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The Latin word rarefactum came to our language as rarefaction . It's about the process and the consequences of rarefacer , an action that consists in getting a matter in a gaseous state lose density , as explained by the Royal Spanish Academy (RAE ) in your dictionary.

It is possible to oppose the rarefaction to the compression : while, in the rarefaction, low pressure and a low number of molecules are recorded in each space, in compression there is high pressure and many molecules that are getting closer together. It can be said, therefore, that the process of rarefaction leads to a body dilate , expanding and occupying more space due to the decrease in density.

Rarefaction spreads through expansive and longitudinal waves that, over time, lengthen. He sound , for example, is formed by the succession of numerous waves of rarefaction and compression whose propagation develops through the air.

In the layers of the atmosphere From Earth we can see a clear example of rarefaction: because of gravity, almost all the atmospheric mass is very close to the ground, which generates that in the upper layers the air has less density (which is rarified) compared to the one in the lower ones. Thus, the concept of rarefaction can serve to describe a decrease in the density of space over a fraction of time, as well as that of a specific area in a given period.

In the field of ecology , is known as rarefaction method to a technique that allows comparing the diversity in two collections that were collected through samples of different intensity. Rarefaction, in this case, consists in reducing the number of individuals in the largest sample but retaining the proportion warned between species.

It's about a method created in 1968 by oceanographer Howard L. Sanders. When sampling individuals from an area, their diversity inevitably increases at every step, since adding individuals gives more species; consequently, although two samples come from populations with equal diversity, the largest will show more species, and this is the problem that Sanders wanted to solve with the rarefaction technique.

Despite having been a useful solution, it was not perfect. For this reason, a few years later other researchers proposed improvements to the equation to obtain more precise results and avoid, for example, the overestimation of the number of species.

For the medicine , the bone rarefaction it involves the loss of bone mass, which is usually linked to the advancing age. One of the most common diseases involving bone rarefaction is the osteoporosis .

Osteoporosis is a disorder that affects the skeleton and can be caused by the alteration of the metabolism of your tissue . Its course is chronic and characterized by a bone rarefaction; In addition, it especially attacks the elderly, mainly women. It is not possible to detect and diagnose osteoporosis by means of radiographs directly, which is why to achieve this, professionals rely on the concept of bone rarefaction to take as a parameter, among others.

From a clinical point of view, osteoporosis consists in the reduction of bone mass to the point of beginning to manifest itself through symptom . For radiology, on the other hand, the perception is different: it is seen as a loss of bone mass that occurs progressively over time, and is known as "physiological involution of bone" or "physiological aging of bone".

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