange.
The rarefaction of the atmosphere produced that painful oppression known by the name of PUNA.
Waves of compression and rarefaction built new nodes of compacted matter and left dark striations between them.
On the other hand, it was very cold, and I was conscious of that peculiar nausea which goes with rarefaction of the air.
Charles Comstock, in Natural Philosophy, and we spent many hours studying the compression and rarefaction of gases in the engines conceived by Mr.
I now began to experience, at intervals, severe pain in the head, especially about the ears, due to the rarefaction of the air.
Hitherto life had successfully adapted itself to the progressive rarefaction of atmosphere, but the human physique had already reached the limit of adaptability in this respect.
They went outside, into the polluted rarefaction of the atmosphere, and Stile donned his Phaze clothing, which Sheen had brought.
Anaximenes affirmed that it was air, of which all things were formed by rarefaction and condensation: on such a supposition it could have no permanent personal identity.
Nothing, for example, could be really more profound than the difference between waves of compression and rarefaction transmitted through the luminiferous ether and the translation of their impact into light.
For miles and miles in the early morning we were climbing up the mountains, till we reached a plateau where the wind blew piercingly keen, and my fingers ached with the cold, and the rarefaction in the atmosphere made breathing uneasy.
PHYSICAL DESCRIPTION The production of extraperceptual auditory stimuli involves manipulation of the laryngeal musculature in a manner that generates overtones well above the 20 000 cycles per second (cps) limit for conscious reception Bene Gessent training enables adepts to control the thyro-arytenoid vocalis and cncothyroid muscles so as to intentionally regulate vocal quality in a man ner that generated specific frequencies with in the 25,000-35,000 cps range Normal phonation, caused by tension of the vocal folds to effect condensations and rarefactions of the airstream, operates within a range of 500 to 4,000 cps, with random and only partially controlled overtones .
The landscape hunched upward in spreading compression waves, then collapsed in the rarefactions that followed.
She wondered if these gravitational perturbations, these spreading rarefactions and condensations, would have any long-term consequence, changing the pattern of subsequent planetary formation.