Lehmann discontinuity

The Lehmann discontinuity that was predicted by the Danish seismologist Inge Lehmann in 1936, separates the outer core from the inner core. 

The condition for valid results in this work is the fact that the system is in the gel-state that is, it is in a state of inner equilibrium, and not in the glass state. Measurements of Hellwege, Knappe, and Lehmann (5) on pure PVC show the expected discontinuity in the compressibility vs. pressure curve at the melting point transition in the glass state. It is inferred from this study that the glass temperature for pure PVC and for the plasticized, gel-type PVC does not rise above 110° C. at pressures of 200 atm. (Figure 7). Our study showed that the system is always in a state of inner equilibrium. 

Lehmann K, Casella R, Blochlinger A, Gasser TC. Reasons for discontinuing intracavernous injection therapy with prostaglandin El (alprostadil). Urology 1999 53(2) 397-400. 

Lehmann, R. L. el al. (Ed.) 1995. Handbook on Discontinuously Reinforced Ceramic Matrix Composites. Am. Ceram. Soc., Westerville, Ohio. 

On account of the fact that all grades of rigidity have been realised between the ordinary solid and the liquid state, in the case both of crystalline and of amorphous substances, it has been proposed to abandon the terms solid and liquid, and to class bodies as crystalline or amorphous, the passage from the one condition to the other being discontinuous crystalline bodies possess a certain regular orientation of their molecules and a directive force, while in amorphous bodies these are wanting (see Lehmann, Annalen d. Physik, 1900 [4], 2,696). See, however, von K Iioid Z, 1908,3, 282 1909,4, 27, 123, 198, 252, 315 5, 62, ny, 150, 212, Poster, ibid, 1910, 7, 29. 

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