If the cholesteatoma invades posteriorly into the aditus ad antrum and the mastoid itself, erosion of the tegmen tympani, with exposure of the dura and/or erosion of the lateral semicircular canal may appear [17] (Fig. 24).
Although IL-17-induced TNF-α, IL-1β, and IL-6 can induce cartilage destruction and bone erosion, IL-17 itself has independent effects on cartilage and bone.
A mechanism that accounts for these associations has been sought for more than a century: the commonly subscribed explanation of erosion of overburden, by itself, is inadequate.
An important aspect is that the scour protection itself causes erosion, inflicted by the local increase in current and/or wave velocities and in turn increased bed shear stresses.
The most obvious are: the tensions between visitors and local inhabitants desiring further development; the problems of degradation and erosion of the land itself; and the conflict between conserving the freedom of the wild places and making them accessible, safe and comprehensible for people who have grown up without any experience of such places.
To stabilize mountain streambeds and stop descending rocks even before they reach the debris basins, numerous crib structures (barriers made of concrete slats) have been emplaced in high canyons — the idea being to convert plunging streams into boulder staircases, and hypothetically cause erosion to work against itself.
But such analyses focus on the aftereffects of erosion, not the process itself, says Frédéric Herman, a geophysicist at the University of Lausanne in Switzerland.
In addition to the natural erosion of the granite itself, during recent decades the structure has been affected by pollution, especially from vehicular traffic, which until recently passed through its arches.
Although this is not a requirement for a properly functioning gold standard system, the historical record shows that the absence of such a requirement often leads fairly quickly to an erosion of the system itself due to what amounts to political corruption.
