QUESTION: Fix punctuation: This results in a tungsten copper heat sink of lower density low CTE and excellent thermal conductivity
ANS: This results in a tungsten copper heat sink of lower density, low CTE and excellent thermal conductivity.

QUESTION: Fix punctuation: 200 m capsized off the cliff
ANS: 200 m capsized off the cliff.

QUESTION: Fix punctuation: In particular IX is just X It turns out that it is often useful to represent a matrix as a product with the identity matrix
ANS: In particular, IX is just X. It turns out that it is often useful to represent a matrix as a product with the identity matrix.

QUESTION: Fix punctuation: He told that the Gothic word for ancestor gods was ansis which appear to be the background for the rune name ansuZ God and the divine group of Ases
ANS:
He told that the Gothic word for ancestor gods was "ansis", which appear to be the background for the rune name "ansuZ" (God) and the divine group of "Ases".