Which preposition to use with intensification

of Occurrences 9%

There must rather be an intensification of these evils.

by Occurrences 1%

More subtle are the difficulties in the way of the deliberate intensification by adult politicians of their own political emotions.

in Occurrences 1%

The feeding of thyroid to a gifted father before procreation might enhance immeasurably the chances of transmission of his gift as well as of its intensification in his offspring.

under Occurrences 1%

Moreover, Hobbes's ethics of interest experiences, first, correction at the hands of Locke (who, along with a complete recognition of the "legal" character of the good, distinguishes the sphere of morality from that of mere law, and brings it under the law of "reputation," hence of a "tacit" agreement), and then a frivolous intensification under Mandeville and Bolingbroke.

Which preposition to use with  intensification